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Cardio-respiratory responses to mental challenge : high, moderate, and low heart rate reactors Hait, Aaron Vincent 1987

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CARDIO-RESPIRATORY RESPONSES TO MENTAL CHALLENGE HIGH, MODERATE, AND LOW HEART RATE REACTORS By AARON VINCENT HAIT B.A., The U n i v e r s i t y of B r i t i s h C o l u m b i a , 1983 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n THE FACULTY OF GRADUATE STUDIES (Department of P s y c h o l o g y ) We a c c e p t t h i s t h e s i s as c o n f o r m i n g to the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA O c t o b e r 1987 (c) A a r o n V i n c e n t H a l t , 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6(3/81) i i A b s t r a c t T h r e e i s s u e s w e r e e x a m i n e d i n t h i s s t u d y : (1) t h e e x t e n t t o w h i c h p s y c h o l o g i c a l c h a l l e n g e o r s t r e s s e l i c i t s c h a n g e s i n t h e b r e a t h i n g p a t t e r n s o f n o r m a l s u b j e c t s ; (2) w h e t h e r b r e a t h i n g p a t t e r n c h a n g e s c o v a r y w i t h c a r d i o v a s c u l a r a r o u s a l ; a n d (3) w h e t h e r i n d i v i d u a l s i d e n t i f i e d a s b e i n g p o t e n t i a l l y a t - r i s k f o r d e v e l o p i n g h y p e r t e n s i o n r e s p o n d t o m e n t a l c h a l l e n g e t a s k s w i t h b r e a t h i n g p a t t e r n a n d c a r d i o v a s c u l a r c h a n g e s t h a t a r e r e l i a b l y d i f f e r e n t f r o m t h o s e o f l o w e r r i s k i n d i v i d u a l s . S u b j e c t s w e r e 100 h e a l t h y y o u n g men d i v i d e d i n t o r e a c t o r q u i n t i l e s on t h e b a s i s o f t h e i r h e a r t r a t e ( H R ) c h a n g e s t o a 1 - m i n u t e c o l d p r e s s o r t e s t . T h o s e i n t h e u p p e r q u i n t i l e w e r e d e s i g n a t e d a s b e i n g a t - r i s k f o r d e v e l o p i n g h y p e r t e n s i o n . T h e i r c a r d i o v a s c u l a r a n d r e s p i r a t o r y c h a n g e s t o two c o u n t e r b a l a n c e d v e r s i o n s o f a 5 - m i n u t e m e n t a l a r i t h m e t i c t e s t ( E a s y & H a r d ) w e r e c o m p a r e d w i t h t h o s e o f t h e t h i r d a n d f i f t h q u i n t i l e s u b j e c t s . M a r k e d i n d i v i -d u a l d i f f e r e n c e s w e r e e v i d e n t i n t h e d i r e c t i o n a n d e x t e n t o f b r e a t h i n g c h a n g e s . O v e r a l l , t h e r a t e , a m p l i t u d e , v a r i a b i l i t y , a n d p r e d o m i n a n t mode o f b r e a t h i n g i n c r e a s e d s u b s t a n t i a l l y o v e r r e s t i n g l e v e l s i n r e s p o n s e t o t h e m a t h t a s k s . O n l y b r e a t h i n g r a t e a n d v a r i a b i l i t y r e l i a b l y c o v a r i e d w i t h t a s k d i f f i c u l t y . L i t t l e c o r r e s p o n d e n c e was f o u n d b e t w e e n b r e a t h i n g c h a n g e s a n d c a r d i o v a s c u l a r a r o u s a l . T h e d a t a d i d i n d i c a t e a t r e n d f o r b r e a t h i n g t o s h i f t t o w a r d s g r e a t e r r i b c a g e d o m i n a n c e a s t a s k d i f f i c u l t y i n c r e a s e d . T h i s was e s p e c i a l l y t r u e f o r t h e a t - r i s k g r o u p a n d l e a s t t r u e f o r t h e l o w r e a c t o r q u i n t i l e . T h e e x p e c t e d i i i g r o u p d i f f e r e n c e s i n c a r d i o v a s c u l a r r e a c t i v i t y w e r e n o t f o u n d h o w e v e r , i m p l y i n g t h a t t h e HR r e a c t i v i t y t o c o l d s t i m u l a t i o n i s n o t a g o o d p r e d i c t o r o f r e a c t i v i t y t o a c u t e m e n t a l c h a l l e n g e o r s t r e s s . O v e r a l l , t h e r e s u l t s s u g g e s t t h a t b r e a t h i n g p a t t e r n s c h a n g e i n r e s p o n s e t o p s y c h o l o g i c a l s t r e s s b u t a r e n o t c l e a r l y a s s o c i a t e d w i t h c a r d i o v a s c u l a r a r o u s a l . T h e a t t e m p t t o i d e n t i f y s u b g r o u p s o f a b e r r a n t b r e a t h e r s o n t h e b a s i s o f HR r e a c t i v i t y a l s o y i e l d e d e q u i v o c a l r e s u l t s . i v Table of Contents 1. ABSTRACT i i 2. TABLE OF CONTENTS iv 3. LIST OF TABLES vi 4. LIST OF FIGURES v i i 5. ACKNOWLEDGEMENTS v i i i 6. INTRODUCTION 1 7. REVIEW OF THE LITERATURE 1 Rationale for respiratory control t r a i n i n g ... 1 Why study acute stress responses? 4 Why measure respiration during stress? 9 Cardio-respiratory measures of stress 13 Respiratory control research 21 Why measure thoracic and abdominal movement? 26 Evidence -for d i f f e r e n t breathing modes 29 Thoracic-abdominal stress responses 31 Conclusions and hypotheses 33 8. METHOD 39 Subjects 39 Apparatus 39 Procedure 42 Experimental Tasks 44 Data Reduction 46 9. RESULTS 49 I. Mental Arithmetic Responses - A l l Subjects 50 II. Stressor Responses - Reactor Subgroups .... 61 10. DISCUSSION 71 Overall e f f e c t s •+ task di-f -f i c u l t y 71 Temporal patterns of response to math tasks .. 75 Reactor subgroups and cardio-respiratory change 76 Conclusion and implications 82 11. REFERENCES 86 12. APPENDIXES A. Health it Fitness Questionnaire 93 B. Script: Experiment Introduction 94 C. Consent Form 98 D. Scrip t : Cold Pressor Task Instructions .... 99 E. Scri p t : Mental Arithmetic Task Instructions 100 F. Post-Experiment Questionnaire 101 G. Scrip t : Debriefing 102 H. Post-task Questionnaire 105 I. Raw mean scores -from baseline and math task 106 L i s t of Tab le s 1. Average change scores f o r easy and hard 52 mental a r i t h m e t i c . 2. Average change scores f o r the three r e c o r d i n g . . . . 54 p e r i o d s of mental a r i t h m e t i c . 3. C o r r e l a t i o n s between easy and hard mental 58 a r i t h m e t i c change s c o r e s : a l l p h y s i o l o g i c a l v a r i a b l e s. 4. Performance l e v e l s and r a t i n g s of task 61 d i f f i c u l t y : easy and hard a r i t h m e t i c . 5. Mean c o l d pres sor change s c o r e s : H i g h , Mid 62 and Low h e a r t ra t e r e a c t o r s and a l l s u b j e c t s combined. 6. Changes i n p h y s i o l o g i c a l a c t i v i t y from b a s e l i n e . . 67 d u r i n g easy and hard mental a r i t h m e t i c : H i g h , Mid and Low h e a r t r a t e r e a c t o r groups . 7. C o r r e l a t i o n s between change scores f o r c o l d p r e s s o r , easy math, and hard math. 69 v i i L i s t of F i g u r e s 1. C a r d i o v a s c u l a r changes from b a s e l i n e : 51 Minutes 1 to 5. 2. R e s p i r a t o r y changes from b a s e l i n e : 51 Minutes 1 to 5. v i i i A c k n o w l e d g e m e n t s I w i s h t o a c k n o w l e d g e my i n d e b t e d n e s s t o D r . W o l f g a n g L i n d e n f o r t h e many h o u r s o f g u i d a n c e and t h e many h e l p f u l s u g -g e s t i o n s he made i n t h e d e v e l o p m e n t o f t h i s t h e s i s . S p e c i a l t h a n k s a l s o n eeds t o go t o D r . D. P a p a g e o r g i s and D r . D. W i l k i e f o r t h e i r i n v a l u a b l e c o n t r i b u t i o n s as members of my t h e s i s c o m m i t t e e . R i c k J u l i u s s o n d e s e r v e s s p e c i a l m e n t i o n f o r t h e many h o u r s he d o n a t e d i n c o l l e c t i n g t h e d a t a and f o r h i s h e l p i n f i n e - t u n i n g t h e e x p e r i m e n t a l p r o c e d u r e . I am a l s o i n d e b t e d t o J i m F r a n k i s h f o r p r o o f - r e a d i n g e a r l i e r d r a f t s o f t h e t h e s i s and f o r h i s a d v i s e on s t a t i s t i c a l p r o c e d u r e s . F r a n Wen c o n t r i b u t e d many h o u r s t o d a t a e n t r y and a n a l y s i s f o r s h i c h I am d e e p l y g r a t e f u l . F i n a l l y , I must t h a n k C a r l a - M a r i e H a i t , whose p a t i e n c e , s u p p o r t and e n c o u r a g e m e n t saw t h i s t h e s i s t h r o u g h t o i t s c o m p l e t i o n . 1 A case w i l l be made f o r q u a n t i f y i n g s t r e s s - i n d u c e d changes i n the b r e a t h i n g p a t t e r n s of a h e a l t h y young p o p u l a t i o n and comparing these changes wi th c a r d i o v a s c u l a r i n d i c e s of sympath-e t i c a r o u s a l . Of p a r t i c u l a r i n t e r e s t i s the ex tent to which the predominant b r e a t h i n g mode of c a r d i a c h y p e r r e a c t o r s ( s u b j e c t s who show e x c e s s i v e h e a r t r a t e i n c r e a s e s to a c o l d p r e s s o r t e s t ) can be d i f f e r e n t i a t e d from those of low and moderate r e a c t o r s . A review of the l i t e r a t u r e w i l l focus on four c e n t r a l i s s u e s : (1) the l a c k of an adequate e m p i r i c a l r a t i o n a l e f o r t each ing d iaphragmat i c b r e a t h i n g as a s t r e s s management t e c h n i q u e ; (2) the r e l e v a n c e of s i m u l t a n e o u s l y a s s e s s i n g a v a r i e t y of r e s p i r a -tory and c a r d i o v a s c u l a r responses to acute p s y c h o l o g i c a l s t r e s s o r s ; (3) the types of r e s p i r a t o r y measures Inc luded i n p r e v i o u s s t r e s s s t u d i e s ; and (4) the u t i l i t y of measuring the r e l a t i v e c o n t r i b u t i o n to v e n t i l a t i o n made by the t h o r a c i c and abdominal compartments. F o l l o w i n g t h i s review of the l i t e r a -t u r e , i n f o r m a t i o n p e r t i n e n t to the cho ice of e x p e r i m e n t a l p r o t o c o l w i l l be p r e s e n t e d , a long with the hypotheses of t h i s s tudy. R e s p i r a t o r y c o n t r o l t r a i n i n g : R a t i o n a l e and E m p i r i c a l S u p p o r t . V o l u n t a r y m o d i f i c a t i o n of one's ra t e and depth of b r e a t h i n g i s c o n s i d e r e d an impor tant aspec t of most r e l a x a t i o n and m e d i t a -t i o n procedures (Beary & Benson, 1974; B e r n s t e i n & Borkovec , 1973). The b r e a t h i n g p a t t e r n g e n e r a l l y p r e s c r i b e d c o n s i s t s of 2 s lower , deeper i n s p i r a t i o n s a c h i e v e d p r i m a r i l y by abdominal e x c u r s i o n ( F a l i n g , 1986). T h i s p a t t e r n r e p o r t e d l y i n v o l v e s a more e f f i c i e n t use of the pr imary muscle of i n s p i r a t i o n , the diaphragm, than does t h o r a c i c - p r e d o m i n a n t b r e a t h i n g . I t i s t h e r e f o r e commonly r e f e r r e d to as d iaphragmat i c b r e a t h i n g ( T o b i n , 1986). A t t e n u a t i o n of autonomic a r o u s a l , and even the i n d u c t i o n of a t r a n s i e n t "hypometabol ic s t a t e " , have been a t t r i -buted to the p r a c t i c e of d i a p h r a g m a t i c b r e a t h i n g (Fenwick, Dona ldson , G i l l i s et a l . , 1977; Heide & Borkovec , 1983; S i n g h , 1984; Wallace & Benson, 1972; W a l l a c e , Benson & W i l s o n , 1971). However, there i s as yet l i t t l e e m p i r i c a l ev idence to s u b s t a n t i a t e these i n i t i a l c l a i m s (Holmes, 1984). In f a c t , s e v e r a l l a b o r a t o r y s t u d i e s have f a i l e d to v e r i f y that r e s p i r a -tory c o n t r o l procedures can a t t enuate acute autonomic a r o u s a l d u r i n g l a b o r a t o r y c h a l l e n g e s (Cappo & Holmes, 1984; H a r r i s , K a t k i n , L i c k , & H a b b e r f i e l d , 1976; M c C a u l , Holmes, & Solomon, 1979). On the o ther hand, a number of treatment s t u d i e s u t i l -i z i n g r e s p i r a t o r y c o n t r o l t r a i n i n g as a pr imary or a u x i l l i a r y component of treatment have r e p o r t e d s i g n i f i c a n t p o s i t i v e out -comes for a number of d i s o r d e r s c h a r a c t e r i z e d by autonomic o v e r -a r o u s a l . These i n c l u d e i d i o p a t h i c s e i z u r e s ( F r i e d , R u b i n , C a r l t o n , & Fox, 1984), panic a t t a c k s ( S a l k o v s k i s , Jones , & C l a r k , 1986), h y p e r v e n t i l a t i o n (Lum, 1976) and h y p e r t e n s i o n ( B a l i , 1979; Datey , Deshmukh, D a l v i et a l . , 1969; E n g l i s h & B a k e r , 1983; J a c o b , Kraemer, & A g r a s , 1977; P a t e l , 1977). 3 The d i s c r e p a n t f i n d i n g s of these two l i n e s of r e s e a r c h r a i s e a number of impor tant ques t ions r e g a r d i n g the methods for i n d u c i n g r e s p i r a t o r y p a t t e r n change and how these r e s p i r a t o r y changes impact other p h y s i o l o g i c a l systems. In p a r t i c u l a r , the mechanism needs to be c l a r i f i e d by which slow, d iaphragmat i c b r e a t h i n g would more e f f e c t i v e l y reduce somatic a n d / o r s u b j e c -t i v e a r o u s a l than some other form of r e s p i r a t o r y c o n t r o l or even the i n d i v i d u a l ' s n a t u r a l p a t t e r n of q u i e t b r e a t h i n g . Under-s t a n d i n g and c l e a r l y s t a t i n g the p h y s i o l o g i c a l mechanism by which a p a r t i c u l a r s t r a t e g y of r e s p i r a t o r y c o n t r o l i s b e l i e v e d to reduce a r o u s a l would seem e s s e n t i a l to the success of f u t u r e e f f o r t s a t v e r i f y i n g a n d / o r maximiz ing the c l i n i c a l u s e f u l n e s s of d i a p h r a g m a t i c b r e a t h i n g . A necessary f i r s t step i n d e t e r m i n i n g whether or not any b r e a t h i n g c o n t r o l s t r a t e g y can e f f e c t i v e l y reduce a r o u s a l i s to e s t a b l i s h that d i f f e r e n t p a t t e r n s of b r e a t h i n g occur at d i f f e r -ent l e v e l s of a r o u s a l . In other words, the r a t e , depth , and /or predominant mode of b r e a t h i n g ( i . e . t h o r a c i c versus abdominal) d u r i n g h igh a r o u s a l s t a t e s should d i f f e r i n c h a r a c t e r i s t i c ways from the p a t t e r n observed d u r i n g p e r i o d s of low a r o u s a l or r e l a x a t i o n . I f such d i f f e r e n c e s are found, the r a t i o n a l e for v o l u n t a r y a l t e r a t i o n s of b r e a t h i n g p a t t e r n s w i l l appear more t e n a b l e . To t e s t f o r a r o u s a l - r e l a t e d d i f f e r e n c e s i n r e s p i r a -t i o n , samples of b r e a t h i n g p a t t e r n s should be o b t a i n e d a c r o s s a v a r i e t y of c o n d i t i o n s , i n c l u d i n g q u i e t r e s t i n g , r e spond ing to p s y c h o l o g i c a l s t r e s s o r s , or engaging i n p h y s i c a l e x e r c i s e . 4 To date , only a handfu l of w e l l - c o n t r o l l e d p s y c h o p h y s i o -l o g i c a l s t u d i e s have looked at r e s p i r a t o r y changes under these c o n d i t i o n s ( e . g . A l l e n , Sherwood, & O b r i s t , 1986; C a r r o l l , T u r n e r , & H e l l a w e l l , 1986; Suess , A l e x a n d e r , Smith et a l . , 1980; Svebak, D a l e n , & S t o r f j e l l , 1981; T u r n e r , C a r r o l l , & C o u r t n e y , 1983). Only one study has i n v e s t i g a t e d changes i n the ampl i tude of r i b c a g e and abdominal e x c u r s i o n s d u r i n g s h o r t p e r i o d s of p s y c h o l o g i c a l s t r e s s (Svebak et a l . , 1981). No study has as yet looked at the r e l a t i v e c o n t r i b u t i o n that e i t h e r mode of b r e a t h -i n g makes to o v e r a l l v e n t i l a t i o n i n s t r e s s f u l s i t u a t i o n s . In a d d i t i o n , the c a r d i o v a s c u l a r c o r r e l a t e s of s t r e s s - i n d u c e d r e s p i r a t o r y changes have t y p i c a l l y been l i m i t e d to h e a r t ra t e and b lood p r e s s u r e . Other measures of c a r d i o v a s c u l a r change, such as T-wave ampl i tude and b lood volume p u l s e , would add to our knowledge of how the c a r d i o v a s c u l a r and r e s p i r a t o r y systems i n t e r a c t d u r i n g p e r i o d s of mental or p h y s i c a l s t r e s s . Why study acute s t r e s s responses? At p r e s e n t , p s y c h o p h y s i o l o g i s t s are only b e g i n n i n g to a p p r e c i a t e the importance of c a r d i o - r e s p i r a t o r y i n t e r a c t i o n s i n r e a c t i o n s to acute s t r e s s o r s . In the p a s t , i n v e s t i g a t o r s focused a lmost e x l u s i v e l y on c a r d i o v a s c u l a r and s u b j e c t i v e responses to s h o r t - t e r m p s y c h o l o g i c a l s t r e s s o r s i n t h e i r at tempts to unders tand the p h y s i o l o g i c a l processes i n v o l v e d i n the e t i o l o g y of c h r o n i c c a r d i o v a s c u l a r d i s o r d e r s such as e s s en -f 5 t i a l h y p e r t e n s i o n and coronary h e a r t d i sease (Krantz & Manuck, 1984). The importance of s t u d y i n g p h y s i o l o g i c a l responses to acute p s y c h o l o g i c a l s t r e s s o r s has i t s b a s i s i n the i n c r e a s i n g body of ev idence l i n k i n g p s y c h o l o g i c a l and b e h a v i o r a l f a c t o r s to d i s e a s e . A c c o r d i n g to one model , e x c e s s i v e p h y s i o l o g i c a l r e s p o n s i v i t y to emot iona l s t r e s s might be a marker of some u n d e r l y i n g p a t h o l o g i c a l process or processes i n v o l v e d i n the development of e s s e n t i a l h y p e r t e n s i o n or c o r o n a r y h e a r t d i s e a s e . While i t can be argued that p o t e n t i a l l y p a t h o l o g i c a l r e a c t i o n s to c h r o n i c s t r e s s c o n d i t i o n s are more complex and v a r i a b l e than acute r e s p o n s e s , there i s ev idence to suggest that r e a c t i o n s to acute s t r e s s o r s are r e l a t e d to the development of c h r o n i c d i s o r d e r s . I t has been found, f o r i n s t a n c e , that some i n d i v i -duals e x h i b i t a c h a r a c t e r i s t i c , t e m p o r a l l y s t a b l e hyperresponse of h e a r t ra t e and b lood pres sure to c e r t a i n tasks and s i t u a -t i o n s ( A l l e n , O b r i s t , Sherwood, & C r o w e l l , 1986; E l i o t , B u e l l , & Dembroski , 1982; F r a n k i s h & L i n d e n , 1985; L i g h t , 1981; O b r i s t , 1981; Schul te & von E i f f , 1985; Wood, Sheps, E l v e b a c k , & S c h i r g e r , 1984). There i s some o v e r l a p between t h i s h y p e r -r e a c t i v i t y subgroup and the o f f s p r i n g of h y p e r t e n s i v e parents ( H a s t r u p , L i g h t , & O b r i s t , 1982; L i g h t , 1981; Manuck & P r o i e t t i , 1982; Warren & F i s c h b e i n , 1980). Based on e p i d e m i o l o g i c a l e v i d e n c e , the l a t t e r group c a r r i e s a s u b s t a n t i a l l y g r e a t e r r i s k of d e v e l o p i n g e s s e n t i a l h y p e r t e n s i o n than do i n d i v i d u a l s wi th normotens ive p a r e n t s . 6 A c c o r d i n g to Steptoe (1985) , the f a c t that h y p e r r e a c t i v i t y to c e r t a i n s t r e s s tasks appears to precede the development of s t a b l e h y p e r t e n s i o n i s one of the most impor tant c o n s i d e r a t i o n s i n d e t e r m i n i n g which t a s k ( s ) to i n c l u d e i n one's s t u d y . He notes that c h a l l e n g i n g , p r o b l e m - s o l v i n g tasks have c o n s i s t e n t l y e l i c i t e d e x c e s s i v e s y s t o l i c b lood pres sure i n c r e a s e s i n h y p e r -t e n s i v e s and b o r d e r l i n e h y p e r t e n s i v e s , and that such i n c r e a s e s are s u s t a i n e d p r i m a r i l y through augmented h e a r t ra te and c a r d i a c o u t p u t . Increased h e a r t r a t e and s y s t o l i c b lood p r e s s u r e are known to r e f l e c t s t r o n g b e t a - a d r e n e r g i c i n f l u e n c e s on the h e a r t ( O b r i s t , 1981; Sherwood, A l l e n , O b r i s t , & L a a g e r , 1986). F u r t h e r m o r e , he ightened sympathet ic r e a c t i v i t y has been i m p l i -ca ted i n the onset of the h y p e r t e n s i v e p r o c e s s . Because of t h e i r a b i l i t y to provoke s y m p a t h e t i c a l l y - m e d i a t e d c a r d i a c changes , tasks that r e q u i r e s u b j e c t s to a c t i v e l y engage i n some form of cop ing behav iour ( e . g . mental a r i t h m e t i c , v ideo games, r e a c t i o n time t e s t s to a v o i d shock or earn monetary bonuses) can t h e r e f o r e be u s e f u l i n a n a l y z i n g the p s y c h o p h y s i o l o g i c a l processes i n e s s e n t i a l h y p e r t e n s i o n . However, as y e t , no l o n g i -t u d i n a l s t u d i e s have been completed which d i r e c t l y l i n k acute autonomic h y p e r r e a c t i v i t y to the development of h y p e r t e n s i o n or coronary h e a r t d i s e a s e . While the p r e d i c t i v e v a l i d i t y of a c t i v e cop in g task responses i s s t i l l not known, t h i s i s not the case f o r c a r d i o -v a s c u l a r r e a c t i v i t y to the c o l d p r e s s o r t e s t , a form of p h y s i c a l 7 c h a l l e n g e . In a 45-year f o l l o w - u p study of 142 s c h o o l c h i l d r e n o r i g i n a l l y t e s t ed i n 1934, Wood e t a l . (1984) found that c h i l d r e n whose s y s t o l i c or d i a s t o l i c b lood pres sure responses to the c o l d p r e s s o r were i n the 90th p e r c e n t i l e or h i g h e r showed a much h i g h e r i n c i d e n c e of h y p e r t e n s i o n l a t e r i n l i f e than d id n o r m o r e a c t o r s . Other s t u d i e s have shown that i n d i v i d u a l s wi th e s s e n t i a l h y p e r t e n s i o n s i m i l a r l y respond to c o l d p r e s s o r t e s t s wi th s i g n i f i c a n t l y l a r g e r i n c r e a s e s i n b lood pres sure than normotens ives do ( B u h l e r , B o l l i , H u l t h e n et a l . , 1983; Greene, B o l t a x , L u s t i g e t a l . , 1965). From a p h y s i o l o g i c a l s t a n d p o i n t , i t i s not c l e a r why b lood p r e s s u r e r e a c t i v i t y to the c o l d p r e s s o r should be p r e d i c t i v e of f u t u r e h y p e r t e n s i o n i n i n d i v i d u a l s who are p r e s e n t l y normo-t e n s i v e . S c h u l t e & von E i f f (1985) r e p o r t e d that males wi th r e s t i n g b lood pres sure l e v e l s i n the b o r d e r l i n e h y p e r t e n s i v e range do not show the exaggerated s y s t o l i c b lood pres sure r e a c t i v i t y that e s t a b l i s h e d h y p e r t e n s i v e s show i n response to a c o l d p r e s s o r c h a l l e n g e . They a l s o found few d i f f e r e n c e s between normotens ive , b o r d e r l i n e , and e s s e n t i a l h y p e r t e n s i v e men In the degree of h e a r t r a t e , s troke volume, and p e r i p h e r a l r e s i s t a n c e changes to the c o l d p r e s s o r t e s t . In c o n t r a s t , h y p e r t e n s i v e s showed s i g n i f i c a n t l y g r e a t e r b lood p r e s s u r e , h e a r t r a t e , and c a r d i a c output r e a c t i v i t y to a mental a r i t h m e t i c task than d i d the other two groups . Such f i n d i n g s l ed S c h u l t e and von E i f f to conclude that i n c r e a s e d r e a c t i v i t y d u r i n g b e t a - a d r e n e r g i c c a r d i a c s t i m u l a t i o n i s one of the c r i t i c a l markers of h y p e r -8 t e n s i o n p a t h o g e n e s i s , and that on ly t e s t s which provoke predomi-n a n t l y c a r d i a c r e a c t i o n s would prove u s e f u l i n p r e d i c t i n g the development of h y p e r t e n s i o n . However, In l i g h t of Wood et a l . ' s r e s u l t s - one of only two completed p r o s p e c t i v e s t u d i e s l i n k i n g some form of l a b o r a t o r y s t r e s s response wi th r i s k f o r l a t e r h y p e r t e n s i o n - t h i s c o n c l u s i o n i s r a t h e r tenuous. The c o l d p r e s s o r t e s t that Wood and h i s a s s o c i a t e s found so u s e f u l f or p r e d i c t i n g h y p e r t e n s i o n development has i t s pr imary e f f e c t on the p e r i p h e r a l v a s c u l a t u r e r a t h e r than on c a r d i a c o u t p u t . I f , as S c h u l t e and von E i f f m a i n t a i n , acute b e t a - a d r e n e r g i c r e a c t i v i t y i s the impor tant p r e d i c t o r of h y p e r t e n s i o n d e v e l o p -ment, how can one e x p l a i n the s t r o n g c o r r e l a t i o n between e x c e s s i v e b lood p r e s s u r e r e a c t i v i t y to the c o l d p r e s s o r and l a t e r development of h y p e r t e n s i o n ? C l e a r l y , at t h i s stage i n the r e s e a r c h , I t i s premature to conclude that h y p e r t e n s i o n development proceeds by one s p e c i f i c p s y c h o p h y s i o l o g i c a l pa thway. Other l i n e s of r e s e a r c h suggest that the s t a b i l i t y of c a r d i a c h y p e r r e a c t i v i t y across s t r e s s c o n d i t i o n s and over time may be an impor tant f a c t o r i n the development of h y p e r t e n s i o n . L i g h t (1981) , f o r i n s t a n c e , found that f u l l y 50% of the normotensive men showing the h i g h e s t h e a r t r a t e s d u r i n g a shock avoidance r e a c t i o n time t e s t a l s o had the h i g h e s t h e a r t r a t e s d u r i n g a c o l d p r e s s o r t e s t . She a l s o found that men with a f a m i l y h i s t o r y of h y p e r t e n s i o n had s i g n i f i c a n t l y h igher h e a r t r a t e s at r e s t and i n response to a r e a c t i o n time task than d i d 9 men wi th normotens ive p a r e n t s . F u r t h e r m o r e , s u b j e c t s wi th the l a r g e s t s y s t o l i c b lood pres sure i n c r e a s e s to a p s y c h o l o g i c a l s t r e s s o r a l s o showed the l a r g e s t h e a r t r a t e i n c r e a s e s . A s i m i l a r f i n d i n g was r e p o r t e d by F r a n k i s h & Linden (1985) . In t h i s s tudy , a 100% o v e r l a p was found between the s y s t o l i c b lood pres sure r e a c t i v i t y and h e a r t ra t e change of s u b j e c t s i n the top t e r c i l e of r e a c t i v i t y to mental a r i t h m e t i c . O v e r a l l , r e s e a r c h suggests that c a r d i o v a s c u l a r h y p e r -r e s p o n s i v i t y i s a f f e c t e d by p r e d i s p o s i t i o n and type of s t imulus e l i c i t i n g the response ( F a u l s t i c h , W i l l i a m s o n , McKenzie e t a l . , 1986; L i n d e n , 1985). A c c o r d i n g to Manuck, K r a n t z and P r o l e f r o n e (1986) , s t i m u l u s f a c t o r s such as task d i f f i c u l t y , performance i n c e n t i v e s , and s t i m u l u s n o v e l t y a l l can a f f e c t the p a t t e r n and magnitude of c a r d i o v a s c u l a r s t r e s s re sponse . To the ex tent that the c a r d i o v a s c u l a r changes induced by l a b o r a t o r y s t r e s s tasks r e f l e c t l e v e l s o c c u r r i n g i n the c h a l l e n g e s of d a i l y l i f e , they may prove to be u s e f u l p r e d i c t o r s of c a r d i o v a s c u l a r d i s o r d e r s . Why measure r e s p i r a t i o n d u r i n g s t r e s s ? The r a t i o n a l e for measuring r e s p i r a t o r y a c t i v i t y d u r i n g acute s t r e s s o r s has not been as w e l l developed as that for r e c o r d i n g s t r e s s o r - i n d u c e d c a r d i o v a s c u l a r changes . N e v e r t h e -l e s s , there are many reasons f o r doing so. Perhaps the most i m p o r t a n t of these i s the f a c t that the r e s p i r a t o r y and c a r d i o -v a s c u l a r systems i n t e r a c t i n the c r i t i c a l task of m a i n t a i n i n g 10 gas exchange between the atmosphere and body t i s s u e s . T o g e t h e r , they ensure that the l e v e l s of oxygen, carbon d i o x i d e , and b lood pH throughout a l l t i s s u e s are kept w i t h i n the narrow parameters necessary for the c o n t i n u a t i o n of normal t i s s u e f u n c t i o n i n g (Sheperd & V a n h o u t t e , 1979). Both systems i n t e r a c t at a number of l e v e l s . R e s p i r a t o r y - c a r d i o v a s c u l a r i n t e r a c t i o n s . P r e s e n t l y , four types of mechanisms have been uncovered by which r e s p i r a t i o n can modulate c a r d i o v a s c u l a r a c t i v i t y . These i n c l u d e ; (1) mechanica l e f f e c t s of i n s p i r a t i o n on venous r e t u r n to the h e a r t ; (2) lung I n f l a t i o n r e c e p t o r s which r e f l e x i v e l y t r i g g e r h e a r t r a t e a c c e l e r a t i o n d u r i n g i n s p i r a t i o n ; (3) chemo-r e c e p t o r s i n the c a r o t i d and a o r t i c bodies s e n s i t i v e to changes i n oxygen and carbon d i o x i d e t e n s i o n s ; and (4) i n t e r c o n n e c t i o n s between the b r a i n stem c e n t e r s that c o n t r o l r e s p i r a t i o n and c a r d i o v a s c u l a r a c t i v i t y v i a descending e f f e r e n t f i b e r s . The i n t e r a c t i o n of these four mechanisms must be c o n s i d e r e d when a n a l y z i n g c a r d i o v a s c u l a r responses (Grossman, 1983; Shepherd, 1981 ) . The a c t i o n of these mechanisms on h e a r t and b lood v e s s e l f u n c t i o n i n g i s observed p r i m a r i l y through f i v e r e s p i r a t o r y parameters . B r e a t h i n g r a te i s one of these parameters . Together wi th r e s p i r a t o r y depth or t i d a l volume, i t determines the volume of a i r v e n t i l a t i n g the lungs i n a g iven p e r i o d of t ime . At r e s t i n g l e v e l s , h e a l t h y a d u l t s breathe 12 - 17 times 11 or c y c l e s per minute (cpm) ( L i n d e n , In p r e s s ; T o b i n , Chadha, J e n o u r i et a l . , 1983). W i t h i n c e r t a i n l i m i t s , b r e a t h i n g ra te has been found to covary wi th h e a r t r a t e and be i n v e r s e l y r e l a t e d to h e a r t h e a r t ra t e v a r i a b i l i t y (Angelone & C o u l t e r , 1964; H i r s c h & B i s h o p , 1981; P o r g e s , McCabe & Yongue, 1982; S r o u f e , 1971). Maximum h e a r t r a t e v a r i a b i l i t y ( a l s o known as r e s p i r a t o r y s inus a r r h y t h m i a ) occurs a t a b r e a t h i n g ra te of 6 cpm: i t q u i c k l y and s t e a d i l y decreases as r e s p i r a t i o n ra te i n c r e a s e s . S e c o n d l y , i n c r e a s e d depth of r e s p i r a t i o n r e s u l t s i n i n c r e a s e d h e a r t ra t e and h e a r t ra t e v a r i a b i l i t y , a long with decreased b lood flow to hands and f ee t (Shepherd & Vanhout te , 1979; S r o u f e , 1971). M a n z o t t i (1958) showed that h e a r t ra te changes are d i r e c t l y p r o p o r t i o n a l to i n t r a t h o r a c i c p r e s s u r e : i n c r e a s e d pres sure a s s o c i a t e d wi th i n s p i r a t i o n r e s u l t s i n i n c r e a s e d h e a r t r a t e . T h i r d l y , pauses between i n s p i r a t i o n s and e x p i r a t i o n s are known to produce a pronounced and r a p i d drop i n h e a r t r a t e , wi th a concomitant i n c r e a s e i n b lood flow to the h e a r t and b r a i n ( D a l y , A n g e l l - J a m e s , & E i s n e r , 1979; H i r s c h & B i s h o p , 1981; H u r w i t z , 1981). The decrease i n h e a r t ra te a p p a r e n t l y r e s u l t s from the spontaneous a c t i v i t y of p a r a -sympathet ic v a g a l e f f e r e n t s that remain s i l e n t d u r i n g i n s p i r a t i o n . In c o n t r a s t , i n s p i r a t i o n i s a s s o c i a t e d wi th sympa-t h e t i c f i b r e f i r i n g and consequent h e a r t ra t e i n c r e a s e s (Porges et a l . , 1982). The r a t i o of i n s p i r a t i o n time to t o t a l r e s p i r a -tory c y c l e time ( T i / T t o t ) i s a l s o r e l a t e d to sympathet ic nervous system a c t i v i t y (Leischow & A l l e n , 1986; Nochomovitz , S u p i n s k i & K e l s e n , 1986). Lengthy I n s p i r a t i o n s , p a r t i c u l a r l y of t h o r a c i c 12 o r i g i n , r e q u i r e g r e a t e r muscular e x e r t i o n that consequent ly r e s u l t s i n i n c r e a s e d c a r d i a c o u t p u t . F o u r t h l y , one's mode of b r e a t h i n g - e i t h e r the predominance of t h o r a c i c or abdominal e x c u r s i o n s - has a n o t a b l e e f f e c t on c a r d i a c o u t p u t . Hurwitz (1981) found that when the depth and predominant mode of i n s p i r a t i o n s were v o l u n t a r i l y and i n d e p e n d e n t l y m a n i p u l a t e d , g r e a t e r i n c r e a s e s i n h e a r t r a t e and p e r i p h e r a l v a s o c o n s t r i c t i o n o c c u r r e d wi th t h o r a c i c l y dominant i n s p i r a t i o n s than wi th a b d o m i n a l - d i a p h r a g m a t i c b r e a t h i n g . The c a r d i a c c y c l e T-wave ampl i tude (TWA), a rough index of sympathet ic nervous system c o n t r o l of the myocardium, was a l s o found to be g r e a t e r d u r i n g abdominal than d u r i n g t h o r a c i c b r e a t h i n g ( H u r w i t z , 1981). F i n a l l y , the c o n c e n t r a t i o n of carbon d i o x i d e i n the b lood i s a c r i t i c a l f a c t o r i n c a r d i o v a s c u l a r r e g u l a t i o n , and i s c o n t r o l l e d p r i m a r i l y v i a the r a t e and depth of r e s p i r a t i o n . A drop i n the a r t e r i a l c o n c e n t r a t i o n of t h i s potent v a s o d i l a t o r , brought on by o v e r b r e a t h i n g ( i . e . b r e a t h i n g i n excess of the body's acute m e t a b o l i c r e q u i r e m e n t s ) , can r e s u l t i n v a s o c o n s t r i c t i o n and decreased oxygen a v a i l a b i l i t y . Increased h e a r t r a t e and c a r d i a c o u t p u t , T-wave f l a t t e n i n g or i n v e r s i o n as w e l l as p e r i p h e r a l v a s o c o n s t r i c t i o n and d i l a t i o n of muscle t i s s u e v e s s e l s have been observed wi th h y p e r v e n t i l a t i o n (Grossman, 1983). The p r e c e d i n g l i s t of r e s p i r a t o r y I n f l u e n c e s on c a r d i o -v a s c u l a r a c t i v i t y i s by no means e x h a u s t i v e . I t does, however, i n d i c a t e the i n t e r r e l a t e d n e s s of the two systems. By I m p l i c a -t i o n , i t a l s o suggests that both r e s p i r a t o r y and c a r d i o v a s c u l a r 13 parameters should be measured i f one i s to adequate ly study p h y s i o l o g i c a l s t r e s s re sponses . C a r d l o - r e s p i r a t o r y measures of s t r e s s . A study by Suess , A l e x a n d e r , Smith et a l . (1980) i l l u s t r a t e s the importance of r e c o r d i n g s e v e r a l measures of c a r d i o - r e s p i r a t o r y a c t i v i t y d u r i n g p s y c h o l o g i c a l s t r e s s . The s t a t e d purpose of the study was to a c c u r a t e l y c h a r a c t e r i z e the extent of s t r e s s - i n d u c e d h y p e r v e n t i l a t o r y responses i n normal i n d i v i d u a l s . To t h i s end, 29 undergraduates (13 female) completed a p e r c e p t u a l judgement task. under the t h r e a t of e l e c t r i c shock f o r subopt imal performance . Record ings of carbon d i o x i d e output , r e s p i r a t i o n r a t e , h e a r t r a t e , and s e l f - r e p o r t e d a n x i e t y were o b t a i n e d both before and d u r i n g the s t r e s s ta sk . A s i g n i f i c a n t p r e - t a s k decrease i n e n d - t i d a l carbon d i o x i d e l e v e l s ( I n d i c a t i v e of h y p e r v e n t i l a t i o n ) o c c u r r e d c o n c o m i t a n t l y w i th i n c r e a s e d h e a r t r a t e and s u b j e c t i v e a n x i e t y l e v e l s . Only h e a r t r a t e showed f u r t h e r s i g n i f i c a n t change from p r e - t a s k to task . R e s p i r a t i o n r a t e , on the other hand, was c o n s i d e r e d an inadequate measure of r e s p i r a t o r y system response to s t r e s s because of i t s low c o r r e l a t i o n wi th e n d - t i d a l carbon d i o x i d e l e v e l s . R e s p i r a t o r y mechanisms other than ra te must t h e r e f o r e have been a c t i n g to i n c r e a s e the amount of carbon d i o x i d e l e a v i n g the l u n g s . Suess et a l . conc luded that f u t u r e e f f o r t s to document r e s p i r a t o r y system r e a c t i v i t y must i n c l u d e a d d i t i o n a l measures of r e s p i r a t i o n change, such as t i d a l volume, 14 oxygen consumpt ion , and l e n g t h of i n s p i r a t i o n . Recent s t u d i e s that d i d i n c l u d e comprehensive measures of c a r d i o - r e s p i r a t o r y a c t i v i t y have y i e l d e d some p o t e n t i a l l y important f i n d i n g s . C a r r o l l e t a l . (1986) and Turner e t a l . (1983) , f o r i n s t a n c e , have found that c a r d i a c output d u r i n g m e n t a l l y c h a l l e n g i n g tasks can exceed m e t a b o l i c demands, a f i n d i n g which suggests that c a r d i a c and m e t a b o l i c f u n c t i o n i n g can become d i s s o c i a t e d d u r i n g p e r i o d s of p s y c h o l o g i c a l c h a l l e n g e or s t r e s s . In the l a t t e r s tudy , 24 young males p layed two v e r s i o n s of a "Space Invaders" computer game whi le t h e i r h e a r t r a t e and v a r i o u s r e s p i r a t o r y parameters were m o n i t o r e d . R e l a t i v e to b a s e l i n e l e v e l s , h e a r t r a t e was found to be much g r e a t e r d u r i n g "Space Invaders" than d u r i n g the c o n t r o l c o n d i t i o n . In compar i son , the t a s k - i n d u c e d i n c r e a s e s i n r e s p i r a t o r y r a t e , depth of b r e a t h i n g ( t i d a l vo lume) , b r e a t h i n g volume per minute (minute v e n t i l a t i o n ) , oxygen consumption or uptake and carbon d i o x i d e p r o d u c t i o n were c o n s i d e r e d modest a l though s i g n i f i c a n t . A s i g n i f i c a n t d i f f e r e n c e i n the l a t t e r two r e s p i r a t o r y measures prevented the i n v e s t i g a t o r s from c o n c l u d i n g that an o v e r a l l c a r d i a c - m e t a b o l i c independence had o c c u r r e d d u r i n g the game. However, the f a c t that a pos t -hoc a n a l y s i s r e v e a l e d no d i f f e r e n c e s between h igh and low h e a r t ra te r e a c t o r s i n e i t h e r oxygen uptake or carbon d i o x i d e p r o d u c t i o n suggests that the s t r e s s o r - i n d u c e d h e a r t ra t e changes e x p e r i e n c e d by the h i g h r e a c t o r s were m e t a b o l i c a l l y exaggerated . 15 C a r r o l l et a l . r e p o r t e d s i m i l a r f i n d i n g s i n a study comparing h e a r t ra t e and r e s p i r a t o r y responses d u r i n g two mental c h a l l e n g e s (mental a r i t h m e t i c and Raven's m a t r i c e s ) that v a r i e d i n l e v e l of d i f f i c u l t y (easy , h a r d , i m p o s s i b l e ) . P h y s i o l o g i c a l a c t i v i t y was a l s o recorded whi le s u b j e c t s engaged i n graded i s o t o n i c e x e r c i s e on a b i c y c l e ergometer . From t h i s i n f o r m a t i o n , r e g r e s s i o n equat ions were d e r i v e d f o r each s u b j e c t r e l a t i n g h e a r t r a t e to oxygen consumption a c r o s s three e x e r c i s e l o a d s . These r e g r e s s i o n equat ions were then used i n c o n j u n c t i o n with oxygen uptake va lues obta ined d u r i n g mental a r i t h m e t i c and Raven's m a t r i c e s to p r e d i c t t a s k - e l i c i t e d h e a r t ra t e va lues f o r each s u b j e c t . The d i f f e r e n c e between a c t u a l and p r e d i c t e d h e a r t r a t e was des ignated " a d d i t i o n a l h e a r t r a t e " or m e t a b o l i c a l l y u n j u s t i f i e d h e a r t r a t e . For most s u b j e c t s , p r e d i c t e d h e a r t ra t e va lues were c o n s i d e r a b l y l e s s than a c t u a l h e a r t ra t e v a l u e s . A n a l y s i s of these " a d d i t i o n a l h e a r t r a t e " scores r e v e a l e d a s i g n i f i c a n t e f f e c t f o r task d i f f i c u l t y , wi th s m a l l e r va lues o c c u r r i n g d u r i n g the easy c o n d i t i o n compared wi th the hard and Imposs ib l e c o n d i t i o n s . C o n v e r s e l y , no such d i f f i c u l t y e f f e c t was o b t a i n e d f o r most measures of r e s p i r a t i o n change. However, these measures d i d show s i g n i f i c a n t changes wi th time on each task , u n l i k e the measure of a d d i t i o n a l h e a r t r a t e . C o n s i d e r i n g the s i g n i f i c a n t e f f e c t of task d i f f i c u l t y on hear t r a t e , but the l a c k of such e f f e c t f o r r e s p i r a t o r y i n d i c e s of m e t a b o l i c demand, i t appears that p s y c h o l o g i c a l l y c h a l l e n g i n g tasks can e l i c i t h e a r t ra te i n c r e a s e s u n r e l a t e d to energy 16 e x p e n d i t u r e . In a d d i t i o n , such i n c r e a s e s are p a r a l l e l e d by s u b j e c t s ' s e l f - r e p o r t s of a c t i v e engagement and a r o u s a l i n the ta sk . The apparent c a r d i a c - m e t a b o l i c independence i s no t , however, a g l o b a l r e sponse . T h i s i s e v i d e n t from the f a c t t h a t , whi l e h e a r t r a t e and oxygen uptake both d e c l i n e d s i g n i f i c a n t l y wi th time on t a s k , no such time e f f e c t was e v i d e n t for " a d d i t i o n a l h e a r t r a t e " . The impact of p s y c h o l o g i c a l and p h y s i c a l c h a l l e n g e on r e s p i r a t o r y v a r i a b l e s was a l s o found to vary c o n s i d e r a b l y . For i n s t a n c e , whereas i n c r e a s e d minute v e n t i l a t i o n d u r i n g e x e r c i s e was a f u n c t i o n of i n c r e a s e s i n both t i d a l volume and r e s p i r a t i o n r a t e , changes i n v e n t i l a t i o n d u r i n g p s y c h o l o g i c a l c h a l l e n g e were l a r g e l y a f u n c t i o n of t i d a l volume v a r i a t i o n s . R e s p i r a t i o n r a t e , on the other hand, was the only r e s p i r a t o r y v a r i a b l e I n f l u e n c e d by the l e v e l of task d i f f i c u l t y . To summarize, C a r r o l l et a l . found c a r d i a c - r e s p i r a t o r y c o v a r i a t i o n to be a complex phenomenon: hear t ra t e v a r i a t i o n s w i th task d i f f i c u l t y appear to be independent of changes i n oxygen consumpt ion , carbon d i o x i d e output , and o v e r a l l v e n t i l a t i o n , but they covary wi th b r e a t h i n g r a t e . S imultaneous r e c o r d i n g of both c a r d i o v a s c u l a r and r e s p i r a t o r y measures d u r i n g acute p s y c h o l o g i c a l and p h y s i c a l c h a l l e n g e was a l s o done by A l l e n e t a l . (1986). Comprehensive measures of p h y s i o l o g i c a l change i n response to a twominute c o l d p r e s s o r , a f i v e - m i n u t e r e a c t i o n time task with the t h r e a t of e l e c t r i c shocks f o r subopt imal performance , and three load l e v e l s on a b i c y l e ergometer ( f i v e minutes at each l o a d ) were 17 o b t a i n e d for 22 male u n d e r g r a d u a t e s . The c a r d i o v a s c u l a r measures i n c l u d e d h e a r t r a t e , c a r d i a c output (the b e a t - b y b e a t product of h e a r t ra t e & s troke vo lume) , p r e - e j e c t i o n p e r i o d , and s y s t o l i c and d i a s t o l i c b lood p r e s s u r e . Ind ice s of r e s p i r a t i o n change i n c l u d e d r e s p i r a t o r y r a t e , t i d a l volume, minute v e n t i l a t i o n (the product of t i d a l volume & r e s p i r a t i o n r a t e ) , oxygen uptake , and e n d - t i d a l carbon d i o x i d e . The means f o r Minutes 5 and 10 of a 15-minute a d a p t a t i o n p e r i o d served as the b a s e l i n e va lues f o r c a l c u l a t i n g change scores f o r each dependent measure. S i n g l e means were a l s o c a l c u l a t e d f o r each dependent measure from the m i n u t e - t o - m i n u t e va lues recorded d u r i n g each of the f i v e c o n d i t i o n s . As e x p e c t e d , the one-way ( c o n d i t i o n s ) ANOVAs executed for each measure showed that i n c r e a s i n g e x e r c i s e l o a d y i e l d e d s i g n i f i c a n t d i f f e r e n c e s on a l l v a r i a b l e s except d i a s t o l i c b lood p r e s s u r e . Responses to the r e a c t i o n - t i m e and c o l d p r e s s o r t a s k s , however, v a r i e d across the d i f f e r e n t p h y s i o l o g i c a l i n d i c e s . For i n s t a n c e , c a r d i a c output was s i g n i f i c a n t l y g r e a t e r , and p r e - e j e c t i o n p e r i o d s i g n i f i c a n t l y l e s s , d u r i n g the r e a c t i o n - t i m e task than d u r i n g the c o l d p r e s s o r . T h i s task d i f f e r e n c e was a t t r i b u t e d to i n c r e a s e d b e t a - a d r e n e r g i c a c t i v i t y i n response to the r e a c t i o n - t i m e / t h r e a t c o n d i t i o n . In g e n e r a l , c a r d i o v a s c u l a r responses to the s t r e s s task d i f f e r e d s u b s t a n t i a l l y from the responses observed when s u b j e c t s were r e s t i n g q u i e t l y . 18 D i f f e r e n c e s i n the p a t t e r n of r e s p i r a t o r y changes induced by the r e a c t i o n t i m e and c o l d p r e s s o r tasks were a l s o found . For i n s t a n c e , only the c o l d p r e s s o r e l i c i t e d a s i g n i f i c a n t a b o v e - b a s e l i n e i n c r e a s e i n t i d a l volume. R e s p i r a t o r y r a t e , on the o ther hand, was g r e a t e r d u r i n g the r e a c t i o n - t i m e task than d u r i n g the c o l d p r e s s o r . A l though the d i f f e r e n c e was not s t a t i s t i c a l l y s i g n i f i c a n t , r e s p i r a t i o n r a t e i n both c o n d i t i o n s s i g n i f i c a n t l y exceeded b a s e l i n e l e v e l s . As expected from the above f i n d i n g s , the t o t a l volume of a i r i n s p i r e d per minute was s i g n i f i c a n t l y g r e a t e r f o r the c o l d p r e s s o r task than f o r the r e a c t i o n - t i m e t a s k , wi th both tasks p rod u c in g s i g n i f i c a n t l y h i g h e r v e n t i l a t i o n l e v e l s than o c c u r r e d d u r i n g b a s e l i n e . A l s o as one might expect from t h i s p a t t e r n of r e s u l t s , e n d - t i d a l carbon d i o x i d e decreased s i g n i f i c a n t l y more d u r i n g the c o l d p r e s s o r than d u r i n g shock t h r e a t . In f a c t , s u b j e c t s were a p p a r e n t l y h y p e r v e n t i l a t i n g d u r i n g the c o l d p r e s s o r . Oxygen uptake , however, d i d not d i f f e r a c r o s s the two c o n d i t i o n s a l though i t was s i g n i f i c a n t l y h i g h e r i n both c o n d i t i o n s r e l a t i v e to b a s e l i n e . In order to f u r t h e r assess the r e l a t i o n s h i p between c a r d i o v a s c u l a r and r e s p i r a t o r y v a r i a b l e s d u r i n g s t r e s s , A l l e n et a l . computed r e g r e s s i o n equat ions for each s u b j e c t , much as C a r r o l l et a l . (1983) had done. In t h i s case , however, r e g r e s s i o n e q u a t i o n s based on r e s t and e x e r c i s e va lues were computed f o r four d i f f e r e n t p a i r s of v a r i a b l e s : 1) c a r d i a c output /minute v e n t i l a t i o n ; 2) c a r d i a c output /oxygen uptake; 3) 19 h e a r t r a t e / m i n u t e v e n t i l a t i o n ; and 4) h e a r t r a t e / o x y g e n uptake . The ex tent to which each of these c a r d i o - r e s p i r a t o r y p a i r i n g s showed an "uncoupl ing" d u r i n g the c o l d p r e s s o r and r e a c t i o n -t i m e / t h r e a t c o n d i t i o n s c o u l d then be seen by l o o k i n g a t whether or not these two means l a y ou t s ide of the 95% conf idence i n t e r v a l f or the r e s p e c t i v e r e g r e s s i o n l i n e . Any s i g n i f i c a n t d e v i a t i o n from the l i n e a r r e l a t i o n s h i p at r e s t and d u r i n g e x e r c i s e was seen as ev idence f o r c a r d i o - r e s p i r a t o r y u n c o u p l i n g . J u s t as C a r r o l l e t a l . had found, h e a r t ra t e and oxygen uptake showed an u n c o u p l i n g d u r i n g the two s t r e s s o r s . A n o n l i n e a r r e l a t i o n s h i p between c a r d i a c output and minute v e n t i l a t i o n was a l s o observed d u r i n g the c o l d p r e s s o r . Dur ing the r e a c t i o n - t i m e task , a s i m i l a r n o n l i n e a r i t y of r e spond ing o c c u r r e d f o r c a r d i a c output and oxygen uptake . A l l e n e t a l . conc luded on the b a s i s of these f i n d i n g s that the r e l a t i o n s h i p between h e a r t r a t e and minute v e n t i l a t i o n i s l e s s s u s c e p t i b l e to d i s r u p t i o n by b e h a v i o r a l s t r e s s o r s than are the r e l a t i o n s h i p s i n v o l v i n g c a r d i a c output and oxygen uptake . Because of s u b s t a n t i a l i n d i v i d u a l d i f f e r e n c e s observed i n the c a r d i o v a s c u l a r and r e s p i r a t o r y parameters d u r i n g the r e a c t i o n - t i m e and c o l d p r e s s o r t a s k s , A l l e n e t a l . a l s o dec ided to examine the responses of extreme v e n t i l a t i o n r e a c t o r s and n o n r e a c t o r s to both s t r e s s o r s . A f u r t h e r purpose was to assess the impact these d i f f e r e n c e s might have on other v a r i a b l e s . C o n t r o l l i n g f o r observed order e f f e c t s i n responses to the two 20 s t r e s s c o n d i t i o n s , they executed t w o - f a c t o r repeated measures ANOVAs ( r e a c t o r group X time on task) on each of the p h y s i o l o g i c a l measures . Reactor groups were based on the 3 h i g h e s t and 3 lowest v e n t i l a t i o n r e a c t o r s i n each task o r d e r , f o r a t o t a l of 6 s u b j e c t s per r e a c t o r group. I t was noted that only three s u b j e c t s were common to the h y p e r r e a c t o r groups of both t a s k s , and three to the low r e a c t o r groups . The r e s u l t s of these ana lyse s r e v e a l e d that v e n t i l a t i o n h y p e r r e a c t o r s had s i g n i f i c a n t l y h igher minute v e n t i l a t i o n and c a r d i a c output va lues d u r i n g the c o l d p r e s s o r than d i d the low r e a c t o r s . T h i s d i f f e r e n c e was due p r i m a r i l y to l a r g e r t i d a l volumes f o r the h y p e r r e a c t o r s r a t h e r than s i g n i f i c a n t l y g r e a t e r r e s p i r a t o r y r a t e s . Oxygen uptake was a l s o s u b s t a n t i a l l y h i g h e r for the h y p e r r e a c t o r s a t the f i r s t minute of the c o l d p r e s s o r , but dropped o f f c o n s i d e r a b l y between Minutes 1 and 2. D u r i n g the r e a c t i o n - t i m e t a s k , h y p e r r e a c t o r s a l s o showed s i g n i f i c a n t l y g r e a t e r changes i n carbon d i o x i d e e x h a l a t i o n and oxygen uptake va lues than low r e a c t o r s . In g e n e r a l , i t was observed that those s u b j e c t s who showed s u b s t a n t i a l minute v e n t i l a t i o n i n c r e a s e s and e n d - t i d a l carbon d i o x i d e decreases d u r i n g e i t h e r of the two s t r e s s o r s a l s o responded with exaggerated c a r d i a c output and p r e - e j e c t i o n p e r i o d changes a s s o c i a t e d wi th b e t a - a d r e n e r g i c a c t i v i t y . A l l e n e t a l . conc luded from these r e s u l t s that some of the sympathet ic e f f e c t s on c a r d i a c f u n c t i o n i n g seen d u r i n g t h e i r b e h a v i o r a l s t r e s s o r s may be due to h y p e r v e n t i l a t i o n . 2 1 The importance of the f i n d i n g s of A l l e n e t a l . and C a r r o l l et a l . extend beyond t h e i r r e s p e c t i v e c o n c l u s i o n s about the e x i s t e n c e of m e t a b o l i c a l l y u n j u s t i f i e d h e a r t ra t e i n c r e a s e s d u r i n g acute p s y c h o l o g i c a l c h a l l e n g e . The f a c t that they measured changes i n r e s p i r a t i o n as w e l l as c a r d i o v a s c u l a r parameters such as h e a r t r a t e i s a t l e a s t as Important , s ince w i thout such measures " a d d i t i o n a l h e a r t r a t e " c o u l d not have been c a l c u l a t e d . The r e s p i r a t o r y measures a l s o p r o v i d e a more complete p i c t u r e of how d i f f e r e n t i n d i v i d u a l s respond to p s y c h o l o g i c a l c h a l l e n g e . Us ing l a r g e r sample s i z e s than those used by the p r e v i o u s i n v e s t i g a t o r s , i t may be p o s s i b l e to i d e n t i f y subgroups that show a b e r r a n t or e x c e s s i v e s t r e s s responses a c r o s s a number of p h y s i o l o g i c a l systems, i n c l u d i n g the r e s p i r a t o r y and c a r d i o v a s c u l a r systems. I d e n t i f y i n g a subgroup of i n d i v i d u a l s whose r e s p i r a t i o n d u r i n g s t r e s s d e v i a t e s s i g n i f i c a n t l y from r e l a x a t i o n p a t t e r n s and whose h e a r t r a t e r e a c t i v i t y c l a s s i f i e s them as be ing at r i s k f o r c o r o n a r y h e a r t d i s ease or e s s e n t i a l h y p e r t e n s i o n has important i m p l i c a t i o n s f o r t rea tment . To the ex tent that v o l u n t a r y s lowing a n d / o r deepening of one's b r e a t h i n g can produce a concomitant decrease i n h e a r t r a t e , i t may be c o n s i d e r e d an impor tant treatment for such h y p e r r e a c t o r s . R e s p i r a t o r y c o n t r o l r e s e a r c h . A number of e m p i r i c a l s t u d i e s have attempted to demonstrate 22 that v o l u n t a r y c o n t r o l of one's b r e a t h i n g p a t t e r n can a t t enuate autonomic and s e l f - r e p o r t e d a r o u s a l to acute p s y c h o l o g i c a l s t r e s s . These s t u d i e s were conducted i n response to the c la ims by m e d i t a t i o n e n t h u s i a s t s and b e h a v i o u r a l t h e r a p i s t s a l i k e that the p r a c t i c e of d iaphragmat i c b r e a t h i n g c o u l d reduce a r o u s a l i n both systems. In g e n e r a l , the r e s u l t s were not e n c o u r a g i n g . One of the e a r l i e s t s t u d i e s to s p e c i f i c a l l y t e s t the e f f e c t of r e s p i r a t i o n c o n t r o l on autonomic responses to p s y c h o l o g i c a l s t r e s s was conducted by H a r r i s , K a t k i n , L i c k and H a b b e r f i e l d (1976) . In t h e i r s tudy , 14 male undergraduates were asked to m a i n t a i n a c o n s t a n t depth of r e s p i r a t i o n whi le matching t h e i r r e s p i r a t o r y r a t e to the pace se t by a f l a s h i n g l i g h t . The other 28 s u b j e c t s were e i t h e r g iven no i n s t r u c t i o n s r e g a r d i n g the pac ing l i g h t ( B a s e l i n e c o n t r o l ) or i n s t r u c t e d to press a sw i t ch on every tenth l i g h t f l a s h ( A t t e n t i o n c o n t r o l ) . A 10-minute p r a c t i c e p e r i o d was a l l o t t e d f o r each c o n d i t i o n . Hear t r a t e and s k i n conductance l e v e l s were moni tored d u r i n g four subsequent p e r i o d s i n which s u b j e c t s wai ted f o r a s i g n a l l e d e l e c t r i c shock. One p a i n f u l 2-second shock was a d m i n i s t e r e d a f t e r the f i r s t 60-second warning tone. These i n v e s t i g a t o r s found that s u b j e c t s who v o l u n t a r i l y reduced t h e i r b r e a t h i n g ra te to match the pace set by a t iming l i g h t d u r i n g a 10-minute p r a c t i c e p e r i o d showed s i g n i f i c a n t l y s m a l l e r i n c r e a s e s i n s k i n conductance l e v e l s d u r i n g p r e - s h o c k and shock e x p e c t a t i o n p e r i o d s than d i d s u b j e c t s i n e i t h e r 23 n o - t r e a t m e n t or a t t e n t i o n c o n t r o l groups . A l t h o u g h such a f i n d i n g suggests that paced r e s p i r a t i o n can a t t enuate autonomic a r o u s a l , no measures of r e s p i r a t i o n ra t e and t i d a l volume were obta ined to v e r i f y that s u b j e c t s had a c t u a l l y adopted the s p e c i f i e d b r e a t h i n g p a t t e r n . A l s o q u e s t i o n a b l e was the h igh hear t r a t e mean (90.0 bpm) observed for paced b r e a t h i n g s u b j e c t s a t p o s t - p r a c t i c e . In c o n t r a s t , the mean h e a r t ra t e for a t t e n t i o n c o n t r o l and b a s e l i n e c o n t r o l s u b j e c t s was 84.1 bpm and 84.9 bpm r e s p e c t i v e l y . T h i s f i n d i n g suggests that a t t e m p t i n g to slow one's b r e a t h i n g r a t e down to a p p r o x i m a t e l y o n e - h a l f of normal r e s t i n g l e v e l s i s a r o u s i n g r a t h e r than r e l a x i n g . Holmes, McCaul and Solomon (1978) r e p o r t e d s i m i l a r f i n d i n g s i n a study comparing I d i o s y n c r a t i c r e s p i r a t o r y c o n t r o l wi th no - t rea tment and a t t e n t i o n c o n t r o l c o n d i t i o n s . In t h e i r s tudy , 111 male and female s tudents sat q u i e t l y for 30 minutes whi le a po lygraph t r a c i n g of t h e i r r e s p i r a t o r y ra t e and ampl i tude was o b t a i n e d . S u b j e c t s spent the next f i v e minutes e i t h e r : (1) s i t t i n g q u i e t l y , (2) hand-copy ing t h e i r own r e s p i r a t i o n t r a c i n g from Minutes 25 - 30 of the a d a p t a t i o n p e r i o d , or (3) a t t empt ing to reproduce t h i s t r a c i n g p a t t e r n i n v i v o . A f t e r t h i s , 50% of the s u b j e c t s i n each c o n d i t i o n were l e d to expect a s i g n a l l e d e l e c t r i c shock In a 90-second i n t e r v a l . The remain ing s u b j e c t s r e c e i v e d no t h r e a t of shock. No group d i f f e r e n c e s i n h e a r t r a t e were found f o r t h i s l a t t e r c o n d i t i o n . In the t h r e a t c o n d i t i o n , however, s u b j e c t s 24 who p r e v i o u s l y cop ied t h e i r a d a p t a t i o n phase r e s p i r a t o r y t r a c i n g by hand or i n v i v o showed s i g n i f i c a n t l y g r e a t e r h e a r t r a t e s and s e l f - r e p o r t e d a n x i e t y than s u b j e c t s i n the no - t rea tment group. One c o n c l u s i o n from these r e s u l t s i s that newly l e a r n e d cop ing s t r a t e g i e s which r e q u i r e c o n c e n t r a t i o n , such as c o n t r o l l e d b r e a t h i n g , i n c r e a s e r a t h e r than decrease autonomic a c t i v i t y , p o s s i b l y because they i n t e r f e r e w i t h one's u s u a l , and a p p a r e n t l y more e f f e c t i v e , methods f o r cop in g with t h r e a t . The f a c t that the c o n t r o l l e d b r e a t h i n g group showed i n c r e a s e d a r o u s a l In the t h r e a t c o n d i t i o n r e l a t i v e to r e s t i n g s u b j e c t s h a r d l y seems s u r p r i s i n g c o n s i d e r i n g how l i t t l e time s u b j e c t s had to p r a c t i c e such an u n n a t u r a l maneuver ( s u b j e c t s had 10 minutes to p r a c t i c e the c o n t r o l s t r a t e g y ) . A l though the i n v e s t i g a t o r s r e c o g n i z e d t h i s problem, they f u r t h e r undermined the m a n i p u l a t i o n ' s p o t e n t i a l e f f e c t i v e n e s s by d e c i d i n g not to i n s t r u c t s u b j e c t s to m a i n t a i n the p r a c t i c e d b r e a t h i n g p a t t e r n d u r i n g the s t r e s s o r p e r i o d . In a more r e c e n t s tudy , Cappo and Holmes (1984) attempted to r e d r e s s some of the weaknesses of e a r l i e r b r e a t h i n g c o n t r o l s t u d i e s by: (1) i n c l u d i n g a l a r g e r number of dependent measures, (2) r e c o r d i n g the p h y s i o l o g i c a l changes that took p l a c e whi le s u b j e c t s p r a c t i c e d one of three d i f f e r e n t b r e a t h i n g t e c h n i q u e s , and (3) I n c l u d i n g a t t e n t i n and no- trea tment c o n t r o l groups . The three d i f f e r e n t b r e a t h i n g techniques were f a s t - s l o w , s l o w - f a s t , and e q u i v a l e n t l e n g t h i n s p i r a t i o n s and e x p i r a t i o n s . A f t e r 5 minutes of p r a c t i c e wi th a s p e c i a l pac ing c l o c k , s u b j e c t s were 25 t o l d to m a i n t a i n the p r a c t i c e d b r e a t h i n g p a t t e r n u n t i l the end of the exper iment . O n e - h a l f of the s u b j e c t s i n each of the f i v e c o n d i t i o n s were then t o l d to expect a s i g n a l l e d e l e c t r i c shock sometime f o l l o w i n g a 90-second "wait p e r i o d " . C o n d i t i o n s were i d e n t i c a l i n the n o - t h r e a t c o n d i t i o n except that no mention was made of e l e c t r i c shocks . The r e s u l t s of t h i s study conf irmed Holmes e t a l . ' s (1978) f i n d i n g that a l t e r i n g one's b r e a t h i n g p a t t e r n to match a predetermined p a t t e r n , e s p e c i a l l y one i n which s u b j e c t s are to b r e a t h at rough ly h a l f t h e i r r e s t i n g r a t e , i n c r e a s e s r a t h e r than decreases a r o u s a l l e v e l s . A l l three b r e a t h i n g s t r a t e g i e s were i n e f f e c t i v e i n r e d u c i n g c a r d i o v a s c u l a r and s e l f - r e p o r t e d a r o u s a l to t h r e a t a l though there was a trend for the f a s t i n s p i r a t i o n - s l o w e x p i r a t i o n method to c o n t a i n the p e r c e p t i o n of a r o u s a l a t p r e - a r o u s a l l e v e l s . Some g e n e r a l c o n c l u s i o n s can be drawn r e g a r d i n g these three l a b o r a t o r y s t u d i e s of c o n t r o l l e d b r e a t h i n g . F i r s t , a l t e r i n g one's r e s p i r a t i o n ra t e a n d / o r l e n g t h of i n s p i r a t i o n to some predetermined l e v e l i n c r e a s e s a r o u s a l r a t h e r than l i m i t s i t . However, i n each of these s t u d i e s p r a c t i c e of the c o n t r o l s t r a t e g y was f a r too b r i e f to f a i r l y assess the p o t e n t i a l of the v a r i o u s b r e a t h i n g techniques f o r a t t e n u a t i n g a r o u s a l . Second, i t i s not c l e a r why the d i f f e r e n t c o n t r o l c o n d i t i o n s were expected to f u r t h e r reduce a r o u s a l l e v e l s a f t e r s u b j e c t s had been r e s t i n g q u i e t l y f o r up to 30 minutes . F l o o r e f f e c t s may 26 have masked any b e n e f i c i a l e f f e c t the b r e a t h i n g techniques might have had. T h i r d , the degree of a r o u s a l induced by the s t r e s s c o n d i t i o n s was minimal and t h e r e f o r e inadequate for t e s t i n g the e f f i c a c y of the b r e a t h i n g c o n t r o l p r o c e d u r e s . F o u r t h , r e s p i r a t i o n a c t i v i t y d u r i n g b r e a t h i n g c o n t r o l p r a c t i c e and the subsequent t h r e a t / n o - t h r e a t p e r i o d s was not measured; t h e r e f o r e , i t i s not known how a c c u r a t e l y s u b j e c t s performed the as s igned b r e a t h i n g m a n i p u l a t i o n s nor i s i t known whether or not the b r e a t h i n g p a t t e r n s of t r a i n e d s u b j e c t s d i f f e r e d from c o n t r o l s u b j e c t s d u r i n g the a n t i c i p a t i o n and t h r e a t c o n d i t i o n s . Without these d a t a , the v a l i d i t y of these s t u d i e s i s open to q u e s t i o n . Why measure t h o r a c i c and abdominal movement? The importance of m o n i t o r i n g changes i n b r e a t h i n g mode has long been r e c o g n i z e d by p h y s i o l o g i s t s ( e . g . Konno & Mead, 1968; S h a r p , G o l d b e r g , Druz et a l . , 1976). P s y c h o p h y s i o l o g i s t s , on the o ther hand, have p a i d r e l a t i v e l y l i t t l e a t t e n t i o n to such changes , a l t h o u g h there are some notab le excep t ions ( e . g . H e l b i c k , 1981; Svebak et a l . , 1981). One reason f o r i n c l u d i n g measures of t h o r a c i c and abdominal e x c u r s i o n when s t u d y i n g s t r e s s responses i s that they r e p r e s e n t the body's p r i n c i p a l method f o r r e p l e n i s h i n g i t s supply of oxygen and e l i m i n a t i n g carbon d i o x i d e . A c c o r d i n g to Konno and Mead (1967) , the thorax or r i b c a g e and the abdomen c o n s t i t u t e the two moving p a r t s or components of the r e s p i r a t o r y system. 27 F u r t h e r m o r e , each of these par t s moves i n d e p e n d e n t l y of the other i n the process of v e n t i l a t i n g the l u n g s . T y p i c a l l y , however, t h o r a c i c and abdominal movement appear to be coupled to some ex ten t d u r i n g i n s p i r a t i o n and e x p i r a t i o n ( H i r s c h & B i s h o p , 1981). U n d e r l y i n g t h i s apparent r ibcage-abdomen c o u p l i n g i s the a c t i o n of the d iaphragm, the pr imary muscle of r e s p i r a t i o n . The diaphragm i s a dome-shaped sheet of muscle s e p a r a t i n g the abdominal and t h o r a c i c compartments. At i t s p e r i p h e r y , i t i n s e r t s i n t o the lower r i b s , forming a zone of a p p o s i t i o n (Nochomowitz, S u p i n s k i , & K e l s e n , 1986). When c o n t r a c t e d , as d u r i n g i n s p i r a t i o n , the diaphragm pushes downward on the contents of the abdomen. Since the abdominal v i s c e r a can be compressed very l i t t l e , the downward f o r c e of t h i s c o n t r a c t i o n causes both the abdominal and r i b c a g e w a l l s to d i s p l a c e outward. C o n t r a c t i o n of the e x t e r n a l i n t e r c o s t a l s , a second group of i n s p i r a t o r y musc les , a l s o r e s u l t s i n an outward d i sp lacement of the r i b c a g e . T h i s outward expans ion of the r i b c a g e a n d / o r abdomen generates a nega t ive i n t r a t h o r a c i c pres sure that r e s u l t s i n lung i n f l a t i o n . E x p i r a t i o n i s e s s e n t i a l l y the reverse p r o c e s s . R e l a x a t i o n of r e s p i r a t o r y muscles a l l o w s the e l a s t i c f o r c e s of the i n f l a t e d lungs to r e t u r n the lung to i t s r e s t i n g volume, f o r c i n g a i r out i n the process ( M c L a u g h l i n , 1977; West, 1974). To the ex tent that the abdominal w a l l i s c o m p l i a n t ab le to move outward) , I n s p i r a t i o n can be c o n s i d e r e d ( i . e . p r e -28 dominant ly abdominal i n o r i g i n . As the abdominal muscles c o n t r a c t , however, the abdominal w a l l becomes l e s s c o m p l i a n t and i n s p i r a t o r y movement s h i f t s towards r i b c a g e predominance . The dominance of e i t h e r source of i n t r a t h o r a c i c pres sure change i s what i s r e f e r r e d to by the term " b r e a t h i n g mode". Whatever the dominant b r e a t h i n g mode, volume changes i n both r e s p i r a t o r y compartments are a f u n c t i o n of the pres sure e x e r t e d by the a s s o c i a t e d r e s p i r a t o r y muscles (Grimsby, Goldman, & Mead, 1976). Because of the way i n which the two r e s p i r a t o r y compartments i n t e r a c t i n the process of b r e a t h i n g , one can o b t a i n a n o n i n v a s i v e , r e l i a b l e e s t imate of i n s p i r a t i o n volume, otherwise known as t i d a l volume. T h i s i s done by t a k i n g the sum of volume changes i n both the r i b c a g e and abdomen ( T o b i n , 1986). Dual s i l a s t i c s t r a i n gauges or dual t r a n s d u c e r bands of the r e s p i r a t o r y - i n d u e t i v e plethysmography are used to o b t a i n these d a t a , one a t t a c h e d around the r i b c a g e and the other around the abdomen. The output of the two s t r a i n gauges or t ransducer bands must be c a l i b r a t e d a g a i n s t the output of a s p i r o m e t e r , the t r a d i t i o n a l means f o r r e c o r d i n g changes i n r e s p i r a t o r y ra te and volume. While t h i s process can be c o m p l i c a t e d and may r e q u i r e e x t e n s i v e s u b j e c t t r a i n i n g , T o b i n argues that i t i s worth the a d d i t i o n a l e f f o r t because of ev idence that the i n v a s i v e sp i rometer apparatus ( s u b j e c t s b r e a t h i n t o a mouthpiece or face mask) causes t i d a l volume to i n c r e a s e and r e s p i r a t o r y ra te to decrease r e l a t i v e to n o n i n v a s i v e methods ( G i l b e r t , A u c h i n c l o s s , Brodsky et a l , 1972; Mead, 1960). Such f i n d i n g s c a l l i n t o 29 q u e s t i o n the r e l i a b i l i t y of the r e s p i r a t i o n data o b t a i n e d i n recen t s t r e s s response s t u d i e s which used e i t h e r mouthpieces or masks to o b t a i n sp irometer r e c o r d i n g s ( e . g . A l l e n et a l . (1986); C a r r o l l e t a l . (1986) ) . Sp irometry poses a d d i t i o n a l problems f o r s t r e s s r e s e a r c h i n that the b r e a t h i n g apparatus p r e c l u d e s the use of s t r e s s tasks i n v o l v i n g speech. Ev idence f o r d i f f e r e n t b r e a t h i n g modes. The r e l a t i v e c o n t r i b u t i o n of the r i b c a g e and abdomen to b r e a t h i n g i n normal s u b j e c t s was e x t e n s i v e l y i n v e s t i g a t e d by Sharp e t a l . (1975) u s i n g n o n i n v a s i v e m o n i t o r i n g dev i ce s known as r e s p i r a t i o n magnetometers. One magnetometer was a t t a c h e d to the s u b j e c t ' s ches t to measure a n t e r o p o s t e r i o r d i s t a n c e changes a s s o c i a t e d wi th r e s p i r a t o r y e x c u r s i o n s . A second dev ice f i x e d to the abdomen p r o v i d e d data on the ampl i tude of abdominal e x c u r s i o n s d u r i n g b r e a t h i n g . R ecord in gs from both magnetometers were o b t a i n e d as 81 male and female s u b j e c t s of v a r i o u s ages p a r t i c i p a t e d i n s i x b r e a t h i n g maneuvers. These maneuvers i n c l u d e d r e l a x a t i o n (deep i n s p i r a t i o n s f o l l o w e d by slow e x p i r a t i o n to f u n c t i o n a l r e s i d u a l c a p a c i t y ) , q u i e t i n g b r e a t h i n g , i n c r e a s i n g t i d a l volume with each s u c c e s s i v e b r e a t h , f o r c e d i n s p i r a t i o n and e x p i r a t i o n , q u i e t speech, and loud speech. Because the magnetometers are s e n s i t i v e to p o s t u r a l changes, each maneuver was done twice , once i n the supine p o s i t i o n and a second time wi th s u b j e c t s seated u p r i g h t . By d i v i d i n g the t h o r a c i c data by the sum of t h o r a c i c and abdominal ampl i tude 30 s c o r e s , a measure of the r e l a t i v e motion of each r e s p i r a t o r y compartment was o b t a i n e d . Sharp et a l . found that for a g iven maneuver, b r e a t h i n g p a t t e r n s v a r i e d somewhat across s u b j e c t s of the same age and gender. N e v e r t h e l e s s , some p a t t e r n s were f a r more common than o t h e r s . For i n s t a n c e , i n the r e l a x a t i o n s u p i n e c o n d i t i o n , 81% of the young men and 93% of the young women showed t h o r a c i c predominant b r e a t h i n g when t i d a l volumes ( i . e a m p l i t u d e s ) were s m a l l ; with l a r g e r t i d a l volumes, abdominal d i sp lacement exceeded r i b c a g e d i s p l a c e m e n t . E s s e n t i a l l y the r e v e r s e p a t t e r n was observed when s u b j e c t s breathed q u i e t l y whi le seated u p r i g h t . For 91% of the men and 83% of the women, b r e a t h i n g was accompl i shed a lmost e x c l u s i v e l y by t h o r a c i c e x c u r s i o n , e s p e c i a l l y at lower t i d a l volumes. Given that the volume change or ampl i tude of a g iven compartment r e f l e c t s the compl iance of that compartment, these f i n d i n g s suggest that the r i b c a g e i s more c o m p l i a n t than the abdomen-diaphragm when s u b j e c t s perform a deep b r e a t h i n g - r e l a x a t i o n maneuver i n the u p r i g h t p o s i t i o n . When s u b j e c t s were asked to s imply r e s t q u i e t l y , the e f f e c t of pos ture on the r a t i o of t h o r a c i c d i sp lacement to t o t a l t i d a l volume d i sp lacement was aga in a p p a r e n t . In the supine p o s i t i o n , t h o r a c i c ampl i tude accounted for 25% 4% (men) to 28% 4% (women) of the t i d a l volume. When seated u p r i g h t , 72% 3% of the t i d a l volume i n young men and 61% 4% i n women was a t t r i b u t a b l e to r i b c a g e d i s p l a c e m e n t . Age and sex had l i t t l e 31 i m p a c t on' b r e a t h i n g mode i n c o m p a r i s o n t o the e f f e c t of p o s t u r e . N e a r l y a l l s u b j e c t s were a b d o m i n a l b r e a t h e r s when s u p i n e and t h o r a c i c b r e a t h e r s when u p r i g h t . G r e a t e r i n t e r - s u b j e c t v a r i a t i o n i n b r e a t h i n g mode o c c u r r e d when s u b j e c t s p u r p o s e l y i n c r e a s e d t h e i r d e p t h o f i n s p i r a t i o n , b r e a t h e d f o r c e f u l l y , o r sp o k e a l o u d . Once a g a i n , b r e a t h i n g i n the u p r i g h t p o s t u r e was p r e d o m i n a n t l y t h o r a c i c f o r most i n d i v i d u a l s , and l e s s so l n t h e s u p i n e p o s i t i o n . Age and g e n d e r , h o w e v e r , were g e n e r a l l y u n r e l a t e d t o the marked d i f f e r e n c e s i n b r e a t h i n g p a t t e r n . O t h e r f a c t o r s , p o s s i b l y of a p s y c h o l o g i c a l n a t u r e ( e . g . l e a r n e d a n x i e t y r e s p o n s e s ) , must t h e r e f o r e be c o n s i d e r e d as p o t e n t i a l s o u r c e s f o r t h e s e d i f f e r e n c e s ( s e e Haas ( 1 9 8 0 ) f o r c o r r e l a t i o n a l d a t a l i n k i n g p e r s o n a l i t y c h a r a c t e r i s t i c s w i t h r e s p i r a t o r y b e h a v i o r ) . S h a r p and h i s c o l l e a g u e s d i d n o t a t t e m p t t o u n c o v e r what t h e s e f a c t o r s m i g h t be. They d i d n o t e t h o u g h t h a t t h e r i b c a g e m u s c l e s a r e c a p a b l e of more r a p i d a c t i o n t h a n t h e d i a p h r a g m and a b d o m i n a l m u s c l e s and t h a t c o n s e q u e n t l y t h o r a c i c e x c u r s i o n s s h o u l d be e x p e c t e d t o p r e d o m i n a t e where b r e a t h i n g i s deep a n d / o r r a p i d . T h o r a c i c - a b d o m i n a l s t r e s s r e s p o n s e s . S v e b a k e t a l . ( 1 9 8 1 ) d e m o n s t r a t e d t h a t b r e a t h i n g mode does change i n r e s p o n s e t o one t y p e o f a c u t e p s y c h o l o g i c a l c h a l l e n g e . I n t h e i r s t u d y , 13 male u n d e r g r a d u a t e s p l a y e d two c o u n t e r b a l a n c e d v e r s i o n s ( e a s y and h a r d ) o f a v i d e o game w h i l e c h a n g e s i n t h e i r h e a r t r a t e , f o r e a r m EMG, s k i n c o n d u c t a n c e and 32 r e s p i r a t i o n were measured. R e c o r d i n g of b r e a t h by b r e a t h changes i n both the c i r c u m f e r e n c e and ampl i tude of the r i b c a g e and abdominal compartments were made p o s s i b l e by f a s t e n i n g one m e r c u r y - f i l l e d s t r a i n gauge around each s u b j e c t ' s ches t and another around h i s abdomen. By comparing the degree of ampl i tude change i n each r e s p i r a t o r y compartment, an e s t imate of b r e a t h i n g mode change c o u l d be o b t a i n e d . A n a l y s i s of the EMG data r e v e a l e d that EMG l e v e l s had i n c r e a s e d g r a d u a l l y d u r i n g both v e r s i o n s of the 150 second long v ideo game. S i m i l a r i n c r e a s e s were found f o r r e s p i r a t i o n ra t e and t h o r a c i c c i r c u m f e r e n c e . In c o n t r a s t , abdominal c i r c u m f e r e n c e decreased throughout the task . A d i f f e r e n t p a t t e r n of r e s u l t s emerged f o r r e s p i r a t i o n a m p l i t u d e . T h o r a c i c and abdominal e x c u r s i o n s both dropped to t h e i r lowest l e v e l s a t the b e g i n n i n g of the game performance , the d i f f i c u l t game e l i c i t i n g the l a r g e s t drop i n a m p l i t u d e s , e s p e c i a l l y for abdominal a m p l i t u d e . By t a s k ' s end, however, the scores for both game v e r s i o n s had i n c r e a s e d to w i t h i n a p p r o x i m a t e l y 90% of b a s e l i n e l e v e l s . On the b a s i s of these f i n d i n g s , Svebak et a l . conc luded that r e s p i r a t o r y changes a s s o c i a t e d with acute p s y c h o l o g i c a l c h a l l e n g e p a r a l l e l i n c r e a s e s i n somatic a c t i v i t y . F u r t h e r m o r e , the rough ly monotonic i n c r e a s e i n p h y s i o l o g i c a l a c t i v i t y o c c u r r i n g throughout t h i s task took p lace only for s k e l e t a l muscle and not f o r the v i s c e r a ( i . e . h e a r t r a t e and s k i n 33 c o n d u c t a n c e ) . In c o n t r a s t , these l a t t e r measures reached t h e i r h i g h e s t l e v e l s s h o r t l y a f t e r the task. began. Such r e s u l t s suggest that a p e r f o r m a n c e - r e l a t e d d i s s o c i a t i o n of c a r d i a c f u n c t i o n i n g and somatic a c t i v i t y occurs i n tasks where outcomes can be p o s i t i v e or n e g a t i v e , depending on the i n d i v i d u a l ' s performance . Of g r e a t e r r e l e v a n c e , they p r o v i d e p r e l i m i n a r y ev idence that acute s t r e s s o r s can induce changes i n the c i r c u m -ference and ampl i tude of the two independent components of the r e s p i r a t o r y system. An e f f e c t i v e means f o r measuring r e s p i r a t o r y changes v i a dual s t r a i n gauges i s a l s o demonstrated . U n f o r t u n a t e l y , the s i g n i f i c a n c e of these f i n d i n g s i s l i m i t e d by the smal l sample s i z e (n = 13) . Given the c o n s i d e r a b l e range of p o s s i b l e r e s p i r a t o r y and autonomic responses , the e x i s t e n c e of r e a c t o r subgroups c o u l d not be determined wi th t h i s sample. As mentioned e a r l i e r , i d e n t i f y i n g i n d i v i d u a l s who show hyperresponses on a number of p h y s i o l o g i c a l measures, i n c l u d i n g r e s p i r a t o r y mode, w i l l p r o v i d e a more c o n v i n c i n g data base for t each ing b r e a t h i n g c o n t r o l t echniques i n attempts to reduce exaggerated s t r e s s responses . C o n c l u s i o n s and hypotheses . In the p r e c e d i n g r e v i e w , a r a t i o n a l e was developed for a s s e s s i n g both r e s p i r a t o r y and c a r d i o v a s c u l a r changes i n response to acute p s y c h o l o g i c a l c h a l l e n g e . I t was f i r s t emphasized that s y m p a t h e t i c a l l y mediated r e a c t i v i t y of the 34 c a r d i o v a s c u l a r system to l a b o r a t o r y s t r e s s o r s may p o s s i b l y be a p r e d i c t o r of c a r d i o v a s c u l a r d i s e a s e . An o u t l i n e of the main mechanisms by which v a r i o u s r e s p i r a t o r y parameters a l t e r c a r d i a c and b lood v e s s e l f u n c t i o n i n g p r o v i d e d some i n i t i a l support f o r measuring s t r e s s - i n d u c e d r e s p i r a t o r y changes c o n c o m i t a n t l y wi th c a r d i o v a s c u l a r r e s p o n s e s . F u r t h e r support came from s t u d i e s by A l l e n e t a l . (1986) and C a r r o l l et a l . (1983) which demonstrated the va lue of i n c l u d i n g comprehensive c a r d i o - r e s p i r a t o r y measures i n s t r e s s r e s e a r c h . A f t e r b r i e f l y c o n s i d e r i n g how v e n t i l a t i o n changes are accompl i shed p h y s i o l o g i c a l l y and how t r a d i t i o n a l assessment methods tend to a l t e r b r e a t h i n g r e s p o n s e s , i t should be c l e a r that the r e s p i r a t o r y data r e p o r t e d i n these s t u d i e s are i n a d e q u a t e . M o n i t o r i n g changes i n the ampl i tude a n d / o r c i r c u m f e r e n c e of the r e s p i r a t o r y system's two independent compartments, the ches t and the abdomen, was c o n s i d e r e d as an a l t e r n a t e source of i n f o r m a t i o n on b r e a t h i n g re sponses . Svebak et a l . ' s (1981) study i s of p a r t i c u l a r r e l e v a n c e i n that i t demonstrates that these l a t t e r measures are s e n s i t i v e not only to the e f f e c t s of p s y c h o l o g i c a l l y c h a l l e n g i n g tasks but a l s o to the l e v e l of task d i f f i c u l t y . Given that b r e a t h i n g p a t t e r n s s h i f t e d towards g r e a t e r t h o r a c i c dominance throughout the c h a l l e n g i n g t a s k s , these f i n d i n g s p r o v i d e some i n i t i a l support f o r t e a c h i n g d iaphragmat i c b r e a t h i n g as a technique f o r r e d u c i n g a r o u s a l . One purpose of the present study i s to at tempt to r e p l i c a t e Svebak et a l . ' s f i n d i n g s u s i n g a l a r g e r s u b j e c t sample and a 35 d i f f e r e n t task of l onger d u r a t i o n . By doing so, the ex t en t to which b r e a t h i n g p a t t e r n changes and c a r d i a c h y p e r r e a c t i v i t y covary i n normal s u b j e c t s should become c l e a r e r . The i n c l u s i o n of a d d i t i o n a l measures of autonomic and somatic a r o u s a l , such as T-wave a m p l i t u d e , b lood volume p u l s e , pulse t r a n s i t t ime, and r e s p i r a t o r y movement v a r i a b i l i t y , w i l l p r o v i d e f u r t h e r , as ye t untapped, i n f o r m a t i o n on c a r d i o - r e s p i r a t o r y i n t e r a c t i o n s d u r i n g p s y c h o l o g i c a l c h a l l e n g e . Another measure i n c l u d e d i n t h i s study which p r e v i o u s l a b o r a t o r y s t r e s s s t u d i e s have not assessed i s the ta sk induced change i n t h o r a c i c e x c u r s i o n s r e l a t i v e to abdominal e x c u r s i o n s . The one other study to i n c l u d e t h i s measure (Sharp et a l . , 1975) found i t to be a u s e f u l index of b r e a t h i n g mode v a r i a t i o n s . Based on the Svebak et a l . d a t a , i t might be expected that b r e a t h i n g mode w i l l s h i f t towards t h o r a c i c dominance wi th the onset of s t r e s s ta sks . The d i f f i c u l t y l e v e l of a c h a l l e n g e task l i k e mental a r i t h m e t i c may a l s o have a d i f f e r e n t i a l e f f e c t on b r e a t h i n g mode g iven Svebak et a l ' s f i n d i n g that easy and hard v e r s i o n s of t h e i r a c t i v e cop ing task (a v ideo game) e l i c i t e d s i g n i f i c a n t l y d i f f e r e n t l e v e l s of r i b c a g e and abdominal a m p l i t u d e . In f a c t , i t can be argued t h a t , i n comparison to a v ideo game s t r e s s o r , easy and hard v e r s i o n s of a mental a r i t h m e t i c task r e p r e s e n t a b e t t e r t e s t of b r e a t h i n g mode s e n s i t i v i t y to s t r e s s l o a d . L i t t l e p h y s i c a l e x e r t i o n i s r e q u i r e d i n mental a r i t h m e t i c t a s k s ; t h e r e f o r e , response d i f f e r e n c e s between d i f f i c u l t y c o n d i t i o n s are l i k e l y to be the r e s u l t of c o g n i t i v e l y mediated a r o u s a l 36 r a t h e r than b y - p r o d u c t s of i n c r e a s e d muscular a c t i v i t y . A second purpose of t h i s study i s to determine whether or not i n d i v i d u a l s whose c a r d i a c adjustments to a c o l d p r e s s o r t e s t may be c o n s i d e r e d e x c e s s i v e r e l a t i v e to o ther s u b j e c t s a l s o respond to subsequent mental c h a l l e n g e tasks wi th s i g n i f i c a n t l y d i f f e r e n t r e s p i r a t o r y and c a r d i o v a s c u l a r changes than those e x p e r i e n c e d by low or moderate h e a r t ra t e r e a c t o r s . On the b a s i s of Wood et a l . ' s (1983) f i n d i n g s , the h i g h r e a c t o r group may be c o n s i d e r e d to be at g r e a t e r r i s k for d e v e l o p i n g h y p e r -t e n s i o n or coronary h e a r t d i s e a s e . Research by A l l e n e t a l . (1986) a l s o suggests that h y p e r r e a c t o r s to a c o l d p r e s s o r t e s t breathe more deeply a n d / o r more r a p i d l y than h y p o r e a c t o r s . In a d d i t i o n , a c o n s i d e r a b l e p r o p o r t i o n of the c o l d p r e s s o r h y p e r -r e a c t o r s a l s o e x p e r i e n c e d the g r e a t e s t c a r d i o v a s c u l a r and r e s p i r a t o r y a r o u s a l to a shock avoidance r e a c t i o n time task . Whether or not such f i n d i n g s can be r e p l i c a t e d wi th a l a r g e r sample of h e a l t h y young males remains to be seen. F u r t h e r m o r e , i t needs to be demonstrated that t h i s apparent c a r d i o -r e s p i r a t o r y c o v a r i a t i o n occurs under d i f f e r e n t l e v e l s of task d i f f i c u l t y and a c r o s s d i f f e r e n t types of a c t i v e cop in g t a s k s . The r e s u l t s of s e v e r a l of the s t u d i e s reviewed here suggest that a c t i v e cop ing to a v o i d a v e r s i v e consequences or ga in monetary bonuses causes an u n c o u p l i n g of the c a r d i a c and r e s p i r a t o r y responses which o r d i n a r i l y operate i n synchrony to meet meta-b o l i c requirements ( e . g . C a r r o l l e t a l . , 1983; Svebak et a l . , 1981). The p o s s i b i l i t y e x i s t s that such u n c o u p l i n g of otherwise 37 p a r a l l e l responses i n the two systems i s l i m i t e d to a subset of s u b j e c t s ( A l l e n e t a l . , 1986; Turner e t a l . , 1981). U n f o r t u -n a t e l y , the sample s i z e s i n these pos t -hoc comparisons were unacceptab ly low, r a n g i n g from n = 3 to n = 6. A study that employs a l a r g e r sample s i z e would c l e a r up t h i s a m b i g u i t y . To the ex tent that c a r d i a c hyperresponders a l s o have a t h o r a c i c l y dominant b r e a t h i n g p a t t e r n d u r i n g s t r e s s , they may b e n e f i t from t r a i n i n g to breathe d i a p h r a g m a t i c a l l y p r i o r to a n d / o r d u r i n g times of s t r e s s . In summary, the f o l l o w i n g q u e s t i o n s are addressed i n the presen t s tudy: 1) To what ex tent does an a c t i v e cop ing task l i k e mental a r i t h m e t i c a f f e c t m u l t i p l e i n d i c e s of r e s p i r a t o r y a c t i v i t y , i n c l u d i n g b r e a t h i n g r a t e , ampl i tude of r i b c a g e and abdominal e x c u r s i o n s , the v a r i a b i l i t y of such e x c u r s i o n s ( i . e . b r e a t h i n g r h y t h m l c i t y ) , and the predominant mode of b r e a t h i n g ( e i t h e r t h o r a c i c or abdominal)? In a d d i t i o n , are these changes s e n s i t i v e to d i f f i c u l t y m a n i p u l a t i o n s ? 2) Are the r e s p i r a t o r y measures mentioned above s e n s i t i v e to a d a p t a t i o n with cont inued performance of a mental a r i t h m e t i c task? 3) To what ex tent do t a s k - e l i c i t e d r e s p i r a t o r y changes 38 correspond to changes In s e v e r a l i n d i c e s of c a r d i o -v a s c u l a r a r o u s a l , i n c l u d i n g h e a r t r a t e , T-wave a m p l i -tude, b lood volume p u l s e , and pulse t r a n s i t time? Are t a s k - e l i c i t e d changes i n c a r d i o - r e s p i r a t o r y a c t i v i t y a s s o c i a t e d wi th s u b j e c t i v e and b e h a v i o u r a l i n d i c e s of task d i f f i c u l t y ? If meaningfu l r e a c t o r subgroups can be formed on the b a s i s of s u b j e c t s ' h e a r t ra t e adjustments to an i n i t i a l c o l d p r e s s o r t e s t , w i l l these subgroups d i f f e r s i g n i f i c a n t l y from each other i n terms of the c a r d i o -v a s c u l a r and r e s p i r a t o r y changes e x p e r i e n c e d i n response to easy and hard v e r s i o n s of a mental a r i t h -met ic task? In essence , the q u e s t i o n be ing asked i s "Do changes i n b r e a t h i n g mode covary wi th expected group d i f f e r e n c e s i n c a r d i o v a s c u l a r r e a c t i v i t y ? " . 39 Me thod S u b j e c t s One hundred male undergraduates p a r t i c i p a t e d i n the study f o r course c r e d i t . Subjec t s ranged i n age from 18 to 30 (mean = 2 0 . 9 , SD = 0 . 3 3 ) . P r i o r to p a r t i c i p a t i o n i n the s t u d y , a l l s u b j e c t s were i n s t r u c t e d to a v o i d s trenuous p h y s i c a l a c t i v i t y and the use of tobacco , a l c o h o l and c o f f e e f o r two hours p r e c e d i n g the exper iment s e s s i o n ( J e n n i n g s , B e r g , Hutcheson et a l . , 1981). Due to r e c o r d i n g equipment d i f f i c u l t i e s , complete data were a v a i l a b l e f o r only 92 of the 100 s u b j e c t s . The d e c i s i o n to employ only male s u b j e c t s was based on two c o n s i d e r a t i o n s . F i r s t , p r e v i o u s s t u d i e s i n t h i s area have used male s u b j e c t s a lmost e x c l u s i v e l y and, i n order to d i r e c t l y compare f i n d i n g s , a s i m i l a r p o p u l a t i o n was r e q u i r e d . Second, us ing s u b j e c t s of both genders c o u l d pose c e r t a i n problems i n data c o l l e c t i o n and i n t e r p r e t a t i o n . For i n s t a n c e , s e v e r a l I n v e s t i g a t o r s have r e p o r t e d gender d i f f e r e n c e s In r e s p i r a t o r y r a t e , ampl i tude a n d / o r predominant mode of r e s p i r a t i o n ( e . g . L i n d e n , i n p r e s s ; Svebak, 1975). In order to f a c i l i t a t e i n t e r p r e t a t i o n of the r e s u l t s , and a l s o to a v o i d the need f o r separate ana lyse s f o r each sex (which would reduce the power of the t e s t ) , i t was dec ided to use only males . Appara tus E l e c t r o c a r d i o g r a p h i c (ECG) a c t i v i t y was recorded wi th 40 b i p o l a r r e c o r d i n g e l e c t r o d e s p l a c e d on l a t e r a l p o s i t i o n s of the lower r i b c a g e . A ground e l e c t r o d e was a l s o a t t a c h e d to the back of the s u b j e c t ' s neck . T h i s c o n f i g u r a t i o n i s known to y i e l d r e l a t i v e l y l a r g e T-waves and produces an ECG s i g n a l v e c t o r i a l l y e q u i v a l e n t to s tandard l ead I ( C o n s t a n t , 1981). The ECG s i g n a l was processed v i a a c a r d i o t a c h o m e t e r c o u p l e r (Sensormedics , Model 9857) i n the " D i r e c t " p o s i t i o n i n order to o b t a i n complete ECG s i g n a l s . The c a r d i o t a c h o m e t e r f i l t e r was set at 30 Hz wi th a s tandard ECG a m p l i f i c a t i o n of 50 uv/mm. These s e t t i n g s were recommended i n the manual for the c o u p l e r and have been found i n p r i o r s t u d i e s to generate the c l e a n e s t ECG s i g n a l s . Blood volume pulse (BVP) was moni tored v i a a Sensormedics photoplethysmograph which was p l a c e d on the t i p of the index f i n g e r of the nondomlnant hand and then i n t e r f a c e d wi th a v o l t a g e / p u l s e / p r e s s u r e coup ler (Sensormedics , Model 9853A). A f i l t e r s e t t i n g of 30 Hz and s tandard a m p l i f i c a t i o n of 5 uv/mm was used f o r t h i s s i g n a l . The method f o r measuring r e s p i r a t o r y a c t i v i t y was based i n p a r t on the methods used by Svebak et a l . (1981) and L i n d e n (1986) . In order to o b t a i n r e c o r d i n g s of both t h o r a c i c and abdominal ampl i tude changes , two Bel lows s t r a i n gauges were a t t a c h e d to each s u b j e c t , one around the ches t at the l e v e l of the armpi t s and the other l o c a t e d at the l e v e l of the abdominal u m b i l i c u s . R e s i s t a n c e changes from one s t r a i n gauge were fed i n t o a Sensormedics v o l t a g e / p u l s e / p r e s s u r e c o u p l e r (Model 9853A) set at 10 uv/mm of a m p l i f i c a t i o n with a f i l t e r s e t t i n g of 3 Hz. 41 Output from the second s t r a i n gauge was channeled i n t o a Beckman s t r a i n gauge c o u p l e r (Model 9872) set at 100 uv/mm of a m p l i f i c a t i o n wi th a f i l t e r s e t t i n g of 30 Hz . The two s t r a i n gauge / coup ler p a i r i n g s were c o u n t e r b a l a n c e d with the two r e s p i r a t o r y compartments to a v o i d a p o s s i b l e confound r e s u l t i n g from undetermined d i f f e r e n c e s i n the s e n s i t i v i t y a n d / o r s i g n a l p r o c e s s i n g of the two c o u p l e r s . For both c o u p l e r s , the f i l t e r and s i g n a l ga in s e t t i n g s were those that y i e l d e d the c l e a n e s t and most i n t e r p r e t a b l e po lygraph t r a c i n g s i n p i l o t t e s t i n g . The c o u p l e r s used f o r both the c a r d i o v a s c u l a r and r e s p i r a t o r y measures were i n t e g r a t e d wi th a 4 -channe l Sensormedics Dynograph, Model R.611, i n t e r f a c e d wi th an a n a l o g u e - t o - d i g i t a i (A/D) c o n v e r t e r and a V i c t o r 9000 microcomputer . S i g n a l p r o c e s s i n g software w r i t t e n f o r t h i s system was set to sample data in 30 second i n t e r v a l s a t predetermined times throughout the exper iment . Heart ra t e was c a l c u l a t e d on the b a s i s of i n t e r b e a t i n t e r v a l s , d e f i n e d as the l e n g t h of time between s u c c e s s i v e R-wave peaks. The peak v o l t a g e r e a d i n g between s u c c e s s i v e R-wave peaks de f ined T-wave ampl i tude (TWA). Pulse t r a n s i t time (PTT) scores were o b t a i n e d by computing the time de lay between each R-wave peak and the c o r r e s p o n d i n g b lood volume pulse peak. A l l c a r d i o v a s c u l a r data from the s i g n a l p r o c e s s i n g program were s t o r e d on a 10 megabyte hard d i s k and on r e a l - t i m e hard copy p r i n t o u t s from an i n t e r f a c e d h i g h speed p r i n t e r . S ince only one r e s p i r a t o r y s i g n a l at a time c o u l d be processed by the waveform a n a l y s i s 42 s o f t w a r e , data from both s t r a i n gauges were recorded on p o l y g r a p h paper f o r manual , p o s t - e x p e r i m e n t a l a n a l y s i s . The c a r d i a c and BVP s i g n a l s were a l s o recorded on the p o l y g r a p h paper to permit c r o s s - v a l i d a t i o n checks . Procedure Throughout the exper iment , s u b j e c t s were seated u p r i g h t i n a r e c l i n e r c h a i r . T h i s s i t u a t i o n minimized extraneous body movements and changes i n posture that o therwise might have a f f e c t e d the c a r d i o v a s c u l a r and r e s p i r a t o r y r e c o r d i n g s . Upon e n t e r i n g the l a b , s u b j e c t s were asked to complete a b r i e f q u e s t i o n n a i r e on t h e i r age, h e i g h t , we ight , smoking h a b i t s , frequency of p h y s i c a l e x e r c i s e , f a m i l y h i s t o r y of h y p e r t e n s i o n , and p e r s o n a l h i s t o r y of r e s p i r a t o r y and c a r d i o v a s c u l a r d i s o r d e r s (see Appendix A ) . Any i n d i v i d u a l s s u f f e r i n g from asthma ( symptomat ic ) , r e s p i r a t o r y i n f e c t i o n , or pulmonary h y p e r t e n s i o n were exc luded from the study because the r e s p i r a t i o n r a t e , t i d a l volume, and minute v e n t i l a t i o n of such i n d i v i d u a l s d i f f e r markedly from those of normal s u b j e c t s ( T o b i n , 1986). A b r i e f overview of the exper iment and p h y s i o l o g i c a l response apparatus was then g iven to s u b j e c t s (Appendix B ) , a f t e r which they were asked to read and s ign a consent form (Appendix C ) . Next , the ECG e l e c t r o d e s were p l a c e d on s k i n abraded and c l eaned wi th r u b b i n g a l c o h o l . F i n a l l y , the r i b c a g e and abdomen s t r a i n gauges were fas tened around the s u b j e c t . In order to ensure a c c u r a t e r e c o r d i n g s of t h o r a c i c and 43 abdominal ampl i tude changes over the e n t i r e range of t i d a l volumes, the p o s i t i o n of these gauges was checked by having s u b j e c t s b r e a t h i n and out deeply one or two t imes . I f e i t h e r gauge s h i f t e d p o s i t i o n , i t was r e a d j u s t e d and r e c h e c k e d . Cables from a l l dev ices were fed through a hole i n the w a l l to the n e i g h b o r i n g r e c o r d i n g room. A 10-minute a d a p t a t i o n p e r i o d f o l l o w e d i n which s u b j e c t s were encouraged to r e l a x and read Herman c a r t o o n s . No s p e c i f i c task i n s t r u c t i o n s were g iven u n t i l the end of the a d a p t a t i o n p e r i o d . T h i s procedure has p r e v i o u s l y been found to f a c i l i t a t e a d a p t a t i o n to the l a b o r a t o r y whi le at the same time l i m i t i n g the e f f e c t that a n t i c i p a t i o n can have on p h y s i o l o g i c a l response a d a p t a t i o n ( L i n d e n , McEachern & F r a n k i s h , 1985). The f i n a l minute of the a d a p t a t i o n p e r i o d served as the b a s e l i n e f o r the f i r s t s t r e s s o r task . Immediately f o l l o w i n g the a d a p t a t i o n p e r i o d , d e t a i l e d i n s t r u c t i o n s f o r the f i r s t s t r e s s task (the c o l d p r e s s o r t e s t ) were p r o v i d e d to s u b j e c t s (see Appendix D for a s c r i p t of these i n s t r u c t i o n s ) . Dur ing the l a s t minute of a 10 minute r e c o v e r y p e r i o d , a second b a s e l i n e r e c o r d i n g was o b t a i n e d . D e t a i l e d i n s t r u c t i o n s f o r the mental a r i t h m e t i c task were then g iven (Appendix E ) . The order of the two mental a r i t h m e t i c t r i a l b locks (easy math and hard math) was c o u n t e r b a l a n c e d across s u b j e c t s . Subjec t s were randomly a s s igned to task o r d e r s . A 5-second break separated the two t r i a l b l o c k s . F o l l o w i n g the 44 second b lock of e q u a t i o n s , s u b j e c t s were g iven a f u r t h e r f i v e minutes to r e l a x before a f i n a l r e c o r d i n g was o b t a i n e d . They then completed a b r i e f p o s t - e x p e r i m e n t a l q u e s t i o n n a i r e (Appendix F) before removal of the r e c o r d i n g a p p a r a t u s . S u b j e c t s were d e b r i e f e d and thanked f o r t h e i r p a r t i c i p a t i o n (see Appendix G for the d e b r i e f i n g s c r i p t ) . To summarize the procedure f o l l o w e d i n t h i s s tudy , s u b j e c t s f i r s t p a r t i c i p a t e d i n a 10-minute a d a p t a t i o n p e r i o d f o l l o w e d by a 1-minute c o l d p r e s s o r t e s t , a 10-minute r e c o v e r y p e r i o d , two 5-minute b locks of a r i t h m e t i c problems , and f i n a l l y a 5-minute r e c o v e r y p e r i o d . In a l l c a s e s , the c o l d p r e s s o r task preceded the a r i t h m e t i c t a s k . For the two math task c o n d i t i o n s , 50% of s u b j e c t s were presented wi th the easy equat ions f i r s t whi le the remain ing 50% responded to the hard problems f i r s t . T h i s procedure approximates a w i t h i n - s u b j e c t m u l t i p l e treatment c r o s s - o v e r d e s i g n : each of the three tasks ( c o l d p r e s s o r , easy math, and hard math) c o n s t i t u t e s a treatment c o n d i t i o n , wi th only the l a t t e r two c o n d i t i o n s be ing c o u n t e r b a l a n c e d a c r o s s s u b j e c t s . E x p e r i m e n t a l Tasks Co ld P r e s s o r . A l l s u b j e c t s were asked to Immerse t h e i r nondominant hand for one minute i n a f o u r - l i t e r c o n t a i n e r f i l l e d wi th of 4 - 6 C e l s i u s i c e water a f t e r be ing t o l d that other s u b j e c t s had 45 s u c c e s s f u l l y completed t h i s ta sk . P r e v i o u s s t u d i e s have found that t h i s task e l i c i t s s i g n i f i c a n t i n c r e a s e s i n such i n d i c e s as b lood p r e s s u r e , c a r d i a c output , t i d a l volume, and r e s p i r a t o r y ra te ( e . g . A l l e n e t a l . , 1986). Other i n v e s t i g a t o r s have a l s o r e p o r t e d c o n s i d e r a b l e i n c r e a s e s i n p e r i p h e r a l r e s i s t a n c e d u r i n g t h i s task (Murakami, Hiwada, & Kokubu, 1980). Menta l A r i t h m e t i c . The mental a r i t h m e t i c task c o n s i s t e d of two 5-minute long b l o c k s of a r i t h m e t i c equat ions p r e - r e c o r d e d on v i d e o t a p e and presented to s u b j e c t s by v ideo m o n i t o r . F i n d i n g s from a p i l o t study (n=10) conf irmed that one b lock of problems was d i f f i c u l t and the other easy: the d i f f i c u l t problems e l i c i t e d h e a r t r a t e i n c r e a s e s a p p r o x i m a t e l y twice as l a r g e as those e l i c i t e d by the easy e q u a t i o n s . The 30 easy problems i n v o l v e d the a d d i t i o n , s u b t r a c t i o n , m u l t i p l i c a t i o n , or d i v i s i o n of o n e - d i g i t and t w o - d i g i t numbers. The 30 d i f f i c u l t problems i n v o l v e d the same mathemat ica l o p e r a t i o n s but wi th two- and t h r e e - d i g i t numbers. P r e v i o u s r e s e a r c h u s i n g a s i m i l a r d i f f i c u l t y m a n i p u l a t i o n f o r mental a r i t h m e t i c has shown t h a t , on average , the more d i f f i c u l t problems e l i c i t s i g n i f i c a n t l y g r e a t e r autonomic responses than do e a s i e r ones ( C a r r o l l et a l . , 1983). Dur ing the easy and hard a r i t h m e t i c b l o c k s , the r e s p e c t i v e a r i t h m e t i c equat ions were d i s p l a y e d on a 51 cm v i d e o screen f o r 10 seconds each . A stopwatch f u n c t i o n l o c a t e d i n the lower l e f t corner of the screen s i m u l t a n e o u s l y marked the passage of time 46 to l / 1 0 0 t h s of a second accuracy ( H i t a c h i v ideo r e c o r d e r , Model VT-7P with an RCA v ideocamera , Model CC017) . S u b j e c t s were i n s t r u c t e d to w r i t e down t h e i r answers to each problem before the onset of the next e q u a t i o n . A prepared r e c o r d i n g sheet , d i v i d e d i n t o two s e c t i o n s numbered from 1 to 30, was p r o v i d e d for t h i s purpose . The importance of c o n c e n t r a t i n g on the task was emphasized s ince the problems presented to the s u b j e c t s by v ideo were not numbered. As a f u r t h e r inducement to c o n c e n t r a t e s u b j e c t s were t o l d that a p p r o x i m a t e l y 90% of other s u b j e c t s had c o r r e c t l y answered a t l e a s t 75% of the problems and that t h e i r own performance would be reviewed wi th them at the c o n c l u s i o n of the s e s s i o n . S e l f - r e p o r t i n d i c e s on the p e r c e i v e d d i f f i c u l t y of the two mental a r i t h m e t i c c o n d i t i o n s were o b t a i n e d immediate ly f o l l o w i n g the task . A 15 cm v i s u a l ana log s c a l e wi th l a b e l l e d endpo in t s was used f o r t h i s purpose (Appendix H ) . Data R e d u c t i o n Samples of autonomic a c t i v i t y o c c u r r i n g over 30-second time i n t e r v a l s were o b t a i n e d at the f o l l o w i n g t imes: (1) Minute 10 of a d a p t a t i o n ( c o l d p r e s s o r b a s e l i n e ) ; (2) seconds 30-60 of the c o l d p r e s s o r task; (3) seconds 570-600 ( M i n . 10) of the c o l d p r e s s o r r e c o v e r y p e r i o d (mental a r i t h m e t i c b a s e l i n e ) ; (4) seconds 30-60 ( M i n . 1 ) , 150-180 ( M i n . 3) and 270-300 ( M i n . 5) of Easy and Hard mental a r i t h m e t i c ; and (5) seconds 270-300 ( M i n . 5) of the f i n a l r e c o v e r y p e r i o d . For a l l sampling times except 47 the f i n a l b a s e l i n e , the raw data (beat to beat or b r e a t h to b r e a t h r e c o r d i n g s ) f o r each s u b j e c t were averaged to y i e l d s i n g l e mean scores for the f o l l o w i n g v a r i a b l e s : h e a r t r a t e , T-wave a m p l i t u d e , b lood volume p u l s e , pu l se t r a n s i t t ime, r e s p i r a t i o n r a t e , t h o r a c i c ampl i tude and i t s v a r i a b i l i t y , and abdominal ampl i tude and i t s v a r i a b i l i t y . A s i x t h measure of r e s p i r a t o r y a c t i v i t y , the r a t i o of t h o r a c i c to abdominal ampl i tude ( T : A ) , was a l s o computed for each of the 10 sampl ing times o u t l i n e d above. By d e f i n i t i o n , the ampl i tude of t h o r a c i c and abdominal e x c u r s i o n s e q u a l l e d the mean i n s p i r a t i o n - e x p i r a t i o n change i n s t r a i n gauge r e s i s t a n c e w i t h i n a g iven measurement p e r i o d . R e s p i r a t o r y ampl i tude v a r i a -b i l i t y was d e f i n e d as the s tandard d e v i a t i o n of b r e a t h by b r e a t h ampl i tude changes f o r each r e c o r d i n g p e r i o d . The r e l a t i v e nature of these ampl i tude and ampl i tude v a r i a b i l i t y scores meant t h a t , for a c r o s s - s u b j e c t comparisons of t a s k - i n d u c e d changes , the raw data needed to be expressed as percentages of the a p p r o -p r i a t e b a s e l i n e v a l u e s . O b v i o u s l y , mean a m p l i t u d e , ampl i tude v a r i a b i l i t y , and T:A scores cou ld not be r e p o r t e d f o r the two b a s e l i n e p e r i o d s . Before computing mean scores from the raw d a t a , a l l data f i l e s were i n s p e c t e d for a r t i f a c t s a s s o c i a t e d with extraneous body movements and r e c o r d i n g equipment e r r o r s . Movement a r t i f a c t s were d e f i n e d as sudden, very l a r g e i n c r e a s e s i n r e s p i r a t i o n ampl i tude noted on the p o l y g r a p h c h a r t t r a c i n g s by 48 the exper imenter a t the time of r e c o r d i n g . Data a s s o c i a t e d wi th these a r t i f a c t s were omit ted from f u r t h e r a n a l y s e s . Computer-generated e r r o r s i n the r e c o r d i n g of c a r d i o v a s c u l a r a c t i v i t y were more d i f f i c u l t to i d e n t i f y . For most s u b j e c t s , the wave-form a n a l y s i s program produced only one type of e r r o r , that i s , i m p o s s i b l y l a r g e h e a r t r a t e e s t imates for the f i r s t second of the r e c o r d i n g p e r i o d . These e r r o r s were e a s i l y i d e n t i f i e d : they o c c u r r e d because the program had no p r e v i o u s R-wave peak with which to compare the c u r r e n t R-wave peak. Comparison of p o l y -graph ECG t r a c i n g s wi th t h e i r r e s p e c t i v e d i g i t a l data p r i n t o u t s r e v e a l e d that for a m i n o r i t y of s u b j e c t s , p a r t i c u l a r l y those wi th very smal l S-waves, the program-generated output o c c a s i o n a l l y appeared to be e r r o n e o u s . Whenever the d i g i t a l r e c o r d i n g s of b lood volume p u l s e , pulse t r a n s i t time a n d / o r T-wave ampl i tudes d e v i a t e d by 100% or more from both (a) t h e i r p r e v i o u s and subsequent va lues i n a g iven r e c o r d i n g i n t e r v a l and (b) t h e i r analogue c o u n t e r p a r t s on the p o l y g r a p h t r a c i n g , the data were d e l e t e d . E x t e n s i v e data e d i t i n g was neces sary f o r l e s s than 15% of s u b j e c t s and, w i t h i n t h i s subgroup, f o r fewer than 50% of the r e c o r d i n g p e r i o d s . 49 R e s u l t s A n a l y s i s o f t h e r e s p o n s e d a t a w i l l be r e p o r t e d i n two m a j o r s e c t i o n s : ( 1 ) c a r d i o v a s c u l a r , r e s p i r a t o r y , a n d s u b j e c t i v e r e s -p o n s e s o f a l l s u b j e c t s t o t h e two m e n t a l a r i t h m e t i c c o n d i t i o n s ; ( 2 ) m e n t a l a r i t h m e t i c r e s p o n s e s o f s u b j e c t s i n t h e f i r s t , t h i r d a n d f i f t h q u i n t i l e s o f h e a r t r a t e r e a c t i v i t y t o t h e c o l d p r e s s o r c h a l l e n g e . I n t h e f i r s t s e c t i o n , f o u r q u e s t i o n s w i l l be a d d r e s s e d . F i r s t , t o w h a t e x t e n t do b r e a t h i n g mode, r a t e o f b r e a t h i n g , t h e a m p l i t u d e o f r i b c a g e a n d a b d o m i n a l e x c u r s i o n s , a n d t h e v a r i a -b i l i t y o f t h e s e e x c u r s i o n s v a r y a s a f u n c t i o n o f t h e e x p e r i m e n -t a l t a s k a n d t h e d i f f i c u l t y l e v e l s o f t h a t t a s k ? S e c o n d , w h a t i s t e m p o r a l p a t t e r n o f r e s p i r a t o r y c h a n g e s d u r i n g s u c h t a s k s ? T h i r d , do r e s p i r a t o r y c h a n g e s c o r r e s p o n d t o s i m u l t a n e o u s l y o c c u r r i n g c h a n g e s i n c a r d i o v a s c u l a r I n d i c e s o f a r o u s a l ? F i n a l l y , t o w h a t e x t e n t a r e t a s k - r e l a t e d c h a n g e s i n c a r d i o v a s c u l a r a n d r e s p i r a t o r y f u n c t i o n i n g c o r r e l a t e d w i t h s u b j e c t i v e a n d b e h a v -i o u r a l a s s e s s m e n t s o f t a s k d i f f i c u l t y ? A n a l y s e s i n t h e s e c o n d s e c t i o n w e r e d e v i s e d t o d e t e r m i n e w h e t h e r o r n o t i n d i v i d u a l s i n t h e u p p e r , m i d d l e , a n d l o w e r q u i n t i l e s o f h e a r t r a t e r e a c t i v i t y t o t h e c o l d p r e s s o r t e s t a l s o r e s p o n d e d d i f f e r e n t i a l l y t o t h e s u b s e q u e n t m e n t a l c h a l l e n g e t a s k s . Of p a r t i c u l a r I n t e r e s t was w h e t h e r o r n o t c h a n g e s I n b r e a t h i n g mode c o v a r i e d w i t h e x p e c t e d g r o u p d i f f e r e n c e s i n 50 c a r d i o v a s c u l a r r e a c t i v i t y . I . Mental A r i t h m e t i c Responses - A l l Subjec t s The mean change scores f o r each p h y s i o l o g i c a l measure a t each r e c o r d i n g p e r i o d of the two mental a r i t h m e t i c c o n d i t i o n s are presented i n F i g u r e s 1 and 2. Mean change scores and s tandard d e v i a t i o n s for the two d i f f i c u l t y c o n d i t i o n s and for the three r e c o r d i n g p e r i o d s are presented i n T a b l e s 1 and 2. For three dependent measures (hear t r a t e , b r e a t h i n g r a t e , and pulse t r a n s i t time) change scores were computed as the d i f f e r -ence between the task and b a s e l i n e raw s c o r e s . For the remain ing seven measures, t h i s method of computing change scores was i n a p p r o p r i a t e s ince the raw scores i n c l u d e d an unknown amount of e r r o r v a r i a n c e a s s o c i a t e d wi th i n d i v i d u a l d i f f e r e n c e s i n p h y s i o l o g y and r e c o r d i n g equipment s e t t i n g s . In order to compare response l e v e l s across s u b j e c t s , each s u b j e c t ' s task responses were expressed as percentages of the r e s p e c t i v e b a s e l i n e v a l u e s . A summary tab le of raw b a s e l i n e means and s tandard d e v i a t i o n s i s i n c l u d e d i n Appendix I for those i n t e r e s t e d i n comparing data c o l l e c t e d i n our l a b o r a t o r y wi th data c o l l e c t e d by other i n v e s t i g a t o r s . The a n a l y s i s began by e x e c u t i n g a 2 (Task d i f f i c u l t y ) X 3 ( R e c o r d i n g p e r i o d ) MANOVA (BMDP:4V) that i n c l u d e d change scores f o r a l l 10 p h y s i o l o g i c a l measures . The m u l t i v a r i a t e t e s t r e s u l t s f o r the Task (F (10 , 82) = 13 .29 , p < .001) and P e r i o d I CHANGE FROM BASELINE (%) CHANGE FROM BASELINE (%) CHANGE FROM BASELINE (cpm) i 52 Table 1 Average change scores f o r Easy and Hard mental a r i t h m e t i c (MA). D i f f i c u l t y C o n d i t i o n (F( 10 , 82 ) = 5 . 77 , p < .001) f a c t o r s conf irmed that f u r t h e r ana lyse s for Task and P e r i o d main e f f e c t s were a p p r o p r i a t e . A Type I e r r o r r i s k of .05 was adopted f o r each of the u n i v a r i a t e ANOVAs. T e s t i n g for s i g n i f i c a n t P e r i o d main e f f e c t s was conducted m u l t i v a r i a t e l y \ to guard a g a i n s t v i o l a -t ions of the s p h e r i c i t y assumption (Vasey & T h a y e r , 1987). Whenever a — s i g n i f i c a n t P e r i o d main e f f e c t was o b s e r v e d , pos t -hoc comparisons of r e c o r d i n g p e r i o d mean scores were executed u s i n g S c h e f f e ' s method (p < . 0 5 ) . Due to the n o n s i g n i f i c a n t m u l t i v a r i a t e t e s t r e s u l t f o r Task x P e r i o d i n t e r a c t i o n s (F (10 , 82) = 1.58, p = . 0 8 ) , s i g n i f i c a n t u n i v a r i a t e I n t e r a c t i o n s were r e - a n a l y z e d u s i n g the G r e e n h o u s e - G e i s s e r c o r -r e c t i o n for degrees of freedom. V a r i a b l e Easy MA Hard MA HR (bpm)*** 6.4 ( 7 . 0) 12.0 ( 10 .0) TWA (%) -4.7 ( 10. 8) -6.3 ( 14 .7) BVP (%)** -29.0 ( 33. 6) -34.7 ( 34 .6) PTT(msec)*** -11.9 ( 20. 2) -16.5 ( 21 .4) RR (cpm)*** 2.3 ( 3. 2) 4 . 2 ( 3 .6) T:A (%) 15.5 ( 54. 6) 21 . 1 ( 56 .2) RA (%) 5.3 ( 33. 0) 7.5 ( 34 .8) AA (%) -0.4 ( 28 . 9) -0.8 ( 33 .2) RAV (%) 86.3 (216. 7) 89.8 (202 • 6) AAV (%)* 41 . 7 ( 127 . 5) 72.3 (181 .3) *p < .05 , **P < .01 9 ***p < .001 Two of the s i x r e s p i r a t o r y change i n d i c e s were found to vary s i g n i f i c a n t l y i n response to the easy and hard a r i t h m e t i c c o n d i -t i o n s . B r e a t h i n g r a te changes to hard math were found to be s i g n i f i c a n t l y g r e a t e r than those o c c u r r i n g to the easy task 53 ( F ( l , 91) = 58 .60 , p < . 0 0 1 ) . On average , the hard task e l i c i t e d rough ly twice as grea t an i n c r e a s e i n b r e a t h i n g r a t e s as d i d the easy c o n d i t i o n (+4.2 cpm versus +2.3 cpm r e s p e c t -i v e l y ) . In comparison to b r e a t h i n g r a t e s at b a s e l i n e , the mean r a t e s d u r i n g each of the math tasks were a l s o found to be s i g n i f i c a n t l y h igher than r e s t i n g l e v e l s ( F ( 2 , 90) = 58 .5 , p < . 0 0 1 ) . V a r i a b i l i t y i n the ampl i tude of abdominal e x c u r s i o n s was a l s o s i g n i f i c a n t l y g r e a t e r d u r i n g the harder of the two a r i t h -met ic tasks ( F ( l , 91) = 5 .75 , p = . 0 2 ) . Once a g a i n , the r a t i o of change was a p p r o x i m a t e l y 2:1 i n favour of the hard task . T a s k - r e l a t e d d i f f e r e n c e s i n abdominal and r i b c a g e a m p l i t u d e , r i b c a g e ampl i tude v a r i a b i l i t y , and b r e a t h i n g mode were not found to be s i g n i f i c a n t , sugges t ing that these i n d i c e s of r e s p i r a t o r y change are i n s e n s i t i v e to v a r i a t i o n s i n s t r e s s l o a d . When d i f f e r e n c e s between r e c o r d i n g p e r i o d s were a n a l y z e d , s i g n i f i c a n t main e f f e c t s were observed for changes i n b r e a t h i n g ra te ( F ( 2 , 90) = 3 .26 , p < .05) and r i b c a g e and abdominal a m p l i -tude ( F ( 2 , 90) = 3 .92 , p < .05 and F ( 2 , 90) = 7 .79 , p < .001 r e s p e c t i v e l y ) . Pos t -hoc comparisons i n d i c a t e d that Minute 1 va lues f o r a l l three r e s p i r a t i o n i n d i c e s d i f f e r e d s i g n i f i c a n t l y from t h e i r r e s p e c t i v e change scores at Minutes 3 and 5, whi le scores for these l a t t e r two p e r i o d s d i d not d i f f e r r e l i a b l y from one another (see T a b l e 2 ) . The ampl i tude of r i b c a g e movements c l e a r l y decreased over t ime: from an average a b o v e - b a s e l i n e i n c r e a s e of +10.5% at Minute 1, r i b c a g e ampl i tudes decreased to +5.1% at Minute 3 and +3.6% at Minute 5. Abdominal a m p l i t u d e , 54 T a b l e 2 Average change s c o r e s f o r the t h r e e r e c o r d i n g p e r i o d s of m e n t a l a r i t h m e t i c (MA). R e c o r d i n g P e r i o d V a r i a b l e M i n u t e 1 Min u t e 3 M i n u t e 5 HR (bpm)*** 11 . A ( 11.1) 7 . 8 ( 8. 3) 8 . 4 ( 7. 1) TWA ( % ) * * -6. 9 ( 14.2) -4. 9 ( 11 . 8) -4. 9 ( 12 . 7) BVP ( % ) * * * -36. 9 ( 33.4) -28. 6 ( 34. 2) -30. 1 ( 34. 5) PTT(msec)** -16. 4 ( 21.2) -14. 0 ( 19. 7) -12. 2 ( 21 . 4) RR (cpm)* 3. 5 ( 3..5) 3. 1 ( 3. 3) 3. 0 ( 3. 7) T : A (%) 18 . 3 ( 59. 6) 17. 8 ( 50. 5) 18. 9 ( 56. 0) RA ( % ) * 10. 5 ( 38.7) 5. 1 ( 32. 1) 3. 6 ( 30. 0) AA ( % ) * * * 3 . 0 ( 31.9) -2 . 1 ( 30. 0) -2 . 8 ( 31. 2) RAV (%) 100 . 2 (264.1) 70. 0 (158. 9) 94. 0 ( 191 . 7) AAV (%) 51 . 3 (129.7) 54. 3 (138. 9) 65. 5 (195. 7) *p < 05 . 01, ***p 001 on the other hand, showed an i n i t i a l average i n c r e a s e of 3.0% from b a s e l i n e l e v e l s f o l l o w e d by a -2.1% decrease a t Minute 3 and a f u r t h e r decrease to -2.8% by Minute 5. In other words, the ampl i tude of r e s p i r a t o r y movements v a r i e d i n response to r e l a t i v e l y b r i e f mental c h a l l e n g e s , i n c r e a s i n g to t h e i r h i g h e s t l e v e l s w i t h i n 2 minutes of task onset and d e c r e a s i n g t h e r e a f t e r . However, u n l i k e r i b c a g e a m p l i t u d e , which remained above b a s e l i n e l e v e l s for the d u r a t i o n of the math t a s k s , the average ampl i tude of abdominal e x c u r s i o n s decreased to below b a s e l i n e l e v e l s some time a f t e r the f i r s t minute or two and remained below b a s e l i n e f o r the remainder of the ta sk . Measures of b r e a t h i n g v a r i a -b i l i t y and the r a t i o of r i b c a g e to abdominal ampl i tude change 55 d i d not show s i g n i f i c a n t v a r i a t i o n d u r i n g task per formance . The e f f e c t of task d i f f i c u l t y on h e a r t r a t e , T-wave a m p l i -tude , b lood volume p u l s e , and pulse t r a n s i t time change appears to have been more c o n s i s t e n t across s u b j e c t s than i t was f o r r e s p i r a t o r y change. Whereas only two of the s i x r e s p i r a t o r y v a r i a b l e s v a r i e d s i g n i f i c a n t l y i n response to the easy to hard mental a r i t h m e t i c , three of the four c a r d i o v a s c u l a r measures showed a s i g n i f i c a n t main e f f e c t f or task d i f f i c u l t y . Heart r a t e i n c r e a s e s to the hard math c o n d i t i o n (mean = +12.0 bpm) c l e a r l y exceeded the mean i n c r e a s e of +6.4 bpm e l i c i t e d by the easy math problems ( F ( l , 91) = 101.27, p < . 0 0 1 ) . S i g n i f i c a n t task main e f f e c t s were a l s o o b t a i n e d for b lood volume pulse ( F ( l , 91) = 9 .86 , p < .01) and pulse t r a n s i t time ( F ( l , 91) 16 .07 , p < . 001 ) . On average , the d i f f i c u l t math problems e l i c i t e d a l a r g e r decrease i n b lood volume pulse waves (-34.7%) and pulse t r a n s i t times ( -13.9 msec) than d i d the easy equat ions ( -11 .9 msec and -28.6% r e s p e c t i v e l y ) . A s i m i l a r response p a t t e r n was apparent f or T-wave ampl i tude but was not s t a t i s t i -c a l l y s i g n i f i c a n t ( F ( l , 91) = 3 .20 , p = . 0 8 ) . Taken t o g e t h e r , these data i n d i c a t e that the harder of the two math c o n d i t i o n s e l i c i t e d the g r e a t e s t Increase i n autonomic a r o u s a l . A n a l y s i s of c a r d i o v a s c u l a r changes over time a l s o r e v e a l e d a marked degree of response c o n s i s t e n c y a c r o s s s u b j e c t s not e v i d e n t f or r e s p i r a t o r y changes. S i g n i f i c a n t main e f f e c t s f o r r e c o r d i n g p e r i o d s were noted f o r a l l four c a r d i o v a s c u l a r 56 m e a s u r e s : 1) h e a r t r a t e ( F ( 2 , 90) = 26.78, p < .001; 2) T-wave a m p l i t u d e (F = 5.17, p < .01; 3) b l o o d volume p u l s e (F = 23.03, p < .001; and 4) p u l s e t r a n s i t time (F = 5.06, p < . 0 1 ) . P o s t - h o c a n a l y s e s of the h e a r t r a t e change d a t a r e v e a l e d t h a t a c r o s s b o t h d i f f i c u l t y c o n d i t i o n s h e a r t r a t e d e c l i n e d s i g n i f i -c a n t l y from the f i r s t (+11.4 bpm) to the t h i r d m i nute (+7.8 bpm) of m e n t a l a r i t h m e t i c and then r e m a i n e d s t a b l e u n t i l M i n u t e 5 (mean = +8.4 bpm). C o m p a r i s o n of the r e c o r d i n g p e r i o d change s c o r e s f o r the o t h e r t h r e e c a r d i o v a s c u l a r measures a l s o r e v e a l e d t h a t the r e s p o n s e l e v e l s r e c o r d e d a t M i n u t e s 3 and 5 d i d n o t d i f f e r r e l i a b l y from one a n o t h e r . However, a t M i n u t e 1 r e s p o n s e l e v e l s were s i g n i f i c a n t l y l o w e r than they were a t any o t h e r time d u r i n g the t a s k . Such f i n d i n g s a r e c o n s i s t e n t w i t h the b r e a t h -i n g r a t e and r i b c a g e a m p l i t u d e changes i n s u g g e s t i n g t h a t a d a p t -a t i o n to the t a s k o c c u r r e d w i t h i n the s econd to f o u r t h minute of r e s p o n d i n g . From the p a t t e r n of r e s u l t s d e s c r i b e d above, i t a p p e a r s t h a t c a r d i o v a s c u l a r f u n c t i o n i n g and, to a l e s s e r e x t e n t , r e s p i r a t o r y a c t i v i t y v a r y b o t h as a f u n c t i o n of time on a m e n t a l c h a l l e n g e t a s k and the d i f f i c u l t y l e v e l of t h a t t a s k . As a means of d e t e r m i n i n g the e x t e n t to w h i c h t a s k - e l i c i t e d changes i n h e a r t r a t e were r e l a t e d to r e s p i r a t o r y c h a n g e s , s t e p w i s e l i n e a r r e g r e s s i o n s were e x e c u t e d f o r e a c h a r i t h m e t i c c o n d i t i o n . B i -v a r i a t e s c a t t e r p l o t s o b t a i n e d p r i o r to t h i s a n a l y s i s s u g g e s t e d t h a t the i n d i c e s of r e s p i r a t o r y change were l i n e a r l y r e l a t e d to h e a r t r a t e c h a n g e s . 57 In the easy math c o n d i t i o n , two r e s p i r a t i o n v a r i a b l e s accounted for 25.8% of the v a r i a n c e i n h e a r t r a t e changes. A p p r o x i m a t e l y 14.7% of the v a r i a n c e was a t t r i b u t a b l e to changes i n b r e a t h i n g r a t e whi le the remain ing 11.1% was a s s o c i a t e d with r i b c a g e ampl i tude change. A f u r t h e r 14.3% of the o v e r a l l v a r i a n c e was accounted for by two c a r d i o v a s c u l a r measures, T-wave ampl i tude and pulse t r a n s i t t ime . In a l l , 40.1% of the h e a r t r a t e v a r i a n c e i n the easy c o n d i t i o n c o u l d be accounted f o r . Of t h i s t o t a l , a p p r o x i m a t e l y 64% was a s s o c i a t e d with r e s p i r a t o r y changes. In c o n t r a s t , only 19.2% of the v a r i a n c e i n h e a r t r a t e changes to the hard task cou ld be a t t r i b u t e d to r e s p i r a t o r y changes. Abdominal ampl i tude v a r i a b i l i t y , the f i r s t r e s p i r a t o r y v a r i a b l e to enter the r e g r e s s i o n e q u a t i o n f o l l o w i n g pulse t r a n s i t time and T-wave a m p l i t u d e , c o n t r i b u t e d to 3.4% of the v a r i a n c e . A f u r t h e r 3.6% was a t t r i b u t a b l e to b r e a t h i n g ra te changes. O v e r a l l , 36.5% of h e a r t r a t e v a r i a n c e was accounted f o r by the nine c a r d i o v a s c u l a r and r e s p i r a t o r y measures. From these a n a l y s e s , i t would appear that h e a r t ra t e responses under i n c r e a s i n g p s y c h o l o g i c a l load ( s t r e s s ) become d i s s o c i a t e d to some ex tent from r e s p i r a t i o n adjus tment s . To the e x t e n t that r e s p i r a t i o n changes r e f l e c t m e t a b o l i c a c t i v i t y or need, hear t ra te d u r i n g the hard a r i t h m e t i c c o n d i t i o n appears to be e x a g g e r a t e d . F u r t h e r i n f o r m a t i o n on c a r d i o - r e s p i r a t o r y i n t e r a c t i o n s 58 T a b l e 3 C o r r e l a t i o n s between easy (E) and h a r d (H) m e n t a l a r i t h m e t i c change s c o r e s : a l l p h y s i o l o g i c a l measures. T:A RA AA RAV AAV RR HR TWA BVP RA-E 0.63* RA-H 0.54* AA-E -0.68* -0.03 AA-H -0.78* -0.07 RAV-E 0.20 0.35* -0.06 RAV-H 0.12 0.28 0.01 AAV-E AAV-H 11 15 0.11 0.19 0. 24 0.29 0. 54* 0.56* RR-E RR-H 18 09 -0. 29 •0. 20 0.08 -0.16 17 22 -0.12 •0. 20 HR-E HR-H 0.17 0 . 07 0 , 0. 27 11 0.09 0.07 , 20 ,12 15 27 0.34* 0.20 TWA-E -0.01 0.04 0.01 0.01 0.18 -0.11 -0.33* TWA-H -0.01 -0.06 -0.07 0.01 -0.04 -0.08 -0.36* BVP-E -0. 20 -0. 29 -0. 01 -0. 09 -0. 08 -0. 16 -0. 37* 0. 18 BVP-H -0. 17 -0. 19 0. 07 -0. 07 -0. 08 -0. 07 -0. 27 0. 17 PTT-E 0. 12 0. 10 -0. 16 0. 00 -0. 10 -0. 22 -0. 33* 0 . 22 0. 22 PTT-H 0. 06 -0. 02 -0. 14 -0. 11 -0 . 21 -0. 10 -0. 44* 0. 27 0. 29 * S i g n i f i c a n t a t p < .001 d u r i n g the two mental a r i t h m e t i c c o n d i t i o n s was o b t a i n e d by c o r r e l a t i n g the mean change scores for each c a r d i o v a s c u l a r and r e s p i r a t o r y measure w i t h i n each d i f f i c u l t y c o n d i t i o n . The r e s u l t i n g c o r r e l a t i o n s are presented i n Table 3. In response to the easy math task , only one r e s p i r a t o r y measure, b r e a t h i n g ra te change, c o r r e l a t e d s i g n i f i c a n t l y wi th any measure of c a r d i o -v a s c u l a r a r o u s a l , i n t h i s case h e a r t ra t e change (r = .34). With an i n c r e a s e i n task d i f f i c u l t y t h i s r e l a t i o n s h i p weakened 59 (r = . 2 0 ) . Hear t r a t e change a l s o showed moderate c o r r e l a t i o n s w i th r i b c a g e ampl i tude and i t s v a r i a b i l i t y d u r i n g the easy math problems but not d u r i n g the hard c o n d i t i o n . The r e v e r s e was true for abdominal ampl i tude v a r i a b i l i t y . C o r r e l a t i o n s of .15 and .27 were o b t a i n e d wi th h e a r t ra t e changes to the easy and hard tasks r e s p e c t i v e l y . The only other c a r d i o - r e s p i r a t o r y c o r r e l a t i o n to approach s i g n i f i c a n c e was between blood volume pulse and r i b c a g e a m p l i t u d e . Once a g a i n , the hard c o n d i t i o n was a s s o c i a t e d wi th the s t r o n g e s t c o r r e l a t i o n (r = .29 versus r = .19 for the easy t a s k ) . In comparison to the moderate to weak c o r r e l a t i o n s obta ined f o r t a s k - i n d u c e d changes i n c a r d i o v a s c u l a r and r e s p i r a t o r y a c t i v i t y , the c o r r e l a t i o n s among the r e s p i r a t o r y measures were n o t i c e a b l y g r e a t e r . V a r i a b i l i t y i n the ampl i tudes of r i b c a g e and abdominal movements, for i n s t a n c e , was found to be h i g h l y c o r r e l a t e d i n both d i f f i c u l t y c o n d i t i o n s (r = .54 or g r e a t e r ) . T h i s suggests that people who breathe i r r e g u l a r l y wi th t h e i r abdomen a l s o do so wi th t h e i r r i b c a g e . The ampl i tude of movements i n each r e s p i r a t o r y compartment a l s o c o r r e l a t e d moderate ly w e l l w i th t h e i r r e s p e c t i v e v a r i a b i l i t y measures (r = .24 or g r e a t e r ) . B r e a t h i n g r a t e , on the o ther hand, c o r r e l a t e d moderate ly and n e g a t i v e l y w i th a l l . i n d i c e s of ampl i tude and ampl i tude v a r i a b i l i t y . To some e x t e n t , i n c r e a s e s i n b r e a t h i n g r a t e were a s s o c i a t e d wi th decreases i n the magnitude of r e s p i r a t o r y e x c u r s i o n s and t h e i r v a r i a b i l i t y . The more d i f f i c u l t the task , the more marked t h i s r e l a t i o n s h i p 60 appears to have been f o r a l l v a r i a b l e s except r i b c a g e ampl i tude and T:A r a t i o . In f a c t , changes i n the abdominal and r i b c a g e ampl i tudes to both math c o n d i t i o n s were v i r t u a l l y u n r e l a t e d . Such a f i n d i n g might be expected for two r e l a t i v e l y independent compartments . C o n t r a r y to t h i s f i n d i n g , the l a r g e c o r r e l a t i o n s found between each ampl i tude measure and i t s composite i n d e x , T:A r a t i o , suggests that a s t r o n g i n v e r s e r e l a t i o n s h i p e x i s t s between them. The ex tent to which s u b j e c t i v e and b e h a v i o r a l assessments of task d i f f i c u l t y corresponded wi th t a s k - r e l a t e d changes i n c a r d i o - r e s p i r a t o r y a c t i v i t y was assessed i n two ways. F i r s t , two one-way ANOVAs were executed to determine whether or not the d i f f i c u l t y m a n i p u l a t i o n had y i e l d e d s i g n i f i c a n t l y d i f f e r e n t e r r o r r a t e s and p e r c e p t i o n s of task d i f f i c u l t y a c r o s s the e n t i r e sample of s u b j e c t s . The r e s u l t s of these ana lyse s conf irmed that the hard math c o n d i t i o n was judged to be more d i f f i c u l t ( F ( l , 99) = 19 .91 , p < .001) and e l i c i t e d more i n c o r r e c t answers ( F ( l , 99) = 150.94, p < .001) than the easy c o n d i t i o n . Mean scores f o r task performance and p e r c e i v e d d i f f i c u l t y are presented i n Tab le 4. Second, c o r r e l a t i o n s between the s u b j e c -t i v e , b e h a v i o u r a l , and p h y s i o l o g i c a l change measures were examined f o r s i g n i f i c a n t r e l a t i o n s h i p s among these v a r i a b l e s . No s i g n i f i c a n t c o r r e l a t i o n s were found . However, the p e r c e i v e d d i f f i c u l t y l e v e l of the hard task d i d show a moderate i n v e r s e r e l a t i o n s h i p wi th task performance (r = - 0 . 2 8 ) . In other words, the h i g h e r the d i f f i c u l t y r a t i n g , the fewer c o r r e c t responses 61 T a b l e 4 P e r f o r m a n c e l e v e l s and r a t i n g s o f t a s k d i f f i c u l t y E a s y and H a r d a r i t h m e t i c . A r i t h m e t i c C o r r e c t D i f f i c u l t y C o n d i t i o n R e s p o n s e s * R a t i n g ** E a s y 29.4 ( 5.4) 48.4 ( 3 7 . 2 ) H a r d 20.8 ( 5.9) 73.8 ( 3 7 . 6 ) •Maximum s c o r e i s 30. • • D i f f i c u l t y r a t i n g s b a s e d on 150 mm v i s u a l a n a l o g s c a l e w i t h a n c h o r p o i n t s 0 ( N o t a t a l l d i f f i c u l t ) and 150 ( V e r y d i f f i c u l t ) . d i f f i c u l t y of the easy task a l s o c o r r e l a t e d moderate ly with b r e a t h i n g r a t e (r = - 0 . 2 8 ) and T:A r a t i o (r = . 2 5 ) . No c l e a r a s s o c i a t i o n s were found between p h y s i o l o g i c a l responses to the hard math c o n d i t i o n and e i t h e r s u b j e c t i v e or b e h a v i o r a l mea-sures of d i f f i c u l t y l e v e l . I I . S t r e s s o r Responses: Heart Rate R e a c t i v i t y Subgroups Before t e s t i n g f o r group d i f f e r e n c e s l n mental a r i t h m e t i c r e a c t i v i t y , i t was neces sary to determine that the c o l d p r e s s o r t e s t e l i c i t e d h e a r t r a t e changes that were l a r g e enough to permit a s u b d i v i s i o n of the e n t i r e s u b j e c t sample i n t o meaning-f u l l y d i f f e r e n t h e a r t r a t e r e a c t o r q u i n t i l e s . The three r e a c t o r groups were f u r t h e r d e f i n e d by comparing t h e i r c o l d p res sor response l e v e l s on the other nine p h y s i o l o g i c a l measures. The degree of a s s o c i a t i o n between h e a r t ra t e change and r e s p i r a t o r y were found . However, the p e r c e i v e d d i f f i c u l t y l e v e l of the hard task d i d show a moderate i n v e r s e r e l a -t i o n s h i p wi th task p e r f o r -mance (r = - 0 . 2 8 ) . In o t h e r , words, the h i g h e r the d i f f i c u l t y r a t i n g , the fewer c o r r e c t responses i iwere made. The p e r c e i v e d 62 T a b l e 5 Mean c o l d p r e s s o r change s c o r e s : H i g h , Mid and Low h e a r t r a t e r e a c t o r s and a l l s u b j e c t s combined. R e a c t o r Group V a r i a b l e Low (n = 18) Mid ( n = 17) High ( n = 19) A l l S u b j e c t s HR (bpm)*** -5. 4 ( 2 .9) 2.8 ( 0.8) 13. 9 ( 5 .9) 3. 5 ( 7.2) TWA (%) 4. 6 ( 11 .0) 1.0 ( 8.5) 0. 6 ( 12 .5) 2 . 9 ( 10.6) BVP (%) -49. 5 ( 22 .9) -63.3 ( 22.0) -46. 1 ( 21 • 7) -55. 0 ( 27.4) PTT ( m s e c ) * -7 . 0 ( 12 .0) -11.5 ( 12.0) -17 . 9 ( 11 .5) -9. 1 ( 14.8) RR (cpm) -0. 3 ( 3 .7) 0.5 ( 3.7) 0. 3 ( 2 .4) 0. 1 ( 3.3) T: A (%) -11 . 0 ( 33 .8) -1.2 ( 68.2) 12 . 4 ( 56 .1) 4 . 8 ( 95.8) RA ( % ) * * -13. 1 ( 27 .4) -0.3 ( 42.8) 39. 1 ( 65 .5) 6. 8 ( 45.6) AA (%) 6 . 0 ( 34 .6) 25.0 ( 49.2) 29. 7 ( 33 .7) 21. 3 ( 41. 5) RAV (%) 57 . 7 (327 • 7) 55.4 ( 121.5) 165. 2 (354 .7) 86 . 7 (260.3) AAV (%) 23 . 2 (119 .4) 101.6 (174.5) 127 . 5 ( 299 .8) 115. 8 (439.8) *p < .05, **p < .01, ***p < .001 change was a l s o a s s e s s e d . Co ld p r e s s o r r e s p o n s e s . T.he mean change scores and s tandard d e v i a t i o n s f o r each dependent measure are presented i n T a b l e 5. As mentioned i n S e c t i o n I , change scores for h e a r t r a t e , pulse t r a n s i t time and b r e a t h i n g ra te were computed as the d i f f e r e n c e between task and b a s e l i n e raw scores and are presented i n t h e i r s tandard u n i t s of measurement. Task responses f o r the remain ing seven v a r i a b l e s had to be expressed as percentages of t h e i r r e s p e c t i v e b a s e l i n e va lues due to the r e l a t i v e nature of these measures. 63 The f i r s t step i n d e t e r m i n i n g whether or not s i g n i f i c a n t l y d i f f e r e n t r e a c t o r groups c o u l d be formed on the b a s i s of h e a r t r a t e r e a c t i v i t y to the c o l d p r e s s o r t e s t was to c o n f i r m that h e a r t r a t e d i d change s i g n i f i c a n t l y i n response to that task . A one-way ANOVA was conducted f o r t h i s purpose , comparing b a s e l i n e and c o l d p r e s s o r h e a r t r a t e l e v e l s . The r e s u l t s i n d i c a t e d that task l e v e l s s i g n i f i c a n t l y exceeded b a s e l i n e h e a r t r a t e s ( F ( l , 99) = 24 .02 , p < . 001 ) . I n f o r m a t i o n on which r e s p i r a t o r y v a r i a b l e s c o n t r i b u t e d s i g n i f i c a n t l y to the observed h e a r t ra t e changes was o b t a i n e d by e x e c u t i n g a s tepwise l i n e a r r e g r e s s i o n . In t h i s a n a l y s i s , a s tep-up procedure was used i n which r e s p i r a t o r y change v a r i a b l e s were entered i n t o the r e g r e s s i o n e q u a t i o n i f t h e i r p a r t i a l c o r r e l a t i o n s w i th the independent measure ( i . e . h e a r t ra t e change) e q u a l l e d or exceeded an F - t o - e n t e r va lue of 4 .00 . B i -v a r i a t e s c a t t e r p l o t s ob ta ined p r i o r to t h i s a n a l y s i s suggested that h e a r t r a t e change was l i n e a r l y r e l a t e d to change i n each r e s p i r a t o r y v a r i a b l e . The r e g r e s s i o n a n a l y s i s r e v e a l e d that only two r e s p i r a t o r y v a r i a b l e s c o n t r i b u t e d s i g n i f i c a n t l y to the v a r i a n c e i n h e a r t r a t e change d u r i n g the c o l d p r e s s o r t e s t . The l a r g e s t c o n t r i b u -t i o n was made by r i b c a g e ampl i tude change. I t a lone accounted f o r 22.4% of the v a r i a n c e . A f u r t h e r 3.5% of the v a r i a n c e was a t t r i b u t a b l e to abdominal ampl i tude change. In t o t a l , r e s p i r a -64 tory changes accounted f o r a p p r o x i m a t e l y 26% of the v a r i a n c e i n h e a r t ra t e change s c o r e s . Subjec t s were then d i v i d e d i n t o r e a c t o r q u i n t i l e s based on the magnitude of t h e i r h e a r t ra te change to the c o l d p r e s s o r t e s t . These r e a c t o r subgroups were d e f i n ed i n the f o l l o w i n g way. S u b j e c t s whose h e a r t r a t e s decreased by two or more beats per minute (mean = -5 .4 bpm, SD = 2 .86 , range = -2 to -12 bpm) formed the Low r e a c t o r group (n=21). The Mid r e a c t o r group (n=18) showed h e a r t ra t e i n c r e a s e s r a n g i n g from two to four beats per minute (mean = +3.4, SD = 0.87) whi l e h e a r t ra t e i n c r e a s e s for the High r e a c t o r group (n=21) ranged from + 9 to +33 beats per minute (mean = +13.9, SD = 5 . 8 7 ) . The second (n=20) and f o u r t h (n=20) r e a c t o r q u i n t i l e s i n c l u d e d s u b j e c t s whose h e a r t ra t e changes ranged from -1 to +1 bpm (mean = +0.1, SD = 0.77) and +5 to +8 bpm (mean = +6.2, SD = 1.15) r e s p e c t i v e -l y . In order to p r e s e n t e f f e c t s from groups that have a g r e a t e r l i k e l i h o o d of showing d i f f e r e n c e s on other p h y s i o l o g i c a l responses bes ides h e a r t r a t e , only data for the f i r s t (Low), t h i r d (Mid) and f i f t h (High) q u i n t i l e s were i n c l u d e d i n subsequent a n a l y s e s . Before c o n d u c t i n g a repeated measures a n a l y s i s to determine whether or not the three r e a c t o r groups d i f f e r e d r e l i a b l y from one another wi th r e s p e c t to c a r d i a c r e a c t i v i t y , a t e s t for the e q u i v a l e n c e of b a s e l i n e hear t r a t e s was u n d er tak en . The r e s u l t s of the one-way ANOVA conf irmed that the three groups were not 65 r e l i a b l y d i f f e r e n t i n t h e i r b a s e l i n e l e v e l s of h e a r t r a t e ( F ( 2 , 57) = 2 .42 , p > . 0 5 ) . On the b a s i s of t h i s f i n d i n g , change scores f o r h e a r t r a t e and f o r the other nine p h y s i o l o g i c a l measures were used i n a MANOVA that compared the responses of s u b j e c t s i n the h i g h , mid and low r e a c t o r groups . By i n c l u d i n g the three other c a r d i o v a s c u l a r i n d i c e s and the s i x r e s p i r a t o r y change measures i n the a n a l y s i s , f u r t h e r i n f o r m a t i o n would be made a v a i l a b l e on p o s s i b l e group d i f f e r e n c e s i n c a r d i o -r e s p i r a t o r y response p a t t e r n s . The mean change scores and s tandard d e v i a t i o n s f o r each r e a c t o r group are presented i n T a b l e 5. The r e s u l t s of the o v e r a l l m u l t i v a r i a t e t e s t i n d i c a t e d that s i g n i f i c a n t between-group d i f f e r e n c e s e x i s t e d i n c o l d p r e s s o r responses ( F ( 1 0 , 47) = 9 .03 , p < . 0 0 1 ) . I n s p e c t i o n of the u n i v a r i a t e ANOVA r e s u l t s r e v e a l e d a h i g h l y s i g n i f i c a n t group d i f f e r e n c e i n h e a r t ra t e change to the c o l d p r e s s o r ( F ( 2 , 55) = 125.30, p < . 0 0 1 ) . Pos t -hoc a n a l y s i s u s i n g S c h e f f e ' s method conf i rmed that s u b j e c t s i n the h igh r e a c t o r group e x p e r i e n c e d s i g n i c a n t l y l a r g e r i n c r e a s e s i n h e a r t ra te (mean = 13.9 bpm) than d i d Mid r e a c t o r s (mean = 2.8 bpm) who, i n t u r n , showed l a r g e r i n c r e a s e s than the low r e a c t o r s (mean = - 5 . 4 ) . S i g n i f i -cant group d i f f e r e n c e s were found for two other measures: 1) pu lse t r a n s i t time ( F ( 2 , 55) = 4 .51 , p = . 0 2 ) ; and 2) r i b c a g e ampl i tude ( F ( 2 , 55) = 6 .55 , p < . 0 1 ) . Pos t -hoc comparisons r e v e a l e d that the h igh r e a c t o r group showed the l a r g e s t a b o v e - b a s e l i n e i n c r e a s e i n r i b c a g e ampl i tude (+39.1%) and the 66 l a r g e s t average decrease i n pulse t r a n s i t time ( -17 .9 msec) . In c o n t r a s t , s u b j e c t s i n the low r e a c t o r group e x p e r i e n c e d the s m a l l e s t average decrease i n pulse t r a n s i t (mean = - 7 . 0 msec) and the l a r g e s t decrease i n r i b c a g e ampl i tude (-13.1%). The Mid r e a c t o r group d i f f e r e d s i g n i f i c a n t l y from the other two groups i n showing moderate changes on both measures (-0.3% change i n ( r i b c a g e ampl i tude and -11 .5 msec decrease i n pulse t r a n s i t t i m e ) . In summary, the above r e s u l t s conf irmed that s u b d i v i d i n g s u b j e c t s i n t o h i g h , mid and low r e a c t o r q u i n t i l e s y i e l d e d r e l i a -b l y d i f f e r e n t groups . Menta l A r i t h m e t i c Responses . T e s t i n g for group d i f f e r e n c e s i n c a r d i o - r e s p i r a t o r y r e a c t i v -i t y to the easy and hard math c o n d i t i o n s c o n s t i t u t e d a 3 ( r e a c t o r group) x 2 ( task d i f f i c u l t y ) repeated measures d e s i g n . A MANOVA was conducted based on change scores f o r the 10 p h y s i o l o g i c a l measures. The Type I e r r o r r i s k was se t a t . 0 5 . Complete data f o r t h i s a n a l y s i s were only a v a i l a b l e f o r 18 s u b j e c t s i n the Low group, 17 i n the Mid group and 19 i n the High group. Change scores f o r these three groups can be seen i n Table 6. The o v e r a l l m u l t i v a r i a t e t e s t r e s u l t f or the grouping f a c t o r was n o n s i g n i f i c a n t , as were a l l 10 of the u n i v a r i a t e ANOVAs. These n o n s i g n i f i c a n t r e s u l t s imply that the three r e a c t o r groups d i d n ' t show any r e l i a b l e d i f f e r e n c e s i n t h e i r c a r d i o - r e s p i r a t o r y responses to the two d i f f i c u l t y l e v e l s of mental a r i t h m e t i c . 67 T a b l e 6 Changes i n p h y s i o l o g i c a l a c t i v i t y from b a s e l i n e d u r i n g easy and hard mental a r i t h m e t i c (MA): H i g h , Mid & Low h e a r t r a t e r e a c t o r g r oups. H e a r t Rate R e a c t o r Group Low ( n * 18) Mid (n = 17) High (n = 19) HR (bpm) - Easy - Hard MA MA 7.3 13 . 1 ( 7 ( 10 .4) .5) 4.4 9.6 ( 3 ( 6 .6) .0) 7 . 7 15.5 ( 6 ( 10 .2) .5) TWA (Z) - Easy - Hard MA MA -5.5 -7 . 7 ( 10 ( 9 .3) .0) -1.3 -4.0 ( 6 ( 11 .7) .9) -6.0 -6.4 ( 10 ( 19 .8) .5) BVP (Z) - Easy - Hard MA MA -26.2 -27.3 ( 44 ( 49 .2) .1) -34.0 -38.6 ( 22 ( 25 .2) .8) -25.1 -32.6 ( 34 ( 33 .4) .8) PTT (msec ) - Easy - Hard MA MA -12.9 -17.4 ( 17 ( 18 .1) .7) -7.0 -13.0 ( 15 ( 18 .9) .6) -15.3 -19 . 8 ( 17 ( 15 .0) .9) RR (cpm) - Easy - Hard MA MA 2.4 4.4 ( 2 ( 3 .1) .5) 3.0 5.3 ( 4 ( 3 .0) .9) 2.3 3.9 ( 3 ( 3 .7) .7) T: A (Z) - Easy - Hard MA MA 10.5 7.5 ( 41 ( 39 .8) .3) 2.5 26.3 ( 42 ( 63 .8) .3) 31.2 35.6 ( 73 ( 61 .6) .8) RA (Z) - Easy - Hard MA MA 7.7 3 . 1 ( 27 ( 29 .8) .4) 1.5 16.5 ( 27 ( 37 • 7) .3) 3.0 9.5 ( 32 ( 30 .2) .1) AA (Z) - Easy - Hard MA MA 3.3 5.0 ( 20 ( 31 .8) .9) 7.2 2.5 ( 27 ( 31 .2) .0) -8.0 -6.6 ( 32 ( 37 .7) .2) RAV (Z) - Easy - Hard MA MA 60.4 66.4 (159 ( 185 .8) .0) 47.8 56.5 ( 81 ( 81 .8) .4) 87.5 91 . 1 ( 206 ( 203 • 2) .3) AAV (Z) - Easy - Hard MA MA 30 . 7 98 .4 ( 96 (208 .0) .5) 51.7 62.0 (121 (158 .6) .9) 42 . 8 54.8 (117 ( 128 .0) .3) 1 I n s p e c t i o n of the m u l t i v a r i a t e and u n i v a r i a t e ANOVAs f o r the d i f f i c u l t y m a n i p u l a t i o n , i r r e s p e c t i v e of r e a c t i v i t y g r o u p i n g , r e v e a l e d that the presen t r e s u l t s l a r g e l y r e p l i c a t e d those 68 r e p o r t e d i n S e c t i o n I . For t h i s r e a s o n , they w i l l not be p r e -sented h e r e . Of p a r t i c u l a r i n t e r e s t were the ana lyse s for p o s s i b l e i n t e r -a c t i o n s between the grouping and task d i f f i c u l t y f a c t o r s . A l though the o v e r a l l m u l t i v a r i a t e t e s t was n o n s i g n i f i c a n t (F(20 , 100) = 2 .35 , p = . 0 9 ) , the e p s i l o n - c o r r e c t e d u n i v a r i a t e ANOVAs for r i b c a g e ampl i tude and T:A r a t i o d i d suggest that the three r e a c t o r groups responded d i f f e r e n t l y to the two d i f f i c u l t y c o n d i t i o n s ( r i b c a g e a m p l i t u d e : ( F ( 2 , 51) = 3 .36 , p < . 0 5 ) ; and T:A r a t i o : ( F ( 2 , 51) = 3 .01 , p = . 0 5 8 ) . Simple e f f e c t s pos t -hoc t e s t i n g r e v e a l e d that the Mid r e a c t o r group e x p e r i e n c e d s i g n i f i -c a n t l y g r e a t e r r i b c a g e e x c u r s i o n d u r i n g hard math (16.5% above b a s e l i n e ) than they d i d d u r i n g easy math (1.5% above b a s e l i n e ) . The High and Low r e a c t o r groups showed no such e f f e c t f o r task d i f f i c u l t y . L o o k i n g a t between-group d i f f e r e n c e s i n T:A r a t i o , a s i m i l a r p a t t e r n was e v i d e n t . Both the High and Low groups showed l i t t l e v a r i a t i o n i n T:A r a t i o from easy math to hard math whereas the hard math c o n d i t i o n e l i c i t e d a g r e a t e r T:A r a t i o i n the Mid group. However, r e l a t i v e to b a s e l i n e l e v e l s , the average change i n T:A r a t i o e l i c i t e d by the hard task appeared to be g r e a t e s t for the High r e a c t o r q u i n t i l e (+35.6%) and l e a s t f o r the Low r e a c t o r group (+7.5%). C o n t r a r y to e x p e c t a t i o n s , no s i g n i f i c a n t Group x Task i n t e r a c t i o n s were found for any of the c a r d i o v a s c u l a r measures. The unexpected absence of between-group d i f f e r e n c e s on a l l 69 p h y s i o l o g i c a l m e a s u r e s T a b l e 7 C o r r e l a t i o n s between change s c o r e s f o r s u g g e s t e d t h e p o s s i b i l i t y c o l d p r e s s o r ( C P ) , easy math (E) and h a r d math (H). t h a t h e a r t r a t e r e a c t i v i t y t o t h e c o l d p r e s s o r i s a V a r i a b l e C P x E C P x H E x H p o o r p r e d i c t o r o f o v e r a l l T:A 0.02 0.24 0 . 67* r e a c t i v i t y t o s u b s e q u e n t RA 0.02 0.16 0.41* m e n t a l c h a l l e n g e t a s k s . AA 0.04 0.10 0.80* . . A s a m eans o f e x p l o r i n g RAV 0.37* 0.24 0.70* t h i s p o s s i b i l i t y , a n d a l s o AAV -0.08 -0.12 0.61* i n o r d e r t o d e t e r m i n e how RR 0. 12 -0.06 0.69* HR 0. 13 0. 13 0. 83* . s t a b l e t h e o t h e r n i n e TWA 0.19 0.29 0.81* p h y s i o l o g i c a l m e a s u r e s BVP 0.36* 0.31 0.85* w e r e a c r o s s t a s k s , c h a n g e PTT 0.42* 0.24 0.81* , s c o r e s f o r e a c h m e a s u r e i n * S i g n i f i c a n t a t p < .001 ' e a c h t a s k ( c o l d p r e s s o r , e a s y m a t h , h a r d m a t h ) w e r e c o r r e l a t e d w i t h o n e a n o t h e r . T h e s e c o r r e l a t i o n s a r e p r e s e n t e d i n T a b l e 7. I t s h o u l d be n o t e d , h o w e v e r , t h a t b e c a u s e t h e c o l d p r e s s o r t a s k p r e c e d e d t h e two c o u n t e r b a l a n c e d m a t h c o n d i t i o n s f o r a l l s u b j e c t s , t h e a c r o s s - t a s k c o r r e l a t i o n s a r e c o n f o u n d e d w i t h o r d e r e f f e c t a n d a r e t h e r e f o r e d i f f i c u l t t o i n t e r p r e t . I n g e n e r a l , t h e r e s u l t s i n d i c a t e d t h a t t h e r e was r e l a t i v e l y l i t t l e c o r r e s p o n d e n c e b e t w e e n c o l d p r e s s o r r e s p o n s e s a n d t h o s e e l i c i t e d b y m e n t a l a r i t h m e t i c . H o w e v e r , r e a c t i v i t y t o t h e e a s y a n d h a r d v e r s i o n s o f m e n t a l a r i t h m e t i c was r e m a r k a b l y s t a b l e a c r o s s a l l m e a s u r e s , r a n g i n g f r o m r = .41 ( r i b c a g e a m p l i t u d e ) t o 70 r = .85 (pu l se t r a n s i t t i m e ) . T h i s f i n d i n g suggests that c a r d i o - r e s p i r a t o r y responses are somewhat task s p e c i f i c . The f a c t that h e a r t r a t e change to the c o l d p r e s s o r c o r r e l a t e d p o o r l y wi th changes e l i c i t e d by e i t h e r of the math c o n d i t i o n s (r = .13 i n both cases ) i s of p a r t i c u l a r i n t e r e s t s ince the l i t -e r a t u r e suggested that h e a r t r a t e r e a c t i v i t y to the c o l d p r e s s o r would be a good p r e d i c t o r of math task r e a c t i v i t y . While t h i s d i d not prove to be the c a s e , two other c a r d i o v a s c u l a r measures, b lood volume pulse and pulse t r a n s i t time r e s p o n s e s , d i d show moderate to h igh l e v e l s of i n t e r - t a s k s t a b i l i t y . In both cases , c o l d p r e s s o r changes were more s t r o n g l y a s s o c i a t e d wi th easy task r e a c t i v i t y than wi th hard task re sponses . T h i s was a l s o true f o r r i b c a g e ampl i tude v a r i a b i l i t y , the only r e s p i r a t o r y v a r i a b l e to show s i g n i f i c a n t c o l d p r e s s o r - m a t h task s t a b i l i t y (r = . 3 7 ) . Ribcage a m p l i t u d e , T:A r a t i o and T-wave ampl i tude showed the o p p o s i t e t r e n d : r e a c t i v i t y to the hard math task was more c l o s e l y r e l a t e d to c o l d p r e s s o r re sponses . Based on these c o r r e l a t i o n s , i t appears that r e s p i r a t o r y changes to one type of task are g e n e r a l l y poor i n d i c a t o r s of the d i r e c t i o n a n d / o r ex tent of changes that may occur to a d i f f e r e n t type of t a sk . In c o n t r a s t , c a r d i o v a s c u l a r responses other than h e a r t ra t e change show a moderate l e v e l of a c r o s s - t a s k s t a b i l -i t y . 7 1 D i s c u s s ! o n O v e r a l l e f f e c t s of task d i f f i c u l t y . One of the c e n t r a l i s s u e s i n t h i s study was whether psycho-l o g i c a l c h a l l e n g e or s t r e s s e l i c i t s s i g n i f i c a n t changes i n the b r e a t h i n g p a t t e r n s of h e a l t h y young males and whether these changes correspond to r e a c t i v i t y i n the c a r d i o v a s c u l a r system. O v e r a l l , the data i n d i c a t e that b r e a t h i n g r a t e s i n c r e a s e s i g -n i f i c a n t l y from r e s t i n g l e v e l s when i n d i v i d u a l s respond to a cont inuous s e r i e s of t i m e - l i m i t e d mental a r i t h m e t i c problems. I t was a l s o apparent that the s t r e s s task e l i c i t e d markedly more i r r e g u l a r and more t h o r a c i c l y dominant b r e a t h i n g than was e v i d e n t when s u b j e c t s s imply sa t q u i e t l y r e a d i n g c a r t o o n s . Two measures of r e s p i r a t o r y change, b r e a t h i n g r a t e and abdominal ampl i tude v a r i a b i l i t y , were a l s o found to have v a r i e d r e l i a b l y wi th the d i f f i c u l t y l e v e l of s t r e s s o r . In c o n t r a s t , three of the four c a r d i o v a s c u l a r measures that were i n c l u d e d i n t h i s study showed s i g n i f i c a n t l y d i f f e r e n t response l e v e l s to the easy and hard v e r s i o n s of t h i s a c t i v e cop in g task . In a l l cases where s i g n i f i c a n t main e f f e c t s for task d i f f i c u l t y were o b s e r v e d , the more d i f f i c u l t task e l i c i t e d the g r e a t e s t changes from b a s e l i n e l e v e l s . In g e n e r a l , s u b j e c t s breathed more r a p i d l y and wi th more i r r e g u l a r i t y i n t h e i r abdominal movements i n response to the hard task than to the easy task . At the same t ime, they a l s o e x p e r i e n c e d f a s t e r h e a r t r a t e s , i n c r e a s e d p e r i p h e r a l r e s i s t a n c e and h i g h e r s y s t o l i c b lood p r e s s u r e . T h i s 72 p a t t e r n of responses suggests that i n c r e a s i n g mental c h a l l e n g e r e s u l t s i n i n c r e a s e d somatic and autonomic a r o u s a l . However, the f a c t that four of the r e s p i r a t i o n measures ( b r e a t h i n g mode, r i b c a g e a m p l i t u d e , abdominal a m p l i t u d e , and r i b c a g e ampl i tude v a r i a b i l i t y ) d id not vary s i g n i f i c a n t l y wi th task d i f f i c u l t y suggests that b r e a t h i n g p a t t e r n s are r e l a t i v e l y u n a f f e c t e d by v a r y i n g d i f f i c u l t y l e v e l s of c o g n i t i v e l y mediated s t r e s s . Two o b s e r v a t i o n s undermine t h i s c o n c l u s i o n . F i r s t , w i th the e x c e p t i o n of abdominal a m p l i t u d e , the average s h i f t i n response l e v e l s from r e s t to mental a r i t h m e t i c was c o n s i d e r a b l e , r e g a r d l e s s of the d i f f i c u l t y l e v e l . U n f o r t u n a t e l y , the r e l a t i v e nature of f i v e of these measures p r e c l u d e d any t e s t i n g f o r s i g -n i f i c a n t d i f f e r e n c e s between r e s t and task response l e v e l s . N e v e r t h e l e s s , the magnitude of the mean change s c o r e s , even i n response to the easy c o n d i t i o n , argues a g a i n s t the c o n c l u s i o n that c o g n i t i v e c h a l l e n g e has no e f f e c t on b r e a t h i n g p a t t e r n s . Second, l a r g e i n d i v i d u a l d i f f e r e n c e s were e v i d e n t i n the d i r e c -t i o n a n d / o r ex tent of most r e s p i r a t i o n changes to the two math c o n d i t i o n s . A c r o s s a l l s i x r e s p i r a t i o n measures , s tandard d e v i a t i o n s exceeded t h e i r r e s p e c t i v e mean scores by a r a t i o of 12:1 ( t h i s va lue drops to 3:1 when the abdominal ampl i tude r a t i o s are e x c l u d e d ) . Given such grea t v a r i a b i l i t y i n r e s p o n s e s , i t Is p o s s i b l e that a number of s u b j e c t s responded s t r o n g l y to the d i f f i c u l t y m a n i p u l a t i o n even though the mean response a c r o s s s u b j e c t s was i n s i g n i f i c a n t . F u r t h e r m o r e , s ince the e a s y / h a r d comparisons were done s e p a r a t e l y f o r each r e s p i r a -7 3 tory v a r i a b l e , i t i s p o s s i b l e that no tab le changes d i d occur i n the b r e a t h i n g p a t t e r n s of most s u b j e c t s but that these changes o c c u r r e d i n d i f f e r e n t parameters from one s u b j e c t to the next . A c a s u a l i n s p e c t i o n of the r e s p i r a t o r y t r a c i n g s suggested that f o r some i n d i v i d u a l s , the hard task e l i c i t e d c o n s i d e r a b l y h i g h e r b r e a t h i n g r a t e s than d i d the easy task , but that l i t t l e concom-i t a n t change o c c u r r e d i n b r e a t h i n g a m p l i t u d e s . Other s u b j e c t s appeared to show the oppos i t e p a t t e r n of change. However, when these data are ana lyzed wi thout regard to the I n t e r a c t i o n among these b r e a t h i n g parameters , the apparent e f f e c t f o r task d i f f i c u l t y i s o b s c u r e d . While t e s t i n g of t h i s p o s s i b i l i t y i s of some i n t e r e s t , i t was c o n s i d e r e d to be beyond the scope of the p r e s e n t s t u d y . E f f o r t s were i n s t e a d focused on t e s t i n g f o r b r e a t h i n g p a t t e r n d i f f e r e n c e s between c a r d i o v a s c u l a r r e a c t i v i t y subgroups . L o o k i n g at the c o r r e l a t i o n c o e f f i c i e n t s f o r c a r d i o v a s c u l a r and r e s p i r a t o r y changes to easy and hard mental a r i t h m e t i c , the d i f f e r e n t i a l e f f e c t of mental c h a l l e n g e on r e s p i r a t o r y and autonomic a r o u s a l becomes even more a p p a r e n t . Of the 24 c a r d i o -r e s p i r a t o r y c o r r e l a t i o n s obta ined for each d i f f i c u l t y c o n d i t i o n , only one ( h e a r t r a t e x b r e a t h i n g r a t e changes to easy a r i t h -met i c ) was s t a t i s t i c a l l y s i g n i f i c a n t . Another three c o r r e l a t i o n s approached s i g n i f i c a n c e . Such f i n d i n g s imply that the two p h y s i o l o g i c a l systems a d j u s t e d to the b r i e f mental c h a l l e n g e s r e l a t i v e l y independent ly of each o t h e r . The u s e f u l n e s s of s t u d y i n g s t r e s s - i n d u c e d r e s p i r a t o r y changes as 74 p r e d i c t o r s of c a r d i o v a s c u l a r changes i n h e a l t h y young men can t h e r e f o r e be c o n s i d e r e d low. The one e x c e p t i o n to t h i s c o n c l u -s i o n , based on the stepwise r e g r e s s i o n ana lyses conducted i n t h i s s t u d y , i s that b r e a t h i n g r a t e and r i b c a g e ampl i tude changes to easy a r i t h m e t i c are more c l o s e l y r e l a t e d to h e a r t r a t e i n c r e a s e s than any of the three c a r d i o v a s c u l a r measures. F u l l y t w o - t h i r d s of the 40.1% of h e a r t ra te change v a r i a n c e accounted f o r i n the easy c o n d i t i o n was a t t r i b u t a b l e to changes i n these two b r e a t h i n g v a r i a b l e s . However, r e s p i r a t o r y responses to the hard task were l e s s v a l u a b l e as p r e d i c t o r s of h e a r t r a t e r e s -ponses , a c c o u n t i n g for l e s s than 19% of the 36.5% of e x p l a i n e d h e a r t ra t e v a r i a n c e . One p o s s i b l e c o n c l u s i o n from these f i n d i n g s i s that i n c r e a s i n g s t r e s s loads r e s u l t i n a d i s s o c i a t i o n of h e a r t r a t e and r e s p i r a t o r y a c t i v i t y . In other words, the more d i f f i c u l t a task l i k e mental a r i t h m e t i c i s , the s m a l l e r the correspondence between h e a r t ra t e adjustments and v e n t i l a t i o n e f f o r t s . T h i s f i n d i n g conf irms A l l e n et a l . ' s (1986) and C a r r o l l e t a l . ' s (1983) c o n c l u s i o n s . These i n v e s t i g a t o r s a l s o suggested t h a t , r e l a t i v e to the i n c r e a s e s i n o v e r a l l v e n t i l a t i o n that o c c u r r e d d u r i n g t h e i r a c t i v e cop ing t a s k s , the observed h e a r t ra te i n c r e a s e s were m e t a b o l i c a l l y unwarranted . To some e x t e n t , the r e s u l t s of the present study are d i r e c t l y comparable wi th those o b t a i n e d by these two groups of i n v e s t i g a t o r s . The h e a r t r a t e and b r e a t h i n g r a t e changes r e p o r t e d i n each study i n d i c a t e d that rough ly e q u i v a l e n t l e v e l s of a r o u s a l had been e l i c i t e d by the 75 d i f f e r e n t s t r e s s o r t a s k s . T h i s adds f u r t h e r credence to the argument that h e a r t r a t e and r e s p i r a t i o n changes d i s s o c i a t e d i n the p r e s e n t s tudy . Temporal p a t t e r n of r e sponses . In comparison to changes a s s o c i a t e d wi th d i f f e r e n t l e v e l s of task d i f f i c u l t y , changes i n r e s p i r a t i o n over time were g e n e r a l l y more c o n s i s t e n t across s u b j e c t s . Three of the s i x measures showed s i g n i f i c a n t l y d i f f e r e n t response l e v e l s over the 5-minute a r i t h m e t i c t a sk . S i g n i f i c a n t task a d a p t a t i o n was a l s o found for the four c a r d i o v a s c u l a r measures . On average , b r e a t h i n g r a t e s i n c r e a s e d to t h e i r h i g h e s t l e v e l s wi th task onse t . T h e r e a f t e r , s u b j e c t s ' b r e a t h i n g g r a d u a l l y s lowed, a l t h o u g h r a t e s s t i l l remained c o n s i d e r a b l y above r e s t i n g l e v e l s even a t the end of the t a s k . With task onse t , s u b j e c t s a l s o tended to b r e a t h more d e e p l y , as i n d i c a t e d by the i n c r e a s e d ampl i tudes of both r i b c a g e and abdominal movements. As time at the task p r o g r e s s e d , a s l i g h t s h i f t i n b r e a t h i n g mode became a p p a r e n t . In g e n e r a l , the c o n t r i b u t i o n that r i b c a g e movements made to t i d a l volume g r a d u a l l y r e t u r n e d to r e s t i n g l e v e l s . At the same t ime, abdominal movements p layed even l e s s of a r o l e i n f i l l i n g the lungs wi th a i r than they d i d when s u b j e c t s were r e s t i n g q u i e t l y . These data s tand i n c o n t r a s t to the r e s u l t s r e p o r t e d by Svebak et a l . (1981) i n t h e i r study of b r e a t h i n g changes d u r i n g a 2 1/2 minute v ideo game s t r e s s o r . Rather than i n c r e a s e i n 76 response to task onse t , r i b c a g e and abdominal ampl i tude were r e p o r t e d to have decreased to t h e i r lowest l e v e l s . Both measures were a l s o found to show a g r a d u a l and p a r a l l e l r e t u r n to n e a r - b a s e l i n e l e v e l s . The f a c t that the d i r e c t i o n of r i b c a g e and abdominal ampl i tude changes d i f f e r e d between the two s t u d i e s may be the r e s u l t of d i f f e r i n g methods used to c a l c u l a t e r e s p i r a t o r y a m p l i t u d e . Svebak et a l . expressed r i b c a g e and abdominal ampl i tude responses to the l a b s t r e s s o r as percentages of the s m a l l e s t r e s p e c t i v e ampl i tude va lues recorded at b a s e l i n e . A l though t h i s procedure was des igned to y i e l d n o n - n e g a t i v e ampl i tude s c o r e s , bas ing the task scores on a s i n g l e data va lue r a t h e r than on mean scores f o r the b a s e l i n e p e r i o d may have r e s u l t e d i n task scores that do not a c c u r a t e l y r e p r e s e n t a c t u a l i n c r e a s e s or decreases from b a s e l i n e l e v e l s . In order to a v o i d t h i s problem, a l l ampl i tude responses i n the present study were expressed as percentages of the average b a s e l i n e v a l u e s . An a l t e r n a t i v e e x p l a n a t i o n f o r the i n c o n s i s t e n t ampl i tude r e s u l t s i n the two s t u d i e s i s that v ideo game performance may s imply e l i c i t a d i f f e r e n t p a t t e r n of p h y s i o l o g i c a l a r o u s a l than that produced by the l e s s p h y s i c a l l y demanding task of answering a r i t h m e t i c q u e s t i o n s . R e a c t i v i t y subgroups and c a r d i o - r e s p i r a t o r y change. The second major purpose of the p r e s e n t s tudy , namely, to determine whether or not b r e a t h i n g p a t t e r n changes covary wi th c a r d i o v a s c u l a r r e a c t i v i t y i n d i f f e r e n t r e a c t o r subgroups , on the 77 whole y i e l d e d no s u p p o r t i v e f i n d i n g s . The three d i s t i n c t r e a c t o r groups formed on the b a s i s of h e a r t ra t e responses to an i n i t i a l c o l d p r e s s o r t e s t d id not show any o v e r a l l group d i f f e r -ences i n c a r d i o v a s c u l a r and r e s p i r a t o r y responses to subsequent mental a r i t h m e t i c t a s k s . S t a t e d d i f f e r e n t l y , c a r d i a c r e a c t i v i t y to c o l d s t i m u l a t i o n , a p u t a t i v e marker of h y p e r t e n s i o n r i s k , was not c l e a r l y a s s o c i a t e d e i t h e r wi th p a r t i c u l a r p a t t e r n s of b r e a t h i n g changes to m e n t a l / p s y c h o l o g i c a l c h a l l e n g e or wi th d i f -f e r e n t i a l c a r d i o v a s c u l a r r e a c t i v i t y to such c h a l l e n g e . However, the data d i d i n d i c a t e that d i f f e r e n t subgroups of c a r d i a c r e a c t o r s do respond to easy and hard v e r s i o n s of mental a r i t h m e t i c w i th d i f f e r e n t l e v e l s of r i b c a g e b r e a t h i n g and p o s s i b l y a l s o wi th d i s t i n c t s h i f t s i n the predominant mode of b r e a t h i n g . In g e n e r a l , s u b j e c t s i n the t h i r d q u i n t i l e f o r h e a r t r a t e r e a c t i v i t y ( d e s i g n a t e d as moderate r e a c t o r s ) breathed more t h o r a c i c l y when the task was hard than when i t was easy . Sub-j e c t s i n the h i g h e s t and lowest q u i n t i l e s , on the other hand, responded to the hard task wi th more or l e s s the same degree of b r e a t h i n g change as they showed to the easy ta sk . In other words, only the moderate r e a c t o r s showed r e s p i r a t o r y system s e n s i t i v i t y to m a n i p u l a t i o n s of task d i f f i c u l t y . As f a r as changes i n the predominant mode of b r e a t h i n g are c o n c e r n e d , i t appears that s u b j e c t s i n the h igh r e a c t o r group e x e r i e n c e d a much g r e a t e r s h i f t towards i n c r e a s e d t h o r a c i c dominance than e i t h e r of the other two groups and that t h i s s h i f t o c c u r r e d i r r e s p e c t i v e of d i f f i c u l t y l e v e l . 78 A l t h o u g h the f i n d i n g s summarized i n the p r e c e d i n g paragraph suggest that c a r d i a c r e a c t i v i t y can be p r e d i c t i v e of s t r e s s -induced r e s p i r a t o r y p a t t e r n changes , s e v e r a l p i eces of ev idence c h a l l e n g e t h i s c o n c l u s i o n . F i r s t of a l l , the task by group I n t e r a c t i o n s f o r r i b c a g e ampl i tude and b r e a t h i n g mode changes to the hard a r i t h m e t i c task were not accompanied by s i m i l a r r e s u l t s f o r c a r d i o v a s c u l a r r e a c t i v i t y . I t can be argued that at l e a s t one of the c a r d i o v a s c u l a r measures should have shown a s i g n i f i -cant e f f e c t f o r the grouping v a r i a b l e or f o r a task by group i n t e r a c t i o n i f , i n f a c t , c a r d i o v a s c u l a r r e a c t i v i t y i s a s t a b l e t r a i t and i s accompanied by c h a r a c t e r i s t i c p a t t e r n s of b r e a t h i n g changes under c o n d i t i o n s of m i l d to moderate s t r e s s . The q u e s t -i o n that a r i s e s i s whether or not the c u r r e n t r e s u l t s were o b t a i n e d because (a) c a r d i o v a s c u l a r r e a c t i v i t y across two l a b o r -a t o r y s t r e s s o r s ( c o l d p r e s s o r and mental a r i t h m e t i c ) i s not a s t a b l e c h a r a c t e r i s t i c of most i n d i v i d u a l s or (b) r e s p i r a t o r y changes to d i f f e r e n t d i f f i c u l t y l e v e l s of mental a r i t h m e t i c are g e n e r a l l y independent of c a r d i o v a s c u l a r changes. The answer to the second p a r t of t h i s q u e s t i o n has been c o n s i d e r e d a l r e a d y . The c o r r e l a t i o n a l data o b t a i n e d for the sample as a whole suggest that changes i n the way normal i n d i v i -duals b r e a t h i n g d u r i n g mental c h a l l e n g e are r e l a t i v e l y u n r e l a t e d to how t h e i r c a r d i o v a s c u l a r systems a d j u s t to the c h a l l e n g e . N e v e r t h e l e s s , these data were viewed as somewhat suspect g iven the l a r g e degree of I n d i v i d u a l d i f f e r e n c e s observed f o r r e s p i r a -79 tory changes . I t was f o r t h i s reason that the sample was sub-d i v i d e d i n t o d i s t i n c t r e a c t o r subgroups . The r e l e v a n t q u e s t i o n to answer, then , was whether or not c a r d i o v a s c u l a r r e a c t i v i t y to the c o l d presor t e s t p r e d i c t s r e a c t i v i t y to mental a r i t h m e t i c . L o o k i n g a t the low c o r r e l a -t i o n s between c o l d p r e s s o r h e a r t r a t e changes and h e a r t r a t e changes e l i c i t e d by the two mental a r i t h m e t i c c o n d i t i o n s (r= .13 i n both c a s e s ) , the answer i s o b v i o u s l y n e g a t i v e . T h i s f i n d i n g i m p l i e s that the subgroups formed on the b a s i s of c o l d p r e s s o r responses were not homogeneous samples of e i t h e r h i g h , moderate, or low c a r d i o v a s c u l a r r e a c t o r s . A homogeneous group of h i g h r e a c t o r s , f or i n s t a n c e , would have i n c l u d e d on ly those s u b j e c t s showing exaggerated c a r d i o v a s c u l a r adjustments a c r o s s a range of tasks and c o n s i s t e n t l y over t ime. Such groups would be p r e f e r -a b l e when t e s t i n g f o r c o v a r i a t i o n between b r e a t h i n g mode and c a r d i o v a s c u l a r r e a c t i v i t y . I n s t e a d , the r e a c t o r groups i n the p r e s e n t study i n c l u d e d a number of i n d i v i d u a l s whose h e a r t r a t e responses to the c o l d p r e s s o r and mental a r i t h m e t i c tasks d i d not r e f l e c t s t a b l e response t e n d e n c i e s . R a t h e r , p e r c e p t i o n s of task d i f f i c u l t y , p r i o r success or f a i l u r e a t s i m i l a r t a s k s , or a hos t of other s t a t e - s p e c i f i c f a c t o r s may w e l l have accounted f o r t h e i r d i f f e r e n t i a l r e a c t i v i t y to the two types of s t r e s s ta sks . One s o l u t i o n to t h i s problem each of the three r e a c t o r groups r a t e changes to the c o l d p r e s s o r would have been to exc lude from those i n d i v i d u a l s whose h e a r t and two math tasks were not 80 c o n s i s t e n t e i t h e r i n the d i r e c t i o n of change or the magnitude of change. A l t e r n a t i v e l y , n o n - o v e r l a p p i n g r e a c t o r groups might have been formed by i n c l u d i n g only s u b j e c t s i n the f i r s t , f i f t h and tenth p e r c e n t i l e s of h e a r t r a t e r e a c t i v i t y to the c o l d p r e s s o r . A s i m i l a r s t r a t e g y was adopted by Wood et a l . (1984) . These i n v e s t i g a t o r s demonstrated that young people whose b lood p r e s s u r e i n c r e a s e s to a c o l d p r e s o r t e s t p l a c e d them i n the 90th p e r c e n t i l e f o r r e a c t i v i t y had a c o n s i d e r a b l y h i g h e r r i s k of d e v e l o p i n g h y p e r t e n s i o n than d i d normoresponders . However, i n the present study t h i s s t r a t e g y would have produced subgroups too s m a l l to y i e l d r e l i a b l e normative d a t a . Another a l t e r n a t i v e would have been to execute a m u l t i p l e r e g r e s s i o n a n a l y s i s to p r e d i c t c o l d p r e s s o r h e a r t ra te responses from r e s p i r a t o r y and c a r d i o v a s c u l a r changes to easy and hard mental a r i t h m e t i c . However, the emphasis l n the p r e s e n t study was not s imply to determine the ex tent to which b r e a t h i n g and c a r d i o v a s c u l a r responses covary d u r i n g mental c h a l l e n g e , but to determine whether or not d i f f e r e n t r e a c t o r groups , one of which i n c l u d e s i n d i v i d u a l s a t - r i s k f o r d e v e l o p i n g h y p e r t e n s i o n , respond to c h a l l e n g e wi th d i f f e r e n t p a t t e r n s of c a r d i o - r e s p i r a t o r y change. Problems a s s o c i a t e d with the way i n which r e a c t o r subgroups were formed extend beyond the apparent h e t e r o g e n e i t y of the groups and the g e n e r a l l a c k of s i g n i f i c a n t d i f f e r e n c e s between them i n response to the mental a r i t h m e t i c task . When one i n s p e c t s the mean change scores f o r each of the three r e a c t o r groups , i t becomes apparent that the terms ' l o w ' and ' m o d e r a t e ' 81 to d e s c r i b e the f i r s t and t h i r d r e a c t o r q u i n t i l e s may be mis -nomers. Low r e a c t o r s to the c o l d p r e s s o r t e s t i n f a c t e x p e r i -enced n o t i c e a b l e decreases i n h e a r t r a t e . The d e s i g n a t i o n ' l o w ' r e a c t o r b e t t e r s u i t s s u b j e c t s i n the t h i r d q u i n t i l e s i n c e they e x p e r i e n c e d h e a r t r a t e i n c r e a s e s of only two to four beats per minute . A more a p p r o p r i a t e d e s i g n a t i o n f o r the f i r s t q u i n t i l e might then be i n v e r s e or h y p o r e a c t o r s . These r . ev i s ions appear j u s t i f i e d when the mean change scores to easy and hard mental a r i t h m e t i c are examined (see Tab le 6 ) . For many of the c a r d i o v a s c u l a r and r e s p i r a t o r y measures, the mean change scores f o r the f i r s t and f i f t h q u i n t i l e s i n d i c a t e t h a t , on average , these two groups showed s i m i l a r l e v e l s of a r o u s a l to the two d i f f i c u l t y c o n d i t i o n s . In g e n e r a l , s u b j e c t s i n both groups showed g r e a t e r r e a c t i v i t y than d i d s u b j e c t s i n the t h i r d q u i n t i l e . The p a t t e r n of easy versus hard task change was a l s o s i m i l a r f o r the f i r s t and f i f t h q u i n t i l e s and d i s t i n c t from that of the ' m i d ' r e a c t o r group. For i n s t a n c e , n e i t h e r group showed d i f f e r e n t i a l r e a c t i v i t y i n r i b c a g e ampl i tude and b r e a t h i n g mode changes to the easy and hard c o n d i t i o n s whereas the ' m i d ' r e a c t o r group d i d . The degree of commonality between the upper and lower r e a c t o r q u i n t i l e s suggests that the r e l a t i o n s h i p between c a r d i o - r e s p i r a t o r y r e a c t i v i t y and v a r y i n g l e v e l s of p s y c h o l o g i c a l c h a l l e n g e i s q u a d r a t i c r a t h e r than a l i n e a r . 82 C o n c l u s i o n s and I m p l i c a t i o n s . The r e s u l t s of t h i s study support the t a c i t assumption of b r e a t h i n g c o n t r o l r e s e a r c h ( e . g . Cappo & Holmes, 1984; McCaul e t a l . , 1978) that s t r e s s - i n d u c e d c a r d i o v a s c u l a r a r o u s a l i s accom-panied by more r a p i d b r e a t h i n g . The data a l s o i n d i c a t e that a c t i v e cop ing tasks such as mental a r i t h m e t i c e l i c i t more i r r e g u l a r b r e a t h i n g from most s u b j e c t s wi th an e v i d e n t trend f o r b r e a t h i n g to become more t h o r a c i c l y dominant wi th i n c r e a s e d s t r e s s l o a d . U n d e r l y i n g t h i s s h i f t i n b r e a t h i n g mode i s an apparent i n c r e a s e i n r i b c a g e movement and a concomitant decrease i n abdominal e x c u r s i o n s . On average , both compartments showed t h e i r g r e a t e s t i n c r e a s e s i n ampl i tude soon a f t e r s t r e s s o r onse t . Such f i n d i n g s suggest that b r e a t h i n g c o n t r o l s t r a t e g i e s which aim at d e c r e a s i n g b r e a t h i n g r a t e s whi le i n c r e a s i n g abdominal e x c u r s i o n s and the o v e r a l l r h y t h m i c i t y of b r e a t h i n g have c o r r e c t l y i d e n t i f i e d those aspects of one's b r e a t h i n g p a t t e r n that d e v i a t e most from r e s t i n g l e v e l s i n response to s t r e s s . T h i s c o n c l u s i o n i s based on mean responses o b t a i n e d from a sample of h e a l t h y young men who showed marked v a r i a b i l i t y i n response l e v e l s to s t r e s s t a s k s . F u r t h e r m o r e , the tasks used i n t h i s study are analogues of the s t r e s s o r s most people e n -counter i n everyday l i f e . For these r e a s o n s , i t would be i n a p p r o p r i a t e f o r c l i n i c i a n s to recommend b r e a t h i n g c o n t r o l t r a i n i n g s o l e l y on the b a s i s of these f i n d i n g s . The data do not c l e a r l y suggest that one group of p o t e n t i a l l y a t - r i s k I n d i v i d -83 u a l s , c a r d i o v a s c u l a r h y p e r r e a c t o r s , cou ld b e n e f i t more from b r e a t h i n g c o n t r o l s t r a t e g i e s than anyone e l s e . I t does appear , however, that r e g a r d l e s s of task d i f f i c u l t y , c a r d i o v a s c u l a r h y p e r r e a c t o r s tend to breathe more t h o r a c i c l y d u r i n g c h a l l e n g i n g tasks than do n o r m o - r e a c t o r s . F u r t h e r r e s e a r c h comparing the b r e a t h i n g p a t t e r n s of h y p e r r e a c t o r s and normoreactors i s necessary before u n e q u i v o c a l c o n c l u s i o n s can be reached i n t h i s r e g a r d . While the r e s u l t s of t h i s study extend our c u r r e n t under -s t a n d i n g of c a r d i o v a s c u l a r and r e s p i r a t o r y changes i n response to mental and p h y s i c a l c h a l l e n g e s , a number of important q u e s t -ions s t i l l remain unanswered. I t needs to v e r i f i e d that one's mode of b r e a t h i n g d u r i n g s t r e s s i s s i g n i f i c a n t l y d i f f e r e n t from r e s t i n g p a t t e r n s . T h i s was demonstrated f o r b r e a t h i n g r a t e , but the technique used to r e c o r d b r e a t h i n g ampl i tudes r u l e d out s i g n i f i c a n c e t e s t i n g to conf i rm the apparent d i f f e r e n c e s between b a s e l i n e and s t r e s s response l e v e l s for ampl i tude measures. N e v e r t h e l e s s , the dual Bel lows s t r a i n gauges p e r m i t t e d the non-i n v a s i v e assessment of b r e a t h i n g mode, a m p l i t u d e , and v a r i a -b i l i t y over time and across d i f f i c u l t y c o n d i t i o n s . Use of a b s o l u t e measures of r e s p i r a t o r y movements, made p o s s i b l e by a technique known as r e s p i r a t o r y - i n d u c t i v e p l e t h y s -mography ( T o b i n , 1986), would a l l o w f u t u r e s t u d i e s to unequ ivo -c a l l y d e s c r i b e the c o n t r i b u t i o n made by each r e s p i r a t o r y compartment to v e n t i l a t i o n under v a r i o u s s t r e s s c o n d i t i o n s . In 8 4 a d d i t i o n , t h i s technique would enable r e s e a r c h e r s to o b t a i n a n o n i n v a s i v e measure of t i d a l volume which , when m u l t i p l i e d by b r e a t h i n g r a t e , would p r o v i d e a s i n g l e index of v e n t i l a t i o n changes . When r e c o r d e d s i m u l t a n e o u s l y wi th h e a r t ra t e and other c a r d i o v a s c u l a r i n d i c e s , t h i s s i n g l e measure of v e n t i l a t i o n would permi t a more d e t a i l e d examinat ion of c a r d i o - r e s p i r a t o r y i n t e r -a c t i o n s than i s p o s s i b l e wi th the i n v a s i v e procedures now i n use . A study i s now needed which u t i l i z e s the r e s p i r a t o r y -i n d u c t i v e plethysmography technique to assess changes i n the b r e a t h i n g mode, volume, r a t e , and v a r i a b i l i t y vary of d i f f e r e n t c l i n i c a l p o p u l a t i o n s as they respond to s t a n d a r d i z e d p s y c h o l o g i c a l c h a l l e n g e s or s t r e s s o r s . A comparison of e s s e n t i a l h y p e r t e n s i v e s wi th matched normal s u b j e c t s , f o r i n s t a n c e , c o u l d i n d i c a t e whether or not p a r t i c u l a r b r e a t h i n g p a t t e r n s are somehow a s s o c i a t e d wi th h y p e r t e n s i o n . L i k e w i s e , comparing the c a r d i o - r e s p i r a t o r y responses of a n x i e t y d i s o r d e r p a t i e n t s w i th those of normal i n d i v i d u a l s might suggest whether or not a b e r r a n t b r e a t h i n g p a t t e r n s are c h a r a c t e r i s t i c of the former group. I f so, the type of s t r e s s - i n d u c e d r e s p i r a t o r y changes observed i n that study c o u l d be used i n d e c i d i n g on the most s u i t a b l e form of r e l a x a t i o n / b r e a t h i n g c o n t r o l t r a i n i n g f o r such i n d i v i d u a l s . Whether r e l a x e d b r e a t h i n g techniques can a t t enuate autonomic a r o u s a l i s a q u e s t i o n that s t i l l needs to be r e s o l v e d 85 e m p i r i c a l l y . Once a g a i n , techniques l i k e r e s p i r a t o r y p l e t h y s -mography or dual s t r a i n gauges f a s t e n e d around each r e s p i r a t o r y compartment c o u l d be used to n o n i n v a s i v e l y monitor the a b i l i t y of i n d i v i d u a l s to produce the d e s i r e d b r e a t h i n g changes . 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P s y c h o p h y s i o l o g y , 21, 326-33. S c h u l t e , W., & von E i f f , A. (1985) . The Importance of c a r d i o v a s c u l a r r e a c t i v i t y to d i f f e r e n t types of s t r e s s for the development of h y p e r t e n s i o n . In A. S t e p t o e , H . Rueddel & H . Neus ( E d s . ) , C l i n i c a l and M e t h o d o l o g i c a l Issues l n  C a r d i o v a s c u l a r P s y c h o p h y s i o l o g y . New Y o r k : S p r i n g e r V e r l a g , 53-65. Sharp , J . , G o l d b e r g , N . , D r u z , W. , & Danon, J . (1975). R e l a t i v e c o n t r i b u t i o n s of r i b c a g e and abdomen to b r e a t h i n g i n normal s u b j e c t s . J o u r n a l of A p p l i e d P h y s i o l o g y , 3 9 , 608-18 . Shepherd , J . (1981) . The lungs as r e c e p t o r s i t e s f o r c a r d i o v a s c u l a r r e g u l a t i o n . C i r c u l a t i o n , 63, 1-10. Shepherd , J . , & Vanhout te , P. (1979) . The Human C a r d i o v a s c u l a r  Sys tern. New York: Raven P r e s s . 91 S h e r w o o d , A., A l l e n , M., O b r i s t , P., & L a n g e r , A. ( 1 9 8 6 ) . E v a l u a t i o n o f b e t a - a d r e n e r g i c i n f l u e n c e s on c a r d i o v a s c u l a r a n d m e t a b o l i c a d j u s t m e n t s t o p h y s i c a l a n d p s y c h o l o g i c a l s t r e s s . P s y c h o p h y s i o l o g y . 2 3 . 8 9 - 1 0 4 . S i n g h , B. ( 1 9 8 4 ) . V e n t i l a t o r y r e s p o n s e t o c a r b o n d i o x i d e : I I . S t u d i e s i n n e u r o t i c p s y c h i a t r i c p a t i e n t s a n d p r a c t i t i o n e r s o f T r a n s c e n d e n t a l M e d i t a t i o n . P s y c h o s o m a t i c M e d i c i n e , 4 6 , 3 4 7 - 6 2 . S r o u f e , L . ( 1 9 7 1 ) h e a r t r a t e 6 4 8 - 5 5 . E f f e c t s o f d e p t h a n d r a t e o f b r e a t h i n g on a n d h e a r t r a t e v a r i a t i o n . P s y c h o p h y s i o l o g y , j $ , S t e p t o e , A. ( 1 9 8 5 ) . T h e o r e t i c a l b a s e s f o r t a s k s e l e c t i o n i n p s y c h o p h y s i o l o g y . I n A. S t e p t o e , H. R u e d d e l & ) , C l i n i c a l a n d M e t h o d o l o g i c a l I s s u e s l n c a r d i o v a s c u l a r H. N e u s ( E d s , C a r d i o v a s c u l a r P s y c h o p h y s i o l o g y . New Y o r k : S p r i n g e r V e r l a g , 6-15. S u e s s , W., A l e x a n d e r , A., S m i t h , D., e t a l . ( 1 9 8 3 ) . E f f e c t s o f p s y c h o l o g i c a l s t r e s s on r e s p i r a t i o n : A p r e l i m i n a r y s t u d y o f a n x i e t y a n d h y p e r v e n t i l a t i o n . P s y c h o p h y s i o l o g y , 1 7 , 5 3 5 - 4 0 . S v e b a k , S., D a l e n , p s y c h o l o g i c a l s o m a t i c a n d 4 0 3 - 0 9 . K S t o r f j e l l , ( 1 9 8 1 ) The s i g n i f i c a n c e o f t a s k - i n d u c e d t o n i c c h a n g e s i n a u t o n o m i c a c t i v i t y . P s y c h o p h y s i o l o g y , 1 8 , T o b i n , M., C h a d h a , T., J e n o u r i , G., e t a l . ( 1 9 8 3 ) . p a t t e r n s : I . N o r m a l s u b j e c t s . Che s t , 84 , 2 0 2 - 0 5 . B r e a t h i n g T o b i n , M. ( 1 9 8 6 ) . N o n i n v a s i v e e v a l u a t i o n m o v e m e n t . I n M. N o c h o m o v i t z & N. N o n i n v a s i v e R e s p i r a t o r y M o n i t o r i n g . New o f r e s p i r a t o r y C h e r n l a c k ( E d s ) . Y o r k : C h u r c h h i l l L i v i n g s t o n e , 2 9 - 5 7 T u r n e r C a r r o l l , D, m e t a b o l i c r e s p o n s e s t o m e t a b o l i c a l l y - e x a g g e r a t e d C o u r t n e y , H. ( 1 9 8 3 ) . ' S p a c e I n v a d e r s ' : An c a r d i a c C a r d i a c a n d i n s t a n c e o f a d j u s t m e n t ? P s y c h o p h y s i o l o g y , 2 0 , 5 4 4 - 4 9 , T u r n e r , J . , C a r r o l l , D., H e l l a w e l l , J & M o r g a n , R. ( 1 9 8 5 ) . A d d i t i o n a l h e a r t r a t e d u r i n g a c u t e p s y c h o l o g i c a l c h a l l e n g e : T h e e f f e c t s o f l e v e l o f d i f f i c u l t y . P a p e r p r e s e n t e d a t t h e S o c i e t y f o r P s y c h o p h y s i o l o g i c a l R e s e a r c h , M o n t r e a l . V a s e y , M., & T h a y e r , p o s i t i v e s i n P s y c h o p h y s i o l o g y : 2 4 , 4 7 9 - 8 6 . J . ( 1 9 8 7 ) . T h e c o n t i n u i n g p r o b l e m o f f a l s e r e s p e a r t e d m e a s u r e s o f ANOVA i n A m u l t i v a r i a t e s o l u t i o n . P s y c h o p h y s i o l o g y , 92 W a l l a c e , R . , & Benson, H. (1972) . The p h y s i o l o g y of m e d i t a t i o n . S c i e n t i f i c Amer ican , 226, 84-90. W a l l a c e , R . , Benson, H . , & W i l s o n , A. (1971) . A wakeful hypometabol ic p h y s i o l o g i c a l s t a t e . American J o u r n a l of P h y s i o l o g y , 221, 795-99. Warren, P . , & F i s c h b e i n , C. (1980) . I d e n t i f i c a t i o n of l a b i l e hyper t e n s i o n i n c h i l d r e n of h y p e r t e n s i v e p a r e n t s . Communications i n M e d i c i n e , 44, 77-79. West, J . (1974) . R e s p i r a t o r y P h y s i o l o g y : The E s s e n t i a l s . B a l t i m o r e : W i l l i a m s & W i l k i n s . Wood, D . , Sheps , S . , E l v e b a c k , L . , & S h i r g e r , A . (1984) . C o l d pre s sor t e s t as a p r e d i c t o r of h y p e r t e n s i o n . Hyper tens i on, 6, 301-06. 9 3 Appendix A H e a l t h and F i t n e s s Q u e s t i o n n a i r e 1 . Age: . . . . years 2. Weight . . . . l b s / k g ( C i r c l e u n i t used) 3. H e i g h t . . . . f t . i n . / c m ( C i r c l e u n i t used) 4. Do you smoke? Yes/No ( C i r c l e answer) I f yes , how much? C i gare t t e s /day 0 - 1 0 11 - 20 21 - 30 30 + 5. In the past 3 months, how o f ten on average have you e x e r c i s e d v i g o r o u s l y ( i . e . at l e a s t 20 minutes of cont inuous e x e r t i o n ) ? . . . 4 or more times per week . . . 1-3 times per week . . . seldom or i r r e g u l a r l y 6. What a c t i v i t i e s does the above apply to? (Rank order f o r frequency of p a r t i c i p a t i o n ) 7. Do you s u f f e r from any of the f o l l o w i n g p h y s i c a l d i s o r d e r s ? Yes/No a) asthma ( p r e s e n t l y a c t i v e ) b) r e s p i r a t o r y i n f e c t i o n c) pulmonary or e s s e n t i a l h y p e r t e n s i o n 8. Do e i t h e r of your n a t u r a l parents have a medica l h i s t o r y of e s s e n t i a l h y p e r t e n s i o n ( i . e . h igh b lood p r e s s u r e ) , coronary h e a r t d i sease or m y o c a r d i a l i n f a r c t i o n ( i . e . h e a r t a t t a c k ) . Yes/No ( C i r c l e answer) 9 4 A p p e n d i x B E x p e r i m e n t I n t r o d u c t i o n W e l c o m e t o t h e l a b My name i s I ' l l be w o r k i n g w i t h y o u t o d a y i n t h i s e x p e r i m e n t . Why d o n ' t y o u make y o u r s e l f c o m f o r t a b l e i n t h e a r m c h a i r w h i l e I g i v e y o u a n i d e a o f w h a t w e ' l l be d o i n g o v e r t h e n e x t 45 m i n u t e s . As y o u ' l l r e c a l l f r o m o u r p h o n e c o n v e r s a t i o n t h e o t h e r d a y , y o u w e r e a s k e d t o p a r t i c i p a t e i n a s t u d y on how y o u r b o d y a d j u s t s u n d e r c o n d i t i o n s t h a t some p e o p l e c o n s i d e r s t r e s s f u l o r c h a l -l e n g i n g . One o t h e r t h i n g I a s k e d y o u a t t h a t t i m e was t o r e f r a i n f r o m d r i n k i n g a n y c a f f e i n a t e d o r a l c o h o l i c b e v e r a g e s , s m o k i n g , o r d o i n g s t r e n u o u s e x e r c i s e i n t h e 2 h o u r s p r e c e d i n g t h e e x p e r i m e n t . T h i s i s q u i t e i m p o r t a n t a s s u c h t h i n g s c a n g i v e us a d i s t o r t e d p i c t u r e o f how y o u r b o d y m i g h t o r d i n a r i l y r e s p o n d t o t h e 3 t a s k s o f t h i s s t u d y . H a v e y o u m a n a g e d t o f o l l o w t h e s e i n s t r u c t i o n s ? G r e a t ! I t ' s a l s o i m p o r t a n t f o r u s t o know w h e t h e r o r n o t y o u a r e p r e s e n t l y b o t h e r e d by a n y o f t h e h e a l t h p r o b l e m s l i s t e d o n t h i s q u e s t i o n n a i r e . <Hand s u b j e c t H e a l t h & F i t n e s s Q u e s t i o n n a i r e > . A l s o i n c l u d e d o n t h i s i n v e n t o r y a r e some q u e s t i o n s a b o u t y o u r e x e r c i s e a n d s m o k i n g h a b i t s a n d y o u r f a m i l y ' s h i s t o r y o f c a r d i o v a s c u l a r d i s o r d e r s . P l e a s e r e s p o n d t o t h e m a s w e l l . ********** I f t h e s u b j e c t a n s w e r s a f f i r m a t i v e l y t o one o r m o r e o f t h e q u e s t i o n s r e : r e s p i r a t o r y p r o b l e m s , t h e n t h a n k h i m f o r v o l u n -9 5 t e e r i n g but s ta t e that because of a p o s s i b l e r i s k to t h e i r h e a l t h and c o n t a m i n a t i o n of the data the experiment must be d i s c o n t i n u e d . ********** F i n e ! Now I'm sure y o u ' r e wondering what t h i s experiment i n v o l v e s . F i r s t of a l l , I ' l l be a t t a c h i n g the m o n i t o r i n g equipment that w e ' l l use to r e c o r d your body's responses throughtout the exper iment . I ' l l be i n the room on the other s ide of t h i s one-way m i r r o r where the m o n i t o r i n g equipment i s k e p t . A f t e r the equipment i s a t t a c h e d and I know i t ' s working c o r r e c t l y , y o u ' l l have 10 minutes to s imply r e l a x and get used to the equipment. You can read these Herman car toons i f you l i k e . T h e r e ' s a c l o c k on the tab le as w e l l f o r your conven ience . At the end of the r e s t p e r i o d , y o u ' l l r e c e i v e some more d e t a i l e d I n s t r u c t i o n s on what the f i r s t task i n v o l v e s . I ' l l come i n t o the room at that p o i n t to g ive these i n s t r u c t i o n s to you and a l s o to see that e v e r y t h i n g i s going okay. The f i r s t task Invo lves a b r i e f p h y s i c a l c h a l l e n g e . Y o u ' l l have a few minutes to r e s t a f t e r the f i r s t task before the second one - a mental c h a l l e n g e task - b e g i n s . Once a g a i n , more d e t a i l e d i n s t r u c t i o n s w i l l be g iven before you s t a r t i t . The same holds true for the t h i r d ta sk . Between tasks y o u ' l l be g iven a few minutes to r e l a x and a l s o to complete a b r i e f q u e s t i o n n a i r e . A f t e r the l a s t r e s t p e r i o d , I ' l l r e t u r n to d i s c o n n e c t the 96 e q u i p m e n t and g i v e you some f e e d b a c k on what y o u r r e s p o n s e s to the d i f f e r e n t c o n d i t i o n s were l i k e . Any q u e s t i o n s so f a r ? Okay. W h i l e I'm a t t a c h i n g the e q u i p m e n t , why d o n ' t you r e a d o v e r t h i s c o n s e n t f o r m . I f you f e e l c o m f o r t a b l e a b o u t c o n t i n u i n g w i t h the e x p e r i m e n t , go ahead and s i g n i t . A g a i n , i f you have a q u e s t i o n , a s k me. < S t a t e the f o l l o w i n g w h i l e a t t a c h i n g the e q u i p m e n t : > 1. I n o r d e r t o a t t a c h e l e c t r o d e s t o y o u r c h e s t f o r m o n i t o r i n g y o u r h e a r t b e a t , I ' l l have t o a s k you to l i f t y o u r s h i r t . I ' l l be c l e a n i n g t he s k i n w i t h a l c o h o l and f i l l i n g t h e e l e c t r o d e s w i t h a c o n d u c t i v e p a s t e i n o r d e r to o b t a i n a c l e a r s i g n a l . T h e r e i s a b s o l u t e l y no d a n g e r of e l e c t r i c s h o c k s w i t h t h i s a p p a r a tu s. 2. T h i s f i n g e r p h o t o p l e t h y s m o g r a p h m e a s u r e s b l o o d f l o w t o y o u r f i n g e r . W h i l e i t ' s on, p l e a s e k e e p y o u r f i n g e r and hand move-ments t o a minimum. i 3. I'm a t t a c h i n g two s t r a i n gauges t o y o u , one a r o u n d y o u r c h e s t and the o t h e r a r o u n d y o u r abdomen. As you b r e a t h i n and o u t , t h e amount of s t r e t c h i n t h e s e t u b e s w i l l be m e a s u r e d . P l e a s e b r e a t h e o u t d e e p l y now so t h a t I c a n f a s t e n them. Good. '•91; Now that a l l the equipment i s a t t a c h e d , we're j u s t about ready to beg in the a d a p t a t i o n phase. For your i n f o r m a t i o n , the two rooms are connected by i n t e r c o m : i f you have any ques t ions at any t ime, ask them and I ' l l respond over the i n t e r c o m . Once a g a i n , you have the r i g h t to d i s c o n t i n u e t h i s exper iment at any time i f you so choose . Okay. I'm going to the other room to c a l i b r a t e the equipment. Make y o u r s e l f comfor tab le f o r the next few minutes . The Herman car toons are there f o r you to read but p l ease keep your movements to a minimum. ,98-Appendix C Consent Form I , , agree to p a r t i c i p a t e as a s u b j e c t i n the r e s e a r c h p r o j e c t e n t i t l e d " C a r d i o - r e s p i r a t o r y responses to mental c h a l l e n g e " conducted i n the C a r d i o v a s c u l a r P s y c h o p h y s i o l o g y L a b , U . B . C , under the d i r e c t i o n of Dr . W. L i n d e n . The procedures of t h i s 45 -minute long study have been adequate ly e x p l a i n e d to me. As I understand i t , t h i s study i s concerned wi th c a r d i o v a s c u l a r and r e s p i r a t o r y change d u r i n g three b r i e f p h y s i c a l and mental t a s k s . I unders tand that I may re fuse to p a r t i c i p a t e or withdraw from t h i s study at any t ime. I a l s o r e a l i z e that the data o b t a i n e d from my p a r t i c i p a t i o n i n t h i s study are s t r i c t l y c o n f i d e n t i a l : a l though i t may be used i n f u t u r e s t u d i e s , there w i l l be no i d e n t i f i c a t i o n of me p e r s o n a l l y on any permanent r e c o r d s . F u r t h e r m o r e , I have been g iven the o p p o r t u n i t y to ask ques t ions p e r t a i n i n g to the procedures of t h i s study and my r i g h t s as a p a r t i c i p a n t and I am s a t i s f i e d wi th the answers r e c e i v e d . Wi tness Research P a r t i c i p a n t Da te 99, Appendix D Cold Pressor I n s t r u c t i o n s We are ready to begin the f i r s t task. T h i s task i n v o l v e s p u t t i n g your r i g h t hand i n t h i s bucket of i c e water and keeping i t there f o r 1 minute. So f a r , a l l of our subjects have managed to complete t h i s task f o r the f u l l minute but you may, i f you wish, remove your hand at any time should you f e e l e x c e s s i v e d i s c o m f o r t . I f you do wish to remove your hand from the water, please speak up and l e t me know. I ' l l hear you over the intercom. Please wait f o r my i n s t r u c t i o n before p u t t i n g your hand i n the water. I w i l l enter the room again when the minute i s up. At that time, I ' l l ask you to complete a b r i e f q u e s t i o n -n a i r e before beginning another 10 minute r e s t p e r i o d . Do you have any questions? Okay, remember to wait f o r my s i g n a l before be g i n n i n g . 100 Appendix E Mental A r i t h m e t i c I n s t r u c t i o n s Over the next 10 minutes , a s e r i e s of a r i t h m e t i c problems w i l l be presented to you over the v ideo screen i n f r o n t of you. Each problem w i l l be presented for 10 seconds . You must determine what the c o r r e c t answer i s and w r i t e I t down on the answer sheet before the next problem i s p r e s e n t e d . There won't be any breaks between problems so y o u ' l l have to c o n c e n t r a t e . So f a r , around 90% of our s u b j e c t s have got ten scores of 75% c o r r e c t or b e t t e r on these problems . I ' l l l e t you know how w e l l you d i d at the end of the s tudy . I f you d o n ' t respond to a problem, I ' l l have to c o n s i d e r i t an e r r o r . Any q u e s t i o n s so far? Good! At the end of the 10 minute t a s k , I ' l l r e t u r n and ask you to f i l l out the next q u e s t i o n n a i r e that y o u ' l l f i n d face down on the tab le to your r i g h t . A f t e r comple t ing t h i s , you can cont inue to r e s t q u i e t l y for the remainder of the 5 minute break . i o i Appendix F Pos t - exper iment Q u e s t i o n n a i r e You have completed a l l the tasks of t h i s s tudy . We would l i k e to know what you thought of the e x p e r i e n c e . P lease c i r c l e on the f o l l o w i n g s c a l e s the s i n g l e number that best r e p r e s e n t s your view. How do you ra te your performance on tasks i n comparison to other people background? the mental a r i t h m e t i c of your age and a l o t worse equa l a l o t b e t t e r 2. P lease i n d i c a t e wi th a " / " how s t r e s s f u l each task was not at a l l s t r e s s f u l very s t r e s s f u l Cold Math 1 Ma th 2 Did you e x p e r i e n c e any n o t i c e a b l e changes the 3 tasks? I f so, I n d i c a t e wi th an "X" o c c u r r e d i n each of the t a s k s . i n your body which one's d u r i n g Cold Math 1 Math 2 Tense muscles P e r s p i r i n g / S w e a t y palms Yawning /Shor t of b r e a t h Rapid or pounding h e a r t beat D i z z i n e s s / l i g h t h e a d e d n e s s Troub le c o n c e n t r a t i n g T i n g l i n g i n hands, f e e t or face •102. Appendix G D e b r i e f i n g S c r i p t The exper iment i s now o v e r . Perhaps you have some ques t ions for me as I d i s c o n n e c t the r e c o r d i n g apparatus? A f t e r I'm f i n i s h e d t h a t , I ' l l g ive you a summary of what e x a c t l y we are l o o k i n g a t i n t h i s experiment? One purpose of t h i s study i s p r i m a r i l y to c o r r e l a t e changes i n the way people breathe i n s t r e s s f u l s i t u a t i o n s wi th t h e i r c a r d i o v a s c u l a r r e s p o n s e s , such as h e a r t ra t e and b lood flow to the e x t r e m i t i e s . We are e s p e c i a l l y i n t e r e s t e d i n the c o n t r i b u -t i o n that both the r i b c a g e and abdomen make to your b r e a t h i n g . I t ' s known that these two compartments a c t i n d e p e n d e n t l y yet to some degree i n synchrony l n the process of drawing f r e s h a i r i n t o the lungs and then e x h a l i n g the used a i r . Most people appear to breathe more wi th t h e i r r i b c a g e than with t h e i r abdomen when t h e y ' r e s i t t i n g or s t a n d i n g . The oppos i t e i s true when t h e y ' r e l y i n g down. I f y o u ' r e b r e a t h i n g most ly by moving your r i b c a g e i n and out then your b r e a t h i n g mode i s s a i d to be t h o r a c i c . Some people appear to breathe more t h o r a c l c l y than o ther s. In t h i s exper iment , we expected p e o p l e ' s b r e a t h i n g mode to s h i f t towards even g r e a t e r t h o r a c i c dominance as they c o n t i n u e d at a c h a l l e n g i n g ta sk . T h i s e f f e c t was expected to be more .103'= marked on the d i f f i c u l t mental a r i t h m e t i c task than on the e a s i e r one. The reason f o r t h i s change i s t h a t s t r e s s appears to e l i c i t i n c r e a s e d muscle t e n s i o n throughout one's body -i n c l u d i n g the abdomen. When te n s e , your abdomen c a n ' t move as f r e e l y . In o r d e r to keep up the volume of i n s p i r e d a i r t h a t your body needs to f u n c t i o n n o r m a l l y , we e x p e c t t h a t your body w i l l compensate by making g r e a t e r use of r i b c a g e movement and/or i n c r e a s i n g the f r e q u e n c y of b r e a t h i n g . Both of these s t r a t e g i e s are r e p o r t e d to r e q u i r e g r e a t e r energy e x p e n d i t u r e than b r e a t h i n g p r e d o m i n a n t l y w i t h one's abdomen. A second purpose of t h i s study i s to determine whether or not people who show exaggerated h e a r t r a t e i n c r e a s e s to one type of s t r e s s o r a l s o e x p e r i e n c e g r e a t e r t h o r a c i c dominance than ot h e r i n d i v i d u a l s d u r i n g o t h e r s t r e s s o r s . The c o l d p r e s s o r t e s t responses are used to s e p a r a t e people i n t o h i g h and low h e a r t r a t e r e a c t i v i t y groups. The b r e a t h i n g p a t t e r n s of these people are then compared to see i f they d i f f e r to any e x t e n t . I f we f i n d t h a t h i g h h e a r t r a t e r e a c t o r s a l s o b r e a t h more t h o r a c i c l y than moderate or low r e a c t o r s then we have a b e t t e r b a s i s f o r a r g u i n g t h a t d i a p h r a g m a t i c b r e a t h i n g i s a u s e f u l s t r a t e g y to teach f o r r e d u c i n g a r o u s a l . Any q u e s t i o n s about what I've s a i d so f a r ? I can show you some of your raw data i f you l i k e . U n f o r t u n a t e l y , i t w i l l be d i f f i c u l t to understand i n i t s p r e s e n t form but you can get an i d e a of what i t l o o k s l i k e and what k i n d •104 ;• of equipment we use f o r o b t a i n i n g i t . I ' d l i k e to thank you for p a r t i c i p a t i n g i n t h i s s tudy . You've been a b i g h e l p . Remember, a l l of your data are s t r i c t l y c o n f i d e n t i a l : your name w i l l be omit ted from a l l permanently r e c o r d s . I have one l a s t reques t to make. W i l l you agree to keep the d e t a i l s of t h i s study a s e c r e t for the next two months. D u r i n g that t ime, w e ' l l be a s k i n g other s tudents l i k e y o u r s e l f to p a r t i c i p a t e i n t h i s s tudy . I f they were to know what to expect ahead of t ime, t h e i r data would be use l e s s to us . Thank you for a g r e e i n g to do so. F i n a l l y , i f you would l i k e to know what the r e s u l t s of t h i s study a r e , you are welcome to c o n t a c t Dr . Wolfgang L i n d e n or Aaron H a l t , a graduate s tudent i n t h i s department , sometime i n the f a l l of t h i s y e a r . Thanks aga in f o r p a r t i c i p a t i n g today. •I 05 Appendix H P o s t - t a s k Q u e s t i o n n a i r e P lease answer the f o l l o w i n g ques t ions by p u t t i n g a s l a s h ("/") at the p o i n t on the l i n e that bes t r e f l e c t s your f e e l i n g s d u r i n g the p r e v i o u s task . 1. How d i f f i c u l t d i d you f i n d the task? no t a t a l l very d i f f i c u l t d i f f i c u l t 2. How w e l l do you th ink you d id a t the task? no t w e l l very at a l l w e l l How aroused or p h y s i c a l l y "keyed up" d i d you f i n d y o u r s e l f d u r i n g the task? not at a l l aroused very much aroused Appendix I Average l e v e l s of p h y s i o l o g i c a l a c t i v i t y d u r i n g b a s e l i n e and easy and hard mental a r i t h m e t i c (MA). Condi t i o n V a r i a b l e B a s e l i n e Easy MA Hard MA HR (bpm) 68 . 7 ( 9. 6) 75 .0 ( 10 .8) 80 .8 ( 13 .1) TWA (mm/mv) 413 .0 (194. 4) 392 .8 ( 183 .0) 383 .5 ( 180 .6) BVP (mm/mv) 997 . 6 ( 395 . 7) 672 .9 ( 367 .6) 606 .5 ( 356 .6) PTT(msec) 347 .9 ( 24. 6) 335 .3 ( 28 . 3) 331 .6 ( 29 .1) RR (cpm) 15 . 3 ( 3. 5) 17 .7 ( 2 .9) 19 .5 ( 3 .3) T:A (%) 100 .0 ( 43. 8) 115 .5 ( 54 .6) 121 . 1 ( 56 .1) RA (mm/mv) 20 . 7 ( 6. 4) 21 .8 ( 6 .8) 22 .3 ( 8 .4) AA (mm/mv) 23 . 1 ( 8. 3) 22 .9 ( 8 .0 22 • 0 ( 8 .7) RAV (mm/mv) 5 . 7 ( 4. 2) 10 .6 ( 4 .7) 10 .8 ( 4 .0) AAV (mm/mv) 4 . 7 ( 3. 5) 6 . 7 ( 2 .9) 8 . 1 ( 3 .6) 

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