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The effects of endurance training upon ratings of perceived exertion Carton, Richard Lee 1983

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THE EFFECTS OF ENDURANCE TRAINING UPON RATINGS OF PERCEIVED EXERTION by RICHARD LEE CARTON B.A., University Of Western Ontario,1980 A. THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PHYSICAL EDUCATION in : THE FACULTY OF GRADUATE STUDIES Department Of Sport Science,School Of Physical Education We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September 1983 © Richard Lee Carton, 1983 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r an advanced degree at the U n i v e r s i t y of B r i t i s h C olumbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department of S p o r t S c i e n c e The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date: 28 September, 1983 i i A b s t r a c t The purpose of t h i s i n v e s t i g a t i o n was t o examine d i f f e r e n c e s i n r a t i n g s of p e r c e i v e d e x e r t i o n (RPE) a t e q u i v a l e n t p e r c e n t a g e s of s u b j e c t s maximal work c a p a c i t y ( e q u i v a l e n t r e l a t i v e w o r k l o a d s ) , b e f o r e and: a f t e r endurance t r a i n i n g . E x p e r i m e n t a l (N=13) and c o n t r o l (N=13) groups c o m p r i s e d of h e a l t h y male s u b j e c t s (x age=21.2 y e a r s , VO2max=50.4 ml - k g " 1 • m i n " 1 ) v o l u n t e e r e d t o p a r t i c i p a t e i n the stu d y . A l l s u b j e c t s completed p r o g r e s s i v e t r e a d m i l l t e s t s a t a p p r o x i m a t e l y the same time of day, p r i o r t o and a t the t e r m i n a t i o n of the 9-week study p e r i o d . Running commenced a t 8 km-hr - 1 and i n c r e a s e d by 0.8 km-hr" 1 per minute t o v o l i t i o n a l f a t i g u e . V a l u e s f o r RPE were o b t a i n e d a t 30 second i n t e r v a l s . The e x e r c i s e program c o n s i s t e d of t r e a d m i l l r u n n i n g , 3 days per week, a t workloads which were s y s t e m a t i c a l l y p r o g r e s s e d ( h e a r t rate=171.5 ± 5.7, x ± SD). S t a t i s t i c a l a n a l y s i s t o measure changes i n RPE over time was performed u s i n g a 2x2x5 ANOVA w i t h r e p e a t e d measures on the t h i r d f a c t o r . R e d u c t i o n s i n RPE averaged 14% and 17% a t a g i v e n V02 and v e l o c i t y , r e s p e c t i v e l y , i n the t r a i n i n g group. At e q u i v a l e n t r e l a t i v e w o r k l o a d s , d e c r e a s e s i n RPE averaged 7.2% f o r V02 and 12.8% f o r v e l o c i t y . When m o d i f i c a t i o n s i n RPE i n the c o n t r o l group were c o n s i d e r e d , the changes i n RPE i n the t r a i n i n g group were not s i g n i f i c a n t (p<0.05). These f i n d i n g s emphasize the n e c e s s i t y of a c o n t r o l group i n s t u d i e s which employ RPE as a dependent v a r i a b l e . D e s p i t e the decrements i n RPE i n the c o n t r o l group, changes i n RPE i n the t r a i n i n g group d i d approach s i g n i f i c a n c e a t f i x e d v e l o c i t i e s (p<0.08) and r e l a t i v e v e l o c i t i e s (p<0.06). These decreases were greatest at moderate workloads (55-75% of maximal capacity), and appeared to be due to a reduction in l o c a l e f f o r t cues. It was concluded that the influence of tr a i n i n g upon RPE at r e l a t i v e workloads is dependent upon the magnitude of corresponding physiological adaptations. The results also support the view that the changes in RPE which become apparent with training are related to the method of analysis which i s used. T a b l e of C o n t e n t s Abstract. i i L i s t of T a b l e s v L i s t of F i g u r e s v i Acknowledgements v i i I . INTRODUCTION . ..1 I I . REVIEW OF THE LITERATURE 8 I . DEVELOPMENT AND USE OF RATING SCALES 8 I I . PHYSIOLOGICAL BASIS FOR RPE ..18 I I I . NON-PHYSIOLOGICAL INPUT INTO RPE ..43 IV. THE EFFECTS OF EXERCISE UPON RPE ..48 I I I . METHODS 58 SUBJECTS • 58 PROCEDURES ...59 TRAINING REGIMEN 60 MEASUREMENTS 60 STATISTICAL ANALYSES 62 IV. RESULTS 63 V. DISCUSSION '. 76 V I . SUMMARY AND CONCLUSIONS 89 BIBLIOGRAPHY 92 APPENDIX A - BORG 15-POINT SCALE FOR RATING PERCEIVED EXERTION .108 APPENDIX B - 9-POINT SCALE FOR RATING PERCEIVED EXERTION 109 APPENDIX C - BORG 10-POINT SCALE FOR RATING OF PERCEIVED EXERTION 110 V L i s t of T a b l e s 1. P h y s i c a l C h a r a c t e r i s t i c s of S u b j e c t s 64 2. Summary of H y p o t h e s i z e d P h y s i o l o g i c a l T r a i n i n g E f f e c t s 65 3. Summary of Non-Hypothesized P h y s i o l o g i c a l T r a i n i n g E f f e c t s 66 4. Summary of T r a i n i n g E f f e c t s Upon S e l e c t e d P e r c e p t u a l V a r i a b l e s 67 5. Summary of E f f o r t R a t i n g s 69 6. P e r c e n t R e d u c t i o n s i n RPE F o l l o w i n g 9 Weeks of T r a i n i n g 71 7. Summary of H y p o t h e s i s T e s t i n g 71 v i L i s t of F i g u r e s 1. Mean RPE a t A b s o l u t e Workloads Based Upon V02 72 2. Mean RPE a t R e l a t i v e Workloads Based Upon V02 73 3. Mean RPE a t A b s o l u t e Workloads Based Upon V e l o c i t y ...74 4. Mean RPE a t R e l a t i v e Workloads Based Upon V e l o c i t y 75 v i i Acknowledgement I would l i k e t o thank the members of my committee, Dr. E.C. Rhodes, Dr. R.W. S c h u t z , Dr. S.R. Brown, and Dr. R.E. Mosher, f o r t h e i r g uidance i n the p r e p a r a t i o n of t h i s t h e s i s , and Dr. G. R o b e r t s o n f o r h i s t e c h n i c a l a s s i s t a n c e . Moreover, I am g r e a t l y i n d e b t e d t o a l l of the s t u d e n t s who v o l u n t e e r e d t o p a r t i c i p a t e i n the s t u d y , f o r t h e i r u n s e l f i s h committment of time and energy. Thanks a r e a l s o extended t o Wade S. Parkhouse, w i t h o u t who's encouragement, h e l p and f r i e n d s h i p t h i s achievement may not have been p o s s i b l e . F i n a l l y , I w i s h t o acknowledge my g r a t i t u d e t o my Mother, f o r a l l of her suf f e r i n g . 1 I . INTRODUCTION S u b j e c t i v e , s e l f - r e p o r t e d e s t i m a t e s of e f f o r t e x p e n d i t u r e may be q u a n t i f i e d u s i n g r a t i n g s of p e r c e i v e d e x e r t i o n (RPE). As an i n v e s t i g a t i v e t o o l , RPE have proved t o be a u s e f u l a d j u n c t f o r s t u d i e s i n e x e r c i s e p h y s i o l o g y . RPE have been employed t o examine i s s u e s i n v o l v i n g the hormonal (Schnabel et a l . , 1982), m e t a b o l i c (Horstman, 1977) and c i r c u l a t o r y ( W i l l i a m s e t a l . 1981) response t o e x e r c i s e , s u p p l e m e n t i n g o b j e c t i v e l y measured v a r i a b l e s . N e v e r t h e l e s s , RPE have not been used e x t e n s i v e l y i n a p p l i e d s p o r t s c i e n c e . The p e r t i n e n c e of RPE f o r e x e r c i s e p r e s c r i p t i o n has been r e c o g n i z e d ( B o r g , 1982), and su g g e s t s t h a t e x e r c i s e i n t e n s i t y may be r e g u l a t e d t h r o u g h e f f o r t e v a l u a t i o n . However, i t has not been shown t h a t e f f o r t e v a l u a t i o n may be used t o c o n t r o l pace d u r i n g c o m p e t i t i o n . D e s p i t e e v i d e n c e t h a t RPE can be used t o p r e d i c t maximal performance c a p a c i t y (Morgan and Borg, 1976), the r e l a t i o n s h i p between a t h l e t i c achievement and the p e r c e p t i o n of e f f o r t i s not w e l l u n d e r s t o o d . I t has been proposed t h a t s p o r t performance (Morgan e t a l . , 1976) and b e h a v i o u r ( R e j e s k i , 1981) are governed t h r o u g h an i n t e g r a t i o n of r e a l and imagined p h y s i o l o g i c a l and p e r c e p t u a l c u e s . In o t h e r words, d u r i n g s p o r t and a t h l e t i c s , how i n d i v i d u a l s respond i s o f t e n dependent upon what they t h i n k they a r e d o i n g , as w e l l as what they a r e a c t u a l l y d o i n g . T h i s h y p o t h e s i s i s s u p p o r t e d by r e s e a r c h ( B a n i s t e r , 1979; I k a i and S t e i n h a u s , 1961; Ki l b o m e t a l . , 1983) which has shown t h a t p e r c e p t u a l l i m i t a t i o n s may f u n c t i o n as c r i t i c a l d e t e r m i n a n t s of 2 performance. In a d d i t i o n , i t appears t h a t an a b i l i t y t o a c c u r a t e l y m onitor e f f o r t may be one c r i t e r i o n f o r s u c c e s s f u l p a r t i c i p a t i o n i n a t h l e t i c s (Morgan, 1977; Morgan and P o l l o c k , 1977). C o l l e c t i v e l y , t h e s e o b s e r v a t i o n s imply t h a t some a s p e c t of e f f o r t p e r c e p t i o n may have s p e c i f i c r a m i f i c a t i o n s w i t h r e s p e c t t o e x e r c i s e performance. S i n c e a t h l e t e s appear t o p r o c e s s incoming s t i m u l i d i f f e r e n t l y from t h e i r n o n - a c t i v e c o u n t e r p a r t s (Ryan and W a l t e r , 1967), i t may be a n t i c i p a t e d t h a t t r a i n i n g a f f e c t s the se n s o r y response t o e x e r c i s e . S e v e r a l r e p o r t s (Ekblom and G o l d b a r g , 1971; K i l b o m , 1971; Knuttgen et a l . , 1973; Knuttgen e t a l . , 1982; Lewis e t a l . , 1980; P a n d o l f et a l . , 1975) have noted t h a t subsequent t o t r a i n i n g , RPE are lower f o r a b s o l u t e submaximal w o r k l o a d s . P r e v i o u s l o n g i t u d i n a l r e s e a r c h ( D o c k t o r and Sharkey, 1971; Ekblom a n d ; G o l d b a r g , 1971; K i l b o m , 1971.) f a i l e d t o observe m o d i f i c a t i o n s i n the RPE r e p o r t e d by t r a i n e d s u b j e c t s when e x e r c i s e i n t e n s i t y b e f o r e and a f t e r t r a i n i n g was equated i n terms of h e a r t r a t e (HR) or r e l a t i v e m e t a b o l i c s t r e s s (%V02max). However, the e x c l u s i o n of c o n t r o l groups i n t h e s e s t u d i e s l i m i t s the v a l i d i t y of t h e i r f i n d i n g s . F u r t h e r m o r e , r e l a t i v e e x e r c i s e i n t e n s i t i e s which a r e e x p r e s s e d i n terms of V02max or HR are unable t o account f o r l a c t a t e p r o d u c t i o n , c a t e c h o l a m i n e e l e v a t i o n , v e n t i l a t o r y hyperpnea ( A s t r a n d and R o d a h l , 1977) or neuromuscular a l t e r a t i o n s (Stamford and N o b l e , 1974). These v a r i a b l e s may be a f f e c t e d by t r a i n i n g , and c o u l d i n f l u e n c e RPE. R e j e s k i et a l . (1982) d i s p u t e d the v a l i d i t y of an o p e r a t i o n a l d e f i n i t i o n of t r a i n i n g e f f e c t s based e x c l u s i v e l y upon 3 c a r d i o v a s c u l a r a d j u s t m e n t s . In t h e i r s t u d y , t r a i n e d c y c l i s t s who wore t o e - c l i p s were a b l e t o demonstrate lower RPE v a l u e s a t a h i g h e r V02max, compared t o when t o e - c l i p s were_ not used. By showing t h a t p e r i p h e r a l a d a p t a t i o n s may reduce RPE d u r i n g maximal e x e r c i s e , t h e i r f i n d i n g c h a l l e n g e s the i n t e r p r e t a t i o n of p r e v i o u s r e s u l t s which have d e f i n e d t r a i n i n g e f f e c t s s o l e l y i n terms of c a r d i o v a s c u l a r p a r a m e t e r s . Comprehension of the c o n f l i c t i n g e v i d e n c e r e g a r d i n g the e f f e c t s of e x e r c i s e upon RPE c o u l d be improved by e s t a b l i s h i n g the t h e o r e t i c a l b a s i s f o r these a d a p t a t i o n s . To d a t e , few a u t h o r s have a d d r e s s e d t h i s i s s u e . The purpose of the p r e s e n t i n v e s t i g a t i o n was t o examine the e f f e c t s of endurance t r a i n i n g upon RPE a t w o r k l o a d s which are equated on a r e l a t i v e b a s i s , b e f o r e and a f t e r t r a i n i n g . A second o b j e c t i v e was t o compare the changes i n RPE a t workloads based upon V02 t o the changes i n RPE obser v e d when w o r k l o a d was measured i n terms of v e l o c i t y . H y p o t h e t i c a l e x p l a n a t i o n s f o r thes e changes a re a l s o d i s c u s s e d . I f t r a i n i n g i s found t o lower the RPE which a r e a s s o c i a t e d w i t h e q u i v a l e n t r e l a t i v e w o r k l o a d s , a p o t e n t i a l l i n k w i l l have been i d e n t i f i e d between the p e r c e p t i o n of e f f o r t and a t h l e t i c performance. The Problem P r e v i o u s s t u d i e s which have i n v e s t i g a t e d d i f f e r e n c e s i n RPE as a f u n c t i o n of p h y s i c a l c o n d i t i o n i n g have not i n c l u d e d c o n t r o l groups, and have o n l y used c a r d i o v a s c u l a r v a r i a b l e s as a measure of f i t n e s s . T h e r e f o r e , the c u r r e n t study w i l l attempt t o 4 determine i f a s i g n i f i c a n t d i f f e r e n c e e x i s t s between RPE, a t the same r e l a t i v e w o r k l o a d s , based upon V02 and v e l o c i t y , b e f o r e and a f t e r a e r o b i c t r a i n i n g . S i g n i f i c a n c e C l a r i f i c a t i o n of the e f f e c t s of p h y s i c a l t r a i n i n g upon the p e r c e p t i o n of e f f o r t c o u l d improve c u r r e n t u n d e r s t a n d i n g of the f a c t o r s which c o n t r i b u t e t o a t h t l e t i c performance. T h i s knowledge c o u l d have i m p o r t a n t i m p l i c a t i o n s f o r t r a i n i n g and c o m p e t i t i o n p r a c t i c e s . L i m i t a t i o n s 1) R a t i n g s of p e r c e i v e d e x e r t i o n a r e i n f l u e n c e d by the e f f e c t s of n o n - p h y s i o l o g i c a l v a r i a b l e s . A l t h o u g h d i f f e r e n c e s i n the age and sex of the s u b j e c t s , and the time of day of t e s t i n g were c o n t r o l l e d f o r i n t h i s s t u d y , o t h e r f a c t o r s such as m o t i v a t i o n were n o t . 2) The a r t i f i c i a l environment ( l a b o r a t o r y ) of the t e s t i n g w i l l l i m i t the v a l u e of making i n f e r e n c e s , based upon the c u r r e n t f i n d i n g s , about e x e r c i s e i n a f i e l d s e t t i n g . 5 D e l i m i t a t i o n s T h i s s t u d y w i l l be d e l i m i t e d t o : 1) A sample s i z e of 15. 2) The s p e c i f i c i t y of the sample group (young, male, c o l l e g e s t u d e n t s . 3) Sea l e v e l c o n d i t i o n s . 4) L a b o r a t o r y c o n d i t i o n s and t r e a d m i l l t r a i n i n g . 5) To a p r o t o c o l which i n v o l v e s e v a l u a t i n g RPE d u r i n g a p r o g r e s s i v e t r e a d m i l l t e s t , as opposed to a t r e a d m i l l t e s t c o n d ucted at a c o n t i n u o u s w o r k l o a d . 6 Hypotheses 1) The 9-week t r a i n i n g program employed i n t h i s s tudy w i l l r e s u l t i n an i n c r e a s e d work c a p a c i t y , measured by: A) V02max ( l - m i n " 1 ) [ t r a i n i n g group (TG) > c o n t r o l group (CG) ] B) AerT ( 1 - m i n " 1 ) (TG>CG) C) AerT (%V02max) (TG>CG) 2) The 9-week t r a i n i n g program employed i n t h i s study w i l l r e s u l t i n reduced RPE, measured a t : A) Given l e v e l s of V02 (TG>CG) B) E q u i v a l e n t r e l a t i v e l e v e l s of V02 (TG>CG) 3) The 9-week t r a i n i n g program employed i n t h i s study w i l l r e s u l t i n reduced RPE, measured a t : A) B) Give n r u n n i n g v e l o c i t i e s (TG>CG) E q u i v a l e n t r e l a t i v e r u n n i n g v e l o c i t i e s (TG>CG) 7 D e f i n i t i o n of Terms and Symbols Used AerT ( V e n t i l a t o r y a e r o b i c t h r e s h o l d ) - The a e r o b i c t h r e s h o l d i s the oxygen consumption imm e d i a t e l y p r i o r t o t h a t a t which p y r u v a t e p r o d u c t i o n exceeds p y r u v a t e o x i d a t i o n , r e s u l t i n g i n the f i r s t s i g n i f i c a n t e l e v a t i o n i n b l o o d l a c t a t e d u r i n g i n c r e m e n t a l e x e r c i s e . S i n c e a e r o b i c t h r e s h o l d was e v a l u a t e d u s i n g r e s p i r a t o r y exchange v a r i a b l e s , i t i s an i n d i r e c t measure of m e t a b o l i c e v e n t s . For t h i s r e a s o n , i t i s d e f i n e d as the v e n t i l a t o r y a e r o b i c t h r e s h o l d . In many of the s t u d i e s which have been c i t e d , t h i s p h y s i o l o g i c a l p o i n t was, i n f a c t , d e s c r i b e d as the a n a e r o b i c t h r e s h o l d . T h i s study has s e l e c t e d the term a e r o b i c t h r e s h o l d i n co m p l i a n c e w i t h the g u i d e l i n e s f o r t e r m i n o l o g y s u g g e sted by S k i n n e r and M c C l e l l a n (1980) and Kinderman e t a l . (1979). E x c e s s C02 (Excess carbon d i o x i d e ) - E x t r a carbon d i o x i d e e x c r e t e d from the l u n g s , due t o the b u f f e r i n g of b l o o d ac i d e m i a . V02max (Maximal oxygen c o n s u m p t i o n ) - The g r e a t e s t d i f f e r e n c e between the volume of i n s p i r e d oxygen e n t e r i n g the lu n g s and the volume of oxygen l e a v i n g the l u n g s d u r i n g maximal e x e r c i s e . VE (Minute v e n t i l a t i o n ) - The volume of a i r i n s p i r e d or e x p i r e d d u r i n g one minute. RR ( R e s p i r a t o r y r a t e ) - The frequ e n c y of b r e a t h i n g . HR (Heart r a t e ) - A measurement of c a r d i a c f r e q u e n c y . AerT-%V02max A e r o b i c t h r e s h o l d , e x p r e s s e d as a p e r c e n t a g e of V02max. RPE ( R a t i n g s of p e r c e i v e d e x e r t i o n ) - S u b j e c t i v e ' , s e l f -r e p o r t e d e s t i m a t e s of e f f o r t e x p e n d i t u r e . P.PE-%V02max R a t i n g s of p e r c e i v e d e x e r t i o n a t a p e r c e n t a g e of maximal oxygen consumption. RPE-AerT R a t i n g s of p e r c e i v e d e x e r t i o n a t the v e n t i l a t o r y a e r o b i c t h r e s h o l d . Vmax Maximal r u n n i n g v e l o c i t y . E q u i v a l e n t R e l a t i v e Workloads - E x e r c i s e w orkloads which may d i f f e r i n a b s o l u t e v a l u e , but are the same when compared t o the maximal w o r k l o a d which i s c a p a b l e of b e i n g performed. 8 I I . REVIEW OF THE LITERATURE I . Development And Use Of R a t i n g S c a l e s I n i t i a l e x p e r i m e n t a l work i n v o l v i n g the s u b j e c t i v e p e r c e p t i o n of e f f o r t was r e p o r t e d by F u l l e r t o n and C a t t e l l (1892). Two s u b j e c t s were r e q u e s t e d t o e x e r t o n e - h a l f and t w i c e as g r e a t a f o r c e on a hand dynamometer as a s t a n d a r d f o r c e which had been p r e s e n t e d t o them. The at t e m p t s were u n s u c c e s s f u l , and due t o an i n a b i l i t y t o e x p l a i n the f i n d i n g s , e x p e r i m e n t a t i o n was d i s c o n t i n u e d . Stevens and Mack (1959) were the next t o conduct r e s e a r c h i n t o s c a l e s of apparent f o r c e . T h e i r study i n v o l v e d the use of t h r e e d i f f e r e n t s c a l i n g p r o c e d u r e s . These i n c l u d e d r a t i o p r o d u c t i o n ( the s u b j e c t must attempt t o e x e r t a f o r c e which i s a g i v e n r a t i o of a r e f e r e n c e f o r c e ) , magnitude p r o d u c t i o n ( the s u b j e c t must e x e r t a f o r c e which i s a g i v e n magnitude of a r e f e r e n c e f o r c e ) and magnitude e s t i m a t i o n ( the s u b j e c t must e s t i m a t e the magnitude of a f o r c e which i s p r e s e n t e d t o him, i n comparison t o a r e f e r e n c e f o r c e ) . Two d i f f e r e n t methods of f o r c e a p p l i c a t i o n were a l s o u t i l i z e d . These i n c l u d e d f o r c e on a g r i p dynamometer, and f o r c e a p p l i e d , p a s s i v e l y t o s k i n . The a u t h o r s found t h a t i n a l l i n s t a n c e s , the apparent magnitude of s u b j e c t i v e f o r c e grew e x p o n e n t i a l l y w i t h the a p p l i e d f o r c e . A range of 1.3-3.1 was e x h i b i t e d as the exponent of the f u n c t i o n , w i t h mean v a l u e s of 1.7 and 1.1 o b t a i n e d f o r a c t i v e and p a s s i v e 9 a p p l i c a t i o n , r e s p e c t i v e l y . E i s l e r (1962) a l s o found s u b j e c t i v e f o r c e t o i n c r e a s e as a f u n c t i o n of p h y s i c a l f o r c e , and c a l c u l a t e d the v a l u e of the exponent t o be 1.65. H u e t i n g (1965) r e p l i c a t e d t h e s e r e s u l t s i n a s i m i l a r s t u d y . In c o n t r a s t , Cooper et a l . (1979) obs e r v e d a l i n e a r r e l a t i o n s h i p t o e x i s t between p e r c e n t a g e of r e l a t i v e e f f o r t and p e r c e n t a g e of maximum f o r c e i n the a d d u c t o r p o l l i c i s and q u a d r i c e p s muscles d u r i n g i s o m e t r i c c o n t r a c t i o n s . However, the upper l i m i t of f o r c e a p p l i c a t i o n was a r b i t r a r i l y s e t , which may have i n a d v e r t e n t l y d e p r e s s e d the r a t i n g of f o r c e a t near maximum f o r c e . An exponent above 1.0 was shown t o d e s c r i b e the r e l a t i o n s h i p between p e r c e n t a g e of r e l a t i v e e f f o r t and perc e n t a g e of maximum f o r c e d u r i n g i s o m e t r i c c o n t r a c t i o n s of the q u a d r i c e p s . Bakers and Tenney (1970) i n v e s t i g a t e d the p e r c e p t i o n of r e s p i r a t o r y s e n s a t i o n s and found t h a t the e s t i m a t e d magnitude of p r e s s u r e , volume and v e n t i l a t i o n was h i g h l y c o r r e l a t e d w i t h the a c t u a l magnitude of the s e v a r i a b l e s . Both a c t i v e l y and p a s s i v e l y a p p l i e d r e s p i r a t o r y p r e s s u r e s were shown t o grow e x p o n e n t i a l l y , w i t h exponents of 1.48 and 1.35, r e s p e c t i v e l y . These v a l u e s a r e s i m i l a r t o the p r e v i o u s l y c i t e d v a l u e s f o r a c t i v e and p a s s i v e f o r c e a p p l i c a t i o n . I t was c o n c l u d e d t h a t r e s p i r a t o r y s e n s a t i o n s a re q u a n t i t a t i v e l y a s s e s s e d i n a manner which i s analogo u s t o f o r c e a p p l i c a t i o n i n the l i m b s . U n l i k e the e a r l i e r s t u d i e s i n v o l v i n g i s o m e t r i c e x e r c i s e , Borg (1962) s t u d i e d the p e r c e p t i o n of e f f o r t d u r i n g a e r o b i c work employing l a r g e muscle masses. He produced a 2 1 - p o i n t 10 c a t e g o r i c a l r a t i n g s c a l e f o r RPE, w i t h v a r i o u s v e r b a l e x p r e s s i o n s c o r r e s p o n d i n g t o d i f f e r e n t l e v e l s of the s c a l e . T h i s s c a l e was based upon a c o r r e l a t i o n between RPE and h e a r t r a t e (HR), which was .found t o be 0.80-0.90 d u r i n g l i g h t t o heavy e x e r c i s e performed on a b i c y c l e ergometer. At a l a t e r date (Borg, 1970), a 1 5 - p o i n t graded c a t e g o r y s c a l e was d e r i v e d t o i n c r e a s e the l i n e a r i t y between the r a t i n g s and the w o r k l o a d (Appendix A ) . U s i n g t h i s s c a l e , RPE v a l u e s have been shown t o be a p p r o x i m a t e l y o n e - t e n t h of e x e r c i s e HR v a l u e s f o r h e a l t h y , m iddle-aged men p e r f o r m i n g moderate t o heavy e x e r c i s e (Borg,1973). In f o r m i n g the new s c a l e , some of the v e r b a l e x p r e s s i o n s were changed, and t h e m i d - p o i n t was l o w e r ed. By c o m p r e s s i n g the lower degrees t o compensate f o r n o n - l i n e a r i t y , the s e n s i t i v i t y of the s c a l e was s l i g h t l y reduced ( L o l l g e n et a l . , 1 9 7 5 ) . P r i o r t o use of the s c a l e d u r i n g any e x p e r i m e n t a l t e s t i n g , each s u b j e c t i s i n s t r u c t e d t o r a t e t h e i r degree of e x e r t i o n as a c c u r a t e l y and n a i v e l y as p o s s i b l e , and the t e s t p r o c e d u r e s a r e then e x p l a i n e d . D u r i n g the p h y s i c a l work t e s t , the s u b j e c t i s p r e s e n t e d w i t h the s c a l e on a l a r g e c a r d and i s r e q u e s t e d t o i n d i c a t e the number a s s o c i a t e d w i t h the e f f o r t he p e r c e i v e s ( B o r g , 1970). A l t e r n a t e s c a l e s have a l s o been u t i l i z e d f o r the measurement of RPE. A second c a t e g o r y s c a l e of 9 p o i n t s (Appendix B) has been used by some i n v e s t i g a t o r s (Robertson et a l . , 1979a; Robertson et a l . , 1979b; Stamford and Noble, 1974). 11 When used t o a s s e s s s e l f - r e p o r t e d e f f o r t d u r i n g e x e r c i s e , the RPE v a l u e s o b t a i n e d from t h i s s c a l e have been shown t o c o r r e l a t e h i g h l y (r=0.92) w i t h those on the 2 1 - p o i n t Borg s c a l e (Robertson et a l . , 1979a). Stevens and Mack (1959) have d e v e l o p e d a r a t i o s c a l e method f o r measurement of RPE. U s i n g t h i s t e c h n i q u e , a s u b j e c t i s r e q u i r e d t o p e r f o r m or r a t e a l e v e l of e x e r c i s e which i s p e r c e i v e d as some f r a c t i o n of a r e f e r e n c e s t i m u l u s . U s i n g t h i s s c a l e , t h e r e i s no i n d i c a t i o n of the r e l a t i v e magnitude of the RPE. That i s , w h i l e i t i s p o s s i b l e t o compare one l e v e l of RPE t o a n o t h e r , i t w i l l be i m p o s s i b l e t o a s c e r t a i n whether t h a t l e v e l i s h i g h , moderate or low ( B o r g , 1972). T h i s f a c t o r makes i n t e r - i n d i v i d u a l comparisons d i f f i c u l t t o p e r f o r m ( B o r g , 1962). In a d d i t i o n , r a t i o s c a l i n g methods may l i m i t d a t a i n t e r p r e t a t i o n because of the d i f f e r e n t i a l i n t e r a c t i o n of p e r c e p t u a l r e c o g n i t i o n and c e r t a i n p s y c h o m e t r i c v a r i a b l e s such as memory span (Borg and L i n d b l a d , 1 9 7 6 ) . R e c e n t l y , Borg (1982) has d e v e l o p e d a 10-point c a t e g o r y s c a l e w i t h r a t i o p r o p e r t i e s (Appendix C) which p e r m i t s the use of d e c i m a l s i n RPE d e t e r m i n a t i o n s . U s i n g t h i s s c a l e , p e r c e i v e d e x e r t i o n was' shown t o i n c r e a s e e x p o n e n t i a l l y w i t h r e s p e c t t o p h y s i c a l work. An exponent of 1.6 was o b t a i n e d f o r t h i s f u n c t i o n d u r i n g b i c y c l e ergometer e x e r c i s e . T h i s f i n d i n g i s s i m i l a r t o t h o s e found i n the p r e v i o u s l y c i t e d f o r c e a p p l i c a t i o n s t u d i e s . The v e r b a l e x p r e s s i o n s which are used w i t h the s c a l e are s e t so t h a t the semantic i n t e n s i t y grows a c c o r d i n g to a power f u n c t i o n . For t h i s r e a s o n , t h i s s c a l e may be p a r t i c u l a r l y u s e f u l f o r measuring the p e r c e p t i o n of e f f o r t d u r i n g a n a e r o b i c 12 a c t i v i t y . T h i s i s because c e r t a i n p h y s i o l o g i c a l measures such as l a c t i c a c i d and pulmonary v e n t i l a t i o n , which r e f l e c t a n a e r o b i c m e t a b o l i s m , grow a c c o r d i n g t o a power f u n c t i o n w i t h e x e r c i s e i n t e n s i t y ( N o b l e , 1982). U s i n g t h i s s c a l e , i n c r e a s e s i n RPE have been shown t o c o i n c i d e c l o s e l y w i t h i n c r e m e n t a l e l e v a t i o n s i n b l o o d l a c t a t e (Noble et a l . , 1981). Subsequent t o the development of r a t i n g s c a l e s d e s i g n e d f o r use i n the s u b j e c t i v e assessment of e x e r t i o n , e x t e n s i v e r e s e a r c h was undertaken t o t e s t the r e l i a b i l i t y and v a l i d i t y of RPE. M i h e v i c and Morgan (1980) have p o s t u l a t e d t h a t the t h r e s h o l d f o r d e t e c t i o n of changes i n e x e r c i s e i n t e n s i t y l i e s near an a b s o l u t e w o r k l o a d of a p p r o x i m a t e l y 15-20W. M i c h a e l and E c k h a r d t (1972) e x e r c i s e d 6 male s u b j e c t s (3 t r a i n e d , 3 u n t r a i n e d ) f o r f i f t e e n m inutes a t a work i n t e n s i t y which s u b j e c t s c o n s i d e r e d t o be "hard" at 0% s l o p e on a t r e a d m i l l . B e f o r e t e s t i n g , a l l s u b j e c t s were e x e r c i s e d s e v e r a l times on the t r e a d m i l l t o become a c q u a i n t e d w i t h the a p p a r a t u s . When asked t o reproduce an e q u i v a l e n t l e v e l of work a t a 10% s l o p e on t h e t r e a d m i l l , no s i g n i f i c a n t d i f f e r e n c e was found between the e x e r c i s e i n t e n s i t i e s u s i n g the two d i f f e r e n t p r o t o c o l s . No d i f f e r e n c e s were obse r v e d i n t h e r e l a t i v e i n t e n s i t i e s s e l e c t e d by the t r a i n e d and u n t r a i n e d s u b j e c t s . A l l r unners s e l e c t e d w orkloads which e l i c i t e d a p p r o x i m a t e l y 80% of t h e i r maximal oxygen consumption , and c o r r e s p o n d e d t o a HR of 170 be a t s per minute. These f i n d i n g s demonstrated the r e l i a b i l i t y of RPE d e s p i t e v a r i a t i o n s i n p r o t o c o l . 13 In an attempt t o c o n t r o l f o r s e q u e n t i a l e f f e c t s , S k i n n e r e t a l . (1973b) compared RPE when workloads were p r o g r e s s i v e l y i n c r e a s e d w i t h RPE when the same workloads were randomly a s s i g n e d . One group of s u b j e c t s began e x e r c i s i n g a t 150 kgm-min" 1, w i t h the wo r k l o a d b e i n g i n c r e a s e d by 150 kgm-min" 1 e v e r y 2 minutes u n t i l a s e l f - i m p o s e d maximum. In the random t e s t , each s u b j e c t e x e r c i s e d f o r 2 minutes a t 150 kgm-min" 1, a t which time the workload was i n c r e a s e d t o a v a l u e of 200, 450, 600, 750 or 900 kgm-min" 1, t o be m a i n t a i n e d u n t i l a steady s t a t e was reached. At t h i s p o i n t , the w o r k l o a d was r e t u r n e d t o b a s e l i n e , and a subsequent w o r k l o a d was implemented. I t was found t h a t t h e r e were no s i g n i f i c a n t d i f f e r e n c e s between the two groups w i t h r e s p e c t t o RPE a t a g i v e n w o r k l o a d , and t h a t s m a l l v a r i a t i o n s i n i n t e n s i t y c o u l d be d e t e c t e d even when p r e s e n t e d i n random o r d e r . L o l l g e n e t a l . (1975) e x e r c i s e d s u b j e c t s on a b i c y c l e ergometer, v a r y i n g the p e d a l l i n g r a t e s between 40 and 100 KPM on s e p a r a t e o c c a s i o n s . A t e s t - r e t e s t r e l i a b i l i t y c o e f f i c i e n t of 0.92 was e s t a b l i s h e d . However, measurements of RPE were found t o be more h i g h l y v a r i a b l e a t i n c r e a s i n g p e d a l l i n g r a t e s . T h i s i n f o r m a t i o n c o i n c i d e s w i t h the f i n d i n g s of Borg (1973) which i n d i c a t e d t h a t c o e f f i c i e n t s between HR and RPE were lower when u s i n g hard t o v e r y hard w o r k l o a d s . U s i n g the Borg 15-point s c a l e , Stamford (1976) e v a l u a t e d the r e l i a b i l i t y and v a l i d i t y of the p e r c e p t u a l r e s p o n s e s of 14 se d e n t a r y f e m a l e s . The s u b j e c t s were p r e v i o u s l y u n f a m i l i a r w i t h . 1 4 a s s e s s i n g v a r y i n g l e v e l s of e x e r t i o n . T h i s was c o n s i d e r e d to be a p p r o p r i a t e f o r t e s t s of r e l i a b i l i t y and v a l i d i t y . Each s u b j e c t was p r e s e n t e d w i t h work t a s k s of e i t h e r t r e a d m i l l w a l k i n g , t r e a d m i l l r u n n i n g , c y c l i n g or s t o o l s t e p p i n g on f o u r s e p a r a t e o c c a s i o n s , each a minimum of 48 hours a p a r t . D u r i n g each of the t e s t s , the e x e r c i s e i n t e n s i t i e s were v a r i e d , and randomly p r e s e n t e d . HR was a l l o w e d t o r e t u r n t o normal f o l l o w i n g each l e v e l of e x e r c i s e w i t h i n a t a s k . In a d d i t i o n , RPE were r e c o r d e d at r e g u l a r p e r i o d s of 1 or 2 minutes ( i n t e r v a l ) or d u r i n g the f i n a l minute of each w o r k l o a d ( t e r m i n a l ) . U s i n g t h i s t e s t -r e t e s t p r o c e d u r e , the RPE v a l u e s which were e l i c i t e d p roved t o be r e p r o d u c i b l e (r=0.76) d u r i n g i n t e n s e (>90% V02max) and l e s s s e v e r e e x e r c i s e . T h i s was found t o be t r u e f o r b o t h i n t e r v a l and t e r m i n a l measurements. A h i g h l i n e a r r e l a t i o n s h i p was e x h i b i t e d between HR response and RPE. The f i n d i n g s i n d i c a t e d t h a t RPE r e a d i n g s were r e l i a b l e and v a l i d , independent of e x e r c i s e i n t e n s i t y . U s i n g a 7 - p o i n t r a t i n g s c a l e , Hogan and F l e i s h m a n (1979) conducted a f i e l d study i n v o l v i n g the s u b j e c t i v e e v a l u a t i o n of t h e m e t a b o l i c c o s t of 30 o c c u p a t i o n a l and 41 r e c r e a t i o n a l t a s k s (N=26). E f f o r t r a t i n g s were found t o be a c c u r a t e e s t i m a t i o n s of the a c t u a l m e t a b o l i c demands of the t a s k s . C o r r e l a t i o n s of 0.81 and 0.83 were found between the mean p e r c e p t u a l r a t i n g s and the t r u e energy c o s t of the o c c u p a t i o n a l and r e c r e a t i o n a l a c t i v i t i e s , r e s p e c t i v e l y . A f o l l o w - u p i n v e s t i g a t i o n by the same a u t h o r s r e p l i c a t e d the f i n d i n g s of the p r e v i o u s s t u d y . I t was c o n c l u d e d t h a t a h i g h r e l i a b i l i t y and v a l i d i t y e x i s t e d f o r 1 5 p e r c e i v e d e f f o r t r a t i n g s , independent of the sex or p r e v i o u s r a t i n g e x p e r i e n c e of the sample group. P u r v i s and C ureton (1981) have r e c e n t l y shown t h a t RPE measurements o b t a i n e d every 30 seconds d u r i n g a p r o g r e s s i v e , l o a d - i n c r e m e n t e d b i c y c l e ergometer t e s t are s i m i l a r a t the a e r o b i c t h r e s h o l d of a l l s u b j e c t s t e s t e d . A e r o b i c t h r e s h o l d was measured by a v e r a g i n g the oxygen consumption v a l u e s a t the time of d e p a r t u r e from l i n e a r i t y of f r a c t i o n a l e x p i r e d oxygen (FE02), minute v e n t i l a t i o n (VE), v e n t i l a t e d carbon d i o x i d e (VC02) and r e s p i r a t o r y q u o t i e n t (R) v a l u e s . They c o n c l u d e d t h a t t h e r e were no d i f f e r e n c e s i n the p e r c e i v e d i n t e n s i t y c o r r e s p o n d i n g t o the a e r o b i c t h r e s h o l d i n d i f f e r e n t i n d i v i d u a l s . T h i s demonstrated the r e l i a b i l i t y of RPE measurements at the a e r o b i c t h r e s h o l d . U s i n g a m o t o r - d r i v e n l a d d e r m i l l , P a n d o l f e t a l . (1978) r e p o r t e d t h a t f o r p o s i t i v e ( c o n c e n t r i c ) work an i n c r e a s e of 10.0 b e a t s per minute i n HR was a s s o c i a t e d w i t h a 0.9 r i s e i n RPE, as would be p r e d i c t e d by Borg's s c a l e . However, f o r n e g a t i v e ( e c c e n t r i c ) work, an RPE i n c r e a s e of o n l y 0.5 was a s s o c i a t e d w i t h the 10 beat i n c r e a s e . T h i s was a t t r i b u t e d t o the f a c t t h a t e x e r t i o n f o r n e g a t i v e work was h i g h e r than f o r p o s i t i v e work at the same HR and oxygen consumption (V02), because of the u n c o m f o r t a b l e and u n u s u a l n a t u r e of the work. As a r e s u l t of the h i g h degree of i n i t i a l d i s c o m f o r t , i t was s u g g ested t h a t a l i m i t was p l a c e d upon i n c r e a s e s i n RPE. These r e s u l t s suggest t h a t the Borg s c a l e may o n l y be v a l i d f o r use i n p r o t o c o l s which i n v o l v e c o n c e n t r i c e x e r c i s e . 16 Borg and L i n d e r h o l m (1970) compared the r e p r o d u c i b i l i t y of work c a p a c i t y based upon HR w i t h work c a p a c i t y based upon RPE. On two s e p a r a t e o c c a s i o n s , work c a p a c i t y a t h e a r t r a t e s of 130 and 170 b e a t s per m i n u t e , and RPE v a l u e s of 13 and 17 were d e t e r m i n e d . R e - t e s t i n g was conducted 2-4 weeks a f t e r t h e i n i t i a l t e s t , t o m i n i m i z e the e f f e c t of memory upon RPE. The sample c o n s i s t e d of both h e a l t h y s u b j e c t s , and p a t i e n t s who s u f f e r e d from a v a r i e t y of c a r d i o v a s c u l a r - r e l a t e d d i s e a s e s . T e s t - r e t e s t c o e f f i c i e n t s were 0.93 and 0.98, r e s p e c t i v e l y , i n the p a t i e n t s and 0.88 and 0.97, r e s p e c t i v e l y , i n t h e h e a l t h y s u b j e c t s . Workloads which were produced based upon e f f o r t p e r c e p t i o n demonstrated c o r r e l a t i o n s of 0.80 and 0.94, r e s p e c t i v e l y , i n the f i r s t group, and 0.91 and 0.98, r e s p e c t i v e l y , i n the second. These r e s u l t s demonstrated t h a t the r e p r o d u c i b i l i t y of work c a p a c i t y based upon RPE i s as good as t h a t based upon HR. The v a l u e s f o r r e l i a b i l i t y o b s e r v e d i n t h i s study a r e s i m i l a r t o the t e s t - r e t e s t c o r r e l a t i o n c o e f f i c i e n t of 0.91 which was o b t a i n e d by Cooper e t a l . (1979), u s i n g i s o m e t r i c muscle c o n t r a c t i o n s . Smutok e t a l . (1980) e x e r c i s e d 10 m o d e r a t e l y f i t (V02max = 55 m l * k g " 1 - m i n " 1 ) s u b j e c t s on a t r e a d m i l l a t speeds of 4.7, 6.5, 9.7, 11.3 and 12.9 km«hr" 1. E x e r c i s e was performed f o r 5 minutes a t each w o r k l o a d , and RPE and HR v a l u e s were measured d u r i n g the l a s t minute spent a t each l e v e l of work. The s u b j e c t s were then a l l o w e d t o c o n t r o l the speed of the t r e a d m i l l , and were randomly a s s i g n e d RPE v a l u e s which c o r r e s p o n d e d t o the numbers which they had p r e v i o u s l y s e l e c t e d 1 7 at each of the work l e v e l s . Four minutes were a l l o w e d t o a d j u s t the t r e a d m i l l speed t o match the a s s i g n e d RPE v a l u e . For RPE >10, no d i f f e r e n c e was found between the HR or V02 a t e q u i v a l e n t RPE v a l u e s when the e x e r c i s e t r i a l and s e l f - r e g u l a t e d e x e r c i s e bouts were compared. A l t h o u g h speed was r e l i a b l y r e g u l a t e d a t RPE <10, HR and V02 demonstrated s i g n i f i c a n t d i f f e r e n c e s (p<0.05). I t was suggested t h a t the d i f f e r e n c e s i n HR may have been due t o g r e a t e r HR v a r i a b i l i t y w i t h i n s u b j e c t s a t low e x e r c i s e i n t e n s i t i e s . The a u t h o r s c o n c l u d e d t h a t RPE c o u l d be r e l i a b l y used t o s e l f - p r e s c r i b e e x e r c i s e a t HR v a l u e s e x c e e d i n g 150 beats per minute. U s i n g a t e s t - r e t e s t a n a l y s i s , Komi and K a r p p i (1977) observed c o r r e l a t i o n c o e f f i c i e n t s of 0.37-0.75 f o r RPE, between the f i r s t and second t e s t s . The l o w e s t c o e f f i c i e n t s were found a t e x e r c i s e i n t e n s i t i e s below 50% of maximal HR v a l u e s . T e g h t s o o n i a n (1977) and h i s co-workers used t h e i r l a b o r a t o r y t o t e s t the p e r c e p t i o n of the muscular e f f o r t of male . c l u b -c y c l i s t s who e x e r c i s e d r e g u l a r l y . I t was noted t h a t w o r k l o a d d e t e c t i o n t h r e s h o l d s appeared t o be s e n s i t i v e t o f a t i g u e . T h i s may h e l p t o e x p l a i n any e x i s t i n g i n c r e a s e s i n v a r i a b i l i t y i n RPE a t h i g h i n t e n s i t y w o r k l o a d s . Noble (1979) demonstated t h a t RPE u s i n g the Borg s c a l e do not p a r a l l e l changes i n HR d u r i n g r e c o v e r y from a v o l u n t a r y run t o e x h a u s t i o n on a t r e a d m i l l . The au t h o r s u g g e s t e d t h a t a more v a l i d s c a l e which more c l o s e l y a p p r o x i m a t e s m e t a b o l i c responses d u r i n g r e c o v e r y from e x e r c i s e needs t o be d e v e l o p e d . Uimer et a l . (1977) a l s o r a i s e d doubts about the v a l i d i t y of the Borg s c a l e , because i t i s based s o l e l y 18 upon the c o r r e l a t i o n between HR and p e r c e i v e d e x e r t i o n . T h e i r r e s e a r c h on w e l l - t r a i n e d endurance a t h l e t e s shows t h a t RPE i s more h i g h l y c o r r e l a t e d w i t h what they c o n s i d e r t o be the s t r e s s (workload) of e x e r c i s e than the s t r a i n (HR). Morgan (1977) has warned t h a t a danger i n u s i n g c r o s s -s e c t i o n a l d ata on p s y c h o p h y s i c a l c a t e g o r y s c a l e s such as Borg's method f o r RPE measurement i s t h a t r e s e a r c h e r s must presume t h a t v e r b a l c a t e g o r i e s are a p p r a i s e d i n a s i m i l a r manner by a l l s u b j e c t s . He a l s o p o i n t s out t h a t a d i f f i c u l t y i n c o n d u c t i n g l o n g i t u d i n a l s t u d i e s i n p s y c h o p h y s i c a l work i s t h a t i t i s d i f f i c u l t t o prevent s u b j e c t s from r e a l i z i n g t h a t RPE v a l u e s a r e e x p e c t e d t o be lower f o l l o w i n g t r a i n i n g . The i n v e s t i g a t o r must d i s c o u r a g e s u b j e c t s from making c o n s c i o u s e f f o r t s t o p r o v i d e the e x p e c t e d r e s p o n s e s . 11. P h y s i o l o g i c a l B a s i s For RPE C o n s i d e r a b l e r e s e a r c h i n the a r e a of RPE has been d i r e c t e d towards the i d e n t i f i c a t i o n of the sensory cues which p r o v i d e d i r e c t i n p u t i n t o the e f f o r t sense. A survey of the l i t e r a t u r e r e v e a l s t h a t numerous p h y s i o l o g i c a l and neuromuscular parameters have been proposed as c o n t r i b u t o r s t o e f f o r t p e r c e p t i o n d u r i n g e x e r c i s e performed at a v a r i e t y of i n t e n s i t i e s , modes, d u r a t i o n s and e n v i r o n m e n t a l c o n d i t i o n s . The e a r l i e s t i n v e s t i g a t i o n s were p r i m a r i l y concerned w i t h i s o l a t i n g cues which c o u l d be u n i v e r s a l l y shown t o predominate the c o g n i t i v e e v a l u a t i o n of 19 e f f o r t . Ekblom and G o l d b a r g (1971) were the f i r s t t o d i s t i n g u i s h between f a c t o r s a f f e c t i n g the p e r c e p t i o n of e f f o r t w hich a r i s e i n the a c t i v e muscles and/or j o i n t s ( p e r i p h e r a l ) and t h o s e which are m a n i f e s t e d i n a more g e n e r a l i z e d c a r d i o - pulmonary response ( c e n t r a l ) . Borg's i n i t i a l p r o p o s a l , t h a t RPE c o v a r i e s d i r e c t l y w i t h HR, has been c h a l l e n g e d by a number of i n v e s t i g a t o r s . P a r e n t h e t i c a l l y , the p r o l i f e r a t i o n of proposed cues f o r the p e r c e p t i o n of e f f o r t r e s u l t e d from r e s e a r c h c o n c e r n e d w i t h v a l i d a t i o n of the RPE-HR r e l a t i o n s h i p . In a d d i t i o n t o HR, c e n t r a l parameters which a r e p u r p o r t e d l y l i n k e d t o e f f o r t p e r c e p t i o n i n c l u d e r e s p i r a t o r y r a t e (RR), VE and V02. F o l l o w i n g Borg's o r i g i n a l r e p o r t of a c o r r e l a t i o n of 0.85 between RPE and HR, numerous o t h e r s t u d i e s have demonstrated the e x i s t e n c e of a s t r o n g l i n e a r r e l a t i o n s h i p between t h e s e two v a r i a b l e s . T h i s a s s o c i a t i o n has been noted f o r b o t h male and female s u b j e c t s ( S k i n n e r et a l . , 1969; S k i n n e r et a l . , 1973a; St a m f o r d , 1976), of v a r y i n g f i t n e s s l e v e l s (Bar-Or, 1972; M i c h a e l and E c k h a r d t , 1972; S k i n n e r e t a l . , 1973a) w h i l e u s i n g e i t h e r b i c y c l e or t r e a d m i l l e x e r c i s e (Borg, 1973; S k i n n e r et a l . , 1973a), i n t e r m i t t e n t or c o n t i n u o u s e x e r c i s e (Edwards et a l . , 1972) and e i t h e r arm or l e g work (Sargeant and D a v i e s , 1973). S i n c e maximal HR d e c l i n e s w i t h age, i t would be e x p e c t e d t h a t RPE would be h i g h e r a t a g i v e n HR i n o l d e r s u b j e c t s . T h i s has been v e r i f i e d by r e p o r t s i n the l i t e r a t u r e ( A r t s i l a e t a l . , 1977; Bar-Or, 1977; Borg and L i n d e r h o l m , 1967). 20 W h i l e HR and RPE may be h i g h l y c o r r e l a t e d , a t no p o i n t has i t been i m p l i e d t h a t t h e s e measures a r e c a u s a l l y r e l a t e d . The RPE s c a l e was d e s i g n e d t o f o l l o w the HR response t o i n c r e a s i n g e x e r c i s e i n t e n s i t y , and t h e s e v a r i a b l e s a r e p r o b a b l y i n d i r e c t l y r e l a t e d t h r o u g h t h e i r common dependence upon p h y s i c a l s t r a i n . A number of s o u r c e s have r e p o r t e d t h a t the c o n n e c t i o n between HR and RPE can be d i s t u r b e d when e x e r c i s e i s performed under i r r e g u l a r c o n d i t i o n s . For example, i t i s p o s s i b l e t o m a n i p u l a t e HR through the use of p a r a s y m p a t h e t i c and s y m p a t h e t i c b l o c k i n g agents w i t h o u t a f f e c t i n g the RPE a t a g i v e n p e r c e n t a g e of V02max (Ekblom and G o l d b a r g , 1971; Da v i e s and Sarg e a n t , 1979). When p e r f o r m i n g a t the same HR, RPE i s g r e a t e r f o r e c c e n t r i c than c o n c e n t r i c e x e r c i s e ( P a n d o l f et a l . , 1978). The r e l a t i o n s h i p between HR and RPE i s s u b j e c t t o d i s p l a c e m e n t d u r i n g r e c o v e r y from a marathon run (Noble e t a l . 1979). When e x e r c i s i n g s u b j e c t s i n hot env i r o n m e n t s , a l t e r a t i o n s i n HR a r e not c o n s i s t e n t l y r e f l e c t e d i n p e r c e p t u a l responses (Kamon e t a l . , 1974; Noble e t a l . , 1973b; P a n d o l f et a l . , 1972), a l t h o u g h t h i s f i n d i n g has been d i s p u t e d ( S k i n n e r e t a l . , 1973a). E v i d e n c e from s t u d i e s which have s t u d i e d a d a p t a t i o n s i n RPE and HR f o l l o w i n g endurance t r a i n i n g a l s o c h a l l e n g e s the p o s t u l a t e d r e l a t i o n s h i p between th e s e v a r i a b l e s . L e w i s et a l . (1980) found t h a t f o l l o w i n g 11 weeks of t r a i n i n g , RPE remained the same eventhough HR was reduced d u r i n g submaximal e x e r c i s e i n v o l v i n g u n t r a i n e d l i m b s . D e s c r i b i n g the e f f e c t s of a 34-week c o n d i t i o n i n g program upon s e d e n t a r y , e l d e r l y s u b j e c t s , Sidney and .Shephard (1977) r e p o r t e d t h a t w h i l e p o s t - t r a i n i n g HR 21 responses were reduced a t an a b s o l u t e w o r k l o a d , RPE remained unchanged. F u r t h e r m o r e , a t the same HR, t r e a d m i l l e x e r c i s e evoked lower e f f o r t r a t i n g s than b i c y c l e ergometer work. At a g i v e n HR, d i s c r e p a n c i e s i n p e r c e p t u a l response as a f u n c t i o n of e x e r c i s e mode have a l s o been noted e l s e w h e r e ( M i c h a e l and H a c k e t t , 1972). Unique from a m e t h o d o l o g i c a l p e r s p e c t i v e , a study by Morgan et a l . (1976) e v a l u a t e d p e r c e p t u a l and m e t a b o l i c responses t o e x e r c i s e by u s i n g h y p n o s i s . D u r i n g the e x p e r i m e n t , r e a c t i o n s t o s u g g e s t i o n of u p h i l l work were i n v e s t i g a t e d by m o n i t o r i n g the responses of 4 t r e a t m e n t groups. The d i f f e r e n t c o n d i t i o n s i n c l u d e d : an awake s t a t e ( c o n t r o l ) , s u g g e s t i o n of u p h i l l work i n an awake s t a t e , a h y p n o t i c s t a t e ( c o n t r o l ) , and s u g g e s t i o n of u p h i l l work i n a h y p n o t i c s t a t e . S t e a d y - s t a t e e x e r c i s e was performed a t 100 W-min" 1 f o r 20 m i n u t e s . H y p n o t i c s u g g e s t i o n of u p h i l l work e l i c i t e d i n c r e a s e s i n e f f o r t r a t i n g s , a l t h o u g h HR and V02 remained s t a b l e . However, e l e v a t i o n s i n VE were found t o p a r a l l e l the a l t e r a t i o n s i n RPE, s u g g e s t i n g t h a t t h i s f a c t o r may be an i m p o r t a n t d e t e r m i n a n t of the p e r c e p t u a l response t o e x e r c i s e . These r e s u l t s were e s s e n t i a l l y i d e n t i c a l t o those o b t a i n e d by the same a u t h o r s on a p r e v i o u s o c c a s i o n (Morgan et a l . , 1973) e x c e p t t h a t a s t r o n g e r r e l a t i o n s h i p was e x h i b i t e d between HR and RPE. Numerous o t h e r r e p o r t s a l s o support the r o l e of VE and/or RR as sensory cues which have impact upon the p e r c e p t i o n of e f f o r t . C o r r e l a t i o n c o e f f i c i e n t s r a n g i n g from 0.52-0.94 have 22 been demonstrated between RPE and b o t h VE and RR (Edwards e t a l . , 1972; Kamon et a l . , 1974; Morgan and P o l l o c k , 1977; Noble et a l . , 1973b; P a n d o l f e t a l . , 1972; Sargeant and D a v i e s , 1973; S k i n n e r et a l . , 1969; Smutok et a l . , 1980). A f t e r examining a number of p h y s i o l o g i c a l v a r i a b l e s , Noble e t a l . (1973b) found VE and RR t o be the b e s t p r e d i c t o r s of RPE, i n e i t h e r a hot or n e u t r a l environment. Edwards et a l . (1972) have noted t h a t u n l i k e HR or V02, VE has a f f e r e n t nervous system i n p u t , which can be c o n s c i o u s l y m o n i t o r e d . W i g e r t z (1970) a n a l y s e d the dynamic c h a r a c t e r i s t i c s of the v e n t i l a t o r y and HR responses of 11 h i g h l y t r a i n e d (V02max = 63.8 ml*kg"•• m i n " 1 ) a t h l e t e s who c y c l e d a t v a r y i n g w o r k l o a d s (mean = 650 kpm/min). A l t h o u g h changes i n VE were d e l a y e d w i t h r e s p e c t t o s h i f t s i n e x e r c i s e i n t e n s i t y and HR, the p e r c e p t i o n of peak e x e r c i s e i n t e n s i t y c o r r e s p o n d e d more c l o s e l y t o peak VE than the a c t u a l time of maximum e x e r c i s e i n t e n s i t y . A t t e m p t s have been made t o t e s t the r e l a t i o n s h i p between VE and RPE by examining the v e n t i l a t o r y response of s u b j e c t s d u r i n g e x e r c i s e , w h i l e b r e a t h i n g h y p o x i c and h y p e r o x i c m i x t u r e s . T h e o r e t i c a l l y , these p r o c e d u r e s s h o u l d a f f e c t r e s p i r a t o r y d r i v e a t a g i v e n w o r k l o a d , and h e l p t o d i f f e r e n t i a t e between the p e r c e p t u a l e f f e c t s of dypsnea or hyperpnea and o t h e r p h y s i o l o g i c a l i n p u t s . Pedersen and Welch (1977) o b s e r v e d t h a t b o t h RPE and VE were s i g n i f i c a n t l y lower d u r i n g p r o g r e s s i v e b i c y c l e e x e r c i s e when s u b j e c t s i n s p i r e d gas m i x t u r e s c o n t a i n i n g 50% and 80% 02. In c o n t r a s t , A l l e n and P a n d o l f (1977) were 23 unable t o show t h a t the r e d u c t i o n s i n RPE which were seen d u r i n g h y p e r o x i c c o n d i t i o n s were r e f l e c t e d i n s i m i l a r d e c r e a s e s i n v e n t i l a t i o n . I n t e r p r e t a t i o n of t h i s l a t t e r f i n d i n g i s d i f f i c u l t , s i n c e the i n c i d e n c e of decrements i n v e n t i l a t i o n as a consequence of b r e a t h i n g o x y g e n - e n r i c h e d gases has been w e l l e s t a b l i s h e d ( W i l s o n and Welch, 1975). Gerben et a l . (1972) and R o b e r t s o n et a l . (1979c) have c o n f i r m e d t h a t RPE and VE i n c r e a s e c o n c o m i t a n t l y when s u b j e c t s i n s p i r e h y p e r o x i c gas, a l t h o u g h e l e v a t i o n s i n RPE may o n l y become apparent a t h i g h e r w o r k l o a d s ( R o b e r t s o n e t a l . , 1979c). S t u d i e s i n v o l v i n g r e d b l o o d c e l l (RBC) r e i n f u s i o n ( R o b e r t s o n e t a l . , 1979c; W i l l i a m s e t a l . , 1978; W i l l i a m s e t a l . , 1981) have been based upon the r a t i o n a l e t h a t by w i t h d r a w i n g a g i v e n volume of b l o o d and r e i n f u s i n g i t a t a l a t e r d a t e , hemoglobin c o n c e n t a t i o n s w i l l be augmented, t h e r e b y i n c r e a s i n g the oxygen c a r r y i n g c a p a c i t y of the b l o o d ( W i l l i a m s , 1981) . I f VE and RPE a r e r e l a t e d , then i t would be e x p e c t e d t h a t i n c r e a s e d a r t e r i a l oxygen c o n t e n t (Ca02), which reduces the s t i m u l u s f o r v e n t i l a t i o n , would be r e f l e c t e d i n s i m i l a r a d a p t a t i o n s i n RPE. U s i n g a d o u b l e - b l i n d e x p e r i m e n t a l d e s i g n , W i l l i a m s e t a l . (1978) f a i l e d t o show a l t e r a t i o n s i n RPE f o l l o w i n g i n d u c e d e r y t h r o c y t h e m i a . i n 16 l o n g - d i s t a n c e r u n n e r s . However, the volume of r e i n f u s e d RBC (200 ml) and the e l a p s e d time between w i t h d r a w a l and r e i n f u s i o n (3 weeks) were both below the recommended r e q u i r e m e n t s f o r i n c r e a s i n g Ca02 ( G l e d h i l l , 1982) . When 5-mile run time was measured f o l l o w i n g the r e i n f u s i o n of 920 ml of b l o o d which had been s t o r e d f o r an 8-24 week p e r i o d , the same a u t h o r s ( W i l l i a m s et a l . , 1981) ob s e r v e d r e d u c t i o n s i n RPE at a g i v e n pace. N e v e r t h e l e s s , no r e p o r t of the e f f e c t s of r e i n f u s i o n upon v e n t i l a t i o n was made i n e i t h e r s t u d y . R o b ertson et a l . (1979c) e x e r c i s e d s u b j e c t s on a b i c y c l e ergometer a t 45 and 70% of t h e i r V02max. F o l l o w i n g r e i n f u s i o n , VE was d e p r e s s e d a t both work i n t e n s i t i e s , but RPE were s i g n i f i c a n t l y m o d i f i e d o n l y a t the h i g h e r w o r k l o a d . A g a i n , the r e s u l t s suggest t h a t the onset of the v e n t i l a t o r y s i g n a l t o e f f o r t p e r c e p t i o n i s r e l a t e d t o the r e l a t i v e e x e r c i s e i n t e n s i t y of the work b e i n g performed. T h i s o b s e r v a t i o n has been r e p o r t e d by p r e v i o u s i n v e s t i g a t o r s ( C a f a r e l l i and Nob l e , 1976; Edwards et a l . , 1972; Horstman e t a l . , 1979b; Morgan and P o l l o c k , 1977). I t appears t h a t the p o i n t a t which VE b e g i n s t o s i g n i f i c a n t l y c o n t r i b u t e t o the p e r c e p t i o n of e f f o r t i s near the a e r o b i c t h r e s h o l d ( R o b e r t s o n , 1982). The r e l a t i o n s h i p between p e r c e i v e d r e s p i r a t o r y r e s i s t a n c e and added r e s p i r a t o r y work may be d e s c r i b e d by a power f u n c t i o n w i t h an exponent of 1.6 (Gamberale, 1978). Mechanisms w h i c h u n d e r l i e the p e r c e p t i o n of v e n t i l a t o r y s t r e s s appear t o be r e l a t e d t o f a c t o r s which o r i g i n a t e from s e n s a t i o n s w i t h i n the c h e s t w a l l (Bakers and Tenney, 1970). W h i l e the pr o p e r f u n c t i o n i n g of v e n t i l a t i o n i s r e g u l a t e d by chemoreceptor a c t i v i t y a t r e s t , d u r i n g e x e r c i s e , c o n t r o l of v e n t i l a t i o n i s p a r t i a l l y assumed by mechanoreceptors i n the c h e s t w a l l , l u n g s and a i r w a y s ( R o b e r t s o n , 1982). R e s p i r a t o r y p r e s s u r e , volume and v e n t i l a t i o n may a l l be p e r c e i v e d w i t h a h i g h degree of a c c u r a c y (Bakers and Tenney, 1970). Changes i n l u n g volume, l u n g 25 p r e s s u r e and r e s p i r a t o r y muscle t e n s i o n a r e a l l d e t e r m i n e d by t i d a l volume ( R o b e r t s o n , 1982). T h i s i s s u p p o r t e d by the f i n d i n g s of Burdon et a l . ( 1 982), who compared the e f f e c t s of e l e v a t i o n s i n r e s p i r a t o r y s t i m u l a t i o n w i t h changes i n the p e r c e i v e d magnitude of i n c r e a s i n g r e s p i r a t o r y l o a d s . I t was c o n c l u d e d t h a t i n c r e a s e s i n s e n s o r y magnitude were p r o p o r t i o n a l t o and dependent upon i n c r e a s e s i n the i n s p i r a t o r y muscle f o r c e d e v e l o p e d . More r e c e n t l y , Mahutte et a l . (1983) have proposed t h a t d u r i n g normal r e s p i r a t i o n , the b r a i n s e t s the n e c e s s a r y muscle p r e s s u r e t o overcome r e s i s t a n c e and e l a s t a n c e f o r each b r e a t h , and then m o n i t o r s r a t e s of change i n f l o w . They suggest t h a t when a c r i t i c a l l a g i n f l o w r a t e i s sensed, an added r e s p i r a t o r y l o a d i s d e t e c t e d (Mahutte et a l . , 1983). Whether t h i s t h e o r y , which c o n s i d e r s the d e t e c t i o n ' of r e s i s t i v e r e s p i r a t o r y l o a d s a t r e s t , i s a p p l i c a b l e t o an e x e r c i s e s e t t i n g , i s u n c l e a r . T h e r e f o r e , any model which a t t e m p t s t o e x p l a i n the manner i n which r e s p i r a t o r y e f f o r t i s p e r c e i v e d must be c o n s i d e r e d t o be t e n t a t i v e . I t has been s u g g e s t e d t h a t any impact t h a t VE or HR e x e r t upon RPE may be e l i m i n a t e d i n terms of r e l a t i v e m e t a b o l i c demand (Sargeant and D a v i e s , 1973). C o r r e l a t i o n s of 0.76-0.97 have been r e p o r t e d between V02 and RPE (Edwards et a l . , 1972; Sargeant and D a v i e s , 1973; Smutok e t a l . , 1980). I n d i v i d u a l d i f f e r e n c e s i n V02 which may e x i s t at e q u i v a l e n t a b s o l u t e w o r k l o a d s d i s a p p e a r a t the same %V02max i n l e a n or obese ( S k i n n e r e t a l . , 1973a), s e d e n t a r y or a c t i v e ( S k i n n e r et a l . , 1969) and t r a i n e d or u n t r a i n e d (Ekblom and G o l d b a r g , 1971) 26 s u b j e c t s . S i m i l a r r e s u l t s are o b t a i n e d when c o n t i n u o u s and i n t e r m i t t e n t e x e r c i s e p r o t o c o l s a r e compared (Edwards et a l . , 1972). I n c r e a s e s i n maximal a e r o b i c power (MAP) f o l l o w i n g i n d u c e d e r y t h r o c y t h e m i a may r e s u l t i n r e d u c t i o n s i n RPE f o r a g i v e n w o r k l o a d , but these are a b o l i s h e d a t comparable e x e r c i s e i n t e n s i t i e s ( R o b e r t s o n et a l . , 1979c). However, o t h e r r e p o r t s i n d i c a t e t h a t the r e l a t i o n s h i p between RPE and V02 may be s p u r i o u s . When e x e r c i s e i n t e n s i t y and r e l a t i v e m e t a b o l i c demand a r e h e l d c o n s t a n t , RPE f l u c t u a t e s as a f u n c t i o n of p e d a l l i n g f r e q u e n c y on a b i c y c l e ergometer ( P a n d o l f and N o b l e , 1973; Stamford and N o b l e , 1974). At u n i f o r m V02 l e v e l s , RPE i s h i g h e r f o r n e g a t i v e than p o s i t i v e work ( H e n r i k k s o n e t a l . , 1972; P a n d o l f et a l . , 1978). S u g g e s t i o n of u p h i l l work i n a h y p n o t i c s t a t e r e s u l t s i n e l e v a t i o n s i n RPE, but not i n V02 (Morgan et a l . , 1973). P r e v i o u s reviews of the l i t e r a u r e (Borg and Noble, 1974; M i h e v i c , 1981) have noted t h a t w h i l e V02 grows l i n e a r l y w i t h r e s p e c t t o w o r k l o a d , RPE i n c r e a s e s a c c o r d i n g t o a p o s i t i v e l y a c c e l e r a t i n g f u n c t i o n which c l o s e l y a p p r o x i m a t e s VE and b l o o d l a c t a t e response c u r v e s . The comparison of e x e r c i s e a t e q u i v a l e n t r e l a t i v e e x e r c i s e i n t e n s i t i e s does not account f o r p h y s i o l o g i c a l r e s p o n s e s such as l a c t a t e p r o d u c t i o n , v e n t i l a t o r y hyperpnea and c a t e c h o l a m i n e e l e v a t i o n , which may d i f f e r between i n d i v i d u a l s ( A s t r a n d R o d a h l , 1970). On t h i s b a s i s , i t cannot be c o n c l u d e d t h a t V02 i s c o n s c i o u s l y m o n i t o r e d per se. I t i s more p l a u s i b l e t h a t V02, l i k e HR, i s i n d i r e c t l y r e l a t e d t o RPE, s i n c e the i n p u t of c e r t a i n p h y s i o l o g i c a l parameters such as VE and b l o o d l a c t a t e a r e l i n k e d t o r e l a t i v e m e t a b o l i c demand. 27 S t u d i e s which have f o c u s e d upon the f a c t o r s i n v o l v e d i n the p e r c e p t i o n of i s o m e t r i c muscular work have c i t e d l o c a l cues such as mechanoreceptor and chemoreceptor s e n s i t i v i t y ( C a i n and S t e v e n s , 1971; Stevens and K r i m s l e y , 1977), and tendon, s k i n , j o i n t amd l i g a m e n t r e c e p t o r s ( C a i n , 1973). However, these same f a c t o r s have a l s o been shown t o e x e r t s i g n i f i c a n t i n p u t i n t o the p e r c e p t u a l response d u r i n g a e r o b i c e x e r c i s e performed on a b i c y c l e ergometer (Ekblom e t a l . , 1975; Gandevia and McCloskey, 1976; H e n r i k k s o n e t a l . , 1972; P a n d o l f and Nob l e , 1973; Stamford and N o b l e , 1974). Support f o r the r o l e of k i n e s t h e t i c or p r o p r i o c e p t i v e feedback may a l s o be i n f e r r e d from the f i n d i n g s of a v a r i e t y of c o m p a r a t i v e s t u d i e s . S e v e r a l i n v e s t i g a t o r s have shown t h a t e f f o r t r a t i n g s d i f f e r a t e q u i v a l e n t power o u t p u t s and m e t a b o l i c r a t e s when p e d a l l i n g f r e q u e n c y i s modulated on a b i c y c l e ergometer ( C a f a r e l l i , 1977; Edwards e t a l . , 1972; L o l l g e n e t a l . , 1977; L o l l g e n e t a l . , 1980; P a n d o l f and Nob l e , 1973; Stamford and Nob l e , 1974). S i m i l a r l y , d u r i n g t r e a d m i l l e x e r c i s e a t the same oxygen consumption, RPE may v a r y , depending on whether the work i s a c h i e v e d t h r o u g h c o n s t a n t ( s t e a d y - s t a t e ) or i r r e g u l a r ( p r o g r e s s i v e ) e x e r c i s e ( D a v i e s and S a r g e a n t , 1979). These s t u d i e s suggest t h a t RPE i s r e l a t e d t o the degree of s t r a i n which i s e x p e r i e n c e d i n t h e a c t i v e m u s c u l a t u r e . I f t h i s c o n s t r u c t i s v a l i d , then i t would be.expected t h a t d i f f e r e n c e s i n t h e RPE a s s o c i a t e d w i t h the performance of a g i v e n t a s k would be p a r t i a l l y e x p l a i n a b l e i n terms of m e c h a n i c a l e f f i c i e n c y . P a n d o l f e t a l . (1978) found t h a t a t the same r e l a t i v e m e t a b o l i c c o s t , e f f o r t was p e r c e i v e d t o be g r e a t e r d u r i n g e c c e n t r i c than 28 c o n c e n t r i c e x e r c i s e . T h i s was a t t r i b u t e d t o the u n c o m f o r t a b l e , u n u s u a l n a t u r e of n e g a t i v e work compared to p o s i t i v e work. E f f i c i e n c y i s known t o be g r e a t e r f o r r u n n i n g than w a l k i n g (Donovan and Brooks, 1977; Pugh, 1971); f o r a g i v e n HR, RPE i s 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 t r e a d m i l l w a l k i n g than t r e a d m i l l r u n n i n g (Noble et a l . , 1973a). These f i n d i n g s and those from o t h e r r e p o r t s ( C a f a r e l l i e t a l . , 1977; Campbell e t a l . , 1976; Molbech and Johansen, 1969; Winsmann and Goldmann, 1976) h e l p t o c o n f i r m t h a t s e n s a t i o n s o r i g i n a t i n g i n the w o r k i n g muscles a r e i m p o r t a n t d e t e r m i n a n t s of RPE. The e x t e n t t o which l o c a l neuromuscular components c o n t r i b u t e t o the o v e r a l l p e r c e p t i o n of e f f o r t i s l e s s c l e a r , and remains s p e c u l a t i v e u n t i l t h e s e i n p u t s can be q u a n t i f i e d . The e x a c t mechanism by which these f a c t o r s a r e c o g n i t i v e l y a p p r a i s e d i s u n c e r t a i n . R e c e n t l y , C a f a r e l l i (1982) p r e s e n t e d a comprehensive r e v i e w of t h i s i s s u e . I t was proposed t h a t a f e e d f o r w a r d mechanism from the motor c o r t e x t o the s e n s o r y c o r t e x , and feedback from p e r i p h e r a l r e c e p t o r s o p e r a t e both i n d e p e n d e n t l y and i n some complex, i n t e g r a t e d manner t o e v a l u a t e the parameters of any muscle c o n t r a c t i o n . U s i n g a v a r i e t y of e x e r c i s e m o d a l i t i e s (Ekblom and G o l d b a r g , 1971; Gamberale, 1972; Horstman et a l . , 1979a), i n t e n s i t i e s (Morgan and P o l l o c k , 1977), e n v i r o n m e n t a l c o n d i t i o n s (Horstman, 1977), f i t n e s s l e v e l s (Ekblom and G o l d b a r g , 1971), and c o n t i n u o u s or i n t e r m i t t e n t e x e r c i s e p r o t o c o l s (Edwards et a l . , 1972), s t r o n g c o r r e l a t i o n s between RPE and b l o o d l a c t a t e 29 c o n c e n t r a t i o n s have been dem o n s t r a t e d . D u r i n g i n c r e m e n t a l e x e r c i s e , b oth b l o o d l a c t a t e and RPE e x h i b i t a s i m i l a r , p o s i t i v e l y a c c e l e r a t i n g f u n c t i o n when p l o t t e d a g a i n s t time (Borg, 1962; Gamberale, 1972). P a n d o l f et a l . (1972) compared the response c u r v e s f o r p e r c e i v e d e x e r t i o n w i t h those of HR, VE, V02, RR, r e c t a l t e m perature and s k i n t e m p e r a t u r e , i n both hot and n e u t r a l e n v i r o n m e n t s . At the h i g h e s t w o r k l o a d s (> 69% V02max) a l l r e s p i r a t o r y responses p l a t e a u e d , w h i l e RPE a c c e l e r a t e d most r a p i d l y d u r i n g t h e s e s t a g e s of e x e r c i s e . Due t o a l a r g e oxygen d e f i c i t and a more pronounced a n a e r o b i c energy y i e l d , i t was c o n c l u d e d t h a t RPE may be p a r t i a l l y m o n i t o r i n g a n a e r o b i c m e t a b o l i t e s d u r i n g h i g h i n t e n s i t y e x e r c i s e . However, no measurement of v a r i a b l e s a s s o c i a t e d w i t h a n a e r o b i c metabolism was a t t e m p t e d . Lewis e t a l . (1980) t r a i n e d s e d e n t a r y young men (N=10) f o r 30 minutes per day, 4 days per week, f o r 11 weeks a t 75-80% V02max. P o s t - t r a i n i n g RPE v a l u e s were found t o be lower a t a g i v e n submaximal w o r k l o a d , but o n l y i n the t r a i n e d l i m b s . T h i s i s c o n s i s t e n t w i t h the e x p e c t e d l a c t a t e response t o t r a i n i n g , where lower b l o o d l a c t a t e c o n c e n t r a t i o n s have been found w i t h t r a i n e d but not u n t r a i n e d l i m b s ( K l a u s e n et a l . , 1972; Ridge e t a l . , 1976). In c o n t r a s t t o the s e v e r a l s t u d i e s which have i m p l i c a t e d b l o o d l a c t a t e c o n c e n t r a t i o n as a f a c t o r which i n f l u e n c e s the p e r c e p t i o n of e f f o r t , s t u d i e s which have i n v e s t i g a t e d the 30 e f f e c t s of b r e a t h i n g h y p e r o x i c gas m i x t u r e s d u r i n g e x e r c i s e do not c o n s i s t e n t l y s u pport a s t r o n g r e l a t i o n s h i p between the s e v a r i a b l e s . Pedersen and Welch (1977) obs e r v e d t h a t d u r i n g p r o g r e s s i v e b i c y c l e e x e r c i s e w h i l e b r e a t h i n g 21%, 50% and 80% 02, c o n c o m i t a n t r e d u c t i o n s i n RPE and b l o o d l a c t a t e were of d i f f e r e n t magnitudes. However, A l l e n and P a n d o l f (1977) e x e r c i s e d s u b j e c t s f o r 5 minutes on a t r e a d m i l l a t 50% and 80% of t h e i r MAP, b r e a t h i n g 21% and 80% 02. W h i l e b r e a t h i n g 80% 02, a t b o t h 50% and 80% MAP, lower b l o o d l a c t a t e v a l u e s were p a r a l l e l e d by s i m i l a r d e c l i n e s i n RPE. The r e s u l t s from some p r e v i o u s r e s e a r c h have not shown any c o r r e l a t i o n between RPE and b l o o d l a c t a t e . S t a m f o r d and Noble (1974) were unable t o show t h a t a r t e r i a l l a c t a t e c o n c e n t r a t i o n s d u r i n g e x e r c i s e a t 960 kgm-min" 1 and p e d a l l i n g r a t e s of 40 rpm d i f f e r e d from those a t 60 rpm when work time was h e l d c o n s t a n t . However, RPE were s i g n i f i c a n t l y lower a t the s l o w e r p e d a l l i n g speed. On the b a s i s of t h i s f i n d i n g , the a u t h o r s c o n c l u d e d t h a t l o c a l muscle s t r a i n was not r e f l e c t e d by b l o o d l a c t a t e as a p e r c e p t u a l cue. However, the d a t a was c o l l e c t e d from a h i g h l y f i t group of s u b j e c t s (V02max = 61.4 ml-kg" 1*min" 1 ) , and the e x e r c i s e i n t e n s i t i e s which were employed may have been i n s u f f i c i e n t t o s t i m u l a t e a l a c t a t e r e s p o n s e . E x e r c i s e was performed a t or l e s s than 65% V02max, and t h i s i n t e n s i t y has been shown t o be below the a e r o b i c t h r e s h o l d of c e r t a i n h i g h l y t r a i n e d i n d i v i d u a l s ( C o s t i l l , 1970; Kinderman et a l . , 1979). That t h i s was the case i s s u p p o r t e d by the f a c t t h a t n e g l i g i b l e i n c r e a s e s i n b l o o d l a c t a t e were obse r v e d d u r i n g the e x e r c i s e 31 p e r i o d s . In a d d i t i o n , i t has been noted elsewhere ( M i h e v i c , 1981) t h a t a 9-point s c a l e was u t i l i z e d t o measure e f f o r t p e r c e p t i o n i n the s t u d y , which may p r e c l u d e the m e a n i n g f u l i n t e g r a t i o n of the s e r e s u l t s w i t h o t h e r r e s e a r c h which has been conducted u s i n g the Borg s c a l e or s t a n d a r d r a t i o - s c a l i n g p r o c e d u r e s . N e v e r t h e l e s s , t h i s i n f o r m a t i o n s u g g e s t s t h a t b l o o d l a c t a t e l e v e l s o n l y a f f e c t the p e r c e p t i o n of e f f o r t once a c r i t i c a l e x e r c i s e i n t e n s i t y t h r e s h o l d has been a c h i e v e d . Kay and Shephard (1969) were a l s o unable t o demonstrate a s i g n i f i c a n t c o r r e l a t i o n between RPE and b l o o d l a c t a t e (r=0.15). However, i t was argued ( M i h e v i c , 1981) t h a t t h i s may merely have r e f l e c t e d the r e s t r i c t e d p e r c e p t u a l v a l u e s which were o b t a i n e d , s i n c e the r e l a t i o n s h i p between RPE and l a c t a t e was o n l y a n a l y s e d a t a s i n g l e e x e r c i s e i n t e n s i t y (80% MAP). A l t h o u g h some e v i d e n c e s u p p o r t s the r o l e of l a c t a t e c o n c e n t r a t i o n as a p o t e n t s t i m u l u s f o r the perception of e f f o r t , the mechanism by which t h i s i n f l u e n c e might be mediated i s vague. I t has been suggested t h a t p a i n and d i s c o m f o r t i n the wo r k i n g muscles may be r e l a t e d t o the s t i m u l a t i o n of f r e e nerve endings due t o the m e t a b o l i c a c i d o s i s which i s in d u c e d by e l e v a t i o n s i n muscle l a c t a t e c o n c e n t r a t i o n s (Kay and Shephard, 1969; P a n d o l f , 1978; Stamford and Noble, 1974). E x p e r i m e n t a l r e s e a r c h does not support t h i s p o s i t i o n . P o u l u s e t a l . (1974) demonstrated t h a t the i n f u s i o n of NaHC03 t o c o r r e c t f o r a c i d e m i a d u r i n g p r o g r e s s i v e l y i n c r e a s i n g e x e r c i s e i n t e n s i t i e s t o e x h a u s t i o n on a b i c y c l e ergometer has no impact upon s u b j e c t i v e e s t i m a t e s of f a t i g u e . K o s t k a and C a f a r e l l i (1982) found t h a t 32 n e i t h e r induced a c i d o s i s (NH4C1) or a l k a l o s i s (NaHC03) had any e f f e c t upon e f f o r t s e n s a t i o n s d u r i n g moderate e x e r c i s e (50% V02max). However, d u r i n g heavy e x e r c i s e (80% V02max), a c i d o s i s i n c r e a s e d sensory i n t e n s i t y by 20% a f t e r 15 m i n u t e s . Thus, a l t h o u g h the e v i d e n c e i s c o n f l i c t i n g , i t appears as though b l o o d l a c t a t e c o n c e n t r a t i o n s may i n f l u e n c e p e r c e i v e d e x e r t i o n by some p r e s e n t l y u n i d e n t i f i e d pathway, r a t h e r than t h r o u g h a r e d u c t i o n i n pH. E a r l y a t t e m p t s t o a n a l y s e the s e n s o r y dimension of e f f o r t e x p e n d i t u r e a l s o r e p o r t e d as a s s o c i a t i o n between RPE and c i r c u l a t i n g c a t e c h o l a m i n e s (Docktor and Sharkey, 1971; Frankenhaeuser, 1969). L i k e b l o o d l a c t a t e and RPE, n o r e p i n e p h r i n e e x c r e t i o n e x h i b i t s a p o s i t i v e l y a c c e l e r a t i n g f u n c t i o n when p l o t t e d a g a i n s t r e l a t i v e work i n t e n s i t y (Howley, 1976). W h i l e e l e v a t i o n s i n n o r e p i n e p h r i n e may o c c u r a t low submaximal e x e r c i s e i n t e n s i t i e s (Howley, 1976), they o n l y become prominent d u r i n g i n t e n s e a c t i v i t y ( A s t r a n d , 1970; Frankenhaeuser, 1969; Howley, 1976). The b e g i n n i n g of the s t e e p i n c r e a s e i n c a t e c h o l a m i n e c o n c e n t r a t i o n appears t o be l o c a t e d a t a w o r k l o a d near 70% V02max (Galbo e t a l . , 1975; Haggendal et a l . , 1970; Schnabel e t a l . , 1982). I t has been p o s t u l a t e d t h a t the p o i n t a t which c a t e c h o l a m i n e l e v e l s a r e augmented c o i n c i d e s w i t h a d ecrease i n muscle g l y c o g e n a v a i l a b i l i t y (Pequignot e t a l . , 1980; Schnabel e t a l . , 1982). I t has been shown ( B e l l et a l . , 1975) t h a t g l u c o s e i n g e s t i o n p r i o r t o e x e r c i s e does produce a r e d u c t i o n i n RPE d u r i n g p r o l o n g e d work. The a u t h o r s suggested t h a t i n p u t from g l u c o s e r e c e p t o r s may be c o n s c i o u s l y m o n i t o r e d 33 by s u b j e c t s d u r i n g e x e r c i s e . S i n c e muscular f a t i g u e has been a t t r i b u t e d t o muscle g l y c o g e n d e p l e t i o n (Bergstrom e t a l . , 1967; Hermansen e t a l . , 1967), i t may be t h a t c a t e c h o l a m i n e s a re r e l a t e d more t o the p e r c e p t i o n of f a t i g u e than the p e r c e p t i o n of e f f o r t , per s e . The importance of d i f f e r e n t i a t i n g between the c o n s t r u c t s of e x e r t i o n and f a t i g u e has been emphasized p r e v i o u s l y ( B o r g , 1962; R e j e s k i , 1981). S i m i l a r l y , s t u d i e s (Kamon et a l . , 1974; P a n d o l f e t a l . , 1972) which have i m p l i c a t e d s k i n or c o r e temperature as p e r c e p t u a l cues a f f e c t i n g RPE may have f a i l e d t o d i s c r i m i n a t e between p e r c e i v e d e f f o r t and p e r c e i v e d d i s c o m f o r t . Consequent t o the i d e n t i f i c a t i o n of the p h y s i o l o g i c a l cues which p u r p o r t e d l y a f f e c t the p e r c e p t i o n of e f f o r t , numerous a t t e m p t s have been made t o a s s e s s the r e l a t i v e c o n t r i b u t i o n of c e n t r a l v e r s u s l o c a l f a c t o r s t o RPE. O r i g i n a l l y (Ekblom and G o l d b a r g , 1971), i t was proposed t h a t l o c a l f a c t o r s dominate e f f o r t p e r c e p t i o n d u r i n g work w i t h s m a l l muscle groups, but t h a t p e r c e p t u a l cues c o u l d be complemented by c e n t r a l i n p u t s when l a r g e muscle groups are employed. However, i t has been shown t h a t l o c a l components may s t i l l p r o v i d e the most i n t e n s e sensory s t i m u l u s , i r r e s p e c t i v e of the s i z e of the muscle mass which i s r e c r u i t e d (Horstman et a l . , 1979b; P a n d o l f and N o b l e , 1973; Stamford and N o b l e , 1974). To e f f e c t i v e l y d i s t i n g u i s h between the magnitude of the p e r i p h e r a l v e r s u s c e n t r a l cues, d i f f e r e n t i a t e d r a t i n g s of p e r c e i v e d e x e r t i o n have been u t i l i z e d ( P a n d o l f , 1982). When 34 u s i n g t h i s t e c h n i q u e d u r i n g c y c l i n g or t r e a d m i l l r u n n i n g , s u b j e c t s are r e q u e s t e d to r e p o r t s e p a r a t e e s t i m a t e s f o r the degree of e f f o r t which they a r e e x p e r i e n c i n g below the w a i s t ( l o c a l ) and above the w a i s t ( c e n t r a l ) . In a d d i t i o n , an i n t e r p r e t a t i o n of the o v e r a l l e f f o r t which i s expended t o p e r f o r m the work i s r e c o r d e d . W h i l e u n d i f f e r e n t i a t e d e x e r t i o n may be r e p r e s e n t a t i v e of n o n - p h y s i o l o g i c a l v a r i a b l e s and g e n e r a l i z e d p h y s i o l o g i c a l e v e n t s , d i f f e r e n t i a t e d r e p o r t s more c l o s e l y r e f l e c t d i s c r e e t p h y s i o l o g i c a l symptoms (Robe r t s o n et a l , 1979b). D u r i n g c y c l i n g e x e r c i s e , i t has been shown t h a t o v e r a l l and l o c a l e f f o r t c o n s i s t e n t l y o v e r i d e c e n t r a l s e n s a t i o n s ( C a f a r e l l i e t a l . , 1977; Gamberale, 1972; Knuttgen et a l . , 1982; M i h e v i c et a l . , 1982; P a n d o l f , 1977; R o b e r t s o n et a l . , 1979a; Young e t a l . , 1982). At h i g h speeds of w a l k i n g w h i l e c a r r y i n g l o a d s , l o c a l RPE i s h i g h e r than o v e r a l l RPE, and c e n t r a l RPE i s lower than o v e r a l l RPE (Robertson et a l . , 1982a). D u r i n g t r e a d m i l l e x e r c i s e , c e n t r a l f a c t o r s e x e r t a p r o p o r t i o n a l l y g r e a t e r i n f l u e n c e (Kay and Shephard, 1969; P a n d o l f e t a l . , 1975). P a n d o l f et a l . (1975) have suggested t h a t on a r e l a t i v e b a s i s , more h i g h - g l y c o l y t i c , f a s t - t w i t c h motor u n i t s a r e a c t i v a t e d d u r i n g c y c l i n g than r u n n i n g . C o n s e q u e n t l y , g r e a t e r a f f e r e n t i n p u t i n t o the r e t i c u l a r a c t i v a t i n g system from p e r i p h e r a l p a i n r e c e p t o r s , muscle s p i n d l e s and G o l g i tendon organs may o ccur d u r i n g c y c l i n g than r u n n i n g ( P a n d o l f et a l . , 1975). T h i s may h e l p t o e x p l a i n the d i f f e r e n c e s i n sensory i n p u t s between the two forms of e x e r c i s e . 35 Young et a l . (1982) used m a n i p u l a t i o n s i n a l t i t u d e t o i n v e s t i g a t e d i f f e r e n t i a t e d RPE. They p o i n t out t h a t when comparing e x e r c i s e a t a l t i t u d e t o t h a t a t sea l e v e l , a g i v e n a b s o l u t e workload p l a c e s a r e l a t i v e l y g r e a t e r m e t a b o l i c demand upon the body. F u r t h e r m o r e , a t t h e same r e l a t i v e i n t e n s i t y , e x e r c i s e a t a l t i t u d e r e s u l t s i n i n c r e a s e d v e n t i l a t i o n , but no changes a r e ob s e r v e d i n HR, c a r d i a c o u t p u t , s t r o k e volume, or b l o o d l a c t a t e . In t h e i r study of d i f f e r e n t a t e d RPE a t sea l e v e l , a c u t e and c h r o n i c exposure t o a l t i t u d e , s u b j e c t s c y c l e d f o r 30 minutes a t a w o r k l o a d which e l i c i t e d 85% V02max d u r i n g each c o n d i t i o n . D e s p i t e d e c r e a s e s i n the a b s o l u t e c o s t of each r e l a t i v e e x e r c i s e i n t e n s i t y d u r i n g a c u t e h i g h a l t i t u d e e x e r c i s e , l o c a l RPE d i d not d i f f e r from the v a l u e s o b t a i n e d a t sea l e v e l . However, d u r i n g c h r o n i c exposure t o h i g h a l t i t u d e , l o c a l RPE was reduced and c e n t r a l RPE became the dominant cue. C e n t r a l RPE v a l u e s d u r i n g c h r o n i c a l t i t u d e exposure were not s i g n i f i c a n t l y d i f f e r e n t from those o b t a i n e d d u r i n g e x e r c i s e a t sea l e v e l or ac u t e a l t i t u d e . A l t e r a t i o n s i n l o c a l RPE were found t o p a r a l l e l changes i n b l o o d l a c t a t e , which d i d not d i f f e r between sea l e v e l and a c u t e a l t i t u d e , but were reduced subsequent t o c h r o n i c a l t i t u d e e x posure. Based on these f i n d i n g s , i t was suggested t h a t the p e r c e p t i o n of c e n t r a l e f f o r t i s r e l a t e d t o r e l a t i v e e x e r c i s e i n t e n s i t y , whereas l o c a l muscular e f f o r t i s more dependent upon the a b s o l u t e m e t a b o l i c demands of the work b e i n g performed. The r e s u l t s from t h i s s tudy s h o u l d be i n t e r p r e t e d c a u t i o u s l y . F o l l o w i n g c h r o n i c exposure t o a l t i t u d e , b l o o d l a c t a t e v a l u e s were r e p o r t e d to be l e s s than 2 m M / l i t r e d u r i n g 36 c y c l i n g which had been p r e v i o u s l y d e s i g n e d t o e l i c i t 85% V02max. T h i s f i n d i n g i s u n u s u a l , p a r t i c u l a r l y when the low f i t n e s s l e v e l of the s u b j e c t s i s c o n s i d e r e d . F u r t h e r m o r e , f o l l o w i n g a c c l i m a t i z a t i o n , i t would be expected t h a t a g i v e n r e l a t i v e e x e r c i s e i n t e n s i t y would c o r r e s p o n d t o a g r e a t e r a b s o l u t e w o r k l o a d . That t h i s o c c u r r e d i s s u p p o r t e d by the f a c t t h a t o v e r a l l e f f o r t p e r c e p t i o n was h i g h e r a f t e r 18 days a t a l t i t u d e , a l t h o u g h t h i s change was not s i g n i f i c a n t . The a u t h o r s r e p o r t e d t h a t e x e r c i s e on the 18th day of h i g h a l t i t u d e was performed a t the same a b s o l u t e and r e l a t i v e e x e r c i s e i n t e n s i t y as d u r i n g a c u t e a l t i t u d e exposure. T h e r e f o r e , the r e s u l t s suggest t h a t a l a r g e d e crease i n b l o o d l a c t a t e o c c u r r e d a t the same a b s o l u t e and r e l a t i v e w o r k l o a d f o l l o w i n g c h r o n i c a l t i t u d e exposure, and t h a t no a c c l i m a t i z a t i o n o c c u r r e d . The p o s s i b l e mechanisms f o r these unusual r e s u l t s a r e u n c l e a r . However, i f as e x p e c t e d , a b s o l u t e w o r k l o a d s c o u l d a c t u a l l y be performed w i t h l e s s m e t a b o l i c s t r e s s , t h e n , t h e decrements i n l o c a l RPE and b l o o d l a c t a t e f o l l o w i n g c h r o n i c a l t i t u d e exposure would be e x p l a i n a b l e . In t h i s c a s e , c e n t r a l RPE would be most c l o s e l y r e l a t e d t o a b s o l u t e e x e r c i s e i n t e n s i t y , and l o c a l RPE t o r e l a t i v e e x e r c i s e i n t e n s i t y . A r e c e n t s t u d y by M i h e v i c e t a l . (1982) s u p p o r t s the p r o p o s a l t h a t c e n t r a l and l o c a l RPE are r e l a t e d t o the. a b s o l u t e and r e l a t i v e i n t e n s i t y of e x e r c i s e , r e s p e c t i v e l y . In t h i s e x periment, s u b j e c t s c y c l e d under normoxic and h y p e r o x i c c o n d i t i o n s . T e s t p r o t o c o l s i n c l u d e d c y c l i n g at 75% V02max ( n o r m o x i c ) , 75% normal V02 max b r e a t h i n g 70% 02, and 75% 37 h y p e r o x i c V02max, b r e a t h i n g 70% V02. C e n t r a l RPE was e l e v a t e d d u r i n g the t h i r d c o n d i t i o n , when the workload was a b s o l u t e l y h i g h e r , but r e l a t i v e l y e q u i v a l e n t t o the f i r s t c o n d i t i o n . O v e r a l l and l o c a l RPE were g r e a t e r d u r i n g the second c o n d i t i o n , when the a b s o l u t e w o r k l o a d was the same, but was r e l a t i v e l y l e s s than d u r i n g the f i r s t c o n d i t i o n . Horstman e t a l . (1979b) have a l s o compared p e r c e p t u a l responses d u r i n g e x e r c i s e a t a l t i t u d e (4300m) t o t h a t performed a t sea l e v e l . They m o n i t o r e d RPE d u r i n g 6 minutes of e x e r c i s e a t 60, 80 and 95% V"02max, and a t 5 minute i n t e r v a l s d u r i n g e x e r c i s e t o e x h a u s t i o n a t 85% V02max. In the lower range of submaximal e x e r c i s e , RPE was s i g n i f i c a n t l y l e s s f o r e q u i v a l e n t r e l a t i v e w o r k l o a d s a t a l t i t u d e than a t sea l e v e l , eventhough VE was e l e v a t e d by 12%. These d i f f e r e n c e s were reduced and e v e n t u a l l y e l i m i n a t e d as the e x e r c i s e p r o g r e s s e d towards maximal l e v e l s , or as p r o l o n g e d e x e r c i s e c o n t i n u e d u n t i l e x h a u s t i o n . The a u t h o r s c o n c l u d e d t h a t l o c a l f a c t o r s such as muscular s t r a i n e x e r t g r e a t e r i n f l u e n c e upon e f f o r t p e r c e p t i o n a t e x e r c i s e i n t e n s i t i e s which do not g r e a t l y s t r e s s c e n t r a l f a c t o r s , w h i l e c e n t r a l f a c t o r s e x e r t g r e a t e r i n f l u e n c e a t h i g h e r l e v e l s of work. The o b s e r v a t i o n s from b o t h of the a l t i t u d e s t u d i e s g i v e f u r t h e r e v i d e n c e t o support the n o t i o n t h a t a c r i t i c a l work t h r e s h o l d must be a c h i e v e d b e f o r e c e n t r a l cues s i g n i f i c a n t l y a f f e c t the p e r c e p t i o n of e f f o r t . R obertson (1982) has noted t h a t RPE b e g i n s t o p a r a l l e l VE when e x e r c i s e exceeds 50% V02max, 38 which i s a p p r o x i m a t e l y the same m e t a b o l i c r a t e a t which peak t i d a l volume i s a c h i e v e d . The t r a n s m i s s i o n of s i g n a l s from mechanoreceptors i n the r e s p i r a t o r y muscles t o the s e n s o r i m o t o r c o r t e x i s c o n s c i o u s l y m o n i t o r e d when the t i d a l volume exceeds 700 ml (Wolkove et a l . , 1981). C a f a r e l l i and Noble (1976) have r e p o r t e d t h a t v e n t i l a t o r y volume must i n c r e a s e by a minimum of 30 l i t r e s per minute i f e f f o r t p e r c e p t i o n i s t o be s i g n i f i c a n t l y a f f e c t e d . Salamon et a l . (1977) have shown t h a t the p s y c h o p h y s i c a l power f u n c t i o n which d e s c r i b e s the r e l a t i o n s h i p between l u n g volumes and e f f o r t p e r c e p t i o n i s d i f f e r e n t above and below the 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 (FRC). In a d d i t i o n , the exponents f o r the judgement of r e s p i r a t o r y volumes were found t o be g r e a t e r f o r e x p i r a t o r y than i n s p i r a t o r y m uscles. T h i s was t r u e even when t i d a l volume r a t h e r than FRC was used as a r e f e r e n c e . E x p i r a t o r y muscles a r e r e c r u i t e d p r i m a r i l y d u r i n g f o r c e d e x p i r a t i o n (West, 1979). These f i n d i n g s may p a r t i a l l y e x p l a i n the g r e a t e r r e l a t i v e i n p u t of VE i n t o e f f o r t p e r c e p t i o n a t h i g h e r w o r k l o a d s . They a l s o i n d i c a t e t h a t c e n t r a l e f f o r t p e r c e p t i o n i s r e l a t e d t o the a b s o l u t e r a t h e r than the r e l a t i v e c o s t of the e x e r c i s e which i s b e i n g performed. A c r i t i c a l a b s o l u t e work t h r e s h o l d must be a c h i e v e d as a p r e r e q u i s i t e t o the onset of the c e n t r a l s i g n a l . Above t h i s p o i n t , the i n t e n s i t y of the c e n t r a l s t i m u l u s i n c r e a s e s p r o p o r t i o n a t e l y as a f u n c t i o n of the a b s o l u t e r a t h e r than r e l a t i v e i n c r e a s e s i n v e n t i l a t i o n . With r e s p e c t t o the source of l o c a l e f f o r t p e r c e p t i o n , the a l t i t u d e s t u d i e s r e p o r t e d c o n f l i c t i n g r e s u l t s . At e q u i v a l e n t 39 r e l a t i v e e x e r c i s e i n t e n s i t i e s , Young et a l . . (1982) found no d i f f e r e n c e s between the p e r c e p t i o n of l o c a l muscle e x e r t i o n d u r i n g e x e r c i s e a t sea l e v e l or a c u t e a l t i t u d e . A p p a r e n t l y , l o c a l RPE was r e l a t e d t o b l o o d l a c t a t e l e v e l s r a t h e r than p h y s i c a l s t r a i n . In c o n t r a s t , Horstman et a l . (1979b) o b s e r v e d a r e d u c t i o n i n RPE d u r i n g l o w - i n t e n s i t y e x e r c i s e a t a l t i t u d e . T h i s was presumably due t o d i m i n i s h e d l o c a l muscle t e n s i o n , because the a b s o l u t e w o r k l o a d was l e s s f o r a g i v e n r e l a t i v e i n t e n s i t y of e x e r c i s e . T h i s apparent c o n t r a d i c t i o n can p r o b a b l y be e x p l a i n e d i n terms of d i f f e r e n c e s i n the sample groups and e x e r c i s e p r o t o c o l s which were used. In the f i r s t i n s t a n c e , u n f i t s u b j e c t s (V02max =42 ml-kg" 1- min" 1 ) c y c l e d a t 85% V02max at sea l e v e l and a l t i t u d e . A l t h o u g h the demands of a g i v e n e x e r c i s e a t a l t i t u d e may have been a b s o l u t e l y l e s s , i t i s c o n c e i v a b l e t h a t l o c a l muscle s t r a i n w h i l e p e r f o r m i n g at 85% V02max would s t i l l be p e r c e i v e d as near maximal i n i n d i v i d u a l s who were unaccustomed t o e x e r c i s e . By c o m p a r i s o n , Horstman et a l (1979b) s e l e c t e d s u b j e c t s who were more f i t (V02max =49 ml> kg" 1-min" 1) . R e d u c t i o n s i n RPE were found a t 60 and 80% V02max when e x e r c i s e was c o n d u c t e d a t a l t i t u d e . These lower e x e r c i s e i n t e n s i t i e s , p a r t i c u l a r l y i n b e t t e r c o n d i t i o n e d s u b j e c t s , may have been below the t h r e s h o l d a t which maximum p h y s i c a l s t r a i n would be p e r c e i v e d . C o n s e q u e n t l y , reduced s t r a i n i n the w o r k i ng muscles d u r i n g e x e r c i s e a t a l t i t u d e may have been more e a s i l y d e t e c t e d . These f i n d i n g s imply t h a t the p r o p o r t i o n of l o c a l s e nsory i n p u t which i s d e r i v e d from s o u r c e s a s s o c i a t e d w i t h b l o o d l a c t a t e or neuromuscular f a c t o r s may a l s o 40 be a f u n c t i o n of the r e l a t i v e e x e r c i s e i n t e n s i t y . That p h y s i c a l s t r a i n i n the e x e r c i s i n g muscles has a s u p e r i o r impact upon the p e r c e p t i o n of e f f o r t a t low work l e v e l s , and b l o o d l a c t a t e g r e a t e r i n f l u e n c e d u r i n g i n t e n s e a c t i v i t y i s s u p p o r t e d by the f i n d i n g s of R o b e r t s o n e t a l . ( 1 9 7 9 b ) . In t h e i r e x p e r i m e n t , 50 male s u b j e c t s performed 3 s e p a r a t e b i c y c l e ergometer t e s t s , w i t h a c o n s t a n t power o u t p u t of 840 kpm/min. P e d a l l i n g r a t e was randomly s e t a t 40, 60, or 80 rpm. C e n t r a l , p e r i p h e r a l and o v e r a l l RPE was h i g h e r a t 40 rpm than a t 60 or 80 rpm, eventhough l a c t i c a c i d was s i m i l a r between p e d a l l i n g r a t e s . I t has been p r e v i o u s l y shown ( C a f a r e l l i , 1977;. H e n r i k k s o n e t a l . , 1972; P a n d o l f and N o b l e , 1973) t h a t the magnitude of the l o c a l s i g n a l f o r e f f o r t p e r c e p t i o n i n c r e a s e s as a f u n c t i o n of the s t a t i c work which i s performed. At lower speeds, b i c y c l e ergometer work r e q u i r e s h i g h e r i n t e n s i t y , slower muscular c o n t r a c t i o n s than work performed a t h i g h e r p e d a l l i n g r a t e s ( C a f a r e l l i e t a l . , 1977; Hermansen and S a l t i n , 1969; P e t r o f s k y et a l . , 1974). T h e r e f o r e , a t lower c y c l i n g r a t e s , the amount of muscle mass which i s r e c r u i t e d would be l e s s than a t h i g h e r f r e q u e n c i e s ( C a f a r e l l i , 1977; P a n d o l f and Noble, 1973; Stamford and Noble, 1974). Under t h e s e c i r c u m s t a n c e s , the muscles would be o p e r a t i n g a t a h i g h e r r e l a t i v e w o r k l o a d . C a f a r e l l i (1977) has a l s o shown s l o w e r p e d a l l i n g r a t e s t o be more e f f o r t f u l than f a s t e r r a t e s , i n the abscence of m e t a b o l i c d i f f e r e n c e s . The p r e v i o u s l y d i s c u s s e d l i t e r a t u r e has shown s t r o n g 41 c o r r e l a t i o n s between b l o o d l a c t a t e and l o c a l RPE d u r i n g i n t e n s e a c t i v i t y . These f i n d i n g s a r e c o r r o b o r a t e d by the r e s u l t s of a s t u d y by R o b e r t s o n e t a l . (1982b). These a u t h o r s found t h a t s i g n a l s of e x e r t i o n d u r i n g i s o l a t e d l i m b e x e r c i s e were l i n k e d to b l o o d pH and plasma b u f f e r i n g . At 80% V02max, induced a l k a l o s i s (NaHC03) produced s i g n i f i c a n t l y lower l o c a l RPE i n the e x e r c i s i n g l i m b s when compared t o a c o n t r o l group who r e c e i v e d a p l a c e b o (CaC03). T h i s was found t o be t r u e whether arm c r a n k i n g or l e g p e d a l l i n g were u t i l i z e d . However, at 40% V02max, l o c a l RPE d i d not d i f f e r between th e t r e a t m e n t group and those r e c e i v i n g the p l a c e b o . P h y s i c a l s t r a i n i n the working muscles may a l s o be p e r c e p t u a l l y prominent a t h i g h e r workloads i f m e c h a n i c a l e f f i c i e n c y i s poor. T h i s was demonstrated by Horstman et a l . (1979a) who found l o c a l RPE t o more markedly dominate c e n t r a l RPE when w a l k i n g was compared t o r u n n i n g , at 80% V02max. In summary, d a t a from s t u d i e s which have examined both d i f f e r e n t i a t e d and u n d i f f e r e n t i a t e d RPE d u r i n g e x e r c i s e s u p p o r t a t w o - f a c t o r t h e o r y f o r p h y s i o l o g i c a l i n p u t i n t o the e f f o r t sense. D u r i n g low l e v e l s of a c t i v i t y , p h y s i c a l s t r a i n i n the w o r k i n g muscles appears t o be the p r i m a r y s t i m u l u s f o r e f f o r t p e r c e p t i o n . When work i n t e n s i t y exceeds the l a c t a t e t h r e s h o l d , i n c r e m e n t a l e l e v a t i o n s i n b l o o d l a c t a t e complement p e r i p h e r a l i n p u t from the neuromuscular mechanisms. Once a c r i t i c a l a b s o l u t e v e n t i l a t o r y t h r e s h o l d i s reached, c e n t r a l i n p u t a l s o c o n t r i b u t e s to e f f o r t p e r c e p t i o n . In most i n s t a n c e s , p e r i p h e r a l i n p u t predominates over c e n t r a l c ues, a l t h o u g h i t has been shown 42 t h a t pronounced c e n t r a l cues may predominate the e f f o r t sense. In terms of magnitude, c e n t r a l s i g n a l s have been r e p o r t e d ( C a f a r e l l i et a l . , 1977; Robertson e t a l . , 1979a) t o v a r y from 30-70% of l o c a l s i g n a l s over a wide, range of submaximal i n t e n s i t i e s . Thus the sensory i n t e g r a t i o n p r o c e s s a p p a r e n t l y i n v o l v e s a weighted a v e r a g i n g of dominant r e g i o n a l s i g n a l s ( R o b e r t s o n e t a l . , 1979a). A l t h o u g h the f i n d i n g s from the m a j o r i t y of the l i t e r a t u r e which has been reviewed may be accomodated by t h i s model, two i n v e s t i g a t i o n s have p r o v i d e d n o t i c a b l y d i f f e r e n t l y r e s u l t s . M i h e v i c et a l . (1981a) showed t h a t when h i g h l y f i t s u b j e c t s (V02max = 66.5 ml'kg~ 1 • min~ 1 ) s e l f - r e g u l a t e t h e i r r u n n i n g pace at p e r c e p t u a l l y c o m f o r t a b l e (62% V02max) and hard (79% V02max) l e v e l s , l o c a l RPE i s h i g h e r than c e n t r a l RPE o n l y d u r i n g the ha r d r u n. C u r r e n t u n d e r s t a n d i n g of the mechanisms which d e t e r m i n e p h y s i o l o g i c a l i n p u t i n t o the e f f o r t sense p r e v e n t s m e a n i n g f u l i n t e r p r e t a t i o n of these r e s u l t s . L o l l g e n e t a l . (1980) found t h a t when c y c l i n g a t z e r o w o r k l o a d , 70% V02max, or maximal i n t e n s i t i e s , RPE was not always r e l a t e d t o any of the c e n t r a l (HR, VE, V02) or l o c a l (muscle l a c t a t e , b l o o d l a c t a t e , NAD, g l y c o g e n , ATP, CP) cues which were m o n i t o r e d . However, RPE was l i n k e d t o c e n t r a l f a c t o r s a t h i g h speeds of l i m b movement, even d u r i n g unloaded p e d a l l i n g . A r e l a t i o n s h i p between c e n t r a l RPE and speed of l i m b movement , independent of w o r k l o a d , has a l s o been shown elsewhere ( C r o i s a n t , 1982). These s t u d i e s h i g h l i g h t both the c o m p l e x i t y of e f f o r t p e r c e p t i o n , and the need f o r a b e t t e r u n d e r s t a n d i n g of the p h y s i o l o g i c a l components upon 43 which i t i s based. I I I . N o n - P h y s i o l o g i c a l Input I n t o RPE C l e a r l y , the p e r c e p t i o n of e f f o r t cannot be a d e q u a t e l y d e s c r i b e d i n terms of p h y s i o l o g i c a l i n p u t a l o n e . Morgan (1973b) has c a l c u l a t e d t h a t p h y s i o l o g i c a l v a r i a b l e s a r e a b l e t o account f o r o n l y 67% of the t o t a l v a r i a n c e i n RPE. I n t u i t i v e l y , the i n f l u e n c e which v a r i o u s p s y c h o m e t r i c and p e r s o n a l i t y v a r i a b l e s such as m o t i v a t i o n e x e r t upon RPE would be a c c e n t u a t e d d u r i n g s t r e n u o u s e x e r c i s e . In p r a c t i c e , t h i s does not appear t o be the c a s e . When p h y s i o l o g i c a l cues are i n t e n s e , the p e r f o r m e r may f i n d i t u n r e a l i s t i c t o a l t e r RPE ( R e j e s k i , 1980). R e j e s k i and R i b i s l (1980) found t h a t d u r i n g moderate e x e r c i s e l a s t i n g 20-30 m i n u t e s , RPE was a f f e c t e d by the a n t i c i p a t e d d u r a t i o n of the t r e a d m i l l r u n . However, towards the t e r m i n a t i o n of e x e r c i s e , when i n t e r n a l cues were maximized, the r o l e of e x t e r n a l cues i n d e t e r m i n i n g RPE was l e s s a p p r e c i a b l e . Many o t h e r i n v e s t i g a t o r s have a l s o f o c u s e d upon the d i s t o r t i o n of RPE as an a r t i f a c t of c o m p e t i t i o n between i n t e r n a l and e x t e r n a l c u e s . D u r i n g e x e r c i s e r a n g i n g from 40-80% V02max, RPE have been shown t o be s t a b l e d u r i n g 3 - d i g i t s u b t r a c t i o n (Pyne, 1980) and 1-2 d i g i t a d d i t i o n (Stamford e t a l . , 1979) which were d e s i g n e d t o be d i s t r a c t i n g . Improvements i n r u n n i n g time over e q u a l - l e n g t h c o u r s e s on c r o s s - c o u n t r y t r a i l s v e r s u s a 44 t r a c k have been a t t r i b u t e d t o d i f f e r e n c e s i n e x t e r n a l a t t e n t i o n r e q u i r e m e n t s (Pennebaker and L i g h t n e r , 1980). A u d i t o r y i n p u t such as music and m e c h a n i c a l n o i s e do not a f f e c t RPE ( C a s p e r s e n , 1974). S t u d i e s of t h i s n a t u r e a r e d i f f i c u l t t o c o n t r o l , and may not v a l i d l y d i s c r i m i n a t e between the e f f e c t s of p h y s i o l o g i c a l and p s y c h o l o g i c a l s t r e s s i n d i c a t o r s , as has been i n f e r r e d . R e s e a r c h e r s who attempt t o measure e f f o r t p e r c e p t i o n d u r i n g p h y s i c a l performance t e s t s s h o u l d be c o g n i z a n t of the f i n d i n g t h a t psychomotor and mental performance t a s k s , i n c l u d i n g RPE, a r e a f f e c t e d by the time of day ( F a r i a and Drummond, 1979; Wojtczak et a l . , 1978). The degree t o which t h e s e r e s u l t s may be a s c r i b e d t o the i n f l u e n c e of c i r c a d i a n rhythms or t i r e d n e s s i s u n c e r t a i n . I n i t i a l l y , M a r t i n (1981) o b s e r v e d d i f f e r e n t p e r c e p t u a l r e s p o n s e s d u r i n g p r o l o n g e d e x e r c i s e f o l l o w i n g s l e e p d e p r i v a t i o n . In a subsequent study ( M a r t i n and Haney, 1982), no d i f f e r e n c e was found i n s e l f - s e l e c t e d work i n t e n s i t y on a t r e a d m i l l f o l l o w i n g 30 s l e e p l e s s h o u r s . In the e a r l i e r s t u d y , s u b j e c t s e s t i m a t e d t h e i r p e r c e p t i o n of e f f o r t f o r a g i v e n t a s k , whereas i n the l a t t e r r e p o r t , they were r e q u e s t e d t o r e p l i c a t e a p r e v i o u s l y a d m i n i s t e r e d w o r k l o a d . Due t o s u b j e c t i v e e x p e c t a n c y of lower r e a d i n g s , the r e s u l t s from the f i r s t i n v e s t i g a t i o n may have been b i a s e d ( M a r t i n and Haney, 1982). A t h e o r e t i c a l b a s i s may e x i s t f o r a l t e r a t i o n s i n RPE f o l l o w i n g s l e e p l o s s , s i n c e a n x i e t y , d e p r e s s i o n , c o n f u s i o n and f a t i g u e have been a s s o c i a t e d w i t h t h i s v a r i a b l e ( R o l l e r et a l . , 1966). Morgan (1973) has demonstrated t h a t n e u r o t i c s and 45 d e p r e s s a n t s may l a c k the a b i l i t y t o a c c u r a t e l y r a t e p e r c e i v e d e x e r t i o n . In a d d i t i o n , the same auth o r has shown t h a t e x t r o v e r t s have a h i g h e r p a i n t o l e r a n c e than i n t r o v e r t s , and d i f f e r s i g n i f i c a n t l y i n RPE (Morgan, 1973). E x t r a v e r s i o n and t e n s i o n a f f e c t RPE most markedly when the s u b j e c t s a r e u n f i t ( M i h e v i c , 1979). Because c h r o n i c e x e r c i s e provokes a s i g n i f i c a n t decrement i n d e p r e s s i o n (Morgan e t a l . , 1970) and d i f f e r e n t amounts of d e p r e s s i o n have been found t o occur on a t r e a d m i l l v e r s u s b i c y c l e ergometer i n the workrange 150-160 bpm (Morgan et a l . , 1971), t h i s f a c t o r may be d i f f i c u l t t o c o n t r o l f o r . E v i d e n c e s u g g e s t s t h a t e f f o r t p e r c e p t i o n v a r i e s w i t h the age ( A r s t i l a et a l . , 1975; Bar-Or, 1977; Borg and L i n d e r h o l m , 1976) and sex ( A r s t i l a et a l . , 1977; R e j e s k i , 1980) of s u b j e c t s . P e r c e p t u a l r a t i n g s by women do not f l u c t u a t e as a f u n c t i o n of m e n s t r u a l c y c l e phase (Stephenson e t a l . , 1982). I t may be t h a t due t o c u l t u r a l t r a i n i n g , women do not have s u f f i c i e n t e x p e r i e n c e w i t h f a t i g u e - l i k e symptoms ( R e j e s k i , 1980). With a d v a n c i n g y e a r s , RPE i s h i g h e r f o r a g i v e n r e l a t i v e e x e r c i s e i n t e n s i t y ( A r s t i l a e t a l . , 1977). In c o n t a s t t o the s e f i n d i n g s , S i d ney and Shephard (1977) found no s i g n i f i c a n t d i f f e r e n c e s t o e x i s t between young and o l d or male and female s u b j e c t s when work was e x p r e s s e d as a r e l a t i v e p e r c e n t a g e of MAP. D i f f e r e n c e s i n RPE may a l s o be obser v e d when comparing v a r i a t i o n s i n the s t a t e of h e a l t h of c e r t a i n i n d i v i d u a l s (Borg and L i n d e r h o l m , 1970). 46 E n v i r o n m e n t a l m a n i p u l a t i o n s may a l s o c r e a t e a l t e r a t i o n s i n RPE. Horstman (1977) found RPE t o be s i g n i f i c a n t l y lower when p e r f o r m i n g e x e r c i s e a t 5 degrees c e l s i u s when compared t o the same t e s t performed a t 25 degrees c e l s i u s . T h i s r e d u c t i o n i n RPE p a r a l l e l e d an i n c r e a s e i n VE and V02, and d e c r e a s e s i n RQ and venous l a c t a t e c o n c e n t r a t i o n a t 5 degrees c e l s i u s . The q u a l i t y of the i n s p i r e d a i r d u r i n g e x e r c i s e a l s o appears t o be a d e t e r m i n a n t of RPE. A i r i o n i z a t i o n and p o l l u t i o n ( S o v i j a r v i e t a l . , 1979) or e l e v a t e d ozone l e v e l s ( M i h e v i c et a l , 1981b) i n c r e a s e RPE a t a g i v e n w o r k l o a d . Numerous i n v e s t i g a t i o n s have shown t h a t the n a t u r e of the e x e r c i s e t e s t i t s e l f may i n f l u e n c e RPE. While p r e - e x e r c i s e warm-up may not i n f l u e n c e the r e s u l t s which are o b t a i n e d ( A r o n c h i u k and Burke, 1976; Wojtczak e t a l . , 1978), a m i n i m a l degree of p r e v i o u s e x e r c i s e e x p e r i e n c e i s n e c e s s a r y t o gauge RPE a c c u r a t e l y (Horstman e t a l . , 1979c). D e s p i t e a p l a t e a u i n most p h y s i o l o g i c a l v a r i a b l e s d u r i n g s t e a d y - s t a t e e x e r c i s e , RPE c o n t i n u e s t o r i s e (Noble e t a l . , 1973a; P a n d o l f et a l . , 1972). T h i s r e l a t i o n s h i p between RPE and e x e r c i s e d u r a t i o n has been noted e l s e w h e r e (Borg, 1962; D a v i e s and S a r g e a n t , 1979). V e n t i l a t i o n s t e a d i l y i n c r e a s e s w i t h o u t l e v e l l i n g o f f d u r i n g heavy l o n g - t e r m e x e r c i s e a t a c o n s t a n t w o r kload ( M a r t i n et a l . , 1979). A l o g i c a l h y p o t h e s i s would be t h a t the s u s t a i n e d e l e v a t i o n s i n RPE d u r i n g p r o l o n g e d e x e r c i s e are g e n e r a t e d by t h i s v e n t i l a t o r y d r i f t . In support of t h i s v iew, C a f a r e l l i e t a l . (1977) found t h a t c e n t r a l f a c t o r s grew 47 more d r a m a t i c a l l y than l o c a l f a c t o r s as a f u n c t i o n of e x e r c i s e d u r a t i o n . N e v e r t h e l e s s , as p r e v i o u s l y d i s c u s s e d , d u r i n g extended a c t i v i t y , symptoms of f a t i g u e may be i n c o r p o r a t e d i n t o RPE, and reduce the v a l i d i t y of t h e s e r e a d i n g s . In a d d i t i o n t o p e r c e p t u a l responses o c c u r r i n g p r o l o n g e d s t e a d y - s t a t e e x e r c i s e , i t has a l s o been demonstrated t h a t w o rkload d e t e c t i o n t h r e s h o l d s a r e s e n s i t i v e t o f a t i g u e ( T e g h t s o o n i a n e t a l . , 1977). Weiser and Stamper (1977) have made an attempt t o a s s e s s the r e l a t i v e i n p u t of v a r i o u s p s y c h o m e t r i c and p h y s i o l o g i c a l f a c t o r s which c o r r e l a t e w i t h t h e a b i l i t y t o m a i n t a i n s t e a d y -s t a t e work on a b i c y c l e ergometer. In o r d e r of i n c r e a s i n g magnitude, l e g f a t i g u e , m o t i v a t i o n , p e r c e i v e d e f f o r t , g e n e r a l f a t i g u e and c a r d i o p u l m o n a r y d i s t r e s s were found t o e n t e r i n t o a r e g r e s s i o n e q u a t i o n which a c c o u n t e d f o r 76% of the v a r i a n c e i n e x e r c i s e time m a i n t a i n e d by the s u b j e c t s i n the s t u d y . However, J a c k s o n e t a l . (1981) have demonstrated t h a t the p h y s i o l o g i c a l and p s y c h o l o g i c a l c o r r e l a t e s of e x e r c i s e performance a r e d i f f e r e n t i n a f i e l d s e t t i n g than i n the l a b . Dishman (1978) has p r e v i o u s l y r e p o r t e d t h a t as much as 18% of performance v a r i a n c e i n the 12-minute run may be a c c o u n t e d f o r by mot i v a t i o n . P a n d o l f et a l . (1975) have produced a h i e r a r c h i c a l model f o r p e r c e i v e d e x e r t i o n which c o n s i s t s of 4 d i f f e r e n t l e v e l s of s u b j e c t i v e r e p o r t i n g . I t s u g g e s t s t h a t the d i s c r e t e symptoms of p h y s i o l o g i c a l s t r e s s c o n t r i b u t e t o a h i g h e r " s u b o r d i n a t e " l e v e l of p e r c e p t i o n which e n t a i l s l o c a l muscular e x e r t i o n , g e n e r a l 48 e x e r t i o n , amd c a r d i o - p u l m o n a r y e x e r t i o n . These f a c t o r s a c t as s o u r c e s of i n p u t t o the " o r d i n a t e " l e v e l , which i s composed of p h y s i c a l e x e r t i o n , m o t i v a t i o n and t a s k a v e r s i o n . The h i g h e s t ( " s u p e r o r d i n a t e " ) o r d e r of t h e model i s r e p r e s e n t e d by u n d i f f e r e n t i a t e d e x e r t i o n , which p r o b a b l y c o r r e s p o n d s t o the measured r e a d i n g s from Borg's s c a l e ( P a n d o l f , 1978). The model i s based upon t h e f i n d i n g s of Kinsman e t a l . (1973) who i d e n t i f i e d b i c y c l i n g f a t i g u e , t a s k a v e r s i o n and m o t i v a t i o n as t h r e e s u b j e c t i v e g r o u p i n g s a s s o c i a t e d w i t h p r o l o n g e d , s t r e n u o u s e x e r c i s e . IV. The E f f e c t s Of E x e r c i s e Upon RPE S i n c e t h e p e r c e p t i o n of e f f o r t i s l a r g e l y governed by p h y s i o l o g i c a l i n p u t , i t i s not s u r p r i s i n g t h a t an i n t e r e s t has been g e n e r a t e d i n the e f f e c t s of e x e r c i s e upon RPE. P r e v i o u s a u t h o r s (Morgan e t a l . , 1976; R e j e s k i , 1981) have i n f e r r e d t h a t p h y s i c a l performance may be r e l a t e d as much t o an i n d i v i d u a l s s e l f - p e r c e p t i o n s of a b i l i t y as t o t h e i r a c t u a l performance c a p a c i t y . Dishman and Getman (1981) have shown t h a t 20 weeks of i s o t o n i c or i s o k i n e t i c t r a i n i n g can produce not o n l y s i g n i f i c a n t improvements i n V02max, but i n c r e a s e s i n p s y c h i c v i g o r , a s s e s s e d u s i n g the P r o f i l e of Mood S t a t e s e v a l u a t i o n . C e r t a i n i n d i v i d u a l s a r e known t o e i t h e r c h r o n i c a l l y reduce or augment the i n t e n s i t y of t h e i r p e r c e p t i o n s , i n c l u d i n g t h e i r p e r c e p t i o n of e f f o r t (Robertson et a l . , 1977). A t h l e t e s have been shown t o have a g r e a t e r tendency t o reduce p e r c e p t u a l r a t i n g s than t h e i r 49 n o n - a c t i v e c o u n t e r p a r t s (Ryan and F o s t e r , 1967). In view of t h e s e o b s e r v a t i o n s , i t i s apparent t h a t a t h e o r e t i c a l framework based upon b o t h p h y s i o l o g i c a l and p s y c h o l o g i c a l c o n s i d e r a t i o n s may e x i s t t o s u p p o r t the concept of t r a i n i n g - i n d u c e d a l t e r a t i o n s i n RPE. C e r t a i n p h y s i o l o g i c a l v a r i a b l e s such as maximal HR and MAP a r e known t o be d e t e r m i n e d , i n p a r t , by g e n e t i c endowment. Thus i t may be e x p e c t e d t h a t h e r e d i t y c o u l d s e r v e as an o b s t a c l e t o s i g n i f i c a n t a d a p t a t i o n s i n the p e r c e p t u a l response t o e x e r c i s e . A f t e r a d m i n i s t e r i n g a number of submaximal and maximal workloads on a b i c y c l e ergometer t o 6 monozygous and 8 d i z y g o u s t w i n s , Komi and K a r p p i (1977) were unable t o show s i g n i f i c a n t l y d i f f e r e n t i n t r a - p a i r v a r i a n c e s i n RPE between groups. T h i s was assumed t o be i n d i r e c t e v i d e n c e t h a t RPE was not s i g n i f i c a n t l y i n f l u e n c e d by h e r e d i t y . K i l b o m (1971) has shown t h a t f o l l o w i n g an a e r o b i c e x e r c i s e program, the m e t a b o l i c c o s t of a g i v e n submaximal a c t i v i t y w i l l be unchanged or s l i g h t l y d e c r e a s e d . I t was a l s o found t h a t when e x p r e s s e d as a r e l a t i v e p e r c e n t a g e of maximal work c a p a c i t y , the m e t a b o l i c demands of a p a r t i c u l a r t a s k were reduced. On t h i s b a s i s , i t would be a n t i c i p a t e d t h a t t h e performance of a s t a n d a r d w o r k l o a d would be p e r c e i v e d as b e i n g l e s s e f f o r t f u l . Whether d i f f e r e n c e s i n p e r c e p t u a l e s t i m a t e s of e x e r t i o n c o u l d be e x p e c t e d a t e q u i v a l e n t e x e r c i s e i n t e n s i t i e s f o l l o w i n g t r a i n i n g i s l e s s c l e a r . Numerous s t u d i e s have i n v e s t i g a t e d the e f f e c t s of e x e r c i s e upon RPE by u s i n g a l o n g i t u d i n a l approach. Lewis et a l . (1980) 50 o b s e r v e d a s i g n i f i c a n t r e d u c t i o n i n RPE a t a f i x e d w o r k l o a d , f o l l o w i n g an 11-week t r a i n i n g program conducted at 75-80% V02max. In a c o n t r o l l e d s t u d y , P a n d o l f et a l . (1975) found RPE t o be lower a t a s p e c i f i e d HR or V02 f o l l o w i n g 3 weeks of low i n t e n s i t y , l o n g d u r a t i o n a c t i v i t y . L i n d e r h o l m (1967) was a b l e t o demonstrate t h a t 4 months of i n t e n s i v e e x e r c i s e c o u l d r e s u l t i n a m o d i f i e d e v a l u a t i o n of e f f o r t a t an a b s o l u t e w o r k l o a d . S i x weeks of r a p i d w a l k i n g , s t a i r c l i m b i n g and s t o o l - s t e p p i n g have been shown t o r e s u l t i n decrements i n RPE d u r i n g submaximal e x e r c i s e i n s u b j e c t s s u f f e r i n g from rheumatoid a r t h r i t i s (Ekblom and G o l d b a r g , 1975). U s i n g a l a r g e sample (N=37), Knuttgen et a l . (1973) r e p o r t e d d e c r e a s e d RPE v a l u e s a t a w o r k l o a d of 150 W when each of 3 t r e a t m e n t groups f o l l o w e d d i s p a r a t e i n t e r v a l t r a i n i n g regimens. The t o t a l time of h i g h i n t e n s i t y e x e r c i s e was 15 minutes per s e s s i o n , and the program was c o nducted over a p e r i o d of 1-3 months. C o l l e c t i v e l y , t h e s e s t u d i e s suggest t h a t r a p i d a d j u s t m e n t s i n the p e r c e p t u a l response t o a c t i v i t y o c c u r when e x e r c i s e programs of v a r y i n g i n t e n s i t y and d u r a t i o n a r e a d m i n i s t e r e d . No attempt was made t o c o r r e l a t e RPE w i t h r e l a t i v e e x e r c i s e i n t e n s i t y i n any of t h e s e i n v e s t i g a t i o n s . In c o n t r a s t to these f i n d i n g s , Sidney and Shephard (1977) found t h a t 23 e l d e r l y s u b j e c t s r e p o r t e d augmented RPE v a l u e s a t a g i v e n w o r k l o a d f o l l o w i n g 34 weeks of t r a i n i n g . A l t h o u g h u n a ble t o e x p l a i n t h e i r r e s u l t s , the a u t h o r s n o ted t h a t a p r e l i m i n a r y study i n v o l v i n g the same sample had c o u p l e d s e l f -r e p o r t s of above average a c t i v i t y w i t h low endurance c a p a c i t y . T h i s may s i g n i f y t h a t o l d e r s u b j e c t s l a c k s u f f i c i e n t e x p e r i e n c e 51 w i t h i n t e n s i v e e x e r c i s e t o a c c u r a t e l y gauge e f f o r t e x p e n d i t u r e . In 1971, a s e r i e s of 3 a r t i c l e s were p u b l i s h e d which i n d i c a t e d t h a t a l t h o u g h r e d u c t i o n s i n RPE a r e v i s u a l i z e d a t an a b s o l u t e w o r k l o a d f o l l o w i n g t r a i n i n g , no changes occur w i t h r e s p e c t t o r e l a t i v e e x e r c i s e i n t e n s i t y . D o c k t o r and Sharkey (1971) examined the p e r c e i v e d e x e r t i o n of 5 h e a l t h y but non-a t h l e t i c c o l l e g e men f o l l o w i n g 5 weeks of c o n d i t i o n i n g . Three tim e s per week, t r a i n i n g commenced w i t h t r e a d m i l l w a l k i n g a t 5 mph, f o l l o w e d by 1% e l e v a t i o n s i n the t r e a d m i l l grade u n t i l a HR of 180 bpm was a c h i e v e d . F o l l o w i n g t r a i n i n g , t h e time r e q u i r e d t o a t t a i n , HR v a l u e s of 150 and 180 bpm was i n c r e a s e d , and t h e r e f o r e o c c u r r e d a t a h i g h e r a b s o l u t e w o r k l o a d . No d i f f e r e n c e s i n RPE were observ e d d u r i n g the 6 t h minute of e x e r c i s e or a t a HR of 150 bpm, p o s t - t r a i n i n g . T h i s i l l u s t r a t e s t h a t f o l l o w i n g t r a i n i n g , i n c r e a s e d w o r k l o a d s w i l l be a s s o c i a t e d w i t h any g i v e n e s t i m a t e of e x e r t i o n , i n the range of moderate t o i n t e n s e e x e r c i s e . T h i s may not be the case d u r i n g l i g h t e r a c t i v i t y , i n t h i s i n s t a n c e , a c h i e v e d d u r i n g the 6 t h minute of e x e r c i s e . U s i n g a more r i g o r o u s t r a i n i n g program (5-7 days per week of outdoor r u n n i n g , i n t e n s i t y u n r e p o r t e d ) , Ekblom and G o l d b a r g (1971) examined changes i n RPE when i n t e n s i t y of e x e r c i s e was a d j u s t e d r e l a t i v e t o V02max. At submaximal w o r k l o a d s , RPE was found t o be 1.5-2.0 p o i n t s lower f o l l o w i n g the 8 week t r a i n i n g program, but maximum RPE d i d not d i f f e r . When r e l a t e d t o r e l a t i v e HR or V02, RPE was unchanged. For a g i v e n oxygen 52 d e f i c i t or b l o o d l a c t a t e c o n c e n t r a t i o n , no d i f f e r e n c e s i n RPE were o b s e r v e d f o l l o w i n g t r a i n i n g . However, problems i n the e x p e r i m e n t a l d e s i g n of t h i s study p r e v e n t m e a n i n g f u l i n t e r p r e t a t i o n of the r e s u l t s . W h i l e t r a i n i n g c o n s i s t e d m o s t l y of outdoor r u n n i n g , b o t h p r e - and p o s t - t e s t i n g were conducted on a b i c y c l e ergometer. T h i s t e c h n i q u e i g n o r e s the p r i n c i p l e of the s p e c i f i c i t y of t r a i n i n g . I n a d d i t i o n , t h e r e s u l t s showed t h a t d u r i n g e x e r c i s e a t a g i v e n l e v e l of c o n d i t i o n i n g and s p e c i f i c V02, p e r c e p t u a l l y , b i c y c l i n g was more d i f f i c u l t than r u n n i n g . T h i s would t e n d t o m i n i m i z e the e f f e c t s of t r a i n i n g , a t a g i v e n V02 d u r i n g the p o s t - t e s t . F i n a l l y , a l t h o u g h i t was c o n c l u d e d t h a t no changes i n RPE were obser v e d a t 25, 50 and 75% V02max f o l l o w i n g t r a i n i n g , the a u t h o r s s t a t e t h a t these workloads were o n l y a p p r o x i m a t e d d u r i n g the t e s t i n g s e s s i o n s . K i l b o m (1971) t r a i n e d female s u b j e c t s f o r 7 weeks, d i v i d i n g the sample i n t o 3 groups who p a r t i c i p a t e d i n v a r i a t i o n s of an i n t e r v a l t r a i n i n g program. E x e r c i s e was performed on a b i c y c l e ergometer, a t a l o a d which c o r r e s p o n d e d t o 70% V02max. E f f e c t i v e work time i n a l l groups was h e l d c o n s t a n t a t 18 m i n u t e s . T r a i n i n g f r e q u e n c y was d e s i g n e d t o be 3 t i m e s per week, but averaged 2.5 t i m e s per week. Mean e x e r c i s e HR v a l u e s ranged from 141-166 bpm. MAP i n c r e a s e d by 11% and submaximal HR v a l u e s were reduced by 10-15 bpm. F o l l o w i n g t r a i n i n g , RPE was lower a t submaximal w o r k l o a d s , but was unchanged i n r e l a t i o n t o HR. O v e r a l l , no d i f f e r e n c e i n RPE o c c u r r e d a t e x h a u s t i o n , but a reduced s u b j e c t i v e r a t i n g was o b s e r v e d i n the o l d e s t group of s u b j e c t s . 53 I t i s known t h a t e x e r c i s e HR may be a f f e c t e d by such f a c t o r s as c a f f e i n e ( A t k i n s o n , 1977) and time of day (Cohen et a l . , 1977). U n l e s s these and o t h e r f a c t o r s which a f f e c t HR a r e c o n t r o l l e d f o r , the v a l i d i t y of drawing c o n c l u s i o n s c o n c e r n i n g changes i n RPE a t a s i n g l e or even m u l t i p l e HR f o l l o w i n g t r a i n i n g i s q u e s t i o n a b l e . No r e p o r t of any attempt t o r e g u l a t e t h e s e p o t e n t i a l l y c o n f o u n d i n g v a r i a b l e s was made i n t h e s e s t u d i e s . There has y e t t o be any e v i d e n c e p r e s e n t e d i n the l i t e r a t u r e t o d e s c r i b e the p o s s i b l e time c o u r s e of t r a i n i n g -i n d u c e d a l t e r a t i o n s i n RPE. The d u r a t i o n of the t r a i n i n g p e r i o d i n t h e s e s t u d i e s was s h o r t , r a n g i n g from 5-8 weeks. To d a t e , a l o n g - t e r m e v a l u a t i o n of the e f f e c t s of t r a i n i n g upon RPE has not been u n d e r t a k e n . P o s s i b l y , a d a p t a t i o n s i n s e n s o r y p e r c e p t i o n s a t a g i v e n r e l a t i v e e x e r c i s e i n t e n s i t y a r e more l a t e n t than c o r r e s p o n d i n g p h y s i o l o g i c a l m o d i f i c a t i o n s . The degree t o which changes i n RPE which a r e s o l i c i t e d d u r i n g t r a i n i n g are i n f l u e n c e d by the frequency and i n t e n s i t y of t r a i n i n g i s e q u a l l y u n c e r t a i n . T r a i n i n g f r e q u e n c y v a r i e d from 2.5-7 days per week, and t r a i n i n g i n t e n s i t y from 141-180 bpm i n the s t u d i e s under d i s c u s s i o n . T h i s a r e a r e q u i r e s f u r t h e r r e s e a r c h . B u r k h a r d t and h i s a s s o c i a t e s ( B u r k h a r d t e t a l . , 1982) randomly a s s i g n e d 18 u n t r a i n e d c o l l e g e females t o arm t r a i n i n g (AT) or l e g t r a i n i n g (LT) groups. P r i o r t o and f o l l o w i n g the program, MAP was a s s e s s e d . E x e r c i s e was conducted a t 50% V02max f o r 21 s e s s i o n s . F o l l o w i n g t r a i n i n g , a comparison was made of 54 both groups f o r both modes of e x e r c i s e , a t the same r e l a t i v e w o r k load (50% V02max). O v e r a l l RPE was lower on the arm t e s t than the l e g t e s t f o r AT, and lower on the arm t e s t f o r AT than LT. In o t h e r words, a l t h o u g h e x e r c i s i n g a t the same m e t a b o l i c r a t e , the p e r c e p t i o n of e f f o r t was d i m i n i s h e d i n the t r a i n e d l i m b s . U s i n g a c r o s s s e c t i o n a l approach, R e j e s k i e t a l (1982) compared the e f f e c t s of, u s i n g t o e - c l i p s d u r i n g : a b i c y c l e ergometer t e s t t o v o l i t i o n a l f a t i g u e i n r u n n e r s v e r s u s c o m p e t i t i v e c y c l i s t s . S u b j e c t s were t e s t e d under 2 c o n d i t i o n s , t o e - c l i p and no t o e - c l i p , w i t h 1 week s e p a r a t i n g the two t e s t s . W h i l e w orking m a x i m a l l y , the t r a i n e d c y c l i s t s demonstrated r e d u c t i o n s i n RPE eventhough V02max was e l e v a t e d w i t h r e s p e c t t o the no t o e - c l i p c o n d i t i o n . T h i s was a t t r i b u t e d t o an i n c r e a s e i n motor e f f i c i e n c y , which was d e r i v e d through c y c l e t r a i n i n g . S i m i l a r changes were not ob s e r v e d i n the group of r u n n e r s . The r e s u l t s from these i n v e s t i g a t i o n s support the concept t h a t f o l l o w i n g t r a i n i n g , RPE i s reduced a t a g i v e n r e l a t i v e w o r k l o a d . D o l l e t a l . . (1980) had s u b j e c t s p e r f o r m 8 t e s t s t o v o l i t i o n a l f a t i g u e on a t r e a d m i l l , implementing v a r i a t i o n s i n speed increment p r o t o c o l s . They d i s c o v e r e d t h a t s i g n i f i c a n t d i f f e r e n c e s i n RPE e x i s t e d a t s i m i l a r l e v e l s of 02, between test s . . In l i g h t of the s e f i n d i n g s , the s u i t a b i l i t y of e v a l u a t i n g v a r i a t i o n s i n RPE s o l e l y on a m e t a b o l i c b a s i s must be re-examined. R e l a t i v e e x e r c i s e i n t e n s i t i e s based upon %MAP do not account f o r a d a p t a t i o n s i n p h y s i o l o g i c a l r e sponses such as l a c t a t e p r o d u c t i o n , v e n t i l a t o r y hyperpnea and c a t e c h o l a m i n e e l e v a t i o n ( A s t r a n d and Rod a h l , 1970). These r e s u l t s and those 55 o b t a i n e d e lsewhere (Stamford and Noble, 1974) i n d i c a t e t h a t t r a i n i n g may t y p i c a l l y i n v o l v e neuromuscular a d j u s t m e n t s as w e l l as c a r d i o v a s c u l a r g a i n s . Other c r o s s - s e c t i o n a l i n v e s t i g a t i o n s have demonstrated t h a t f i t and u n f i t s u b j e c t s r a t e the e f f o r t r e q u i r e d t o p e r f o r m s t a n d a r d w o r k l o a d s e q u a l l y (Bar-Or, 1977; Bar-Or e t a l . , 1972; M i c h a e l and E c k h a r d t , 1972; Morgan, 1977; Morgan and P o l l o c k , 1977; P a t t o n et a l . , 1977; S k i n n e r e t a l . , 1969). M i c h a e l and E c k h a r d t (1972) r e q u e s t e d t r a i n e d and u n t r a i n e d s u b j e c t s t o choose a t r e a d m i l l work l e v e l which they c o n s i d e r e d t o be "hard" a t 0% s l o p e . They were then asked t o reproduce an e q u i v a l e n t work bout, w i t h the t r e a d m i l l r e - s e t a t a 10% grade. No d i f f e r e n c e s were d e t e c t e d between groups i n e i t h e r of the work l o a d s s e l e c t e d . P a t t o n e t a l . (1977) found no d i f f e r e n c e s i n RPE d u r i n g a 6 minute run a t 6 mph on a t r e a d m i l l i n m i l i t a r y c o n s c r i p t s who d i f f e r e d i n f i t n e s s l e v e l . However, f o l l o w i n g 6 weeks of t r a i n i n g , an 11% r e d u c t i o n i n RPE o c c u r r e d f o r a l l s u b j e c t s d u r i n g submaximal e x e r c i s e . In a st u d y performed upon a t h l e t e s a t the 1972 American Olympic w r e s t l i n g team t r i a l s , Morgan (1977) d i s c o v e r e d t h a t no d i f f e r e n c e s i n RPE e x i s t e d between s u c c e s s f u l and u n s u c c e s s f u l c a n d i d a t e s . T h i s was d e s p i t e the f a c t t h a t s u c c e s s f u l i n d i v i d u a l s had a h i g h e r V02max, and a lower submaximal HR than t h e i r c o u n t e r p a r t s , a t the same w o r k l o a d . I t i s d i f f i c u l t t o i n t e r p r e t t h e s e f i n d i n g s . A common c h a r a c t e r i s t i c of a l l of the s e i n v e s t i g a t i o n s i s t h a t they e v a l u a t e d d i f f e r e n c e s i n RPE a t low t o moderate a b s o l u t e w o r k l o a d s . As d e s c r i b e d p r e v i o u s l y , i t may be t h a t i n c e r t a i n 56 i n d i v i d u a l s , d i f f e r e n c e s i n RPE as a consequence of t r a i n i n g a r e o n l y m a n i f e s t e d d u r i n g i n t e n s e a c t i v i t y . W i l b e r t e t a l . (1974) have p r e v i o u s l y suggested t h a t any d i s s i m i l a r i t i e s between the p e r c e p t u a l response of v a r i o u s groups appear o n l y i n h i g h e r ranges of e x e r c i s e i n t e n s i t y . Morgan and P o l l o c k (1977) o b s e r v e d t h a t e l i t e and c o l l e g e l e v e l r u n n e r s had the same p e r c e p t i o n of e f f o r t a t v a r i o u s w orkloads eventhough they were e x p e r i e n c i n g d i f f e r e n t degrees of p h y s i c a l s t r e s s . However, a t speeds above 10 mph, the l e s s f i t r u n n e r s d i d r a t e t h e i r e f f o r t e x p e n d i t u r e s i g n i f i c a n t l y h i g h e r . R o s e n t s w i e g and W i l l i a m s (1979) t e s t e d the e f f o r t p e r c e p t i o n of 18 p r o f e s s i o n a l hockey p l a y e r s d u r i n g t r e a d m i l l e x e r c i s e . The run was i n i t i a t e d a t a 0% grade at a speed of 3.3 mph. At every minute t h e r e a f t e r , a 1% grade i n c r e a s e was implemented u n t i l a HR of 180 bpm was a c h i e v e d . The p l a y e r s r a t e d the maximal workload as "somewhat h a r d " , r e g i s t e r i n g a mean RPE v a l u e of 13.06 on the Borg s c a l e . T h e o r e t i c a l l y , e x e r c i s i n g at a HR of 180 bpm s h o u l d have demanded "very h a r d " work from the p l a y e r s (Rosentswieg and W i l l i a m s , 1977). The a u t h o r s suggested t h a t the p l a y e r s were s u f f i c i e n t l y accustomed t o h i g h l y v i g o r o u s e x e r c i s e t o e x h i b i t lower RPE v a l u e s f o r a g i v e n w o r k l o a d . F u r t h e r r e s e a r c h i n t o t r a i n i n g - r e l a t e d changes i n RPE i s r e q u i r e d . The l i t e r a t u r e which has been r e v i e w e d s t r o n g l y s u g g e s t s t h a t RPE w i l l be reduced a t a g i v e n submaximal w o r k l o a d , f o l l o w i n g p h y s i c a l c o n d i t i o n i n g . T h i s appears t o be 57 p a r t i c u l a r l y t r u e i n the h i g h e r ranges of e x e r c i s e i n t e n s i t y . In support of the p r o p o s a l t h a t r e d u c t i o n s i n RPE e x i s t when e x e r c i s e i s equated on a r e l a t i v e b a s i s b e f o r e and a f t e r t r a i n i n g , i t i s known t h a t f i t i n d i v i d u a l s have a e r o b i c t h r e s h o l d s which a r e s u b s t a n t i a l l y h i g h e r than s e d e n t a r y i n d i v i d u a l s ( C o s t i l l , 1970; D a v i s et a l . , 1979; Kindermann et a l . , 1979; Londeree and Ames, 1975). S i n c e i t has been shown t h a t e f f o r t e v a l u a t i o n s are s i m i l a r between s u b j e c t s a t the a e r o b i c t h r e s h o l d ( P u r v i s and C u r e t o n , 1981), t h i s i m p l i e s t h a t w e l l - t r a i n e d i n d i v i d u a l s w i l l r a t e a h i g h e r r e l a t i v e e x e r c i s e demand t o be e a s i e r . P a r t of the problem i n r e a c h i n g a c o n c l u s i o n on the i s s u e of RPE t r a i n a b i l i t y c e n t r e s upon agreement as t o what s h o u l d be r e c o g n i z e d as a " s i g n i f i c a n t " decrement i n RPE. Morgan (1977) has p o i n t e d out t h a t a r e d u c t i o n of 1-2 RPE u n i t s on the Borg s c a l e t r a n s l a t e s t o a 10-20% change, which c o u l d p o t e n t i a l l y be v e r y s i g n i f i c a n t i n endurance e v e n t s such as the marathon. I t would be of v a l u e t o g i v e t h i s i s s u e f u r t h e r c o n s i d e r a t i o n . 58 I I I . METHODS S u b j e c t s T h i r t y - f i v e h e a l t h y male s u b j e c t s agreed t o p a r t i c i p a t e i n the study as members of e i t h e r a t r a i n i n g or c o n t r o l group. W i t h the e x c e p t i o n of t h r e e i n d i v i d u a l s , a l l s u b j e c t s were p h y s i c a l e d u c a t i o n undergraduate s t u d e n t s a t the U n i v e r s i t y of B r i t i s h C olumbia. Each v o l u n t e e r was accustomed t o e x e r c i s e , but none were t r a i n e d . P r i o r t o p a r t i c i p a t i o n i n the s t u d y , the s u b j e c t s were a d v i s e d of the n a t u r e of the t e s t i n g and t r a i n i n g p r o c e d u r e s , and the p o t e n t i a l r i s k s which were i n v o l v e d . S i g n e d , i n f o r m e d consent was o b t a i n e d from each s u b j e c t who p a r t i c i p a t e d i n the s t u d y . No e x p l a n a t i o n was o f f e r e d r e g a r d i n g the s i g n i f i c a n c e of or purpose f o r the p e r c e p t u a l r a t i n g s t o be r e c o r d e d d u r i n g t e s t i n g . The s u b j e c t s appeared t o b e l i e v e t h a t p h y s i o l o g i c a l measurements were t o be e v a l u a t e d as the dependent v a r i a b l e s . Those s u b j e c t s who commented upon the use of the p e r c e p t u a l r a t i n g s assumed t h a t they were b e i n g u t i l i z e d t o m o n i t o r the p r o g r e s s i o n of the e x e r c i s e t e s t , and t o s e r v e as an i n d i c a t o r of p h y s i c a l s t r e s s t o a l e r t the i n v e s t i g a t o r s t o the onset of f a t i g u e . Upon c o m p l e t i o n of the s t u d y , s u b j e c t s were p e r m i t t e d a c c e s s t o t h e i r r e s u l t s , and a d e s c r i p t i o n of the r e s e a r c h and i t s f i n d i n g s was o f f e r e d . 59 P r o c e d u r e s At the o u t s e t of the stu d y , each s u b j e c t performed an e x e r c i s e s e s s i o n on a t r e a d m i l l t o become f a m i l i a r w i t h t h i s a p p a r a t u s . W i t h i n the f o l l o w i n g 2 d a y s , s u b j e c t s underwent a p r o g r e s s i v e t r e a d m i l l run t o v o l i t i o n a l f a t i g u e . D u r i n g t h i s t e s t , r u n n i n g commenced a t 8 km-hr" 1 (5 mph). At 1 minute i n t e r v a l s t h e r e a f t e r , the speed of the t r e a d m i l l was i n c r e a s e d by 0.8 km«hr~ 1 (0.5 mph). P r i o r t o the t e s t , s u b j e c t s were i n s t r u c t e d as t o the use of the Borg s c a l e (Borg, 1970) and were a d m i n i s t e r e d 5 minutes of t r e a d m i l l r u n n i n g t o p r o v i d e p h y s i o l o g i c a l warm-up. C o n s t r a i n t s p l a c e d upon the a v a i l a b i l i t y of the s u b j e c t s and the t r e a d m i l l p r e v e n t e d c e r t a i n c o m b i n a t i o n s of s u b j e c t s from p a r t i c i p a t i n g i n t h e e x e r c i s e program. A p a r t from t h i s r e s t r i c t i o n , assignment of the s u b j e c t s t o e i t h e r the t r a i n i n g (N=20) or c o n t r o l (N=15) group was performed randomly. Those i n the c o n t r o l group were r e q u e s t e d t o m a i n t a i n t h e i r normal a c t i v i t y l e v e l f o r the subsequent 9-week p e r i o d . D u r i n g the p o s t - t e s t , a l l s u b j e c t s performed a t r e a d m i l l run u s i n g a p r o t o c o l which was i d e n t i c a l t o t h a t used d u r i n g the i n i t i a l t e s t . Both t e s t s were conducted a t a p p r o x i m a t e l y the same time of day. S u b j e c t s i n the t r a i n i n g group were r e - t e s t e d w i t h i n 3 days of the f i n a l t r a i n i n g s e s s i o n . 60 Training Regimen The 9-week tra i n i n g program involved treadmill running at a frequency of 3 days per week. Independent a c t i v i t y was not r e s t r i c t e d . Preceeding each tr a i n i n g session, subjects performed a brief warm-up, comprised of stretching and l i g h t to moderate jogging. The i n i t i a l week of training consisted of 20 minutes of exercise performed 0.8 km-hr"1 (0.5 mph) above the individual ventilatory aerobic threshold. During each of the subsequent 4 weeks, subjects were required to increase their time of exercise by 3 minutes, so that by the end of the 5th week of tr a i n i n g , each subject ran for 32 minutes at this v e l o c i t y . At th i s time, individual training v e l o c i t i e s were increased by 0.8 km-hr - 1 (0.5 mph) and exercise duration was re-set at 23 minutes. During each consecutive week, subjects were again required to run for an additional 3 minutes, so that by the end of the 9th week of tr a i n i n g , exercise was performed for 32 minutes at the re-adjusted workrate. This program was selected to provide the subjects with an intense t r a i n i n g stimulus. Measurements Data was obtained for both the training and control groups, both before and after a 9-week period. Expired gases were colle c t e d and analysed (Beckmann Metabolic Measurement Cart), and measurements were fed into a data acquisition system 61 ( H e w i t t - P a c k a r d 3052A) f o r d e t e r m i n a t i o n of 15 second r e s p i r a t o r y gas exchange v a r i a b l e s . Heart r a t e s were c a l c u l a t e d d u r i n g the l a s t 10 seconds of e x e r c i s e at each w o r k l o a d , from an ECG t r a c e ( A v i o n i c s 4000). V e n t i l a t o r y a e r o b i c t h r e s h o l d (AerT) measurements were a s s e s s e d u s i n g the p o i n t • of n o n - l i n e a r i n c r e a s e i n Excess C02 (VC02-RQ-V02), and were not c o n s i d e r e d t o be v a l i d u n l e s s agreed upon by 2 s e p a r a t e i n v e s t i g a t o r s . Oxygen consumption (V02) v a l u e s a t the AerT were e v a l u a t e d by a v e r a g i n g the f o u r 15-second V02 r e a d i n g s c o l l e c t e d at the w o r k l o a d p r i o r t o t h i s i n c r e a s e . V02max and maximal v e n t i l a t i o n (VEmax) v a l u e s were c a l c u l a t e d from the 4 h i g h e s t c o n s e c u t i v e V02 and VE r e a d i n g s , r e s p e c t i v e l y . Maximal v e l o c i t y (Vmax) was c o n s i d e r e d t o be the h i g h e s t v e l o c i t y which a s u b j e c t c o u l d m a i n t a i n f o r g r e a t e r than 15 seconds. E f f o r t r a t i n g s which were r e p o r t e d a t the onset of V02max were r e c o r d e d as maximum RPE (RPEmax). Body c o m p o s i t i o n v a l u e s were d e t e r m i n e d u s i n g an underwater w e i g h i n g t e c h n i q u e ( K a t c h and M c A r d l e , 1977). E x e r c i s e HR v a l u e s were measured manually v i a the c a r o t i d p u l s e , i m m e d i a t e l y f o l l o w i n g the t e r m i n a t i o n of e x e r c i s e . P e r c e p t u a l r e a d i n g s were r e c o r d e d u s i n g the s c a l e and p r o c e d u r e s d e v i s e d by Borg (1970), and were c o l l e c t e d a t the 25th and 55th seconds of e x e r c i s e a t each w o r k l o a d . F o l l o w i n g the i n i t i a l r e a d i n g s e l e c t e d by the s u b j e c t , the p r e v i o u s r e a d i n g i n d i c a t e d was p o i n t e d t o a t the a p p r o p r i a t e t i m e , and the s u b j e c t s communicated any changes i n the d i r e c t i o n and magnitude of the r a t i n g s v i a hand s i g n a l s . V a l u e s f o r RPE a t 55, 65, 75, 85 and 95% Vmax and V02max were de t e r m i n e d by 62 i n t e r p o l a t i n g between minute v a l u e s f o r RPE, v e l o c i t y and V02, and were r e c o r d e d t o the n e a r e s t 1/I0th of a u n i t . S t a t i s t i c a l A n a l y s e s D i f f e r e n c e s i n the v a l u e s o b t a i n e d f o r V02max, AerT, and AerT as %V02max measured pre t o post i n both the t r a i n i n g and c o n t r o l groups were t e s t e d u s i n g a MANOVA. A second MANOVA was used t o a n a l y s e changes i n body c o m p o s i t i o n , w e i g h t , time t o v o l i t i o n a l f a t i g u e , VEmax and HR a t AerT. Maximum RPE and RPE at the AerT d a t a were a l s o i n c l u d e d i n t h i s a n a l y s i s . Changes i n RPE a t a b s o l u t e and r e l a t i v e work i n t e n s i t i e s were a n a l y s e d u s i n g a 2x2x5 ANOVA, w i t h r e p e a t e d measures on the t h i r d f a c t o r . S e p a r ate o r t h o g o n a l c o n t r a s t s were used t o t e s t f o r t r e n d s i n the RPE d a t a r e c o r d e d a t the v a r i o u s p r o p o r t i o n s of Vmax and V02max. The same t e c h n i q u e was used t o e v a l u a t e changes i n t r e n d s a t e q u i v a l e n t a b s o l u t e and r e l a t i v e work i n t e n s i t i e s . S t a t i s t i c a l s i g n i f i c a n c e f o r a l l comparisons was a c c e p t e d a t the 0.95 l e v e l of c o n f i d e n c e . 63 IV. RESULTS Due t o m o r b i d i t y or c o n f l i c t i n g time committments, seven s u b j e c t s i n the o r i g i n a l t r a i n i n g group, and two s u b j e c t s from the o r i g i n a l c o n t r o l group f a i l e d t o complete the second t e s t i n g s e s s i o n . A t t e n d a n c e at the t r a i n i n g program was e x c e l l e n t , w i t h f i n a l members of the t r a i n i n g group c o m p l e t i n g 97% of a l l s c h e d u l e d s e s s i o n s , or p e r f o r m i n g the workouts a t an a l t e r n a t e t i m e . E x e r c i s e h e a r t r a t e v a l u e s i n the t r a i n i n g group were 171.5 ± 5.7 bpm (mean ± SD). P h y s i c a l C h a r a c t e r i s t i c s S t a t i s t i c s f o r the p h y s i c a l c h a r a c t e r i s t i c s of the s u b j e c t s a r e p r e s e n t e d i n Table 1. I n i t i a l l y , s u b j e c t s i n the t r a i n i n g group were s i g n i f i c a n t l y t a l l e r (p<0.0l) and h e a v i e r (p<0.05) than the s u b j e c t s i n the c o n t r o l group, but no s i g n i f i c a n t d i f f e r e n c e s e x i s t e d i n terms of p e r c e n t body f a t or age. A s i g n i f i c a n t time main e f f e c t was observed f o r body f a t (p<0.000l), and changes i n body weight a c r o s s groups and over time approached s i g n i f i c a n c e (p<0.06). When the group by time i n t e r a c t i o n e f f e c t was c o n s i d e r e d , d e c r e a s e s i n body weight i n the t r a i n i n g group were g r e a t e r than i n the c o n t r o l group ( p < 0 . 0 l ) . Body f a t d e c l i n e d by 2.5% i n the t r a i n i n g group, and 1.2% i n the c o n t r o l group, w i t h the i n t e r a c t i o n e f f e c t a p p r o a c h i n g s i g n i f i c a n c e (p<0.08). 64 Table 1 - P h y s i c a l C h a r a c t e r i s t i c s of S u b j e c t s D e s c r i p t i v e S t a t i s t i c s U n i v a r i a t e 1 Summary (p:) V a r i a b l e Group P r e - T r a i n i n g P o s t - T r a i n i n g Time Group x Time Age ( y e a r s ) TG 2 CG 21.1 ± 2.1 21.4 ± 1.9 Body h e i g h t (cm) TG CG 183.0 ± 5.6 176.4 ± 4.7 Body weight (kg) TG CG 79.9 ± 7.4 73.5 ± 6.5 78.1 ± 6.9 73.8 ± 7.0 .06 .01 Body f a t (%) TG CG 13.4 ± 5.5 13.3 ± 5.6 10.9 ± 4.7 12.1 ± 5.5 .001 .08 N TG CG 20 1 5 1 3 1 3 1. The p v a l u e s a re based upon u n i v a r i a t e ANOVAS. M u l t i v a r i a t e F=2.75, p<0.04 f o r Group x Time e f f e c t s f o r v a r i a b l e s i n T a b l e s 1, 3 and 4. 2. TG, t r a i n i n g group; CG, c o n t r o l group. V a l u e s a r e means ± SD. Performance Measures A summary of p r e - and p o s t - t r a i n i n g performance measures and the p r o b a b i l i t y l e v e l s a s s o c i a t e d w i t h o b s e r v e d changes i n thes e v a r i a b l e s are shown i n Ta b l e 2 and T a b l e 3. Table 2 i n c l u d e s a summary of a l t e r a t i o n s i n performance measures which were h y p o t h e s i z e d , and Ta b l e 3 c o n t a i n s a s y n o p s i s of changes i n p e r t i n e n t but n o n - p o s t u l a t e d performance measures. The e x e r c i s e program r e s u l t e d i n a 7.5% improvement i n V02max i n the t r a i n i n g group. When the s i g n i f i c a n t l o s s i n body weight was acc o u n t e d f o r , t h i s i n c r e a s e was reduced t o 5.9% These v a l u e s were h i g h e r than the 1-2% e l e v a t i o n s i n V02max 65 which were observed i n the c o n t r o l group, but no s i g n i f i c a n t group by time i n t e r a c t i o n e f f e c t s were found i n V02max e x p r e s s e d i n e i t h e r m l - k g " 1 • m i n " 1 or 1-min" 1. When i n i t i a l f i t n e s s l e v e l was b l o c k e d f o r ( h i g h , l o w ) and d i f f e r e n c e s i n V02max were a n a l y s e d u s i n g a 2x2x2 ANOVA, the time main e f f e c t was s i g n i f i c a n t ( p< 0 . 0 5 ) and the time by group by l e v e l i n t e r a c t i o n approached s i g n i f i c a n c e ( p < 0 . 0 9 ) . S u b j e c t s i n the t r a i n i n g group who were i n i t i a l l y a t a low f i t n e s s l e v e l e x h i b i t e d g r e a t e r i n c r e a s e s i n V02max than s u b j e c t s who were more f i t a t the o u t s e t of the s t u d y , who showed l i m i t e d change. No d i f f e r e n c e s e x i s t e d i n the degree of change i n V02max between i n i t i a l l y f i t and u n f i t c o n t r o l s u b j e c t s . T a b l e 2 - Summary of H y p o t h e s i z e d P h y s i o l o g i c a l T r a i n i n g E f f e c t s D e s c r i p t i v e S t a t i s t i c s U n i v a r i a t e Summary (p:) V a r i a b l e Group P r e - T r a i n i n g P o s t - T r a i n i n g Time Group x Time V02max (1-min" 1) a TG CG 3.90 ± 0.5 3.77 ± 0.4 4.13 ± 0.3 3.83 ± 0.5 .06 >.20 V02max (ml- kg" 1. min" 1 )b TG CG 49.4 ± 5.8 51.4 ± 4.6 53.1 ± 4.1 52.0 ± 5.8 .04 .13 AerT (1-min" 1) c TG CG 3.02 ± 0.3 2.86 ± 0.3 3.21 ± 0.3 2.72 ± 0.4 >.20 .01 AerT (ml- kg" 1- min" 1 )d TG CG 38.5 ± 4.5 39.6 ± 5.9 41.6 ± 4.8 38.1 ± 5.6 >.20 .01 AerT (%V02max) e TG CG 77.0 ± 5.9 75.9 ± 7.0 77.0 ± 6.0 72.0 ± 8.0 .16 . 1 7 M u l t i v a r i a t e F=2.67, p<.07 f o r Group x Time e f f e c t , v a r i a b l e s a,c,e. M u l t i v a r i a t e F=4.85, p<.0! f o r Group x Time e f f e c t , 66 v a r i a b l e s b,d,e. A h i g h l y s i g n i f i c a n t (p<0.01) group by time i n t e r a c t i o n e f f e c t o c c u r r e d f o r a e r o b i c t h r e s h o l d ( A e r T ) . The t r a i n i n g group e x h i b i t e d an 8.0% i n c r e a s e i n AerT, which was reduced t o 6.3% when weight l o s s was c o n s i d e r e d . In the c o n t r o l group, AerT d e c l i n e d by 5% ( l ' m i n - 1 ) and 4% (ml* kg" 1 - m i n - 1 ) , r e s p e c t i v e l y . E x p r e s s e d i n terms of %V02max, no s i g n i f i c a n t changes i n AerT were o b s e r v e d . C o e f f i c i e n t s of c o r r e l a t i o n (Pearson r ) were c a l c u l a t e d a c r o s s l e v e l s of %V02max w i t h i n each group. These d i f f e r e d by l e s s than 1 p e r c e n t from p r e - t o p o s t -t e s t , a v e r a g i n g 0.89 i n the t r a i n i n g group, and 0.84 i n the c o n t r o l group. Table 3 - Summary of N o n - H y p o t h e s i z e d . P h y s i o l o g i c a l T r a i n i n g E f f e c t s D e s c r i p t i v e S t a t i s t i c s U n i v a r i a t e Summary (p:) V a r i a b l e Group P r e - T r a i n i n g P o s t - T r a i n i n g Time Group x Time T i m e - v o l i t i o n a l f a t i g u e (mins) TG CG 11.6 ± 1.7 12.0 ± 1.8 12.7 ± 1.5 12.5 ± 2.2 .001 .09 VEmax (1« min" 1,BTPS) TG CG 144.9 ± 20. 1 134.2 ±13.1 152.9 ± 17.8 134.9 ± 17.8 .01 .09 HR a t AerT (bpm) TG CG 171.7 ± 9.7 173.8 ± 11.5 171.7 ± 3.1 171.2 ± 10.8 >.20 >.20 Mean v a l u e s f o r maximum v e n t i l a t i o n (VEmax) improved by 5.5% i n the t r a i n i n g group, and l e s s than 1% i n the c o n t r o l group. The i n t e r a c t i o n e f f e c t w i t h the c o n t r o l group approached s i g n i f i c a n c e ( p < 0 . 0 9 ) . A h i g h l y s i g n i f i c a n t ( p < 0 . 0 0 0 l ) time 67 main e f f e c t was observed f o r time t o v o l i t i o n a l f a t i g u e . The group by time i n t e r a c t i o n e f f e c t f o r t h i s v a r i a b l e d i d not a c h i e v e s t a t i s t i c a l s i g n i f i c a n c e (p<0.09). H e a r t r a t e a t t h e AerT d i d not v a r y s i g n i f i c a n t l y over time or group, and averaged 87.2% of the maximum HR. ; P e r c e p t u a l E f f e c t s P r e - and p o s t - t e s t v a l u e s f o r RPEmax and RPE a t the AerT are p r e s e n t e d i n Ta b l e 4. A h i g h l y s i g n i f i c a n t (p<0.0l) i n t e r a c t i o n e f f e c t o c c u r r e d between groups f o r RPE a t the AerT. A l t h o u g h RPE a t the AerT was lower i n the c o n t r o l group, t h i s e f f e c t was not obser v e d i n the t r a i n i n g group. RPEmax was found t o i n c r e a s e s i g n i f i c a n t l y (p<0.001) when averaged over the two groups, but no d i f f e r e n c e s i n improvement were found between groups f o r t h i s v a r i a b l e . T a b l e 4 - Summary of T r a i n i n g E f f e c t s Upon S e l e c t e d P e r c e p t u a l V a r i a b l e s D e s c r i p t i v e S t a t i s t i c s U n i v a r i a t e Summary (p:) Var i a b l e Group P r e - T r a i n i n g P o s t - T r a i n i n g Time Group x Time RPE a t AerT TG CG 12.5 ± 1.9 13.2 ± 2.6 12.5 ± 2.0 11.5 ± 2.4 .02 .01 RPEmax TG CG 18.8 ± 1.3 19.0 ± 1.0 19.4 ± 1.1 19.6 ± 1.0 .001 >.20 V a l u e s f o r RPE a t wor k l o a d s e x p r e s s e d as a perc e n t a g e of maximum v e l o c i t y (Vmax) and V02max are p r e s e n t e d i n Ta b l e 5. 68 Changes i n RPE a t e q u i v a l e n t a b s o l u t e and r e l a t i v e w o r k l o a d s have been c a l c u l a t e d as p e r c e n t r e d u c t i o n s , and are shown i n Table 6. Comparing p r e - and p o s t - t e s t v a l u e s , the RPE a s s o c i a t e d w i t h a g i v e n volume of oxygen consumption [ I n i t i a l V02max (pre) v e r s u s I n i t i a l V02max ( p o s t ) ] was s i g n i f i c a n t l y reduced ( p < 0 . 0 l ) . The i n t e r a c t i o n e f f e c t f o r t h i s v a r i a b l e was n o n - s i g n i f i c a n t , and f a i l e d t o d i s t i n g u i s h between the changes noted i n the c o n t r o l and t r a i n i n g groups ( F i g u r e 1). When the RPE a t e q u i v a l e n t r e l a t i v e w o r k l o a d s based upon V02 were examined [ i n i t i a l V02max (pre) v e r s u s F i n a l V02max], no d i f f e r e n c e s were demonstrated over the 9-week p e r i o d . 69 Table 5 - Summary of E f f o r t R a t i n g s V a r i a b l e Group Workload 55% 65% 75% 85% 95% I n i t i a l V 02max(pre) 1 (1«min" 1 ) TG CG 7.9 ±1 .2 8.9 ±2.2 9.7 ±1 .8 10.5 ±2.8 11.9 ±2.1 12.5 ±2.4 14.5 ±1 .7 15.3 ±1.7 17.1 ±1.6 17.7 ±1 .5 I n i t i a l V 0 2 m a x ( p o s t ) 2 (1- min- 1 ) TG CG 6.4 ±0.5 7.5 ±1.5 7.7 ±1 .7 9.8 ±2.1 9.7 ±2.5 11.7 ±2.6 12.2 ±2.6 14.6 ±2.6 15.7 ±3. 1 17.4 ±2.6 F i n a l V02max 3 ( 1 - m i n - 1 ) TG CG 6.7 ±0.4 7.9 ±1 .7 8.5 ±1.8 9.6 ±2.5 11.0 ±2.2 11.6 ±2.6 13.9 ±2.1 14.6 ±2.2 17.7 ±1 .9 17.4 ±1 .9 I n i t i a l Vmax(pre)" (km-hr- 1) TG CG 9.2 ±1 .7 9.2 ±2.4 11.9 ±2.0 11.6 ±2.0 14.3 ±1 .6 14.2 ±1 .7 17.0 ±1 .2 16.3 ±1 .3 19.3 ±0.7 18.9 ±0.8 I n i t i a l V m a x ( p o s t ) 5 (km-hr- 1) TG CG 6.8 ±0.9 8.1 ±2.4 9.0 ±1.8 10.7 ±2.0 11.9 ±1 .9 13.2 ±1 .7 14.8 ±1.8 15.9 ±1.3 18. 1 ±1.6 18.8 ±0.8 F i n a l Vmax 6 (km-hr- 1) TG CG 7.2 ±1 .2 8.7 ±1 .7 9.5 ±1 .9 11.1 ±1 .9 12.6 ±1 .8 13.6 ±1 .7 15.5 ±2.0 16.7 ±1 .4 18.9 ±1 .6 19.5 ±1 .0 1. V02max l e v e l d u r i n g the p r e - t e s t , measured a t the p r e - t e s t 2. V02max l e v e l d u r i n g the p r e - t e s t , measured a t the p o s t - t e s t 3. V02max l e v e l d u r i n g the p o s t - t e s t , measured a t the p o s t - t e s t . 4. V e l o c i t y l e v e l d u r i n g the p r e - t e s t , measured a t the p r e - t e s t 5. V e l o c i t y l e v e l d u r i n g the p r e - t e s t , measured a t the p o s t - t e s t . 6. V e l o c i t y l e v e l d u r i n g the p o s t - t e s t , measured a t the p o s t - t e s t 70 A n a l y s i s showed t h a t the RPE r e p o r t e d a t a g i v e n r u n n i n g v e l o c i t y were s i g n i f i c a n t l y ( p < 0 . 0 0 l ) reduced a c r o s s groups and over time [ I n i t i a l Vmax ( p r e ) v e r s u s I n i t i a l Vmax ( p o s t ) ] . E f f o r t r a t i n g s were a l s o d i m i n i s h e d a t r e l a t i v e l y e q u i v a l e n t r u n n i n g v e l o c i t i e s [ I n i t i a l Vmax (pre) v e r s u s F i n a l Vmax ( p o s t ) ] . W h i l e n e i t h e r of thes e t r e n d s were found t o be s i g n i f i c a n t when the group by time i n t e r a c t i o n e f f e c t was c o n s i d e r e d , the changes i n RPE a t comparable a b s o l u t e (p< 0 . 0 8 ) and r e l a t i v e (p< 0 . 0 6 ) v e l o c i t i e s d i d approach s i g n i f i c a n c e . These r e s u l t s a r e d i s p l a y e d i n F i g u r e 3 and F i g u r e 4 . Trend a n a l y s i s r e v e a l e d t h a t i n a l l i n s t a n c e s , the r e l a t i o n s h i p between RPE and wo r k l o a d was h i g h l y l i n e a r . However, a s i g n i f i c a n t q u a d r a t i c component was a l s o i d e n t i f i e d i n t h e r e l a t i o n s h i p between RPE and g i v e n ( p < 0 . 0 0 1 ) or r e l a t i v e l y e q u i v a l e n t ( p < 0 . 0 0 0 l ) V 0 2 l e v e l s . Changes i n the magnitude of t h e s e components were not s i g n i f i c a n t over t i m e . No s i g n i f i c a n t q u a d r a t i c component was found i n the r e l a t i o n s h i p between RPE and e i t h e r a b s o l u t e or r e l a t i v e r u n n i n g v e l o c i t y . A h i g h l y s i g n i f i c a n t ( p < 0 . 0 0 l ) change o c c u r r e d i n the i n t e n s i t y by c o n d i t i o n i n t e r a c t i o n , when r e l a t i v e v e l o c i t y was a n a l y s e d . I n s p e c t i o n r e v e a l e d t h a t the d e c r e a s e s i n RPE from p r e - t o p o s t -t r a i n i n g were g r e a t e s t a t the lower i n t e n s i t i e s of e x e r c i s e , and t h a t t h e s e d i f f e r e n c e s were reduced as the s u b j e c t s approached the p o i n t of v o l i t i o n a l f a t i g u e . T h i s e f f e c t d i d not o p e r a t e d i f f e r e n t i a l l y between groups. A l t h o u g h s i m i l a r t r e n d s were e x h i b i t e d i n the a b s o l u t e v e l o c i t y and r e l a t i v e V 0 2 d a t a , these d i d not a c h i e v e s t a t i s t i c a l s i g n i f i c a n c e . 71 Ta b l e 6 - P e r c e n t R e d u c t i o n s i n RPE F o l l o w i n g 9 Weeks of T r a i n i n g D e s c r i p t i v e S t a t i s t i c s ANOVA Summary (p:) V a r i a b l e Group Workload Time Group x Time 55% 65% 75% 85% 95% A RPE (% I n i t i a l V02max) TG CG 19.8 15.7 20.0 6.7 18.1 6.6 15.9 3.9 8.2 1 .2 .01 >.20 A RPE (% V02max) TG CG 15.5 10.3 12.5 8.6 7.8 7.4 3.9 5.9 -3.5 1 .9 . 1 3 >.20 A RPE (% I n i t i a l Vmax) TG CG 25.8 11.3 24.4 7.7 16.3 6.5 12.9 2.4 5.6 0.1 .001 .08 A RPE (% Vmax) TG CG 21.6 5.3 19.9 4.6 11.6 4.2 8.8 -1.2 2.1 -3.1 .03 .06 Ta b l e 7 p r e s e n t s a summary of h y p o t h e s i s t e s t i n g . Hypotheses 3A and 3B demonstrated a t r e n d towards s i g n i f i c a n c e , but they c o u l d not be s u p p o r t e d a t the 0.95 l e v e l of c o n f i d e n c e . T a b l e 7 - Summary of H y p o t h e s i s T e s t i n g No. H y p o t h e s i s R e s u l t 1 . An i n c r e a s e d work c a p a c i t y i n the t r a i n i n g group, measured by: A) V02max ( l - m i n " 1 ) (TG>CG) B) AerT (1. m in" 1) (TG>CG) C) AerT (%V02max) (TG>CG) Non-supported Supported Non-supported 2. Reduced e f f o r t r a t i n g s , measured a t : A) Gi v e n V02 l e v e l s (TG>CG) B) R e l a t i v e l y e q u i v a l e n t l e v e l s of V02 (TG>CG) Non-supported Non-supported 3. Reduced e f f o r t r a t i n g s , measured a t : A) Given r u n n i n g v e l o c i t i e s (TG>CG) B) R e l a t i v e l y e q u i v a l e n t r u n n i n g v e l o c i t i e s (TG>CG) Non-supported Non-supported 72 F i g u r e 1 - Mean RPE a t A b s o l u t e Workloads Based Upon V02 2 0 _ 1 5 J LU CL 1 0 J X C o o t r o l ( p r e ) -4- C o n t r o l C p o s O i><| T r d i n l n g C p r e ) ^ T r a i n i n g ( p o s t ) T T 1 55 65 75 85 95 INTENSITY CA INITIAL V02max) 73 F i g u r e 2 - Mean RPE a t R e l a t i v e Workloads Based Upon V02 2 3 _ I S J LU CL 1 3 4 ^ C o n t r o l Cpr«} 4- C o n t r o l C p o s t ) I X T r a i n i n g C p r e > ^ T r a i n i n g C p o s t ) + \ \ 1 1 1 r— 55 65 75 85 INTENSITY CAV02 nax ) 95 74 F i g u r e 3 - Mean RPE at A b s o l u t e Veloc i t y Based Upon 2 0 _ IS J X + X C o n t T r LU CL 1 0 J ^ r 1 — — i 1 1 55 65 75 85 95 INTENSITY CA VELOCITY) c 75 F i g u r e 4 - Mean RPE a t R e l a t i v e Workloads Based Upon V e l o c i t y 22 _ 15 J LU a. 1 0 J X C o n t r o l Cpr«) - h C o n t r o l C p o s O t X T r o f n Ing Cpr«) Infr>9 C p o c t ) ~T 1 1 1 1 55 65 75 85 95 INTENSITY CA INITIAL VELOCITY!) 76 V. DISCUSSION The r e s u l t s of t h i s study cannot c o n f i r m t h a t the RPE a s s o c i a t e d w i t h r e l a t i v e w o r k l o a d s , based upon e i t h e r V02 or v e l o c i t y , a r e a f f e c t e d by endurance t r a i n i n g . N e v e r t h e l e s s , a t workloads l e s s than 85% of the maximal v e l o c i t y , a s t r o n g t r e n d e x i s t e d toward s i g n i f i c a n t r e d u c t i o n s i n RPE. F u r t h e r m o r e , t h e r e was a n o t i c e a b l e d i f f e r e n c e between the p r o b a b i l i t y of t h i s change and the change o b s e r v e d f o r RPE at a p e r c e n t a g e of V02max. P h y s i o l o g i c a l a d a p t a t i o n s , from which m o d i f i c a t i o n s i n the p e r c e p t i o n of e f f o r t a r e a t l e a s t p a r t i a l l y d e r i v e d , a re r e l a t e d t o the i n t e n s i t y , f r e q u e n c y and d u r a t i o n of t r a i n i n g . The impact which m a n i p u l a t i o n s i n t h e s e t r a i n i n g v a r i a b l e s have upon RPE has not been a s s e s s e d . C o n s e q u e n t l y , i t i s not known whether g r e a t e r changes i n RPE than those o b s e r v e d i n the c u r r e n t s t u d y would occur d u r i n g p r o l o n g e d t r a i n i n g . Perhaps the o b t a i n e d r e d u c t i o n s i n RPE a t r e l a t i v e w o r k l o a d s based upon v e l o c i t y would c o n t i n u e and a c h i e v e s i g n i f i c a n c e i f the d u r a t i o n of the program was extended. In o r d e r t o p r o v i d e the s u b j e c t s i n t h e p r e s e n t i n v e s t i g a t i o n w i t h a h i g h - i n t e n s i t y t r a i n i n g s t i m u l u s , e x e r c i s e was conducted a t workloads above the AerT. As a r e s u l t , a l t h o u g h the 19% decrease o b s e r v e d i n p e r c e n t body f a t was non-s i g n i f i c a n t when compared t o the c o n t r o l group, t h i s change was g r e a t e r than t h a t r e p o r t e d i n p r e v i o u s s t u d i e s ( M i s n e r e t a l . , 1974; Wilmore e t a l . , 1970) of s i m i l a r e x e r c i s e d u r a t i o n , frequency and mode. In c o n t r a s t , the i n t e n s i t y of the t r a i n i n g program was not r e f l e c t e d by s i g n i f i c a n t e l e v a t i o n s i n V02max. 77 T h i s may be a t t r i b u t e d t o the f a c t t h a t s e v e r a l of the s u b j e c t s who were m o d e r a t e l y f i t d u r i n g the p r e l i m i n a r y t e s t , f a i l e d t o demonstrate s u b s t a n t i a l improvements i n V02max. I n c r e a s e s i n V02max i n the c o n t r o l group, which were i d e n t i c a l i n magnitude ( 1 - m i n - 1 ) t o t h o s e r e p o r t e d e l s e w h e r e ( D a v i s e t a l . , 1 9 7 9 ) f o r c o n t r o l s u b j e c t s over a 9-week p e r i o d , may have c o n t r i b u t e d t o t h i s f i n d i n g as w e l l . I n c r e a s e s i n AerT and maximum v e n t i l a t i o n , which averaged a p p r o x i m a t e l y 6%, a l s o appeared t o be l i m i t e d by the i n i t i a l f i t n e s s l e v e l of the s u b j e c t s . C l e a r l y , more d r a m a t i c p h y s i o l o g i c a l e f f e c t s c o u l d be produced i n a l e s s a c t i v e sample, p a r t i c u l a r l y i f the d u r a t i o n and f r e q u e n c y of the t r a i n i n g program were i n c r e a s e d . H y p o t h e t i c a l l y , RPE c o u l d show d e c r e a s e s of a c o r r e s p o n d i n g magnitude. Depending upon the l e v e l of p h y s i c a l c o n d i t i o n i n g of the s u b j e c t s , AerT may be l o c a t e d a t 50-85% V02max ( C o s t i l l , 1970; D a v i s et a l . , 1979; D r e s s e n d o r f e r e t a l . , 1981; Kindermann et a l . , 1979; Londeree and Ames, 1975). D a v i s et a l . (1979) r e p o r t e d t h a t AerT, e x p r e s s e d as a p e r c e n t a g e of V02max (AerT-%V02max), i n c r e a s e d by 15% subsequent t o 9-weeks of c y c l e t r a i n i n g c o n ducted a t V02 l e v e l s 50-70% above the o r i g i n a l AerT. The s u b j e c t s i n t h e i r study were i n i t i a l l y a t a low l e v e l of p h y s i c a l f i t n e s s (V02max = 31.1 m l - k g - 1 - m i n - 1 ) , and e x p e r i e n c e d a 44% i n c r e a s e i n AerT e x p r e s s e d as a b s o l u t e V02 ( 1 - m i n - 1 ) . Ready and Quinney (1982) o b s e r v e d i n c r e a s e s of 70.4% and 19.4% i n AerT ( 1 - m i n - 1 ) and AerT-%V02max, r e s p e c t i v e l y , f o l l o w i n g 9 weeks of c y c l e t r a i n i n g a t 80% V02max. However, the change i n 78 AerT-%V02max was not found t o be s i g n i f i c a n t . The s u b j e c t s i n the c u r r e n t study were i n i t i a l l y b e t t e r p h y s i c a l l y c o n d i t i o n e d , based upon V02max and AerT-%V02max, than those i n e i t h e r of the c i t e d s t u d i e s . C o n s e q u e n t l y , the i n c r e a s e i n AerT ( 1 - m i n - 1 ) which r e s u l t e d was more modest, and no d i f f e r e n c e i n AerT-%V02max was o b s e r v e d . I t would appear t h a t e l e v a t i o n s i n AerT-%V02max are m a n i f e s t e d o n l y when the r a t e of improvement i n AerT exceeds t h a t of V02max. However, d a t a p e r t a i n i n g t o the AerT must be i n t e r p r e t e d w i t h c a u t i o n . T h i s s t u d y has s e l e c t e d E xcess C02 as a measure of the AerT, w h i l e p r e v i o u s r e s u l t s have been based upon a v a r i e t y of o t h e r t e c h n i q u e s . Moreover, v a l u e s f o r AerT may be a f f e c t e d by the r a t e of work i n c r e a s e d u r i n g i n c r e m e n t a l e x e r c i s e t e s t s (Hughson and Green, 1982). T h e r e f o r e , AerT-%V02max i n t h i s s t u d y , which o c c u r r e d a t 77% V02max, may be d i f f i c u l t t o compare t o AerT-%V02max i n o t h e r r e p o r t s . Reviews which have d i s c u s s e d s ensory cues t o p e r c e i v e d e x e r t i o n ( M i h e v i c , 1981; R o b e r t s o n , 1982) have f a v o u r e d t h e i n t e r p r e t a t i o n t h a t %V02max i s an i m p o r t a n t d e t e r m i n a n t of RPE d u r i n g dynamic e x e r c i s e . The t h e o r y t h a t e x e r c i s e may be p r e s c r i b e d based upon e f f o r t e v a l u a t i o n (Borg, 1982; Smutok et a l . , 1980) assumes t h a t d i f f e r e n t i n d i v i d u a l s p e r c e i v e comparable degrees of p h y s i c a l s t r a i n i n an analogous manner. T h i s s u i t s the concept t h a t RPE i s commensurate w i t h %V02max. However, the onset of the AerT i s a s s o c i a t e d w i t h s u s t a i n e d e l e v a t i o n s i n plasma l a c t a t e and v e n t i l a t i o n ( S k i n n e r and M c C l e l l a n , 1980). F l u c t u a t i o n s i n these v a r i a b l e s have been 79 shown t o c o r r e l a t e w i t h RPE (Horstman, 1977; Horstman e t a l . , 1979c; Kamon e t a l . , 1974; Noble e t a l . , 1973; Morgan and P o l l o c k , 1977; Pederson and Welch, 1977) and appear t o i n f l u e n c e e f f o r t e v a l u a t i o n . S i n c e AerT-%V02max may be e l e v a t e d by t r a i n i n g , i n p u t from e f f o r t cues which a r e a s s o c i a t e d w i t h v e n t i l a t i o n and/or b l o o d l a c t a t e become dominant a t d i f f e r e n t l e v e l s of %V02max. E v i d e n t l y , RPE cannot always be c o m p a t i b l e w i t h a model of e f f o r t p e r c e p t i o n which i s based upon b l o o d l a c t a t e s , v e n t i l a t i o n and %V02max s i m u l t a n e o u s l y . I f p e r c e i v e d e f f o r t c o r r e s p o n d s c l o s e l y t o AerT, then v a l i d a t i o n of the r e l a t i o n s h i p between RPE and r e l a t i v e V02 (RPE-%V02max) may be c o n t i n g e n t upon the homogeneity of the sample group. W i t h i n the c o n t e x t of t h i s paradigm, RPE-%V02max would not be e x p e c t e d t o d e v i a t e among i n d i v i d u a l s u n l e s s AerT-%V02max v a r i e d as w e l l . F u r t h e r m o r e , comparisons of i n d i v i d u a l s who do not d i f f e r s u b s t a n t i a l l y i n p h y s i c a l c o n d i t i o n i n g s h o u l d y i e l d s i m i l a r v a l u e s f o r RPE at the AerT. T h i s has been c o n f i r m e d i n the l i t e r a t u r e ( P u r v i s and C u r e t o n , 1981). I t has a l s o been shown t h a t RPE a r e h i g h e r a t the AerT f o r w e l l - t r a i n e d a t h l e t e s than s e d e n t a r y s u b j e c t s , who d i f f e r r a d i c a l l y i n AerT-%V02max (Simon e t a l . , 1983). C r o s s - s e c t i o n a l s t u d i e s which have f a i l e d t o demonstrate d i f f e r e n c e s i n RPE-%V02max as a f u n c t i o n of f i t n e s s ( F l e m i n g e t a l . , 1982; Horstman et a l , 1979c) have not r e p o r t e d v a l u e s f o r AerT-%V02max. In the p r e s e n t s t u d y , n e i t h e r RPE a t the AerT or AerT-%V02max changed i n the t r a i n i n g group. Decrements i n RPE a t the AerT were p a r a l l e l e d by a n o n - s i g n i f i c a n t t r e n d towards r e d u c t i o n s i n 80 AerT-%V02max i n the c o n t r o l group. T h i s i n d i c a t e s t h a t RPE were c l o s e l y r e l a t e d t o AerT. S i n c e the 6% d i f f e r e n c e i n c o r r e l a t i o n between RPE and %V02max among groups was a p p r o x i m a t e l y the same as the 5% d e c r e a s e i n AerT-%V02max, RPE may a l s o appear t o have been r e l a t e d t o %V02max. However, s i n c e c o r r e l a t i o n s between RPE and %V02max were n e a r l y i d e n t i c a l b e f o r e and a f t e r t e s t i n g , t h i s seems u n l i k e l y . The lower RPE a t the AerT i n the c o n t r o l group c o u l d a l s o be a t t r i b u t e d t o f a m i l i a r i z a t i o n w i t h the t e s t i n g equipment and p r o t o c o l , d e s p i t e an attempt t o c o n t r o l f o r t h i s c o n f o u n d i n g v a r i a b l e . T h e o r e t i c a l l y , t h i s p r o c e s s c o u l d e f f e c t e f f o r t r a t i n g s . I n e x p e r i e n c e i n the performance of an e x e r c i s e t a s k has been r e f l e c t e d i n e l e v a t i o n s i n RPE d u r i n g p r e l i m i n a r y t e s t i n g e l s e w h e r e (Horstman e t a l . , 1979c). T h i s mechanism c o u l d e x p l a i n the i n c r e a s e i n time t o v o l i t i o n a l f a t i g u e and r e d u c t i o n s i n RPE a t a g i v e n V02 (6.8%) or v e l o c i t y (5.6%) i n the c o n t r o l group, which o c c u r r e d w i t h o u t s i g n i f i c a n t changes i n c a r d i o v a s c u l a r i n d i c e s . I t may a l s o account f o r the f a c t t h a t a l t h o u g h the average RPE of s u b j e c t s i n the e x e r c i s e group were 16.4% and 17% l o w e r , r e s p e c t i v e l y , a t a g i v e n V02 or v e l o c i t y d u r i n g the p o s t - t e s t , t h i s e f f e c t c o u l d not be a t t r i b u t e d t o t h e t r a i n i n g program. N e v e r t h e l e s s , the s u b j e c t s i n each group were e q u a l l y u n f a m i l i a r w i t h t r e a d m i l l r u n n i n g p r i o r t o the s t u d y , and f a m i l i a r i z a t i o n would not be ex p e c t e d t o d i f f e r e n t i a l l y a f f e c t RPE-AerT among groups. C o n c e i v a b l y , i f t r a i n i n g enhances p e r c e p t u a l s e n s i t i v i t y t o e f f o r t cues such as b l o o d l a c t a t e s and v e n t i l a t i o n , RPE-AerT would be l e s s dependent upon %V02max, and 81 the e f f e c t s of f a m i l i a r i z a t i o n upon the RPE-AerT r e l a t i o n s h i p would be d i m i n i s h e d . T h i s c o u l d e x p l a i n the d i f f e r e n c e i n RPE-AerT which was observed between groups. An i m p o r t a n t i m p l i c a t i o n of the p o s t u l a t e d r e l a t i o n s h i p between RPE and %V02max i s t h a t t h e e f f e c t s of t r a i n i n g upon e f f o r t p e r c e p t i o n w i l l t e n d t o be obscured when RPE a r e equated i n terms of V02max. E a r l y e v i d e n c e suggested t h a t when V02 or HR a r e a d j u s t e d on a r e l a t i v e b a s i s , RPE do not change (Docktor and Sharkey, 1971; Ekblom and G o l d b a r g , 1971; K i l b o m , 1971; S k i n n e r e t a l . , 1969). Recent d a t a ( B u r k h a r d t e t a l . , 1982; K l e i n , 1982) c o n f l i c t s w i t h t h e s e r e s u l t s . In the p r e s e n t i n v e s t i g a t i o n , no s i g n i f i c a n t changes were obse r v e d i n the RPE r e p o r t e d by the t r a i n i n g group, a t r e l a t i v e w o r k l o a d s based upon V02. Because the mechanisms which r e g u l a t e p e r c e p t u a l a d a p t a t i o n s t o e x e r c i s e t r a i n i n g a r e not p r e s e n t l y u n d e r s t o o d , i t i s u n c e r t a i n whether d i f f e r e n c e s i n RPE c o u l d have been e x p e c t e d from a t h e o r e t i c a l p e r s p e c t i v e . V e n t i l a t o r y volume, p r e s s u r e and r a t e may a l l be p e r c e i v e d w i t h a h i g h degree of a c c u r a c y and e x e r t c o n s i d e r a b l e impact upon e f f o r t p e r c e p t i o n (Bakers and Tenney, 1970; M i h e v i c , 1981). Compared t o non-a t h l e t e s , endurance a t h l e t e s have low v e n t i l a t o r y chemoresponses and low e x e r c i s e VE a t e q u i v a l e n t r e l a t i v e work l e v e l s , but i t i s not c l e a r whether t h i s t r a i t i s i n n a t e or a f f i l i a t e d w i t h t r a i n i n g ( M a r t i n et a l . , 1979). A l t h o u g h RPE i n c r e a s e s u n i f o r m l y w i t h r e l a t i v e m e t a b o l i c r a t e ( R o b e r t s o n , 1982; Sargeant and D a v i e s , 1973; S k i n n e r e t a l . , 1973a), no a f f e r e n t nervous system i n p u t e x i s t s t o mo n i t o r V02 (Edwards et a l . , 82 1972). In a d d i t i o n , no co r r e s p o n d e n c e can be shown between e f f o r t and V02 when the p e r i p h e r a l s i g n a l t o the e f f o r t sense i s h e l d c o n s t a n t ( C a f a r e l l i , 1978). C a t e c h o l a m i n e e x c r e t i o n has a l s o been a s s o c i a t e d w i t h the e v a l u a t i o n of e f f o r t ( D o c k t o r and Sharkey, 1971; Frankenhaeuser, 1969; Schnabel e t a l . , 1982)! and i s p u r p o r t e d l y a f u n c t i o n of r e l a t i v e m e t a b o l i c r a t e (Howley et a l . , 1970). However, d u r i n g s t e a d y - r a t e r u n n i n g a t the AerT, c a t e c h o l a m i n e l e v e l s p r o g r e s s i v e l y i n c r e a s e and appear t o be r e l a t e d t o g l y c o g e n a v a i l a b i l i t y ( Schnabel e t a l . , 1982). A e r o b i c t r a i n i n g i s known t o produce an i n c r e a s e i n muscle g l y c o g e n s t o r e s (Bergstrom and Hultman, 1966). I t a l s o r e s u l t s i n a g r e a t e r p r o p o r t i o n of energy d e r i v a t i o n from f a t s than c a r b o h y d r a t e s d u r i n g submaximal e x e r c i s e , r e s u l t i n g i n a g l y c o g e n s p a r i n g e f f e c t ( H o l l o s z y , 1973). C o n s e q u e n t l y , i t would be e x p e c t e d t h a t g l y c o g e n d e p l e t i o n would occur a t a slo w e r r a t e i n t r a i n e d i n d i v i d u a l s , t h e r e b y augmenting c a r b o h y d r a t e a v a i l a b i l i t y . T h i s would s i g n i f y a more p o t e n t i n p u t from the c a t e c h o l a m i n e - r e l a t e d component of e f f o r t p e r c e p t i o n as e x e r c i s e p r o g r e s s e s . I t has p r e v i o u s l y been demonstrated t h a t endurance t r a i n i n g r e s u l t s i n decrements i n c a t e c h o l a m i n e l e v e l s a t workloads of 60, 70 and 80% V02max and may be r e s p o n s i b l e f o r r e d u c t i o n s i n the c e n t r a l c o n t r i b u t i o n t o RPE ( S k r i n a r e t a l . , 1983). I n l i g h t of t h e s e f i n d i n g s , e a r l i e r s t a t e m e n t s t h a t no t h e o r e t i c a l b a s i s e x i s t s f o r m o d i f i c a t i o n s i n RPE at r e l a t i v e l e v e l s of V02 ( M i h e v i c , 1981) may have been premature. R e c e n t l y , i t has been acknowledged ( R e j e s k i et a l . , 1982) 83 t h a t examining t r a i n i n g - i n d u c e d a l t e r a t i o n s i n RPE s o l e l y from the p o i n t of view of c a r d i o v a s c u l a r g a i n s may be in a d e q u a t e . An a l t e r n a t i v e approach t o t h i s i s s u e i n v o l v e s an e v a l u a t i o n of changes i n RPE from the p e r s p e c t i v e of p e r i p h e r a l l y - m e d i a t e d a d a p t a t i o n s . Few s t u d i e s have a s s e s s e d the p e r c e p t u a l response t o c h r o n i c e x e r c i s e u s i n g t h i s p r o c e d u r e . In t h i s s t u d y , a d i f f e r e n c e of a p p r o x i m a t e l y 11% e x i s t e d between the d e c l i n e s o b s e r v e d i n the c o n t r o l and t r a i n i n g groups,when RPE were a n a l y s e d a t r e l a t i v e v e l o c i t i e s . T h i s t r e n d emphasizes the m u l t i - d i m e n s i o n a l n a t u r e of p h y s i c a l t r a i n i n g . In c o n t r a s t t o the p r e s e n t f i n d i n g s , S k i n n e r e t a l . (1969) c o u l d not d i s c r i m i n a t e between the RPE v a l u e s which were r e p o r t e d a t a p e r c e n t a g e of maximal w o r k l o a d on a b i c y c l e ergometer by p h y s i c a l l y f i t and u n f i t s u b j e c t s . The same a u t h o r s n o ted t h a t a l t h o u g h no d i f f e r e n c e s e x i s t e d i n the work performed a t a HR of 150 or RPE of 15 on a b i c y c l e , s u b j e c t s who were h e a v i e r and f a t t e r a c c o m p l i s h e d l e s s work a t these s t a n d a r d s on a t r e a d m i l l ( S k i n n e r et a l . , 1969). C o n s i d e r a b l e e v i d e n c e s u p p o r t s the r o l e of s e n s a t i o n s a r i s i n g i n tendon, s k i n , j o i n t and l i g a m e n t r e c e p t o r s i n the p e r c e p t i o n of e f f o r t (Ekblom e t a l . , 1975; Gandevia and McCloskey, 1976; H e n r i k k s o n et a l . , 1972; Pa n d o l f and N o b l e , 1973; Stamford and N o b l e , 1974). These r e s u l t s imply t h a t i t may be i n a p p r o p r i a t e t o compare the sensory response t o t r a i n i n g o c c u r r i n g i n w e i g h t - b e a r i n g and w e i g h t - s u p p o r t e d a c t i v i t i e s . T h i s does not n e c e s s a r i l y mean t h a t RPE a t r e l a t i v e e x e r c i s e i n t e n s i t i e s which a re measured i n terms of neuromuscular parameters a r e u n a f f e c t e d by c y c l e t r a i n i n g . When 84 c o m p e t i t i v e c y c l i s t s become s k i l l e d i n the use of muscle-s p e c i f i c i n s t r u m e n t s such as t o e - c l i p s , RPE may be lower d u r i n g maximal e x e r c i s e ( R e j e s k i e t a l . , 1982). Limb speed and RPE a r e h i g h l y c o r r e l a t e d d u r i n g b i c y c l e e x e r c i s e a t r a p i d p e d a l l i n g r a t e s ( C r o i s a n t , 1982; L o l l g e n e t a l . , 1980). I f p r o p r i o c e p t i v e feedback r e s p o n d i n g t o l i m b speed : i s a s t i m u l u s t o e f f o r t p e r c e p t i o n which can be m o d i f i e d by t r a i n i n g , then b i c y c l e t r a i n i n g programs which i n c r e a s e w o r k l o a d e x c l u s i v e of w o r k r a t e may have a reduced impact upon RPE. Thus p e r c e p t u a l a d a p t a t i o n s t o c h r o n i c b i c y c l e e x e r c i s e may depend upon the n a t u r e of the t r a i n i n g program which i s employed. The c u r r e n t f i n d i n g , t h a t RPE may be reduced t o a g r e a t e r e x t e n t when e x p r e s s e d as a r e l a t i v e p e r c e n t a g e of neuromuscular r a t h e r than c a r d i o v a s c u l a r measures, s u g g e s t s t h a t a g r e a t e r r e d u c t i o n o c c u r s i n l o c a l than c e n t r a l cues t o e f f o r t p e r c e p t i o n w i t h t r a i n i n g . T h i s h y p o t h e s i s has g e n e r a l l y been s u p p o r t e d i n the l i t e r a t u r e (Knuttgen e t a l . , 1982; L ewis e t a l . , 1980; R e j e s k i e t a l . , 1982). S t u d i e s have shown t h a t b l o o d l a c t a t e l e v e l s are lower at the same %V02 f o l l o w i n g t r a i n i n g (Hermansen et a l . , 1967; S a l t i n and K a r l s s o n , 1971). T h e r e f o r e , due t o the h i g h e r AerT-%V02max i n t r a i n e d s u b j e c t s , t h e r e i s a t h e o r e t i c a l b a s i s f o r e x p e c t i n g l o c a l RPE t o be reduced a t e x e r c i s e i n t e n s i t i e s w hich a r e below the e l e v a t e d AerT but above the i n i t i a l AerT. A l t h o u g h b l o o d l a c t a t e s were not measured d i r e c t l y i n t h i s i n v e s t i g a t i o n , the r e s u l t s do not s u pport the concept of l a c t a t e - m e d i a t e d d e c l i n e s i n RPE a t r e l a t i v e e x e r c i s e i n t e n s i t i e s , subsequent t o t r a i n i n g . Both the l a c t a t e and 85 e f f o r t responses t o e x e r c i s e a re d e s c r i b e d by a p o s i t i v e l y a c c e l e r a t i n g f u n c t i o n (Borg, 1962; Gamberale, 1972). I t may be surm i s e d t h a t the c u r v i l i n e a r i n c r e a s e i n RPE as a f u n c t i o n of %V02max i n t h i s s t u d y was a r e f l e c t i o n of the e f f e c t of the l a c t a t e r e s p o n s e , and/or t h a t of v e n t i l a t i o n , which responds i n a s i m i l a r f a s h i o n ( S k i n n e r and M c C l e l l a n , 1980). S i n c e no change was ob s e r v e d i n the magnitude of the q u a d r a t i c component f o l l o w i n g t r a i n i n g , i t would not be e x p e c t e d t h a t t h e s e v a r i a b l e s would e x e r t a d i f f e r e n t degree of i n p u t i n t o the e f f o r t sense a t t h i s t i m e . The r e l a t i o n s h i p between RPE and r e l a t i v e v e l o c i t y was not c u r v i l i n e a r i n n a t u r e , and g r e a t e r r e d u c t i o n s i n r a t e d e f f o r t were obse r v e d than when RPE was p l o t t e d a g a i n s t %V02max. T h e r e f o r e , a l t h o u g h no d i r e c t e v i d e n c e e x i s t s , i t appears t h a t d e c r e a s i n g s t r a i n e x p e r i e n c e d i n the a c t i v e muscles was the dominant l o c a l p e r c e p t u a l response t o t r a i n i n g . S i n c e l o c a l f a c t o r s appear t o dominate c e n t r a l c o n t r i b u t o r s t o e f f o r t p e r c e p t i o n a t e x e r c i s e i n t e n s i t i e s below the AerT, the f a c t t h a t d e c r e a s e s i n RPE were g r e a t e s t a t moderate e x e r c i s e i n t e n s i t i e s (55-85% Vmax) s u p p o r t s t h i s c o n c l u s i o n . I t a l s o c o i n c i d e s w i t h the f i n d i n g t h a t t r a i n i n g may d e c r e a s e the i n f l u e n c e of l o c a l cues d u r i n g maximal e x e r c i s e a t an e l e v a t e d V02max, w i t h o u t a p p r e c i a b l e changes i n plasma l a c t i c a c i d c o n c e n t r a t i o n ( R e j e s k i et a l . , 1982). S l o w - t w i t c h muscle f i b r e s appear t o be more e f f i c i e n t than f a s t - t w i t c h f i b r e s ( D a v i e s , 1965; Gibbs and G i b s o n , 1972; Wendt and G i b b s , 1973) and p r o v i d e a more s e n s i t i v e measure of e f f o r t e x p e n d i t u r e ( B a n i s t e r , 1979; Hore et a l . , 1976). In t h i s c a s e , 86 muscle f i b r e c o m p o s i t i o n may mediate the p e r c e p t i o n of e f f o r t , as has been suggested elsewhere (Weiser and Stamper, 1977). C o n s i d e r a b l e e v i d e n c e e x i s t s t o support the n o t i o n t h a t endurance t r a i n i n g r e s u l t s i n l o c a l i z e d p h y s i o l o g i c a l a d a p t a t i o n s ( G o l l n i c k e t a l . , 1973; Magel et a l . , 1975; McArdle et a l . , 1978). W h i l e i t i s not c l e a r whether f a s t - t w i t c h f i b r e s may be c o n v e r t e d t o s l o w - t w i t c h f i b r e s ( H o l l o s z y , 1973), r e p o r t s of i n c r e a s e d m e c h a n i c a l e f f i c i e n c y w i t h t r a i n i n g ( P a n d o l f e t a l . , 1975; Robinson and Harmon, 1941; Ekblom et a l . , 1978) s u b s c r i b e t o the concept t h a t endurance t r a i n i n g promotes the r e c r u i t m e n t of e x e r c i s e - s p e c i f i c motor u n i t s t o more e f f e c t i v e l y meet the demands of a g i v e n t a s k ( E d g e r t o n , 1976). On the b a s i s of t h e s e f i n d i n g s , i t i s l o g i c a l t o c o n c l u d e t h a t n e u r o l o g i c a l a d a p t a t i o n s which accompany endurance t r a i n i n g r e s u l t i n r e d u c t i o n s i n RPE a t r e l a t i v e e x e r c i s e v e l o c i t i e s by i n c r e a s i n g the e f f i c i e n c y of motor u n i t s e l e c t i o n and i m p r o v i n g the c o r r e s p o n d e n c e between e f f o r t e v a l u a t i o n and a c t u a l p h y s i o l o g i c a l demands. With r e s p e c t t o the c u r r e n t s t u d y , t h i s might e x p l a i n both the r e d u c t i o n s i n RPE a t r e l a t i v e w o r k l o a d s based upon v e l o c i t y , and the s t a b i l i t y of RPE-AerT i n the t r a i n i n g group, as d i s c u s s e d p r e v i o u s l y . I t would a l s o h e l p t o c o n f i r m the r e s u l t s of Morgan and P o l l o c k (1977), who found t h a t h i g h l y - t r a i n e d a t h l e t e s i n t e r p r e t e f f o r t s e n s a t i o n s more a c c u r a t e l y than t h e i r l e s s s u c c e s s f u l c o u n t e r p a r t s . No e x p l a n a t i o n can be o f f e r e d f o r the s i g n i f i c a n t i n c r e a s e which was observed i n maximum RPE. P o s s i b l y , by becoming more f a m i l i a r w i t h the t e s t p r o t o c o l , the s u b j e c t s were a b l e t o judge 87 t h e i r c a p a c i t y t o c o n t i n u e r u n n i n g more a c c u r a t e l y . B e i n g more c o g n i z a n t of a p p r o a c h i n g f a t i g u e , they may have s e l e c t e d e f f o r t r a t i n g s which seemed more a p p r o p r i a t e f o r the t e r m i n a t i o n of e x e r c i s e . Other i n v e s t i g a t o r s have not found d i f f e r e n c e s i n maximum RPE f o l l o w i n g t r a i n i n g (Ekblom and G o l d b a r g , 1971, Lewis et a l . , 1980). An e x c e p t i o n c o n c e r n s the r e s u l t s of R e j e s k i e t a l . (1982), who observed a d e c r e a s e i n l o c a l r a t i n g s of RPE a t a h i g h e r V02max i n t r a i n e d s u b j e c t s who wore t o e - c l i p s . P o t e n t i a l l y , both maximum RPE and RPE a t r e l a t i v e workloads c o u l d be lowered by h a b i t u a l e x e r c i s e , due t o a m o d i f i c a t i o n of the p e r c e p t u a l p r o c e s s i n g of e n v i r o n m e n t a l and/or p h y s i o l o g i c a l s t i m u l i . Many i n d i v i d u a l s e i t h e r c o n s i s t e n t l y reduce or augment the i n t e n s i t y of t h e i r p e r c e p t i o n s ( P e t r i e , 1967; Ryan and F o s t e r , 1967; Sweeney, 1966), i n c l u d i n g t h e i r p e r c e p t i o n of e f f o r t ( R o b e r t s o n e t a l . , 1977). The f a c t t h a t h i g h - i n t e n s i t y s t i m u l a t i o n appears t o d e v e l o p the r e d u c t i o n response (Robertson et a l . , 1977) c o u l d a p p l y t o e x e r c i s e . Reducers te n d t o d i s p l a y a low p e r c e p t u a l r e a c t a n c e t o muscular e f f o r t , a h i g h t o l e r a n c e t o p a i n ( P e t r i e e t a l . , 1960; Sweeney, 1966), and p a r t i c i p a t e i n a t h l e t i c s (Ryan and F o s t e r , 1967). P a i n and e f f o r t d u r i n g e x e r c i s e a r e t e m p o r a l l y r e l a t e d , and o f t e n cannot be d i s t i n g u i s h e d from each o t h e r ( C a l d w e l l and S m i t h , 1967). S i n c e p a i n t o l e r a n c e may be c r i t i c a l t o s u c c e s s f u l p a r t i c i p a t i o n i n c e r t a i n a t h l e t i c s (Tahu, 1981), p e r c e p t u a l r e d u c t i o n s may c o n t r i b u t e t o i n c r e a s e d e x e r c i s e performance. In t h i s r e s p e c t , i t i s of i n t e r e s t t o note t h a t maximal e x e r c i s e performance appears t o be l i m i t e d by a p e r c e p t u a l b a r r i e r ( B a n i s t e r , 1979; 88 K i l b o m et a l . , 1983), which imposes r e s t r i c t i o n s on the f u l l e x p r e s s i o n of p h y s i o l o g i c a l c a p a c i t y . A n a l y s i s of the impact of r e d u c t i o n s i n e f f o r t p e r c e p t i o n upon the magnitude pf t h i s c o n s t r a i n t t o performance i s worthy of c o n s i d e r a t i o n . 89 V I . SUMMARY AND CONCLUSIONS The purpose of t h i s i n v e s t i g a t i o n was t o examine m o d i f i c a t i o n s i n the p e r c e p t i o n of e f f o r t a t r e l a t i v e l y e q u i v a l e n t workloads f o l l o w i n g t r a i n i n g , and compare the r e s u l t s o b t a i n e d u s i n g d i f f e r e n t t e c h n i q u e s of a n a l y s i s . T h i r t e e n s u b j e c t s completed a p r o g r e s s i v e , 9-week endurance t r a i n i n g program, which i n v o l v e d r u n n i n g a t v e l o c i t i e s above the v e n t i l a t o r y a e r o b i c t h r e s h o l d ( A e r T ) . Changes i n the p e r c e p t u a l and p h y s i o l o g i c a l r e sponses of the t r a i n i n g group (N=13) were compared t o those o b s e r v e d i n a c o n t r o l group (N=13). Improvements i n V02max, time t o v o l i t i o n a l f a t i g u e and maximum v e n t i l a t i o n were not found t o be s i g n i f i c a n t a t the 0.05 p r o b a b i l i t y l e v e l . H i g h l y s i g n i f i c a n t (p<0.0l) improvements i n AerT appeared t o be the dominant p h y s i o l o g i c a l e f f e c t of t r a i n i n g . A e r o b i c t h r e s h o l d a t a %V02max (AerT-%V02max) was not a f f e c t e d by t r a i n i n g . In the c o n t r o l group, d e c r e a s e s i n r a t i n g s of p e r c e i v e d e x e r t i o n (RPE) a t the AerT were p a r a l l e l l e d by r e d u c t i o n s i n AerT-%V02max. In the t r a i n i n g group, RPE were 14% and 17% lower a t a g i v e n V02 and v e l o c i t y , r e s p e c t i v e l y , a t the p o s t - t e s t . At e q u i v a l e n t r e l a t i v e w o r k l o a d s , d e c r e a s e s i n RPE averaged 7.2% f o r V02 and 12.8% f o r v e l o c i t y . When m o d i f i c a t i o n s i n RPE i n the c o n t r o l group were c o n s i d e r e d , the changes i n RPE i n the t r a i n i n g group were not s i g n i f i c a n t (p<0.05). D e s p i t e the decrements i n RPE i n the c o n t r o l group, changes i n RPE i n the t r a i n i n g group approached s i g n i f i c a n c e a t f i x e d v e l o c i t i e s (p<0.08) and r e l a t i v e v e l o c i t i e s (p<0.06). 90 Maximum RPE were found t o i n c r e a s e s i g n i f i c a n t l y i n both the t r a i n i n g and c o n t r o l groups. A l t h o u g h RPE i n c r e a s e d l i n e a r l y w i t h w o r k l o a d , a s i g n i f i c a n t q u a d r a t i c component was a l s o i d e n t i f i e d i n the r e l a t i o n s h i p between RPE and g i v e n ( p < 0 . 0 0 l ) or r e l a t i v e l y e q u i v a l e n t ( p < 0 . 0 0 0 l ) V02 l e v e l s . Changes i n the magnitude of these components were not o b s e r v e d over t i m e . No s i g n i f i c a n t q u a d r a t i c component was found i n the r e l a t i o n s h i p between RPE and e i t h e r a b s o l u t e or r e l a t i v e r u n n i n g v e l o c i t y . On the b a s i s of the f i n d i n g s which have been p r e s e n t e d , i t i s c o n c l u d e d t h a t i n a m o d e r a t e l y f i t sample: 1) E l e v a t i o n s i n AerT can be a c h i e v e d independent of changes i n V02max. 2) Changes i n AerT as a p e r c e n t a g e of V02max a r e not a t y p i c a l m a n i f e s t a t i o n of t r a i n i n g , but RPE appear t o be r e l a t e d t o AerT-%V02max. 3) When t r a i n i n g i s e v a l u a t e d i n terms of improvements i n r u n n i n g v e l o c i t y r a t h e r than V02, g r e a t e r r e d u c t i o n s i n RPE a r e observ e d a t moderate e x e r c i s e i n t e n s i t i e s (55-75% maximum w o r k l o a d ) . C o n s e q u e n t l y , the changes i n RPE which are observed f o l l o w i n g t r a i n i n g a r e r e l a t e d t o the method of a n a l y s i s which i s used. 4) Measured i n terms of %V02max, RPE are not s i g n i f i c a n t l y a l t e r e d by endurance t r a i n i n g . However, when equated i n terms of % maximum v e l o c i t y , r e d u c t i o n s i n RPE approach s i g n i f i c a n c e . In the p r e s e n t s t u d y , t h i s change was p r o b a b l y due to a l o w e r i n g of l o c a l e f f o r t cues, p a r t i c u l a r l y those o r i g i n a t i n g from 91 neuromuscular r e c e p t o r s which monitor p h y s i c a l s t r a i n . However, s i n c e RPE appear to be r e l a t e d t o AerT-%V02max, when t h i s v a r i a b l e i s a f f e c t e d by t r a i n i n g , the mechanisms which a r e r e s p o n s i b l e f o r changes i n RPE may be d i f f e r e n t . T h e r e f o r e , the i n f l u e n c e t h a t t r a i n i n g has upon RPE may be s p e c i f i c t o the n a t u r e of u n d e r l y i n g p h y s i o l o g i c a l a d a p t a t i o n s . T h i s e f f e c t s h o u l d be s t u d i e d f u r t h e r , under c o n d i t i o n s i n which s u b j e c t s a c h i e v e g r e a t e r improvements i n p h y s i c a l c o n d i t i o n i n g , over p r o l o n g e d p e r i o d s . 5) C o n t r o l groups a r e a n e c e s s i t y i n s t u d i e s which employ RPE as a dependent v a r i a b l e . When RPE are t o be r e c o r d e d d u r i n g d a t a c o l l e c t i o n , s u b j e c t s s h o u l d become w e l l a c q u a i n t e d w i t h t e s t p r o c e d u r e s and p r o t o c o l s p r i o r t o p a r t i c i p a t i o n . I t i s recommended t h a t r e p e a t e d t e s t i n g be performed a t the o u t s e t of the s t u d y , u n t i l the e f f e c t s of f a m i l i a r i z a t i o n have been e l i m i n a t e d . 92 BIBLIOGRAPHY A l l e n , P.D. and K.B. P a n d o l f . 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S p o r t s E x e r c . 14: 223-228, 1 982. 108 APPENDIX A - BORG 15-POINT SCALE FOR RATING PERCEIVED EXERTION 7 v e r y , v e r y l i g h t 8 9 v e r y l i g h t 10 1 1 f a i r l y l i g h t 1 2 13 somewhat hard Borg, G. P e r c e i v e d e x e r t i o n as an i n d i c a t o r of somatic s t r e s s . Scand. J . Rehab. Med. 2: 92-98, 1970. p.93 14 15 hard 16 17 v e r y h a r d 18 19 v e r y , v e r y h a r d 20 109 APPENDIX B - 9-POINT SCALE FOR RATING PERCEIVED EXERTION 2 Not a t a l l s t r e s s f u l 8 V e r y , v e r y s t r e s s f u l R o b e r t s o n , R.J. D i f f e r e n t i a t e d p e r c e p t i o n s of e x e r t i o n : P a r t I . Mode of i n t e g r a t i o n of r e g i o n a l s i g n a l s . P e r c e p t . Mot. S k i l l s 14: 683-689, 1979, p. 685. 1 10 APPENDIX C - BORG 1Q-POINT SCALE FOR RATING OF PERCEIVED EXERTION 0 N o t h i n g a t a l l 0.5 V e r y , v e r y weak ( j u s t n o t i c e a b l e ) 1 Very weak 2 Weak (weak) 3 Moderate 4 Somewhat s t r o n g 5 S t r o n g (heavy) 6 7 Very s t r o n g 8 9 10 V e r y , v e r y s t r o n g (almost max) Maximal Borg, G. P s y c h o p h y s i c a l b a s i s of p e r c e i v e d e x e r t i o n . Med. S c i . S p o r t s E x e r c . 14: 377-381, 1982, p. 380. 

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