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Relationship between training heart rate and aerobic threshold in exercising cardiac patients Goodman, Leonard Stephen 1982

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RELATIONSHIP BETWEEN TRAINING IN EXERCISING HEART RATE AND AEROBIC THRESHOLD CARDIAC PATIENTS by LEONARD STEPHEN GOODMAN B.P.H.E., U n i v e r s i t y Of Toronto, 1979 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER IN PHYSICAL EDUCATION in THE FACULTY OF GRADUATE STUDIES P h y s i c a l Education And Re c r e a t i o n We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA October 1982 © Leonard Stephen Goodman, 1982 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 requirements 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 Columbia, I agree that 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 study. I f u r t h e r agree that permission f o r e x t e n s i v e copying 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 granted 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 understood that copying 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 gain s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of P h y s i c a l Education The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Dat>e: J October 13, 1982 i i A b s t r a c t The purpose of t h i s study was to examine the r e l a t i o n s h i p between t r a i n i n g heart r a t e (THR) and the HR o c c u r r i n g at the Aerobic Threshold (AerTHR), and to examine the AerT as an index of t r a i n i n g i n t e n s i t y i n s e l e c t e d coronary a r t e r y d i s e a s e (CAD), post-myocardial i n f a r c t i o n (MI), and post-coronary a r t e r y bypass surgery (CABS) p a t i e n t s . Twenty male s u b j e c t s (age=54.9; wt=73.7 kg; %body fat=25.8) were r e c r u i t e d on the b a s i s of re g u l a r p a r t i c i p a t i o n i n a c a r d i a c r e h a b i l i t a t i o n program (CRP) (3/week at 70 - 85% HRmax) f o r 6 months; no b e t a - a d r e n e r g i c medication; and symptom-free d u r i n g e x e r c i s e . F i e l d measurements of THR durin g the a e r o b i c phase at CRP was c a r r i e d out by computer-assisted p o r t a b l e telemetry with mean THR computed from each 30 minute value per s u b j e c t . A maximal t r e a d m i l l t e s t s t a r t i n g at 2.5 mph at 0% grade with speed i n c r e a s i n g 0.5 mph each minute was c a r r i e d out using a Beckman MMC f o r 30 second d e t e r m i n a t i o n s of r e s p i r a t o r y gas v a l u e s . The AerT was determined by v i s u a l i n s p e c t i o n of the f i r s t departure from l i n e a r i t y of Ve and excess C02 . V02max was 35.6 ±5.6 ml/kg/min - 1, with HRmax 166.2 ±11.8 bpm. P a i r e d t - t e s t s were performed; AerTHR was 124.8 ±15.3 bpm with THR 133.7 ±13.4 bpm (p < .03). Percent HRmaxAerT was 75.1 ±8.05 and %HRmaxTHR was80.6 ±8.3 (p < .03). Mean %V02maxAerT (54.4 ±6.7) i s c o n s i s t e n t with other r e p o r t e d data showing .lower values i n l e s s t r a i n e d i n d i v i d u a l s . Stepwise c o r r e l a t i o n s were performed, and a r e g r e s s i o n equation was produced to p r e d i c t AerT grom HRmax, he i g h t , and weight with a m u l t i p l e r = .74 (p < .01). These data suggest that i n t h i s p o p u l a t i o n , THR, as c a l c u l a t e d by the r e l a t i v e percentage of maximum method, produces t r a i n i n g i n t e n s i t i e s above the AerT expressed as a b s o l u t e or r e l a t i v e p e rcents of HRmax. Th i s f i n d i n g may have i m p l i c a t i o n s f o r optimal body f a t r e d u c t i o n s , p a t i e n t compliance to the e x e r c i s e program, and s a f e t y in CRP's. Table of Contents A b s t r a c t . . . . i i L i s t of Tables v L i s t of F i g u r e s ,. . . . v i Acknowledgement vi'..; I.. INTRODUCTION . 1 II . METHODS .6 III . RESULTS 11 IV. DISCUSSION 16 V. CONCLUSIONS 24 VI. REFERENCES 26 APPENDIX A - REVIEW OF LITERATURE 33 APPENDIX B - INDIVIDUAL SUBJECTS PHYSIOLOGICAL DATA 57 APPENDIX C - RELIABILITY STUDY 58 APPENDIX D - SAMPLE OF COMPUTER GENERATED MEAN TRAINING HEART RATE 59 APPENDIX E - SAMPLE OF COMPUTER GENERATED PLOT OF TRAINING HEART RATE 60 APPENDIX F - SAMPLE OF COMPUTER GENERATED PLOT OF MINUTE VENTILATION 61 APPENDIX G - SAMPLE OF COMPUTER GENERATED PLOT OF EXCESS CARBON DIOXIDE 62 APPENDIX H - SAMPLE. OF COMPUTER GENERATED PLOT OF RESPIRATORY EXCHANGE RATI.O 63 APPENDIX I - SAMPLE OF INFORMED CONSENT FORM 64 APPENDIX J - PERMISSION FORM FOR APPENDICIES USE 65 APPENDIX K - STEPWISE CORELLATION MATRIX 66 V L i s t of Tables I . 1 4 I I .... 1 5 v i Ac knowledgement I would l i k e to f i r s t thank my a d v i s o r f o r t h i s study, Dr. Don McKenzie, f o r h i s v a l u a b l e l e a d e r s h i p and i n s p i r a t i o n f o r r e a l i z i n g t h i s goal with me. Many thanks go to Dr. Jack Taunton and Dr. Max Walters f o r t h e i r e x c e l l e n t input and i n t e r e s t i n t h i s study. Thanks to a l l my f r i e n d s at UBC f o r t h e i r h e lp i n making t h i s t h e s i s p o s s i b l e ; they are B i l l Hearst, Wade Parkhouse, Jim P o t t s , f o r help i n the l a b data c o l l e c t i o n , and Doug Dunwoody f o r h i s h e l p i n times of c r i s i s . Many thanks to a l l the s u b j e c t s i n v o l v e d i n the study, as w e l l as t h e i r program d i r e c t o r s at the New Westminister YM-YWCA , Downtown and South Slope YMCA's, Vancouver. F i n a l l y , without the support of my wife, R i s a , and a l l of our f a m i l y , t h i s p r o j e c t would have been much more of an arduous task to deal with over the l a s t year. I than you a l l . 1 I. INTRODUCTION The i n f l u e n c e of a e r o b i c e x e r c i s e programs on the t e r t i a r y p r e v e n t i o n and r e h a b i l i t a t i o n of p a t i e n t s with coronary a r t e r y d i s e a s e (CAD) and post-myocardial i n f a r c t i o n (Ml) p a t i e n t s r e c e i v e d c o n s i d e r a b l e a t t e n t i o n over the l a s t decade (Kavanagh et a l . , 1973; Wilson et a l . , 1981). S e v e r a l s t u d i e s have o f f e r e d i n s i g h t s i n t o the c e n t r a l and p e r i p h e r a l p h y s i o l o g i c a l a d a p t a t i o n s which occur i n the CAD p a t i e n t with t r a i n i n g (Barnard et a l . , 1977; Clausen et a l . , 1970; Sim et a l . , 1974). Recently, however, r e s e a r c h e r s have begun to ques t i o n the accuracy and v a l i d i t y of p r e v i o u s l y accepted methods of p r e s c r i b i n g i n d e c i e s of e x e r c i s e i n t e n s i t y f o r these p a t i e n t s . For CAD p a t i e n t s i n c a r d i a c r e h a b i l i t a t i o n programs (CRP), p r e s c r i b i n g e x e r c i s e i n t e n s i t y i n v o l v e s complex i n t e r r e l a t i o n s h i p s among v a r i a b l e s not evident i n a healthy p o p u l a t i o n ; these i n c l u d e ischemic symptoms, decreased stroke volume with a r e d u c t i o n i n myocardial c o n t r a c t i l i t y , beta- a d r e n e r g i c medications, m u s c u l o s k e l e t a l l i m i t a t i o n s , and p s y c h o l o g i c a l problems (Kavanagh et a l , 1973; Wilson, 1975; Wilson et a l . , 1981). Determining the c o r r e c t e x e r c i s e i n t e n s i t y f o r CAD p a t i e n t s i s thus necessary i f the p a t i e n t i s to achieve f u l l b e n e f i t s of ae r o b i c e x e r c i s e programs with minimal r i s k . In determining the e x e r c i s e p r e s c r i p t i o n , most CRPs u t i l i z e a combination of Karvonen's (1957) formula, r e l a t i v e percent values of 70-85 % of maximal heart r a t e (HRmax) and 57-78 % of maximal oxygen consumption (V02max), or 60-70 % of maximum 2 metabolic e q u i v a l e n t s (METS) (American C o l l e g e of Sports Medicine, 1980; Fox et a l . , 1972; Wilson, 1975). These values are d e r i v e d on the b a s i s of maximal performances on graded e x e r c i s e t r e a d m i l l or b i c y c l e ergometer t e s t s (GXT). The types and d e s c r i p t i o n of these p r o t o c o l s are d e s c r i b e d elsewhere (Bruce, 1971; E l l e s t a d , 1975); most e x e r c i s e p r e s c r i p t i o n s , however, are c a l c u l a t e d from observed maximal HR f o r age and sex. F r o e l i c h e r et a l (1975) found t h a t the method of p r e d i c t i n g V02max from age and maximal t r e a d m i l l time f o r the Bruce and Balke p r o t o c o l s was inadequate. Other s t u d i e s have demonstrated e r r o r s i n assuming a g e - p r e d i c t e d maximal HR i n CAD p a t i e n t s , (Poweles et a l . , 1979), and e r r o r s in the Bruce p r o t o c o l i n p r e d i c t i n g f u n c t i o n a l c a p a c i t y ( S u l l i v a n et a l . , 1982) . Smith et a l . , (1982) found that the Karvonen equation f a i l e d to a c c u r a t e l y estimate t r a i n i n g HR (THR) in CAD p a t i e n t s , while Katch et a l . , (1978) demonstrated d i s c r e p a n c i e s i n the use of the " r e l a t i v e percent" concept f o r determination of t r a i n i n g i n t e n s i t i e s . Wilmore et a l . , (1981) and others (Dressendorfer et a l . , 1981; Dwyer et a l . , 1981; Katch, 1978) have recommended the use of the anaerobic t h r e s h o l d (AT) as a more accurate b a s i s f o r e x e r c i s e p r e s c r i p t i o n i n t e n s i t y . The AT, as o r i g i n a l l y d e f i n e d by Wasserman et a l . ( l 9 6 4 ) i d e n t i f i e s a f a l l i n blood pH and bicarbonate (HC03) with n o n - l i n e a r i n c r e a s e s i n the volume of carbon d i o x i d e (VC02), minute v e n t i l a t i o n (Ve) and the r e s p i r a t o r y exchange r a t i o (R) with respect to HR and oxygen consumption, which i n c r e a s e s l i n e a r l y . These breakaway p o i n t s 3 observed d u r i n g a GXT i n d i c a t e a p o i n t of t r a n s i t i o n from predominately a e r o b i c , to more anaerobic pathways i n the working muscles. Weltman et a l . , (1976) demonstrated that the AT c o u l d be u t i l i z e d as a c r i t e r i o n of submaximal f i t n e s s e v a l u a t i o n . Other more recent workers have re-examined the AT and have subsequently suggested a l t e r n a t e t e r m i n o l o g i e s , where the aer o b i c t h r e s h o l d (AerT) i s e q u i v a l e n t to the AT, and the anaerobic T h r e s h o l d (AnT) d e s c r i b e s a second break p o i n t , o c c u r r i n g at higher i n t e n s i t i e s , r e c r u i t i n g more f a s t o x i d a t i v e - g l y c o l y t i c and f a s t - g l y c o l y t i c muscle f i b e r s , and r e s u l t i n g i n higher blood l a c t a t e values (Kinderman et a l . , 1979; Skinner et a l . , 1981). For the purpose of t h i s t h e s i s the AerT w i l l be con s i d e r e d synonymous with the AT as d e f i n e d by Wasserman (et a l . , 1973; 1975). McLellan and Skinner (1981), using these c r i t e r i a found s i g n i f i c a n t l y g r e a t e r improvements i n V02max i n a group using AerT r a t h e r than % V02max as an index of t r a i n i n g i n t e n s i t y . Wilmore (et a l . , 1981) suggests t h a t p a t i e n t s who p a r t i c i p a t e i n CRPs co u l d be e x e r c i s i n g s i g n i f i c a n t l y below or above t h e i r AerT, independent of a " c o r r e c t " e x e r c i s e p r e s c r i p t i o n based on a p r e v i o u s l y determined " r e l a t i v e percent" of HRmax or V02max. While d i f f e r e n c e s between i n d i v i d u a l s whose HRmax d i f f e r s i s accounted f o r by the r e l a t i v e percentage of HRmax method, d i f f e r e n c e s between i n d i v i d u a l s at submaximal work loads i s not taken i n t o c o n s i d e r a t i o n . A l s o , there are s i g n i f i c a n t d i f f e r e n c e s between s u b j e c t s in r e l a t e d s t r e s s and t r a i n i n g 4 e f f e c t s i f s u b j e c t s work at the same assigned r e l a t i v e percent of HRmax (Katch, 1978; Powles et a l . , 1974). I t has been suggested that CAD p a t i e n t s should most o p t i m a l l y t r a i n at a HR j u s t below the AerT (Wilmore et a l . , 1981). T h i s would t h e o r e t i c a l l y prevent metabolic a c i d o s i s d u r i n g e x e r c i s e due to a l a r g e r dependence on o x i d a t i v e r a t h e r than g l y c o l y t i c mechanisms. In the CAD and post-myocardial i n f a r c t i o n p a t i e n t , the d e c o n d i t i o n e d and damaged myocardium cannot maintain a high stroke volume to i n c r e a s e c a r d i a c output dur i n g anaerobic work. In a d d i t i o n , a higher heart r a t e ( o c c u r r i n g above the AerT) i n c o n j u n c t i o n with severe coronary a r t e r y o c c l u s i o n i s u n d e s i r a b l e and might be p o t e n t i a l l y dangerous f o r c e r t a i n p a t i e n t s during the t r a n s i t i o n from a e r o b i c to anaerobic s t a t e s (Wilmore et a l . , 1981). Few s t u d i e s have d e a l t with the CAD p a t i e n t i n CRPs with regard to t r a i n i n g i n t e n s i t i e s and the AerT. Although Wasserman's paper in 1964 d e a l t with AerT d e t e c t i o n i n i t s r e l a t i o n to c a r d i a c d i s e a s e , i t i s unclear to what extent he was r e f e r r i n g to CAD or v a l v u l a r and c o n g e n i t a l d i s e a s e s . Since i n t e n s i t y i s s t i l l the most c r u t i a l but l e a s t understood v a r i a b l e in the e x e r c i s e p r e s c r i p t i o n with CAD p a t i e n t s in CRPs, the metabolic demands of the e x e r c i s e p r e s c r i p t i o n w i l l be examined with regard to the AerT. Hence, the purpose of t h i s study i s to determine the r e l a t i o n s h i p between p r e v i o u s l y p r e s c r i b e d THRs f o r e x e r c i s i n g CAD p a t i e n t s and the AerT. • In a d d i t i o n , t h i s study w i l l examine the p o s s i b i l i t y of using the AerT, HR, and other v a r i a b l e s to 5 c o n s t r u c t r e g r e s s i o n equations that can be u t i l i z e d f o r p r e c i s e and safe e x e r c i s e p r e s c r i p t i o n s i n a d d i t i o n to standard methods of p r e s c r i b i n g e x e r c i s e i n t e n s i t y . I t i s hoped that these equations w i l l maximize the c o n d i t i o n i n g e f f e c t s f o r the CAD, post surgery, or post-MI p a t i e n t , without o v e r l o o k i n g the need to prevent t r a i n i n g from o c c u r r i n g at or above the AerT i n CAD and Post-MI p a t i e n t s . 6 I I . METHODS Twenty male s u b j e c t s (age 41-63), were r e c r u i t e d v o l u n t a r i l y from l o c a l CRPs in the Greater Vancouver area. A l l s u b j e c t s had e i t h e r documented CAD a f f e c t i n g at l e a s t one v e s s e l as determined by angiography, one or more Mi's as documented by ECG and enzyme changes, -or a h i s t o r y of coronary a r t e r y bypass surgery (CABS). A d e s c r i p t i o n of the s u b j e c t s i s summarized i n Table 1. Subjects were made aware of the p o t e n t i a l r i s k s i n v o l v e d , and informed consent was obtained (Appendix I ) . P a t i e n t s r e c e i v i n g b eta-adrenergic b l o c k i n g medication or with medical c o n t r a i n d i c a t i o n s such as pulmonary d i s e a s e , h y p e r t e n s i o n , unstable angina, c o n g e s t i v e heart f a i l u r e , or h i s t o r y of e c t o p i c v e n t r i c u l a r arrhythmias were not i n c l u d e d i n the study. A l l p a t i e n t s were e x e r c i s i n g r e g u l a r l y . 3 times per week fo r 6 months to 4 years d u r i n g the course of the study. Data c o l l e c t i o n c o n s i s t e d of two phases. Subjects were i n i t i a l l y i n v e s t i g a t e d in the f i e l d , d uring attendance at a CRP, and were i n d i v i d u a l l y i n s t r u c t e d to c a r r y on with t h e i r p r e s c r i b e d walk/jog t r a i n i n g s e s s i o n , at the usual i n t e n s i t y or THR while being c o n t i n u a l l y telemetered by a Burdick p o r t a b l e Cardiodyne telemeter during the a e r o b i c phase. A CM5 le a d c o n f i g u r a t i o n was u t i l i z e d , and ECG r e c o r d i n g s were obtained f o r 30 minutes on micro c a s s e t t e tapes. The tape c a s s e t t e s were replayed i n t o an A v i o n i c s 4000 Cardiogard i n t e r f a c e d with a Hewlett-Packard 3052A Data A c q u i s i t i o n System, where HR values at 15, 30, 45 and 60 seconds of each minute, plu s the mean HR fo r each minute were a u t o m a t i c a l l y computed and recorded. 7 E l e c t r o c a r d i o g r a m r e c o r d i n g s were simultaneously obtained at i n t e r v a l s of 2 minutes f o r r e l i a b i l i t y purposes. The f i r s t 5 minutes and l a s t 5 minutes of the re c o r d i n g s were omitted to allow f o r normal attainment of the s t e a d y - s t a t e THR and c o o l - down p e r i o d , r e s p e c t i v e l y . Mean THR was obtained by averaging a l l 20 mean minute v a l u e s , with any s i g n a l a r t i f a c t values being omitted from the c a l c u l a t i o n (see samples i n Appendix D and E ) . Subjects were t o l d p r i o r to the r e c o r d i n g s e s s i o n that the i n v e s t i g a t i o n was to observe heart rhythm, so as not to produce a n x i e t y and i n f l u e n c e or b i a s e x e r c i s e performance. A l l s u b j e c t s ' THRs had been p r e v i o u s l y determined by a s s i g n i n g an average of 75% of symptom l i m i t e d HRmax on the b a s i s of the l a s t p r e v i o u s Bruce GXT. The telemetry procedure was repeated s e v e r a l times to ensure the r e l i a b i l i t y of the data, with the a d d i t i o n a l use of a Resperonics E x e r s e n t r y heart r a t e monitor to v a l i d a t e THR. Computed THR was a l s o compared to THR as repor t e d by i n d i v i d u a l s u b j e c t s in the r e g u l a r CRP d a i l y e x e r c i s e l og sheets ( p a l p a t a t i o n of r a d i a l p u l s e ; counting f o r 10 seconds and mu l t i p l y i n g - by 6). The second phase of data c o l l e c t i o n occurred i n the J.F. Buchannan Research and F i t n e s s Centre at the U n i v e r s i t y of B r i t i s h Columbia (see Appendix J ) . Measurement of body weight, height and e s t i m a t i o n of percent body f a t with s k i n f o l d measurements (Yuhasz, 1978) was fol l o w e d by a maximum t r e a d m i l l t e s t (MTT) to determine V02max, HRmax and the AerT. The MTT p r o t o c o l was performed on the t r e a d m i l l and was c o n s i s t e n t with Wasserman's (et a l . , 1964) method f o r dete r m i n a t i o n of the AerT, 8 u t i l i z i n g T-minute work increments. T r e a d m i l l s t a r t i n g speed was 2.5 mph at 0 % grade ( i n c l u d i n g a 4 minute warm up at the same speed and grade), and i n c r e a s e d 0.5 mph every minute u n t i l t e r m i n a t i o n . Subjects e x e r c i s e d to maximum with the major c o n s i d e r a t i o n of te r m i n a t i o n being f a t i g u e . Heart r a t e s were recorded by d i r e c t ECG, u t i l i z i n g a CM5 lead c o n f i g u r a t i o n and A v i o n i c s 4000 Cardiogard with o s c i l l i s c o p e and ST-segment s h i f t d i s p l a y . E x p i r e d gases were c o n t i n u a l l y sampled and analyzed by a Beckman Metabolic Measurement Cart i n t e r f a c e d i n t o a Hewlett-Packard 3052A Data A c q u i s i t i o n system for 15-second determinations of r e s p i r a t o r y gas exchange values (see Appendix F,G and H ). The v e l o c i t y of the t r e a d m i l l at the onset of anaerobic metabolism (Vtam), the percent of maximal oxygen uptake (%Vo2max) and the percent of HRmax (%HRmax) at the AerT were c a l c u l a t e d . The AerT was determined by v i s u a l examination of f i r s t d e v i a t i o n from l i n e a r i t y of the excess C02 curve a c c o r d i n g to methods d e s c r i b e d by Volkov et a l . (1975) and the Ve curve, as d e s c r i b e d by Wasserman (et a l . 1964, 1973, 1975). Computer-generated curves were examined i n d i v i d u a l l y by three i n v e s t i g a t o r s . AerT was de f i n e d as the Vtam, HR, and corresponding %V02max and %HRmax o c c u r r i n g immediately below these n o n - l i n e a r changes in excess C02 and Ve. AerTs were determined f o r i n d i v i d u a l s u b j e c t s . V02max, HRmax, the HR at the AerT (AerT-HR), Vtam, %HRmax at the AerT (%HRmax AerT), %HR max at the AerT (%HRmax AerT), and the d i f f e r e n c e between THR and the AerT-HR were c a l c u l a t e d and .9 recorded. P a i r e d t - t e s t s was u t i l i z e d to determine any d i f f e r e n c e s between mean THR and mean AerT-HR, and between %HRmax of THR UHR-THR) and %HRmax of AerT-HR (%HR-AerT-HR). BMDP P3D program at the U n i v e r s i t y of B r i t i s h Columbia's Computer Science Department f o r c o r r e l a t e d t - t e s t s was u t i l i z e d f o r the an a l y s e s . These were t e s t e d at the .05 l e v e l of s i g n i f i c a n c e . If there e x i s t e d s i g n i f i c a n t d i f f e r e n c e s between s u b j e c t s Vo2max scores, a t - t e s t on V02max was performed to separate s u b j e c t s of high and low f i t n e s s . A stepwise regresson a n a l y s i s was subsequently performed u t i l i z i n g a BMDP P2R program to observe the r e l a t i o n between the v a r i a b l e s , and to d e r i v e m u l t i p l e r e g r e s s i o n equations from these observed data.Two equations were produced. One p r e d i c t i n g THR from AerT data (with r e l a t e d v a r i a b l e s omitted) and one p r e d i c t i n g AerT-HR with i t s r e l a t e d v a r i a b l e s omitted from the equation. M u l t i p l e c o r r e l a t i o n c o e f f i c i e n t s were analyzed between the v a r i a b l e s for. v a l i d i t y of the r e g r e s s i o n equations. In order to determine the r e l i a b i l i t y of the measurement of the AerT i n these s u b j e c t s over time, f i v e s u b j e c t s were brought back to the l a b o r a t o r y a second time. Subjects were chosen on the b a s i s that no changes i n t h e i r f i t n e s s l e v e l and p r o g r e s s i o n of t h e i r e x e r c i s e c a p a c i t y from the previous t r e a d m i l l t e s t had occu r r e d . The t r e a d m i l l p r o t o c o l and measurements were the same as p r e v i o u s l y o u t l i n e d . P a i r e d t - t e s t s were performed on AerT- HR1 vs AerT-HR2 with c o r r e l a t i o n c o e f f i c i e n t s compared with those from t r i a l 1 f o r r e l i a b i l i t y purposes. These were t e s t e d 10 at the .05 l e v e l of s i g n i f i c a n c e (r = .97 ). For raw data and r e s u l t s , see Appendix C. 11 I I I . RESULTS Mean age f o r the group was 54.9 ± 5.51 years height was 174.9 ± 7.64 cm, body weight 73.7 ± 9.79 kg and percent body f a t was 25.82 ± 4.36. Nine s u b j e c t s had r e c i e v e d coronary g r a f t bypass surgery on at l e a s t one v e s s e l , while 13 were post-MI p a t i e n t s andtwo had angiographic evidence of CAD. The p h y s i o l o g i c a l data i s summarized i n Table 1, and i n d i v i d u a l s u b j e c t s ' data can be found in Appendix B. V02max ranged from 27.2 to 52.7 ml/kg/min""1 and the mean was 35.57 ± 5.57 ml/kg/min" 1 for the group. The AerT, as determined by v i s u a l i n s p e c t i o n of the excess C02 and Ve curves was recorded at a Vtam of 4.55± 0.64 mph. T h i s was e q u i v e l l e n t to 54.45 ± 6.77 percent of V02 max. HRmax was 166.2 ± 11.88bpm. AerT-HR was found to be 124.85 ± 15.3 bpm, and represented 75.1 ± 8.05 percent of HRmax. The mean THR when measured i n the f i e l d s e t t i n g and checked f o r accuracy a g a i n s t p a t i e n t s ' p e r s o n a l d a i l y e x e r c i s e l og sheets was found to be 133.75 ± 13.42 bpm, and represented 80.65 ± 8.26 percent of HRmax. Mean THR was found to be s i g n i f i c a n t l y g r e a t e r than mean AerT-HR by 8.9 bpm (133.75±13.42 vs 124 ±l5.53bpm) (p < .0304). A c o r r e l a t i o n of .30 was found between THR and AerTHR. When mean %HRmaxTHR and %HRmaxAerTHR were examined , %HRmaxTHR was found to be s i g n i f i c a n t l y g r e a t e r (p < .0293 ) with values of %80.65 ±8.26 and % %75.1 ±8.05, r e s p e c t i v e l y . S e v e r a l c o r r e l a t i o n s were subsequently performed on the data to i n v e s t i g a t e the r e l a t i o n s h i p between the AerT, THR and 12 other recorded p h y s i o l o g i c a l data (see Appendix K f o r c o r e l l a t i o n m a t r i x ) . Stepwise r e g r e s s i o n a n a l y s i s was performed using f i r s t THR as the dependent v a r i a b l e i n the f i r s t a n a l y s i s , f o l l o w e d by AerTHR as the dependent v a r i a b l e i n the second a n a l y s i s . A n a l y s i s using the dependent v a r i a b l e THR with r e l a t e d v a r i a b l e %HRmaxTHR omitted from the a n a l y s i s r e s u l t e d i n a negative c o r r e l a t i o n c o e f i c i e n t of -.11 between V02max and %V02maxAerT, while V02max was h i g h l y c o r r e l a t e d to Vtam (r = .79 ). Stepwise r e g r e s s i o n proceded through 2 steps, t e r m i n a t i n g a f t e r F - l e v e l s below 1.5 were a t t a i n e d . P r e d i c t o r s HRmax and age r e s u l t e d i n the f o l l o w i n g equation f o r p r e d i c t i o n of THR with a standard e r r o r of estimate of 12.57: y= 0.434(a)+ 0.85(b)+ 14.64 where (a) i s HRmax and (b) i s age. The second stepwise r e g r e s s i o n equation with AerTHR as the dependent v a r i a b l e , and_ i t s r e l a t e d v a r i a b l e s omitted (Vtam,%V02AerT and %HRmaxAerT ) was then generated. A moderate c o r r e l a t i o n of .51 between HRmax and AerTHR was found. The f o l l o w i n g p r e d i c t i o n of AerTHR with the r e g r e s s i o n equation, u t i l i z i n g HRmax,weight, and height was produced, y i e l d i n g a standard e r r o r of estimate of 10.91: y = 1.21(a)+ 0.68(b) - 1.04(c) - 123.23 where (a) i s height in cm, (b) i s HRmax, and (c) i s body weight 13 in kg. The equation f o r p r e d i c t i o n of AerTHR y i e l d e d a m u l t i p l e c o r r e l a t i o n of .74, which was s t a t i s t i c a l l y s i g n i f i c a n t (p < .01). The equation f o r p r e d i c t i o n of THR y i e l d e d a m u l t i p l e c o r r e l a t i o n of .46 (p < .05). 14 Table I - P h y s i c a l C h a r a c t e r i s t i c s of Subjects Subject Age Status Height(cm) Weight(kg) %Body RM 58 MI,CABS 171 .6 69.4 29.9 WK 61 MIn 1 69.8 81.3 30.3 DG 53 CAD" 170. 1 73.7 33.9 BD 57 MI,CABS 174.6 67.2 21.2 JB 63 CAD 1 66.2 62. 1 20.0 PH 52 CABS 0 167.4 62.4 20.9 PM 57 MI 167. 1 66.6 23.4 LC 55 MI,CABS 182.2 77.9 20.8 RS 53 MI 198.6 102.3 26.2 JD 51 CABS 173.6 72.4 26.7 PD 49 CABS 182.4 78.9 26.9 NK 61 CABS 1 68. 1 74.9 29.5 JH 63 CABS 177.2 85.0 30.0 BS 59 MI 173.5 63.7 23.7 MS 52 MI,CABS 177.7 72.8 26. 1 VM 58 MI 1 73.5 68.6 32.7 FD 41 MI 168.2 78.2 19.2 CK 50 MI 175. 1 85. 1 27.5 TW 56 MI 183.4 64.9 26.0 SG 49 MI 177.7 67.2 21.6 Mean 54.9 174.9 73.7 25.8 SD 5.51 7.64 9.97 4.36 n MI - Myocardial I n f a r c t i o n ° CABS- Coronary G r a f t Bypass Surgery • CAD - Coronary A r t e r y Disease 15 Table II - P h y s i o l o g i c a l Data Aerobic Threshold and R e l a t i v e Percent Heart Rates V02max %V02maxAerT Vtam HRmax (ml/kg/min" 1) (mph) (bpm) Mean SD 35.57 5.57 54.45 6.77 4.55 0.64 1 66.2 1 1 .88 THR AerTHR ^HRmaxAerT %HRmaxTHR (bpm) (bpm) Mean SD 133.75n 1 3.42 124.8 15.3 75. 1 8.05 80.65" 8.26 n s i g n i f i c a n t l y g r e a t e r than AerTHR (p < .03) • s i g n i f i c a n t l y g r e a t e r than %HRmaxAert (p< .03) 16 IV. DISCUSSION The s u b j e c t s examined i n t h i s i n v e s t i g a t i o n represents a homogeneous sample, as i n d i c a t e d by the r e l a t i v e l y small standard d e v i a t i o n s f o r v a r i a b l e s such as hei g h t , weight, age, and percent body fat,and are comparable to v a r i a b l i l i t y found i n other s t u d i e s (Weltman, et a l . , 1976; Weltman and Katch, 1979). The s u b j e c t s had been i n v o l v e d i n a re g u l a r e x e r c i s e program f o r at l e a s t s i x months and as the time between the t r e a d m i l l t e s t and the f i e l d e v a l u a t i o n was l e s s than 4 weeks, i t i s assumed that no s i g n i f i c a n t p h y s i o l o g i c a l changes occ u r r e d in response to t r a i n i n g . Mean V02max values of 35ml/kg/min" 1 are c o n s i s t e n t with values r e p o r t e d by others f o r t r a i n e d CAD or post-MI p a t i e n t s , u t i l i z i n g a s i m i l a r a e r o b i c e x e r c i s e p r o t o c o l (Kavanagh, et a l . , 1973; Wilson, et a l . , 1981 ). HRmax was w i t h i n l i m i t s of that expected f o r t h i s age range, although the v a r i a b i l i t y of HRmax observed here agrees with Ryan, et a l . ( l 9 8 0 ) o b s e r v a t i o n of the wide range of HRmax found d u r i n g maximal GXTs. A low negative c o r r e l a t i o n of -.20 between age and HRmax found in the present i n v e s t i g a t i o n supports t h i s o b s e r v a t i o n . Mean THR values of 133 bpm, when expressed as a percentage of HRmax was 80.6%. T h i s t r a i n i n g i n t e n s i t y i s i n agreement with others f o r e x e r c i s e p r e s c r i p t i o n based on the r e l a t i v e percent method using between 70 and 80% HRmax (Fox et al.,1972; P o l l o c k , 1973; Wilson, 1975; Zohman, et a l . , 1970). The mean AerTHR (124 bpm) was s i g n i f i c a n t l y lower than mean THR. T h i s was a l s o true when AerTHR was expressed as a 1 7 percentage of HRmax. T h i s f i n d i n g i s i n agreement with Katch et a l . (1978), and Dressendorfer, et a l . (1981) r who s t a t e that the r e l a t i v e percent method of p r e s c r i b i n g THR does not take i n t o account i n d i v i d u a l metabolic d i f f e r e n c e s at submaximal workloads.These data i n d i c a t e that although these s u b j e c t s are wi t h i n the 70 - 85% of HRmax zone f o r t r a i n i n g u s ing the popular r e l a t i v e percent method, in f a c t , thy are e x e r c i s i n g above t h e i r AerT values as a group. T h i s a l s o comfirms Wilmore's (1981) s p e c u l a t i o n that i n some cases, c a r d i a c p a t i e n t s , when e x e r c i s i n g at the p r e s c r i b e d r e l a t i v e percent i n t e n s i t y of HRmax co u l d i n f a c t be s i g n i f i c a n t l y above t h e i r AerT, and hence e x e r c i s i n g more a n a e r o b i c a l l y than i s d e s i r e d f o r t h i s p o p u l a t i o n . A low c o r r e l a t i o n of .30 between THR and AerTHR and .16 f o r %HRmaxAerTHR and %HRmaxTHR shows a r e l a t i v e lack of r e l a t i o n s h i p between these v a r i a b l e s . T h i s d i s s a g r e e s with the data of Parkhouse and McKenzie, (1982) and Patton et a l . (1979) that HR i s a good p r e d i c t o r of AerT. T h i s f i n d i n g , however i s c o n s i s t a n t with data r e p o r t e d by Wasserman and M c l l r o y (1964) and more r e c e n t l y Dressendorfer et a l . (1981) that HR i s a poor p r e d i c t o r of AerT i n middle aged males, and as suggested i n t h i s i n v e s t i g a t i o n , in t r a i n e d c a r d i a c p a t i e n t s as w e l l . The AerT occurred at 54.4% V02max i n t h i s study, and the i n d i v i d u a l range in AerT values (42.1 - 72.7 %V02max) i s i n agreement with data re p o r t e d by Davis et a l . ( l 9 7 6 ) , M c L e l l a n and Skinner (1981) and , Weltman and Katch, (1979) who found v a l u e s ranging from 41 -71 %V02max. The l i t e r a t u r e however r e p o r t s AerT as a percentage of V02max i n p o p u l a t i o n s that are u n l i k e the present sample. 18 Patton, et a l . (1979) and Parkhouse and McKenzie (1982) examined these v a r i a b l e s i n young healthy s u b j e c t s and t r a i n e d a t h l e t e s . Wasserman's et a l . (1964) c a r d i a c s u b j e c t s were younger, were u n t r a i n e d , and had v a l v u l a r and c o n g e n i t a l d i s e a s e s . N e v e r t h e l e s s , Wyndham et a l . , i n 1965 found AerT to occur at 45 -50% i n p a t i e n t s with cardiomyopathy, with AerT at 50 to 60% in normal middle-aged males. Davis et a l . (1979) and Dressendorfer et a l . (1981) both u t i l i z e d middle-aged males i n t h e i r s t u d i e s with s i m i l a r AerT v a l u e s . Our s u b j e c t s , although CAD, CABS and post-MI p a t i e n t s , seem to resemble normal or s l i g h t l y t r a i n e d middle aged males as f a r as metabolic performance on a MTT when comparing t h e i r AerT to other p o p u l a t i o n s . However, t h e i r d i f f e r e n c e s i n terms of c a r d i a c d i s e a s e and the subsequent f u n c t i o n a l impairment make comparison to other groups unacceptable i n t h i s r e s p e c t . Stepwise r e g r e s s i o n a n a l y s i s produced c o r r e l a t i o n s which r e f l e c t e d the d i f f e r e n c e s between the r e l a t i v e percent concept and the AerT method of e x e r c i s e p r e s c r i p t i o n . A low negative c o r r e l a t i o n of -.11 between V02max and %V02maxAerT i s d i f f e r e n t than that r e p o r t e d in other s t u d i e s . Weltman et a l . ( l 9 7 9 ) r e p o r t e d c o r r e l a t i o n of .69 between V02max and V02 at the AerT, and Davis, et a l . (1976) r e p o r t e d a s l i g h t l y s maller value (r = .52). In a l a t e r study, Weltman and Katch (1979) rep o r t e d a c o r r e l a t i o n of .85 between V02max and V02 at the AerT. However, the s u b j e c t s were young males and the p r o t o c o l was done using a b i c y l e ergometer. Our r e s u l t s are s i m i l a r to that found more r e c e n t l y by McLellan and Skinner (1982) who found a h i g h l y 19 s i g n i f i c a n t negative c o r r e l a t i o n of -.64 between V02max and %V02maxAerT. Se v e r a l e x p l a n a t i o n s were o f f e r e d to account f o r t h i s r e v e r s a l of what would normally be expected from the prev i o u s l i t e r a t u r e . As i n McLeLlan and Skinner's study, t h i s negative c o r r e l a t i o n c o u l d have been a f u n c t i o n of the wide range of %V02maxAerT on e i t h e r end of the continum, coupled with the o b s e r v a t i o n made e a r l i e r by Wasserman et a l . (1973) that an abs o l u t e lower l i m i t of AerT values e x i s t s and i s equal to about 3.5 mph at a 0%grade or 13 to 14 ml/kg/min" 1 f o r a 70 to 75 kg male. Thus i n d i v i d u a l s who have lower V02max va l u e s would have r e l a t i v e l y higher %V02AerT scores, thus accounting f o r the low negative r e l a t i o n s h i p found here. A s i g n i f i c a n t c o r r e l a t i o n on the other hand, was found between Vtam and V02max (r = .79 ), agreeing with Weltman and Katch's f i n d i n g (1979), but Vtam was only moderately c o r r e l a t e d with AerTHR (r = .46 ) although s i g n i f i c a n t (p< .05), r e f l e c t i n g Katch et a l ' s . (1978) f i n d i n g that the high c o r r e l a t i o n c o u l d be spurious when the time element i s not removed from the a n a l y s i s . The r e g r e s s i o n equations produced i n t h i s i n v e s t i g a t i o n are s p e c i f i c only to the p o p u l a t i o n s t u d i e d here. Namely, middle- aged post-MI, CAD, or post-surgery p a t i e n t s not on beta- a d r e n e r g i c medication. The p r e d i c t i o n of AerTHR r a t h e r than THR seems to be a b e t t e r index of t r a i n i n g i n t e n s i t y , s i n c e AerTHR i s more s p e c i f i c to the v a r i a b l i t i y i n i n d i v i d u a l response of submaximal work, and thus would be the optimal HR that a e r o b i c t r a i n i n g 20 occurs at i n these p a t i e n t s , a c c o r d i n g to the a v a i l a b l e data. In a d d i t i o n , the m u l t i p l e r of .74 (although accounting f o r only 54% of the v a r i a n c e ) compared to .46 f o r p r e d i c t i o n of THR, pro v i d e s b e t t e r accuracy, and u n l i k e Weltman and Ratch's (1979) r e g r e s s i o n equation f o r p r e d i c t i o n of V02max, the present equation u t i l i z i n g h e i g h t , HRmax and body weight does not depend on metabolic measurment equipment, p l u s c o n v e r s i o n of V02max i n t o p r e d i c t e d percentages of t r a i n i n g V02max. However, s i n c e HRmax i s r e q u i r e d , a t r e a d m i l l t e s t would s t i l l r e q u i r e a p h y s i c i a n i n attendance with a p p r o p r i a t e r e s c u e i t a t ion equipment, which makes t h i s equation i m p r a c t i c a l i n YMCAs, r e c r e a t i o n c e n t r e s and f i t n e s s c l u b s without medical s u p e r v i s i o n . Thus, a p r e c i s e i n t e n s i t y index u t i l i z i n g AerTHR i s presented which accounts f o r i n d i v i d u a l submaximal metabolic v a r i a b l i l i t y found i n t h i s study. The d e r i v a t i o n of AerT using Vtam and subsequent comparison of c orresponding metabolic v a r i a b l e s deserves d i s c u s s i o n . The a l i n e a r r i s e in Ve and excess C02, h e r a l d i n g the AerT corresponded to a mean Vtam of 4.5 mph. The small v a r i a b l i t y of scores as observed in the standard d e v i a t i o n of 0.65 was i n t e r e s t i n g i n that most s u b j e c t s ' Vtam values appeared to occurr e d at the speed at which running commenced. I t was p o s t u l a t e d that t h i s i n i t i a l breakaway of r e s p i r a t o r y values c o u l d have been a r e s u l t of the sudden recruitment of muscle mass d u r i n g the t r a n s i t i o n from walking to jogging, g i v i n g r i s e to a l i n e a r i n c r e a s e s in r e s p i r a t o r y v a r i a b l e s . T h i s c o u l d have i m i t a t e d the f i r s t true breakaway poin t (AerT) as d e f i n e d by 21 Skinner and McLellan (1980). In some s u b j e c t s , a second breakaway p o i n t was observed, but corresponded with u n r e a l i s t i c a l l y high percentages of V02max (85 - 90%) to j u s t i f y t h i s as being the AerT in these s u b j e c t s (low to moderately t r a i n e d s u b j e c t s ). T h i s problem c o u l d be a f u n c t i o n of the p r o t o c o l , which we b e l i e v e might not c o n t a i n small enough work increments. When dropping a v e r t i c a l l i n e down from the f i r s t a l i n e a r r i s e i n Ve and Excess C02, the speed increments of 0.5mph allow f o r too much spread i n the determination of Vtam w i t h i n small fractions,-, which can i n r e a l i t y mean l a r g e d i f f e r e n c e s i n metabolic a c t i v i t y at v a r i o u s running paces. A work increment of 0.5mph each minute r e p r e s e n t s a s i g n i f i c a n t i n c r e a s e i n running pace. In a d d i t i o n , t h i s . p r o t o c o l might not a f f o r d s u f f i c i e n t time per workload f o r c a r d i a c p a t i e n t s to a t t a i n a true steady s t a t e . The change b i o m e c h a n i c a l l y from walking to slow jogging may a l s o represent a confounding v a r i a b l e to the i n t e r p r e t a t i o n of these curves, and c o u l d represent the f i r s t v i s i b l e breakaway p o i n t due to the i n c r e a s e d muscle mass involvement and r e s u l t a n t i n e f f i c i e n c y mentioned above.When one of the present i n v e s t i g a t o r s (V02 max = 65 ml/kg/min) performed t h i s p r o t o c o l on the t r e a d m i l l , s i m i l a r breakawaypoints were a l s o observed at 4.5 mph ( i n i t i a t i o n of running), with a 'second' breakaway p o i n t observed at 9.5 mph. Undoubtedly, t h i s i n c o n s i s t a n c y c o u l d be avoided by u t i l i z i n g a b i c y c l e ergometer p r o t o c o l f o r smooth work increments, but would s e r i o u s l y reduce the s p e c i f i c i t y f o r walking and jogging e x e r c i s e p r e s c r i p t i o n s . I t i s our 22 recommendation that f u r t h e r i n v e s t i g a t i o n with samples such as that s t u d i e d i n the present i n v e s t i g a t i o n be undertaken. The emphasis should be p l a c e d on determining the exact c h a r a t e r i s t i c s of r e s p i r a t o r y curves in a v a r i e t y of t r e a d m i l l p r o t o c o l s u t i l i z i n g v a r i a b l e speeds (0.25 mph/min), grades(0% to 20%), and increments to uncover whether the f i r s t b reakoff p o i n t i s i n f a c t the AerT, or simply i n c r e a e d metabolic a c t i v i t y . T h i s c o u l d be done by i n c o r p o r a t i n g breath-by-breath a n a l y s i s or l a c t a t e s t u d i e s i n a MTT and c o r r e l a t i n g these to changes in r e p i r a t o r y v a l u e s , as has been done in e l i t e a t h l e t e s . The method of v i s u a l i n s p e c t i o n of the r e s p i r a t o r y v a r i a b l e curves, though more d i f f i c u l t to i n t e r p r e t i n l e s s t r a i n e d s u b j e c t s (Dunwoody, 1981) have been shown to be as v a l i d compared to computer generated a n a l y s i s . Orr, et a l . (1982) r e c e n t l y compared s u b j e c t i v e v i s u a l d eterminations of r e s p i r a t o r y AerT with a multi-segmental l i n e a r r e g r e s s i o n computer a l g o r i t h m , and found a c o r r e l a t i o n of .94. S u b s t r a t e u t i l i z a t i o n i n r e l a t i o n to the AerT i s a l s o r e l e v e n t i n t h i s d i s c u s s i o n . During predominately a e r o b i c e x e r c i s e below the AerT, the i n c r e a s e d u t i l i z a t i o n and m o b i l i z a t i o n of FFA from adipose s t o r e s has a s i g n i f i c a n t i n h i b i t i n g e f f e c t on g l y c o l y s i s ( through c i t r a t e ' s i n h i b i t i o n of the Krebs c y c l e enzyme p h o s f o f r u c t o k i n a s e ) . However, as e x e r c i s e i n t e n s i t y i n c r e a s e s above the AerT, t h i s i n h i b i t i o n i s reduced, l e a d i n g to more g l y c o l y s i s and l e s s FFA c a t a b o l i s m and l i p o l y s i s (Skinner and McLellan, 1981). In a d d i t i o n , adipose t i s s u e l i p o l y s i s c o u l d be reduced in workloads above the AerT. 23 Since reduced epinepherine r e l e a s e (which i s i n h i b i t e d d u r i n g g l y c o l y s i s ) r e s u l t s in l e s s s t i m u l a t i o n of adipose c e l l beta r e c e p t o r s , c y c l i c AMP p r o d u c t i o n i s reduced, r e s u l t i n g i n l e s s FFA r e l e a s e i n t o the blood (Issekutz and M i l l e r , 1962). Since r e d u c t i o n s i n body f a t i s o f t e n an important complimentary goal in CRP'.s, e x e r c i s e above the AerT should be avoided, and body f a t l o s s e s through mainly aerobic means should be encouraged. Despite these f i n d i n g s however, more needs to be l e a r n e d about how the AerT can be d e t e c t e d r e l i a b l y and e a s i l y i n c a r d i a c p a t i e n t s . S t u d i e s with s i m i l a r groups u t i l i z i n g blood l a c t a t e s t u d i e s and breath-by-breath a n a l y s i s (which have al r e a d y been documented r e l i a b l y i n healthy and a t h l e t i c samples), needs to be undertaken to f u r t h e r uncover these processes d u r i n g e x e r c i s e . 24 V. CONCLUSIONS Based on the r e s u l t s of t h i s study, s e v e r a l o b s e r v a t i o n s can be made concerning e x e r c i s e i n t e n s i t y (as measured by HR ) and a e r o b i c a l l y t r a i n e d CAD or post-MI p a t i e n t s . F i r s t l y , the r e l a t i v e percent method of p r e s c r i b i n g THR does not take i n t o account i n d i v i d u a l v a r i a t i o n i n submaximal metabolic v a r i a b l e s , and that the use of the AerTHR might be a more accurate and perhaps s a f e r e s t i m a t i o n of e x e r c i s e i n t e n s i t y f o r t h i s s p e c i a l e x e r c i s i n g p o p u l a t i o n . T h i s i s e s p e c i a l l y c r u t i a l in terms of long-term p a t i e n t compliance with the e x e r c i s e program. In a d d i t i o n , i t i s p o s s i b l e that e x e r c i s e above the AerT might reduce FFA m o b i l i z a t i o n and metabolism, and hence r e t a r d the g e n e r a l l y d e s i r a b l e body f a t l o s s e s because of the i n h i b i t o r y e f f e c t s of g l y c o l y s i s on FFA metabolism. Secondly, the r e g r e s s i o n equations c o n s t r u c t e d based on these f i n d i n g s might be u s e f u l in c o n j u c t i o n with the r e l a t i v e percent method of p r e d i c t i n g a p p r o p r i a t e i n d i v i d u a l i z e d THR in s u p e r v i s e d or non-supervised c a r d i a c r e h a b i l i t a t i o n programs when combined with standard GXTs. However, two drawbacks to t h i s equation e x i s t ; 1., although metabolic measurement equipment i s not necessary with these equations, a p h y s i c i a n with oxygen and r e s u c i t a t i o n equipment would s t i l l be r e q u i r e d s i n c e a maximum t e s t i s performed to o b t a i n HRmax; 2., the equation, though s i g n i f i c a n t , can only account for 54% of the v a r i a n c e , and i s thus l i m i t e d i n i t s use as an independent method of e x e r c i s e p r e s c r i p t i o n . T h i r d l y , more i n v e s t i g a t i o n i n t o the t r e a d m i l l p r o t o c o l and 25 i t s a p p l i c a b i l i t y and r e l i a b i l i t y i n determining AerT f o r t h i s p o p u l a t i o n needs to be undertaken, e s p e c i a l l y with regards to the work increments. F o u r t h l y , more s t u d i e s i n v e s t i g a t i n g the AerT i n e x e r c i s i n g CAD and post-MI p a t i e n t s needs to be undertaken to f u l l y understand how t h i s index of p r e s c r i b i n g e x e r c i s e i n t e n s i t y f o r t r a i n i n g can be used for these p a t i e n t s . F i n a l l y , because the great m a j o r i t y of e x e r c i s i n g CAD, post-MI, and p o s t - s u r g e r y p a t i e n t s r e c i e v e many forms of beta- a d r e n e r g i c or c a l c i u m a g o n i s t i c medication which a l t e r age- p r e d i c t e d HR response, i n v e s t i g a t i o n s i n t o the AerT i n these p a t i e n t s needs to be i n i t i a t e d . 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The s i g n i f i c a n c e of the a e r o b i c - a n a e r o b i c t r a n s i t i o n for the d e t e r m i n a t i o n of work load i n t e n s i t i e s d u r i n g endurance t r a i n i n g . European J o u r n a l of A p p l i e d Physiology , 1979, 42, 25-34. La Fontaine, T., Londeree, B.R., Fay, L. and B a r r e t t , T. The e f f e c t of i n t e n s i t y and q u a n t i t y of e x e r c i s e on the a e r o b i c and anaerobic t h r e s h o l d . Medicine and Science i n Sport and E x e r c i s e , 1982, J_4(2), 127, A b s t r a c t . L e s t e r , M., S h e f f i e l d , L.T., Trammell, P. and Reeves, T. The e f f e c t of age and a t h l e t i c t r a i n i n g on the maximal heart r a t e d u r i n g muscular ' e x e r c i s e . American Heart J o u r n a l , 1968, 7_6, 370. MacDougall, J.D. The anaerobic t h r e s h o l d : i t s s i g n i f i c a n c e f o r the endurance a t h l e t e . Canadian J o u r n a l of A p p l i e d Sport Science , 1977, 2, 137-140. Mazzeo, R., R i b i s l , P., Boone, W.T. and M i l l e r , H.S. 24- hour a n a l y s i s of heart r a t e v a r i a b i l i t y of c a r d i a c p a t i e n t s p a r t i c i p a t i n g i n a r e h a b i l i t a t i o n program. J o u r n a l of Cardiac R e h a b i l i t a t i o n , 1982, 2(3), 238-242. McL e l l a n , T.M. and Skinner, J.S. The use of the a e r o b i c t h r e s h o l d as a b a s i s for t r a i n i n g . Canadian J o u r n a l of A p p l i e d Sport Science , 1981, 6(4), 197-201. Noble, B.J. Cardiac r e h a b i l i t a t i o n : p s y c h o l o g i c a l i m p l i c a t i o n s . (In) Research and P r a c t i c e in P h y s i c a l Education . Champaign, Human K i n e t i c s , 1977. 3 0 Orr, G.W., Green, H.J., Hughson, R.L., and Bennett, G.W. A computer l i n e a r r e g r e s s i o n model to determine v e n t i l a t o r y anaerobic t h r e s h o l d . J o u r n a l of ( A p p l i e d Physiology , 5 2 ( 5 ) , 1 3 4 9 - 1 3 5 2 , 1 9 8 2 . Parkhouse, W.S., McKenzie, D.S. and Rhodes, E.C. E x e r c i s e p r e s c r i p t i o n i n r e l a t i o n to anaerobic t h r e s h o l d . European J o u r n a l of A p p l i e d Physiology , In p r i n t . Patton, R.W., Heffner, K., Baun, W., Ayers, J . , Gettman, H. and Raven, P. Heart r a t e as a p r e d i c t o r of anaerobic t h r e s h o l d i n runners and non-runners. Medicine and Science in Sport , 1 9 7 9 , J _ _ ( 1 ) , 9 4 . P o l l o c k , M.L. E f f e c t of walking on body composition and c a r d i o v a s c u l a r f u n c t i o n of middle-aged men. J o u r n a l of A p p l i e d Physiology , 1 9 7 7 , 3 0 ( 1 ) , 1 2 6 - 1 3 0 . P o l l o c k , M.L., The q u a n t i f i c a t i o n of endurance t r a i n i n g programs. E x e r c i s e and Sports Science Reviews , 1 9 7 3 , j_, 1 5 5 - 1 8 3 . Powles, A.P., Sutton, J.R., Wicks, J.R., O l d r i d g e , N.B. and Jones, N.L. Reduced heart r a t e response to e x e r c i s e i n ischemic heart d i s e a s e : the f a l l a c y of the t a r g e t heart r a t e in e x e r c i s e t e s t i n g . Medicine and Science i n Sports , 1 9 7 9 , _ ( 3 ) , 2 2 7 - 2 3 3 . R e c h n i t z e r , P.A. The e f f e c t of e x e r c i s e p r e s c r i p t i o n on the recurrance rate of myocardial i n f a r c t i o n i n men. American J o u r n a l of C a r d i o l o g y , 1 9 8 1 , 4 J 7 , 4 1 9 . Ryan, T., Weiner, D.H., and McCabe, C H . Value of the e x e r c i s e ECG f o r diagnosing coronary d i s e a s e . J o u r n a l of C a r d i o v a s c u l a r Medicine , 1 9 8 0 , 5 ( 1 ) , 6 1 - 7 1 . Shaw, L.W. E f f e c t s of a p r e s c r i b e d s u p e r v i s e d e x e r c i s e program on m o r t a l i t y and c a r d i o v a s c u l a r m o r b i d i t y i n p a t i e n t s a f t e r a myocardial i n f a r c t i o n . American J o u r n a l of C a r d i o l o g y , 1 9 8 1 , 4 8 , 3 9 - 4 6 . S h e f f i e l d , L.T., and Reeves, T.J. Graded e x e r c i s e i n the d i a g n o s i s of angina p e c t o r i s . Medical Concepts of C a r d i o v a s c u l a r Disease , 1 9 6 5 , 3 4 . ' 1 « Shephard, R.J., Corey, P. and Kavanagh, T. E x e r c i s e compliance and the p r e v e n t i o n of a recurrance of myocardial i n f a r c t i o n . Medicine and Science i n Sports and E x e r c i s e , 1 9 8 1 , J _ 3 ( 1 ) , 1 - 5 . Sim, D.N., and N e i l l , W.A. I n v e s t i g a t i o n of the p h y s i o l o g i c a l b a s i s f o r i n c r e a s e d t h r e s h o l d f o r angina p e c t o r i s a f t e r p h y s i c a l c o n d i t i o n i n g . J o u r n a l of C l i n i c a l 31 I n v e s t i g a t i o n , 1974, 54, 763. Skinner, J.S., and M c L e l l a n , T.H. The t r a n s i t i o n from a e r o b i c to anaerobic metabolism, Research Q u a r t e r l y f o r E x e r c i s e and Sport , 1980, 5J_, 234-248. Smith, J.L., Dressendorfer, R., Borysyk, L., Gordon, S. and Timmis, G.C. F a i l u r e of the Karvonen formula to a c c u r a t e l y estimate t r a i n i n g heart r a t e in coronary a r t e r y disease p a t i e n t s . Medicine and Science i n Sports and E x e r c i s e , 1982, J_4(2), 149, A b s t r a c t . S t r e j a , D. and Mymin, D. Moderate e x e r c i s e and high d e n s i t y l i p o p r o t e i n c h o l e s t e r o l : o b s e r v a t i o n s d u r i n g a c a r d i a c r e h a b i l i t a t i o n program. J o u r n a l of the American Medical A s s o c i a t i o n , 1979, 242, 2190-2196. S u l l i v a n , M., and McKirnan, D. E r r o r s i n p r e d i c t i n g f u n c t i o n a l c a p a c i t y f o r c a r d i a c p a t i e n t s using a modified Bruce p r o t o c o l . Medicine and Science i n Sports and Exerc i s e , 1982, j_4(2), 129, A b s t r a c t . Sucec, A.A., Tucker, S., Ponton, L and Macy, B. The r e p r o d u c i b i l i t y of the anaerobic t h r e s h o l d by venous blood l a c t a t e and gas exchange measurements, Medicine and Science in Sports and E x e r c i s e , 1982, j_4(2), 127, A b s t r a c t . Volkov, N., S h i r k a v e t s , R. and B o u l k e v i c h , V. Assessment of a e r o b i c and anaerobic c a p a c i t y of a t h l e t e s i n t r e a d m i l l running. European J o u r n a l of A p p l i e d Physiology , 1975, 34(2), 212-230. Wasserman, R. and M c l l r o y , M.B. D e t e c t i n g the t h r e s h o l d of anaerobic metabolism in c a r d i a c p a t i e n t s . American J o u r n a l of C a r d i o l o g y , 1964, J_4, 844-852. Wasserman, K., Whipp, B.J., Koyal, S.N. and Beaver, W.L. Anaerobic t h r e s h o l d and r e s p i r a t o r y gas exchange duri n g e x e r c i s e . J o u r n a l of A p p l i e d Physiology , 1973, 3_5, 236- 243. Wasserman, K., and Whipp, B.J. E x e r c i s e p h y s i o l o g y in h e a l t h and d i s e a s e . American Review of R e s p i r a t o r y Disease , 1975, _H_2, 219-228. Wells, G., Balke, B. and Van Fossan, D. L a c t i c a c i d accumulation d u r i n g work. A suggested s t a n d a r d i z a t i o n of work c l a s s i f i c a t i o n . J o u r n a l of A p p l i e d Physiology , 1957, Weltman, A., Katch, S., Sady, S. and Freedson, P. Onset of a c i d o s i s (anaerobic t h r e s h o l d ) as a c r i t e r i o n measure of submaximal f i t n e s s . Research Q u a r t e r l y , 1976, 49(2), 218- 226. 32 Weltman, A., and Katch, V. R e l a t i o n s h i p between the onset of metabolic a c i d o s i s and maximal oxygen uptake. J o u r n a l of Sports Medicine , 1979, J_9, 135-142. Wilson, P.K., Fardy, P.S. and F r o e l i c h e r , V.F. Cardiac R e h a b i l i t a t i o n , Adult F i t n e s s and E x e r c i s e T e s t i n g P h i l a d e l p h i a , Lea and Febiger, 1981. Wilmore, J.H. and Norton, A.C. Heart and Lungs at Work . Beckman Instruments, 1981, 7-11. Wilson, P.K. (Ed.). Adult F i t n e s s and Cardiac R e h a b i l i t a t i o n . Balt i m o r e , U n i v e r s i t y Park Press, 1975. Wood, P.D. and H a s k e l l , W.L. The e f f e c t of e x e r c i s e on plasma high d e n s i t y l i p o p r o t e i n s . L i p i d s , 1979, 14(4), 417-427. Wyndham, C , S e f t e l , H., W i l l i a m s , C , Wilson, V., Strydom, G., B r e d e l l , G. and von Rahden, M. C i r c u l a t o r y mechanisms of anaerobic metabolism i n working muscle. South A f r i c a n M e dical J o u r n a l , 1965, 3_9, 1008-1014. Yuhasz, M.S. P h y s i c a l F i t n e s s A p p r a i s a l and E x e r c i s e P r e s c r i p t i o n . London, U n i v e r s i t y of Western O n t a r i o , 1 978. Zohman, L.R. and To b i s , J.S. Cardiac R e h a b i l i t a t i o n New York, Grune and S t r a t t o n , 1970. 33 APPENDIX A - REVIEW OF LITERATURE I n t r o d u c t i o n In, e x e r c i s i n g a n g i n a l and post-myocardial i n f a r c t i o n p a t i e n t s , p h y s i o l o g i c a l and biochemical v a r i a b l e s i n t e r a c t through t r a i n i n g to r e s u l t in i n c r e a s e d work c a p a c i t y (Kavanagh et a l . , 1973; Kavanagh et a l . , 1979; F r o e l i c h e r et a l . , 1980), r e d u c t i o n of symptoms, and a l t e r a t i o n of r i s k f a c t o r s (Wilson & Fardy, 1981). One of the primary reasons of using m i l d to moderate ae r o b i c e x e r c i s e such as walking and jogging i n c a r d i a c r e h a b i l i t a t i o n programs (CRP) i s to enable an i n d i v i d u a l to perform gr e a t e r p h y s i c a l a c t i v i t y with r e d u c t i o n s in the metabolic c o s t s to the myocardium (Barnard et a l . , 1977; Clausen & Trap-Jensen, 1970). Sim and N e i l l i n 1974 showed i n c r e a s e s in the a n g i n a l t h r e s h o l d in 9 p a t i e n t s with coronary a r t e r y disease (CAD) a f t e r t r a i n i n g 3 days per week f o r 9 - 1 1 weeks by walking or j o g g i n g . These improvements were s i g n i f i c a n t (P<.05) e i t h e r by work l e v e l a t t a i n e d , or by d u r a t i o n of time e x e r c i s i n g (P<.005), although no d i r e c t improvements i n myocardial oxygen uptake were found. Ba n n i s t e r and Taunton (1971) found that a f t e r 14 male CAD and post-MI p a t i e n t s were d i v i d e d i n t o 3 t r a i n i n g groups, continuous c y c l e t r a i n i n g r e s u l t e d in higher p h y s i c a l working c a p a c i t y than i n t e r v a l or c a l i s t h e n i c - w a l k / j o g g i n g methods. A l l groups demonstrated r e d u c t i o n s i n working HR (p < .01), d i a s t o l i c and s y s t o l i c blood p r e s s u r e , c h o l e s t e r o l (p < .05 ), 34 and t r i g l y c e r i d e s a f t e r the t r a i n i n g program. Detry et a l . (1971). a t t r i b u t e d s i g n i f i c a n t improvements in 12 CAD p a t i e n t s ' maximal oxygen uptake (V02max) (P<.001) of 22.5% a f t e r t r a i n i n g to i n c r e a s e s in a r t e r i o v e n o u s 02 d i f f e r e n c e s (A-V02). These changes were thought to be a r e s u l t of i n c r e a s e d p e r i p h e r a l 02 e x t r a c t i o n , i n c r e a s e d a r t e r i a l 02 content, or i n c r e a s e d hemoglobin p o s t - t r a i n i n g . To a l a r g e extent, the b e n e f i c i a l e f f e c t s of submaximal aer o b i c t r a i n i n g are a r e s u l t of s p e c i f i c s k e l e t a l muscle m i t o c h o n d r i a l o x i d a t i v e c a p a c i t y improvements ( G o l l n i c k & King, 1969; H o l l o s z y , 1 9 7 3 ) . These changes i n c l u d e i n c r e a s e s i n slow- t w i t c h (Type I) muscle f i b e r m i t o c h o n d r i a l enzymes (SDH, c i t r a t e s y n t h a t a s e ) , i n c r e a s e d s i z e and number of mitochondria per muscle f i b e r ( H o l l o s z y , 1973), improvements i n A-V02 d i f f e r e n c e s (Detry et a l . , 1971), i n c r e a s e s i n the c a p i l l a r y to f i b e r r a t i o in the e x e r c i s e d muscles (Brodal et a l . , 1976), i n c r e a s e d myoglobin content, and the improved shunting c a p a c i t y of the c i r c u l a t i o n from n o n - e x e r c i s i n g t i s s u e s to the working muscles (Astrand and Rodahl, 1977). In a d d i t i o n to the p e r i p h e r a l e f f e c t s , changes in l e f t v e n t r i c u l a r p e r f u s i o n , s t r u c t u r e and f u n c t i o n as measured in recent r a d i o n u c l i d e s t u d i e s c o n t r i b u t e to a c e n t r a l t r a i n i n g e f f e c t . F r o e l i c h e r et a l . , (1980) found s l i g h t but n o n - s i g n i f i c a n t improvements in v e n t r i c u l a r f u n c t i o n a f t e r c y c l e , t r e a d m i l l and arm ergometer t r a i n i n g 3 times a week at 60%-85% V02max in CAD p a t i e n t s . Jensen et a l . (1980) found s i g n i f i c a n t improvements a f t e r step c l i m b i n g , rowing, arm c r a n k i n g , c y c l e t r a i n i n g , and t r e a d m i l l running 3 times a week 35 at 65% - 85% V02max i n submaximal e j e c t i o n f r a c t i o n , maximal work load, V02max, and maximal r a t e - p r e s s u r e product, but non- s i g n i f i c a n t i n c r e a s e s i n maximal e j e c t i o n f r a c t i o n . Body f a t r e d u c t i o n s have been documented i n e x e r c i s i n g middle-aged men ( P o l l o c k , 1977) and t r a i n e d post-myocardial i n f a r c t i o n (Ml) p a t i e n t s (Kavanagh et a l . , 1973). Favorable changes i n blood l i p i d p r o f i l e s , p a r t i c u l a r l y , i n c r e a s e s i n plasma h i g h - d e n s i t y l i p o p r o t e i n c h o l e s t e r o l (HDL-C) have been demonstrated i n e x e r c i s i n g CAD p a t i e n t s ( S t r e j a and Mymin, 1979). They found s i g n i f i c a n t (P<.01) i n c r e a s e s i n HDL-C i n 32 CRP p a r t i c i p a n t s a f t e r 13 weeks of 3/week ae r o b i c e x e r c i s e . High l e v e l s of HDL-C have been shown to be a s s o c i a t e d with lower r i s k f o r CAD, and p o s i t i v e l y c o r r e l a t e d with lean i n d i v i d u a l s and i n c r e a s e d ' a e r o b i c f i t n e s s . HDL-C i s reduced with CAD, o b e s i t y , i n a c t i v i t y , i n middle-aged males, and i s a s s o c i a t e d with i n c r e a s e d l e v e l s of plasma low-density l i p o p r o t e i n c h o l e s t e r o l (LDL-C) (Wood and H a s k e l l , 1979). Improved p s y c h o l o g i c a l parameters have been r e p o r t e d f o l l o w i n g t r a i n i n g i n post-MI p a t i e n t s (Noble, 1977). Kavanagh et a l . (1977) found r e d u c t i o n s in dep r e s s i o n as recorded on the Min n i s s o t a M u l t i p l e P e r s o n a l i t y Inventory s c a l e in h i g h l y t r a i n e d post-MI runners compared to a c o n t r o l group. Cardiac r e h a b i l i t a t i o n programs emphasizing a e r o b i c e x e r c i s e t r a i n i n g have, in the m a j o r i t y of s t u d i e s , not s t a t i s t i c a l l y shown a r e d u c t i o n i n the inc i d e n c e of subsequent Mis or an inc r e a s e i n the l o n g e v i t y of CAD p a t i e n t s . Despite s e v e r a l l a r g e m u l t i c e n t r e t r i a l s u t i l i z i n g l a r g e sample s i z e s , 36 no changes i n l o n g e v i t y a f t e r p a r t i c i p a t i o n i n CRPs were noted ( K a l i o et a l . , 1979; R e c h n i t z e r , 1981; Shaw et a l . , 1981). These s t u d i e s , however, have l e a d to f u r t h e r in-depth i n v e s t i g a t i o n i n t o the p r o g n o s t i c i m p l i c a t i o n s of c a r d i a c r e h a b i l i t a t i o n programs. Kavanagh and a s s o c i a t e s (1979) and Shephard et a l . (1981) have l i n k e d compliance with the e x e r c i s e p r e s c r i p t i o n as f a v o r a b l y i n f l u e n c i n g long term s u r v i v a l and the chance of fu t u r e " f a t a l and n o n - f a t a l i n f a r c t i o n s . Admission to a CRP i s u s u a l l y preceded or fol l o w e d by an i n i t i a l medical s c r e e n i n g process and graded e x e r c i s e t e s t (GXT). The purpose of t h i s t e s t i s to determine the f u n c t i o n a l s t a t u s , readiness and s a f e t y f o r e x e r c i s e therapy (Bruce, 1971; E l l e s t a d , 1975; H e l l e r s t e i n , 1973), and to a s s i s t i n the for m u l a t i o n of the e x e r c i s e p r e s c r i p t i o n (Zohman and To b i s , 1970). In a d d i t i o n , r e g u l a r assessments throughout a CRP serve to provide a d d i t i o n a l p a t i e n t m o t i v a t i o n , q u a n t i f y improvement of f u n c t i o n a l c a p a c i t y , and determine i f any m o d i f i c a t i o n of the e x e r c i s e p r e s c r i p t i o n i s r e q u i r e d . Numerous s t u d i e s have a l r e a d y focused on the a p p l i c a t i o n s , s e n s i t i v i t y , r e l i a b i l i t y , e l e c t r o c a r d i o g r a p h i c e s s e n t i a l s and procedures of the t e s t p r o t o c o l s a v a i l a b l e today (Bruce, 1971; E l l e s t a d , 1975; F r o e l i c h e r et a l . , 1975). The e x e r c i s e p r e s c r i p t i o n i s o f t e n d e s c r i b e d i n terms of four v a r i a b l e s ; i n t e n s i t y , d u r a t i o n , frequency, and mode (Fox et a l . , 1972), with c o n s i d e r a t i o n of the i n t e r a c t i o n s and l i m i t a t i o n s imposed by age, medications, myocardial s t a t u s , m u s c u l o s k e l e t a l problems and program design (Wilson et a l . , 37 1981). Of the four v a r i a b l e s , i n t e n s i t y i s the most important, but l e a s t understood and agreed upon component of the e x e r c i s e p r e s c r i p t i o n . Heart Rate and the E x e r c i s e P r e s c r i p t i o n An e a r l y study to determine the e f f e c t s of d i f f e r e n t t r a i n i n g i n t e n s i t i e s , and to form the b a s i c p r i n c i p l e s and i m p l i c a t i o n s f o r o p t i m i z i n g t r a i n i n g programs was by Karvonen et a l . (1957). They s t u d i e d 6 young male s u b j e c t s who were t r a i n e d f o r 30 minutes, 4-5 days per week for 4 weeks on a h o r i z o n t a l t r e a d m i l l . I t was found that i f t r a i n i n g was performed at g r e a t e r than 60% of " a v a i l a b l e range of pulse r a t e s " t h i s would r e s u l t i n an eventual slowing of the heart rate at r e s t and f o r any given submaximal workload. The most s i g n i f i c a n t aspect of t h i s study was the i n t r o d u c t i o n of a formula to d e r i v e an index of t r a i n i n g i n t e n s i t y as measured by heart rate (THR). THR = (HRmax - HRrest) x ( 60% - 70% ) + HRrest T h i s formula has been used e x t e n s i v e l y i n the past and continues to be used as the b a s i s of e x e r c i s e p r e s c r i p t i o n i n many e x e r c i s e and r e h a b i l i t a t i o n programs (American C o l l e g e of Sports Medicine, 1980). Although the authors used young a d u l t s in t h e i r study, the equation remains contemporary and v a l i d s i n c e they took i n t o account the a g e - r e l a t e d maximal HR which has been shown to d e c l i n e with age (Astrand & Rodahl, 1977). 38 I n v e s t i g a t o r s have examined these p r i n c i p l e s i n terms of e x e r c i s e s t r e s s t e s t i n g i n a h o s p i t a l s e t t i n g , mainly to diagnose the presence of . CAD and to d e f i n e the p a t i e n t ' s p h y s i c a l c a p a c i t y . S h e f f i e l d and Reeves (1965) encorporated the p r i n c i p l e of " p r e d i c t e d " percent HRmax to a r r i v e at t h e i r suggestion of 90% as t e r m i n a t i o n p o i n t f o r most GXTs. The concept of a p r e d i c t e d maximal HR was i n v e s t i g a t e d f u r t h e r by Le s t e r et a l . , (1968) where normal but a t h l e t i c a l l y t r a i n e d s u b j e c t s were found to have s l i g h t l y lower maximal HRs than u n t r a i n e d s u b j e c t s . I t was found, however, t h a t HRmax had a standard d e v i a t i o n of ±12 beats per minute (bpm), and that there was a wide spread of HRs at a given workload o c c u r r i n g around the r e g r e s s i o n l i n e , thus showing l a r g e v a r i a b i l i t y i n HR responses to e x e r c i s e between i n d i v i d u a l s . T h i s was s u b s t a n t i a t e d by Ryan i n 1980 who noted that 67% of those t e s t e d in a GXT w i l l d e v i a t e from the p r e d i c t e d r a t e by ±10 bpm. Exten s i v e research throughout the 1970's, producing e x c e l l e n t c o r r e l a t i o n s between V02max and HR was c a r r i e d out by Astrand (Astrand & Rodahl, 1977) which r e s u l t e d in important p r i n c i p l e s of t r a i n i n g i n t e n s i t y . Based on the l i n e a r r e l a t i o n s h i p between V02 and HR at any given workload, THR (as an index of t r a i n i n g i n t e n s i t y ) was b e l i e v e d to be 70% to 85% of maximum a g e - r e l a t e d HRmax, or 57% to 78% of V02max f o r normal he a l t h y young a d u l t , up to middle-aged a d u l t s . They subsequently produced nomograms f o r easy det e r m i n a t i o n of p r e d i c t e d V02max from submaximal b i c y c l e ergometry HR p l o t t e d a g a i n s t workload. These nomograms i n c l u d e d age, body weight, 39 and an age c o r r e c t i o n f a c t o r to p r e d i c t V02max, and s t i l l used e x t e n s i v e l y today. Much of the l i t e r a t u r e agrees with the b a s i c p r e r e q u i s i t e s of u t i l i z i n g these r e l a t i v e percentages as i n d i c e s of i n t e n s i t y (Fox et a l . , 1972; P o l l o c k , 1973; H e l l e r s t e i n et a l . , 1973). As the f i e l d of c a r d i a c r e h a b i l i t a t i o n developed i n l a t e r years, these same p r i n c i p l e s were a p p l i e d to the e x e r c i s e p r e s c r i p t i o n s of post-MI and CAD p a t i e n t s . Zohman and Tobis (1970) suggested t r a i n i n g c a r d i a c p a t i e n t s at 75% to 85% of HRmax or 57% to 78% of V02max. Kavanagh et a l . (1973) used these g u i d e l i n e s i n a e r o b i c a l l y t r a i n e d post-MI p a t i e n t s e n r o l l e d in a CRP and found s i g n i f i c a n t improvements i n p h y s i c a l working c a p a c i t y , V02max and ischemic symptoms. The American C o l l e g e of Sports Medicine o u t l i n e s s e v e r a l methods of p r e s c r i b i n g e x e r c i s e i n t e n s i t y (ACSM, 1980). They recommend that e x e r c i s e i n t e n s i t y i s best expressed as a percentage of f u n c t i o n a l c a p a c i t y , and that i n t e n s i t i e s not exceed 90% but not be lower than 60% of f u n c t i o n a l c a p a c i t y , although with c a r d i a c p a t i e n t s , i n i t i a l i n t e n s i t i e s of 40% to 60% should be p r e s c r i b e d . Method 1 u t i l i z e d p r e s c r i p t i o n by METS. One MET i s equal to a r e s t i n g 02 consumption taken i n a s i t t i n g p o s i t i o n and i s approximately 3.5 ml/kg/min" 1. E x e r c i s e P r e s c r i p t i o n U t i l i z i n g METS Average C o n d i t i o n i n g I n t e n s i t y = .70 x (METSmax) Peak C o n d i t i o n i n g I n t e n s i t y = .90 x (METSmax) 40 Method 2 i n v o l v e s p r e s c r i b i n g e x e r c i s e i n t e n s i t y by heart r a t e . Heart r a t e i s i n one method, p l o t t e d a g a i n s t METS and V02 based on upper and lower percentages of V02max or METSmax (60% or 90%). A l t e r n a t e methods i n c l u d e use of the Karvonen equation p r e v i o u s l y o u t l i n e d , or by c a l c u l a t i n g a given percentage of HRmax to determine THR: THR = (HRmax x Percent ( 60%-90%) of maximum HR on a GXT) Th i s l a s t method of using heart r a t e s to determine e x e r c i s e i n t e n s i t y however underestimates THR for a given MET l e v e l by 15%, and must be c o r r e c t e d by adding 15% to the c a l c u l a t e d THR (ACSM, 1980). H e l l e r s t e i n et a l . , (1973) i n a review a r t i c l e agreed that c a r d i a c p a t i e n t s c o u l d b e n e f i t from the same p r i n c i p l e s of e x e r c i s e p r e s c r i p t i o n as a t h l e t e s and healthy normal middle-aged males. They i l l u s t r a t e t h a t f o r CAD p a t i e n t s there e x i s t s a good r e l a t i o n s h i p between %V02max and %HRmax. However, they poin t out some severe flaws in Karvonen's formula, which demand a t t e n t i o n when w r i t i n g e x e r c i s e p r e s c r i p t i o n s f o r those on beta- b l o c k i n g medications, or symptom-limited maximal HRs. They recommend i n t e n s i t i e s of 57% to 75% V02max and 70% to 85% of symptom-limited : HRmax fo r CAD and post-MI p a t i e n t s , with symptoms and ECG signs (maximum 4-5mm ST segment depression) taken i n t o account. Wilson (1975) introduced the concept of the " t a l k t e s t " f o r an a d d i t i o n a l s u b j e c t i v e cue f o r s e l f - d e t e r m i n a t i o n of c o r r e c t e x e r c i s e i n t e n s i t y , apart from the 70%-85% HRmax equation. If one can c a r r y on a c o n v e r s a t i o n while e x e r c i s i n g without 41 e x c e s s i v e d i f f i c u l t y , ( i . e . moderate v e n t i l a t i o n ) then the t r a i n i n g pace i s assumed to be a p p r o p r i a t e . Fardy (1977) p o i n t e d out that when t r a i n i n g at about 70% of V02max, a peak of 82% gain i n t r a i n i n g a d a p t a t i o n responses w i l l occur fo r the CAD p a t i e n t . However, i n t e n s i t i e s above 70% r e s u l t i n a p l a t e a u , and an eventual d i m i n i s h i n g response due to f a t i g u e . Hence, the e x e r c i s e p r e s c r i p t i o n must c o n s i d e r a multitude of f a c t o r s , yet be s p e c i f i c enough to allow f o r i n d i v i d u a l v a r i a t i o n ( H e l l e r s t e i n et a l . , 1972). When c a r d i a c p a t i e n t s and those at high r i s k are given a GXT, the purpose, apart from determining the presence and/or s e v e r i t y of s i g n i f i c a n t d i s e a s e , i s to estimate the maximal working c a p a c i t y and hence be able to p r e s c r i b e a safe and e f f e c t i v e index of e x e r c i s e i n t e n s i t y (Wilson et a l . , 1981). Bruce (1971) showed that e x e r c i s i n g i n t e n s i t y expressed as a percentage of HRmax or V02max r e f l e c t e d not only f u n c t i o n a l c a p a c i t y , but more importantly, myocardial oxygen demand. Thus e x e r c i s e i n t e n s i t y i s r e l a t e d to myocardial f u n c t i o n and p e r f u s i o n s t a t u s . The Bruce s t r e s s t e s t p r o t o c o l i s e x t e n s i v e l y used i n the c l i n i c a l s e t t i n g f o r d i a g n o s i s of coronary a r t e r y d i s e a s e as w e l l as an a i d i n the f o r m u l a t i o n of the e x e r c i s e p r e s c r i p t i o n . I t c o n s i s t s of continuous 3-minute stages of simultaneously i n c r e a s i n g t r e a d m i l l grade and speed. 42 Bruce T r e a d m i l l GXT T r e a d m i l l Speed (mph) % Grade Est imated V02max (ml/kg/min|" 1) METS 1 .2 1 .7 1 .7 2.5 3.4 4.2 5.0 5.5 0 5 10 1 2 1 4 1 6 18 20 8.0 15.0 17.5 24.5 34.3 43.8 55.5 58.0 4.6-5.7 6.6-7.4 8.6-10.6 11.7-14.0 15.1-16.6 16.6 + 2.3 4.3 T h i s p r o t o c o l and nomogram, which estimates V02max from the stage a t t a i n e d has been c r i t i c i s e d . F r o e l i c h e r et a l . (1975) demonstrated an inadequate r e l a t i o n s h i p f o r p r e d i c t i n g V02max from maximal t r e a d m i l l t r e a d m i l l time and age. Bruce's F u n c t i o n a l Aerobic Impairment index (FAI) has a l s o continued to be regarded as an a l t e r n a t e measurement or e x p r e s s i o n of a p a t i e n t ' s a e r o b i c c a p a c i t y or c a r d i o v a s c u l a r impairment: FAI = Predicted-Observed V02max / P r e d i c t e d V02max x 100 Values in the FAI r a t i n g range from normal, which equals a value of 0 i n d i c a t i n g 100% of normal a e r o b i c c a p a c i t y , to values below 0, i n d i c a t i n g b e t t e r than average f i t n e s s . Values on the p o s i t i v e s i d e , i n d i c a t e v a r y i n g l e v e l s of a e r o b i c impairment. Bruce F u n c t i o n a l Aerobic Impairment Index 43 More r e c e n t l y , i n v e s t i g a t o r s have begun to que s t i o n these pr e v i o u s methods of p r e s c r i b i n g e x e r c i s e i n t e n s i t y f o r CAD p a t i e n t s based on p h y s i o l o g i c a l p r i n c i p l e s such as maximal age- r e l a t e d HRmax from a GXT. Mazzeo et a l . , (1982) telemetered 16 CAD p a t i e n t s f o r a 24 hour p e r i o d which i n c l u d e d p a r t i c i p a t i o n i n a CRP (10 minutes warm-up), 20 minutes a e r o b i c , 15 minutes cool-down). THR du r i n g the ae r o b i c p o r t i o n were c a l c u l a t e d to be at 54.2% HRmax. Although the p a t i e n t s remained i n t h i s THR zone f o r only 10.3 minutes of the 20 minute a e r o b i c s e s s i o n , a s i g n i f i c a n t improvement (P<.05) i n f u n c t i o n a l c a p a c i t y over a 4.7 month p e r i o d was found (7.18 METS to 8.19 METS). T h i s improvement, e q u i v a l e n t to 3.46 ml/kg/min" 1., represented a 20% to 30% r e l a t i v e improvement in f u n c t i o n a l c a p a c i t y in these p a t i e n t s . Mean HR at any given submaximal workload decreased a f t e r t r a i n i n g , e n a b l i n g p a t i e n t s to-achieve higher workloads before the onset of angina symptoms. The authors concluded that lower than accepted i n t e n s i t i e s of 40% to 60% HRmax reserve can e l i c i t a e r o b i c t r a i n i n g e f f e c t s i n s e l e c t e d CAD p a t i e n t s e n r o l l e d i n a CRP. D o l l et a l . , (1982) found that i n a sample of 150 CAD p a t i e n t s , HRmax in c r e a s e d a f t e r 6 months of t r a i n i n g i n a CRP 3 times per week at 80% to 90% HRmax. It was not i n d i c a t e d whether t h i s i n c r e a s e was s i g n i f i c a n t . The s i g n i f i c a n c e of t h i s f i n d i n g , the authors concluded, was that a g e - p r e d i c t e d HRmax from data based on normals over-estimates maximal r a t e s and thus e x e r c i s e HR p r e s c r i p t i o n s f o r e x e r c i s i n g CAD p a t i e n t s . S u l l i v a n and McKirnan (1982) measured V02 i n 12 normal and 12 CAD 44 p a t i e n t s d u r i n g a Bruce p r o t o c o l GXT. They found that a c t u a l V02max f o r p a t i e n t s f o r the 3 stages a t t a i n e d ranged from 1.8 to 7.3 ml/kg/min. lower than would be e x t r a p o l a t e d by the Bruce p r o t o c o l . I t was not i n d i c a t e d whether t h i s data was s t a t i s t i c a l l y s i g n i f i c a n t . The authors suggested that i n CAD or post-MI p a t i e n t s , myocardial damage may a l t e r or slow oxygen " k i n e t i c s " and r e s u l t i n lower a c t u a l V02 during t r e a d m i l l GXTs, and that the Bruce p r o t o c o l might not take t h i s i n t o account. A recent study i n v e s t i g a t e d the Karvonen equation f o r determination of t r a i n i n g i n t e n s i t y . Smith et a l . , (1982) s t u d i e d 42 male CAD p a t i e n t s , and compared THR, as determined by Karvonen's equation to the %V02 method THR, and HR durin g a t r i a l t r e a d m i l l run. The t r e a d m i l l run c o n s i s t e d of a 20 minute steady s t a t e run at 60% of V02max. The authors found mean t r i a l HR to be 104±16 bpm, mean Karvonen THR of 114117 bpm, and a mean V02 method THR of 103±16 bpm. Karvonen's THR was s i g n i f i c a n t l y higher than a c t u a l steady s t a t e t r i a l HR (P<.005). THRs from the' %V02 method was not s i g n i f i c a n t l y d i f f e r e n t from the t r i a l HR. Karvonen's method was acc u r a t e w i t h i n ±6 bpm i n 42% of the p a t i e n t s t e s t e d compared to 57% of those t e s t e d by the %V02 method. The authors concluded that the Karvonen equation overestimates THR, and should be used with c a u t i o n in e x e r c i s e p r e s c r i p t i o n s f o r c a r d i a c p a t i e n t s . A survey of the l i t e r a t u r e thus r e v e a l s c o n f l i c t i n g f i n d i n g s on the accuracy and r e l i a b i l i t y of c u r r e n t methods of d e r i v i n g e x e r c i s e p r e s c r i p t i o n i n t e n s i t y on the b a s i s of maximum performance on GXTs. Heart r a t e , as the e a s i e s t v a r i a b l e or 45 index of e x e r c i s e i n t e n s i t y can d i f f e r , depending on the method u t i l i z e d to c a l c u l a t e i t . Current methods used t o c a l c u l a t e THR in c l u d e the Karvonen equation, which i n c o r p o r a t e s HRrest, HRmax and a s l i d i n g percentage of HRmax; 70% to 85% HRmax a t t a i n e d on a GXT; or 70% to 90% of maximal METS a t t a i n e d on a GXT. Anaerobic Metabolism and the Anaerobic T h r e s h o l d L a c t i c a c i d has fo r q u i t e some time been i d e n t i f i e d as a major c o n t r i b u t o r to f a t i g u e d u r i n g e x e r c i s e . The in-depth study i n t o i t s r e l a t i o n s h i p to e x e r c i s e continues to be a major focus of i n v e s t i g a t i o n . As l a c t a t e i s produced i n the working muscles as a r e s u l t of anaerobic g l y c o l y s i s , i t d i f f u s e s out of the c e l l s , and i n t o the c i r c u l a t i n g venous blood. There are many f a t e s of l a c t a t e , some of which i n c l u d e r e c o n v e r s i o n to pyruvate and then complete o x i d a t i o n i n the l i v e r , heart and other organs, or as a n u t r i e n t substance i n w e l l oxygenated s k e l e t a l muscle dur i n g r e s t (Guyton, 1976). T u r r e l l and Robinson i n 1942 s t u d i e d the biochemical processes of l a c t i c a c i d p r o d u c t i o n and acid-base balance d u r i n g anaerobic c o n d i t i o n s . They i l l u s t r a t e d the in c r e a s e i n l a c t i c a c i d with d e c r e a s i n g bicarbonate (BHC03), and pro v i d e d the model and equation where BHC03 b u f f e r s l a c t a t e : (HLa): HLa + BHC03 = B(La) + H2C03 = C02 + H20 Carbonic a c i d , a weak a c i d , e a s i l y d i s s o c i a t e s t o C02 and H20. The C02 i s exhaled, accounting f o r the in c r e a s e i n the volume of 46 e x p i r e d C02 (VC02). The i n c r e a s e i n minute v e n t i l a t i o n (Ve) i s a l s o augmented by the produced H+ which s t i m u l a t e medullary c e n t r e s , c a r o t i d and a o r t i c bodies, thus i n c r e a s i n g b r e a t h i n g r a t e (Guyton, 1976). The authors a l s o demonstrated that the r i s e i n HLa c o n c e n t r a t i o n e q u a l l e d the C02 c a p a c i t y of the blood. I s s e l r u t z and Rodahl (1961) int r o d u c e d the concept of the r e s p i r a t o r y exchange r a t i o , or R, d e f i n e d by the equation: R = VC02/V02 and found that i t not only r e f l e c t e d changing acid-base balance, f u e l u t i l i z a t i o n and anaerobic metabolism, but to a l s o to i n c r e a s e with greater workloads. T h i s r e l a t i o n s h i p was however e a r l i e r e n l i g h t e n e d by a study by Balke et a l . (1954), where he s t r e s s t e s t e d sedentary blood donors before and a f t e r donation and found that VC02 i n i t i a l l y i n c r e a s e d p r o p o r t i o n a t e l y to the V02 i n c r e a s e . However a f t e r i n c r e a s i n g workloads, VC02 exceeded V02. When R was g r e a t e r than 1.0, i t was assumed that the l i m i t s of a e r o b i c metabolism had been exceeded. They a l s o observed a sudden d e c l i n e i n a l v e o l a r pC02 with a r i s e i n Ve a l i n e a r l y to V02. In a l a t e r study, Wells and co-workers(1957) examined La p r o d u c t i o n i n terms of e x e r c i s e i n t e n s i t y and equated La changes with changes i n R. F u r t h e r s t u d i e s looked e x c l u s i v e l y at e x e r c i s e i n t e n s i t i e s , and methods to p i n p o i n t the onset of anaerobic metabolism. Using 102 s u b j e c t s , Issekutz and Rodahl (1961) found a c o r r e l a t i o n of .92 between the change in La and excess C02 d u r i n g b i c y c l e ergometry. They hypothesized 47 that the excess C02 ( d e r i v e d from the b u f f e r i n g of HLa by HC03) was a more u s e f u l i n d i c a t o r of a n a e r o b i o s i s than HLa r e l e a s e , thus demonstrating i t s r e l i a b i l i t y and v a l i d i t y f o r use i n determining a n a e r o b i o s i s . T h i s l e a d to the equation f o r c a l c u l a t i o n of excess, or non-metabolic C02: Excess C02 = VC02 - (Resting R x V02) Wasserman and M c l l r o y (1964) suggested that the onset of anaerobic metabolism, or the anaerobic t h r e s h o l d (AT) occurred at the workload j u s t below the p o i n t of n o n - l i n e a r change in Ve and VC02 in e x e r c i s i n g c a r d i a c p a t i e n t s . They noted that although the onset of anaerobic metabolism c o u l d be measured by an i n c r e a s e i n HLa c o n c e n t r a t i o n s , a decrease i n a r t e r i a l blood. pH and HC03, and a r i s e i n R, the non-invasive methods of d e t e r m i n a t i o n u t i l i z i n g r e s p i r a t o r y parameters were more a t t r a c t i v e . L a t e r s t u d i e s by Wasserman et a l . , (1973, 1 9 7 5 ) using breath-by-breath a n a l y s i s of r e s p i r a t o r y exchange v a r i a b l e s found good c o r r e l a t i o n s between excess C02 and HC03 (r = .98). The measurement of blood l a c t a t e i t s e l f in determination of the AT has been s t u d i e d e x t e n s i v e l y , but with l e s s agreement upon i t s v a l i d i t y . Graham (1978) argued that HLa d i f f u s i o n out of muscles can be delayed. As w e l l , muscle La and blood La are not equal due to the v a r i a b l e c h a r a c t e r i s t i c s of blood sampling time, blood flow, d i f f u s i o n r a t e and f i b r e type. An e a r l y study to d e s c r i b e the r e l a t i o n s h i p between AT and V02max was c a r r i e d out by Wyndham et a l . , (1965). They examined the sudden 48 c o n c e n t r a t i o n of HLa as the onset of anaerobic metabolism and found that the AT occurred at 50 - 60% of V02max in normal men, and 45 - 50% in h o s p i t a l p a t i e n t s with cardiomyopathy. Wasserman in 1975 s t u d i e d the occurrence of the AT i n incremental e x e r c i s e t e s t s using breath by breath gas a n a l y s i s . He i l l u s t r a t e d that the advantages of using a 1-minute as opposed to a 4-minute increment to d e t e c t the AT in GXTs are that the 1-minute increment allows d i s c r i m i n a t i o n between the AT and other p o s s i b l e causes of non-anaerobiotic i n c r e a s e s i n R such as h y p e r v e n t i l a t i o n , a n x i e t y , or hypoxia. The p h y s i o l o g i c a l b a s i s of t h i s advantage, a c c o r d i n g to the author i s that e n d - t i d a l P02 i n c r e a s e s with no changes in e n d - t i d a l PC02, c o n t r a r y to a 4-minute increment, where e n d - t i d a l P02 i n c r e a s e s but e n d - t i d a l PC02 decreases at the AT. In a d d i t i o n , the s h o r t e r increment allows f o r a s h o r t e r t o t a l GXT d u r a t i o n , s u b j e c t s recover more r a p i d l y a f t e r the t e s t , and i t y i e l d s a b e t t e r p l a t e a u i n g of V02 with p r o g r e s s i v e work increments (Wasserman, 1975). Wasserman et a l . , (1973) found the AT d e t e c t i o n u t i l i z i n g breath by breath methods using the 1-minute work increment to be c o n s i s t e n t l y r e p r o d u c i b l e over 1 hour, 4 hours, 1 week and 9 months. I t was a l s o e x p l a i n e d however that though d e t e c t i o n of the AT in normal s u b j e c t s or i n p a t i e n t s with c i r c u l a t o r y i n s u f f i c i e n c i e s i s v a l u a b l e , i t has l i m i t e d use in p a t i e n t s with r e s p i r a t o r y impairments. In 1975, Volkov et a l . examined the excess C02 concept in d e t e r m i n a t i o n of the AT. In c o n j u n c t i o n with i t s a l i n e a r r i s e at a s p e c i f i c t r e a d m i l l v e l o c i t y (Vtam), the AT c o u l d be 49 c o n f i d e n t l y determined. The author found Vtam values to be high in t r a i n e d s u b j e c t s , with excess C02 remaining constant at submaximal, or sub-AT speeds. In a study i n v o l v i n g middle-aged males, Davis et a l . (1976) produced high c o r r e l a t i o n s between the AT determined by HLa and gas exchange v a r i a b l e (r=.95). However, R was not co n s i d e r e d a r e l i a b l e c r i t e r i o n of the AT si n c e i t d i d not d i s c r i m i n a t e between true a n a e r o b i o s i s and h y p e r v e n t i l a t i o n at higher workloads, thus d i s a g r e e i n g with Wasserman's (1973) •findings that the n o n - l i n e a r i n c r e a s e i n R i s a r e l i a b l e v a r i a b l e c h a r a c t e r i z i n g the AT. Weltman and Katch (1979) showed the c l o s e r e l a t i o n s h i p between the V02 at the AT and V02max (r=.85). The authors concluded that a e r o b i c a l l y t r a i n e d i n d i v i d u a l s c o u l d work at higher percentages of t h e i r V02max before they produce l a c t a t e as a r e s u l t of a n a e r o b i o s i s . AT has been s t u d i e d i n r e l a t i o n to i t s use i n other e x e r c i s e e v a l u a t i o n p r o t o c o l s . Davis et a l . (1976) compared three e x e r c i s e modes ( b i c y c l e , walk, run) and found that V02max and %V02max at AT were s i m i l a r f o r each task, and demonstrated the r e p r o d u c i b i l i t y of the AT f o r most p r o t o c o l s . A l a t e r study (Davis et a l . , 1979) demonstrated s i g n i f i c a n t improvements in the AT of up to 44% i n u n t r a i n e d middle-aged men a f t e r c y c l i n g 45 min./day, 4 days a week, f o r 9 weeks. T h i s r e s u l t was i n agreement with MacDougall (1977) who showed that the AT i s t r a i n a b l e and' can be in c r e a s e d by a balance of long d u r a t i o n submaximal t r a i n i n g p l u s s p e c i f i c anaerobic h i g h - i n t e n s i t y i n t e r v a l t r a i n i n g . He s i t e d v a r i o u s 50 f a c t o r s i n c l u d i n g i n c r e a s e d muscle c a p i l l a r y d e n s i t y , myoglobin, m i t o c h o n d r i a l s i z e and enzyme a c t i v i t y , and i n c r e a s e d shunting of pyruvate to the a l a n i n e c y c l e to account f o r t h i s improved u t i l i z a t i o n of V02max. LaFontine et a l . (1982) demonstrated that an i n t e n s i t y t h r e s h h o l d must be achieved d u r i n g t r a i n i n g , f o r i n c r e a s e s i n the aerT to take p l a c e independently of i n c r e a s e s i n V02max. The authors found that s u b j e c t s who t r a i n e d at the medium and high i n t e n s i t i e s (AerT-HR and AnT-HR, r e s p e c t i v e l y ) improved the AerT, whereas t r a i n i n g at the low i n t e n s i t y (AerT-HR-20 bpm) produced no changes i n AerT. The r e l a t i o n s h i p of a e r o b i c f i t n e s s l e v e l s and the onset of the AT by examination of Blood La was examined by C o s t i l l (1970) and i t was shown that e l i t e d i s t a n c e runners (V02max = 73 ml/kg/min" 1) demonstrated extremely low La l e v e l s a f t e r a marathon run and at below 70% of V02max during a t r e a d m i l l run. In a l a t e r study, C o s t i l l et a l . (1973) found a h i g h l y s i g n i f i c a n t r e l a t i o n s h i p between %V02max and d i s t a n c e running performance (r = .94) on a t r e a d m i l l run at 10 mph. I t was concluded that %V02max at the AT w i l l vary between i n d i v i d u a l s of d i f f e r e n t f i t n e s s l e v e l s and there i s an optimal pace dependent on l a c t a t e p r o d u c t i o n and subsequent metabolism. T h i s data i s s i g n i f i c a n t f o r n o n - a t h l e t i c p o p u l a t i o n s and those t r a i n i n g f o r h e a l t h , f i t n e s s and r e h a b i l i t a t i o n . Some i n v e s t i g a t o r s have shown that not only does the AT determine the c a p a b i l i t y to perform a e r o b i c e x e r c i s e , but can a l s o determine which s u b s t r a t e s the i n d i v i d u a l i s u t i l i z i n g . MacDougall (1977) and Katch et a l . (1978) suggested that f a t metabolism i s 51 reduced when e x e r c i s i n g above the AT. T r a i n i n g above the AT w i l l tend to promote glycogen u t i l i z a t i o n and a c c e l e r a t e muscle glycogen d e p l e t i o n , e s p e c i a l l y with prolonged a c t i v i t y . Research by Kinderman et a l . (1979) has attempted to take a l l the p r e v i o u s data and r e c l a s s i f y anaerobic metabolism d u r i n g e x e r c i s e (the AT as p r e v i o u s l y d e f i n e d by Wasserman) i n t o three t r a n s i t i o n a l phases, r e f l e c t i n g changes i n blood l a c t a t e c o n c e n t r a t i o n s . The "aerobic t h r e s h o l d " occurs at about 2 mmol/L"1 La with prolonged e x e r c i s e maintained f o r 4 hours. The "ae r o b i c / a n a e r o b i c t r a n s i t i o n " occurs between 2 and 4 mmol/L"1 and a c t i v i t y i s p o s s i b l e f o r an hour. The "anaerobic t h r e s h h o l d " i s c h a r a c t e r i z e d by extreme l a c t a t e values i n excess of 4 mmol/L" 1, where a c t i v i t y can only be maintained f o r s u b s t a n t i a l l y under 1 hour. T h i s c o n s t i t u t e s the f i n a l phase. The authors, using t r a i n e d c r o s s country s k i i e r s found that 4 mmol/L"1 La occu r r e d at above 80% of maximal t r e a d m i l l speed with HRs between 169 and 180 bpm. They concluded that optimal work i n t e n s i t i e s should occur i n the a e r o b i c / a n a e r o b i c t r a n s i t i o n zone (2-4 mmol/L" 1) f o r optimal improvement of o x i d a t i v e pathways and hence endurance. T h i s terminology was expanded by Skinner and McLellan i n t h e i r 1980 review. They a l s o suggested an a e r o b i c to anaerobic t r a n s i t i o n a l process with an a e r o b i c phase 1, where 02 uptake s a t i s f i e s ATP demand, hence minimizing La p r o d u c t i o n . They r e d e f i n e d Wasserman's et a l . (1973) anaerobic t h r e s h o l d as the "aerobic t h r e s h o l d " (AerT) preceding phase 2, where La can reach 2-4 mmol/L"1 and which corresponds to a point between 40% and 52 60% of V02max. The t h i r d phase, corresponding to 65% to 90% V02max with s t e e p l y r i s i n g La above 4 mmol/L"1 occurs at maximal workloads, and d e p i c t s an even g r e a t e r n o n - l i n e a r breakaway of Ve and VC02 to compensate f o r the metabolic a c i d o s i s . H y p e r v e n t i l a t i o n becomes evident by a drop in FEC02 and a r i s e in FE02. Phase 3, f o l l o w i n g the anaerobic t h r e s h o l d i s c h a r a c t e r i z e d by: 1. r e d u c t i o n / o c c l u s i o n of muscle blood flow. 2. recruitment t r a n s i t i o n from SO to FOG and FG muscle f i b e r s 3. decreased FFA u t i l i z a t i o n . 4. i n c r e a s e d glycogen u t i l i z a t i o n E x e r c i s e P r e s c r i p t i o n and the Aerobic/Anaerobic Threshold In 1976, Weltman et a l . s t u d i e d 28 moderately t r a i n e d students and determined The AerT using Ve, VC02, and FE02 changes. They showed that those s u b j e c t s matched f o r V02max d i d not n e c e s s a r i l y show s i m i l a r V02 at AT v a l u e s , i n d i c a t i n g that at submaximal workloads, there are metabolic d i f f e r e n c e s that V02max does not take i n t o account. A l a t e r study by Weltman and Katch et a l . (1978) using stepwise c o r r e l a t i o n s of performance and r e s p i r a t o r y data i n d i c a t e d that "heart r a t e a t t a i n e d on a t e s t , or HR at the p o i n t of metabolic a c i d o s i s shows l i t t l e r e l a t i o n s h i p with the other v a r i a b l e s " , thus agreeing with Wasserman's et a l . (1973) o b s e r v a t i o n that HR response i s a poor p r e d i c t o r of metabolic a c i d o s i s . They a l s o presented a 53 method of r e g r e s s i o n f o r p r e d i c t i o n of V02max from V02 at AT (V02maxAT), which the authors suggested " i s a p o s s i b l e method of determining f u n c t i o n a l c a p a c i t y i n a c l i n i c a l s e t t i n g where e x e r c i s e through metabolic a c i d o s i s i s unadvised". The use of the a e r o b i c t h r e s h o l d as a b a s i s f o r t r a i n i n g was r e c e n t l y examined by McLellan and Skinner (1981). Fourteen male s u b j e c t s were t r a i n e d at e i t h e r a r e l a t i v e percent of V02max or percent of a e r o b i c t h r e s h o l d (AerT) f o r 30 - 45 minutes/day, 3/week, f o r 8 weeks. S i g n i f i c a n t improvements i n V02max between pre and p o s t - t r a i n i n g (23.8% AerT vs. 18.3% %V02) were found, but there were no in c r e a s e s i n AerT values a f t e r t r a i n i n g as expressed as %V02max. The authors concluded that using the AerT as an index of i n t e n s i t y , equal improvements in a e r o b i c f i t n e s s are p o s s i b l e . Poweles et a l . (1979) s t u d i e d 39 middle-aged post- i n f a r c t i o n males and found 18 who were 2 standard d e v i a t i o n s below age p r e d i c t e d HRmax. Despite the p a t h o l o g i c a l reasons behind t h i s poor HR response, the authors f e l t that t h i s was a case where the p r e s c r i b e d t a r g e t HR would have been g r o s s l y overestimated and unsafe. The anaerobic t h r e s h h o l d (AerT) was determined by observing an a l i n e a r Ve response and detected i n 82% of the s u b j e c t s , with mean post e x e r c i s e La of 7.5 mmol/L" 1. They concluded t h e i r study with s t r o n g recommendations that i n these types of p a t i e n t s , d e t e r m i n a t i o n of the AT can s a f e l y determine the c a r d i o v a s c u l a r l i m i t a t i o n s to e x e r c i s e . Katch et a l . ( l 9 7 8 ) found a c o r r e l a t i o n of .97 between V02"- max and HRmax in 31 male s u b j e c t s . However, when the author 54 removed the time element from the equation, t h i s value dropped to .17. Katch evaluated the use of the " r e l a t i v e percent" concept i n p r e s c r i b i n g t r a i n i n g HRs. He questioned the use of HR as the s o l e index of t r a i n i n g i n t e n s i t y , as s i g n i f i c a n t d i f f e r e n c e s between s u b j e c t s were found i n the responses i n t r a i n i n g i n t e n s i t i e s when i n d i v i d u a l s were working at the same r e l a t i v e percentage of HRmax. At 80% HRmax, 17 s u b j e c t s were t r a i n i n g at or above the AT, with 14 t r a i n i n g below i t . Hence, the author a d v i s e d that s i n c e the r e l a t i v e percent concept might be i n v a l i d f o r equating t r a i n i n g i n t e n s i t i e s , the AT c o u l d be used to do so more r e l i a b l y , thus accounting f o r i n d i v i d u a l v a r i a t i o n of HR and submaximal metabolic responses. In a study by Dwyer and Bybee, (1981), u t i l i z i n g low to moderately t r a i n e d females, HRs between 60% and 80% of V02max r e s u l t e d i n i n c o n s i s t e n t work s t r e s s among the s u b j e c t s . and i s was concluded that the AT was a b e t t e r b a s i s f o r e x e r c i s e p r e s c r i p t i o n s than an a r b i t r a r i l y determined %HRmax or %V02max. Dressendorfer et a l . (1981), studying u n t r a i n e d healthy middle-aged men agreed, reported ATs o c c u r r i n g w e l l above the upper zone of THR recommended f o r safe t r a i n i n g . T h i s r e s u l t was s t a t i s t i c a l l y s i g n i f i c a n t (P<.05). Parkhouse and McKenzie (1982) s t u d i e d u n t r a i n e d , t r a i n e d , and h i g h l y t r a i n e d young a d u l t s , and, c o n t r a r y t o Katch'set a l . (1978) f i n d i n g s , concluded that HR was i n f a c t an adequate p r e d i c t o r of AT. A l l three groups had d i f f e r e n t ATs; those h i g h l y t r a i n e d having i n c r e a s e d ATs. Both absolute and r e l a t i v e HRs at AT were e s s e n t i a l l y the same f o r a l l groups, but i t was 55 c a u t i o n e d that t h i s c o u l d be a r e s u l t of the l a r g e i n t r a g r o u p v a r i a b i l i t y . These r e s u l t s were a l s o in agreement with data by Patton et a l . , (1980). Wilmore et a l . , (1981) a s s i m i l a t e t h i s i n f o r m a t i o n with regard to the e x e r c i s i n g c a r d i a c p a t i e n t . They o u t l i n e a r a t i o n a l e f o r c a r d i a c r e h a b i l i t a t i o n p a r t i c i p a n t s to be e x e r c i s i n g at a %HRmax which i s j u s t below the ae r o b i c t h r e s h o l d of Skinner and McLellan (1980). They suggest that the ae r o b i c t h r e s h o l d should be used i n a GXT along with %HRmax t a r g e t HR to f u r t h e r i n d i v i d u a l i z e the e x e r c i s e p r e s c r i p t i o n . Since an impaired myocardium cannot achieve high stroke volumes, and a t a c h y c a r d i a at low workloads accommodates f o r t h i s , HRs do not r e f l e c t the true metabolic requirement. I t was a l s o noted that c a r d i a c output i s l i m i t e d by HRmax, which can vary i n c a r d i a c p a t i e n t s , agreeing with observatons by Poweles et a l . , (1979). Other v a r i a b l e s such as p s y c h o l o g i c a l , medication, m u s c u l o s k e l e t a l l i m i t a t i o n s and compliance with the e x e r c i s e program e x i s t , hence e x t r a c a u t i o n must be i n c o r p o r a t e d i n t o the fo r m u l a t i o n of the e x e r c i s e p r e s c r i p t i o n ' s l e v e l of i n t e n s i t y (Kavanagh et a l . , 1973). The e x e r c i s e program must i n c o r p o r a t e and f u l f i l two requirements; i t must provide the d e s i r e d p h y s i o l o g i c a l adaptive e f f e c t s , and be c o n s i s t e n t l y enjoyable and t o l e r a b l e (Wilson et a l . , 1981). Kavanagh et a l . (1979) found that compliance with the e x e r c i s e protocol.was the most important s i n g l e determinant of pr o g n o s i s . The r i s k r a t i o f o r f a t a l and n o n - f a t a l r e i n f a r c t i o n s was 23.6 times higher for poor c o m p i l e r s . Further a n a l y s i s of 56 these r e s u l t s i n subsequent s t u d i e s suggested that 22% of the non-compliers compared to'4.4% of compilers had a combined f a t a l and n o n - f a t a l recurrence r a t e (Shephard et a l . , 1981). George e t ' a l . (1981) a l s o found that p a t i e n t s who sensed c o n s i d e r a b l e f a t i g u e d u r i n g the e x e r c i s e s e s s i o n had g r e a t e r dropout r a t e s . Thus, improper e x e r c i s e i n t e n s i t i e s , as f a r as very recent r e s e a r c h suggests, c o u l d be one f a c t o r i n these non-compliance and r e i n f a r c t i o n data (Wilmore et a l . , 1981). The study of the onset of anaerobic metabolism i n both normal and c a r d i a c p a t i e n t s suggests that " r e l a t i v e percent" methods of p r e s c r i b i n g e x e r c i s e i n t e n s i t y might not account f o r d i f f e r e n c e s in i n d i v i d u a l v a r i a t i o n s i n metabolism at submaximal workloads. Using the Aerobic T h r e s h o l d i n a d d i t i o n to other standard methods might optimize the c o n d i t i o n i n g e f f e c t s of the s u b j e c t . T h i s has great value i n the t e s t i n g and t r a i n i n g of e x e r c i s i n g CAD p a t i e n t s , whose e x e r c i s e p r e s c r i p t i o n i n t e n s i t i e s must be i n d i v i d u a l l y based. 57 APPENDIX B - INDIVIDUAL. SUBJECTS PHYSIOLOGICAL DATA V02max %V02mAerT Vtam HRmax THR AerTHR %HRmaxAerT %HRmaxT (ml/kg/min) (mph) (bpm) (bpm) (bpm) 42.91 52.50 5.00 157 1 26.0 1 1.2 71.0 80.0 34.90 43.40 4.50 152 1 28.2 108 71.0 84.3 33.30 55.90 5.00 186 132.0 151 81.1 71.1 35.46 61 .73 5.50 166 137.3 1 48 89. 1 82.7 32.20 58.20 4.50 168 137.3 1 40 83.3 82.0 40.87 47.90 5.00 161 1 34.0 125 77.6 83.2 35.97 53.90 4.50 1 55 124.0 1 1 7 75.4 80.0 34.43 54.00 5.00 1 60 1 44.3 141 88. 1 90. 1 39.20, 50.40 4.50 186 160.0 130 69.8 86.0 39.20 55.24 4.50 159 123.0 1 18 74.2 77.3 52.70 58.97 6.50 1 78 125.0 1 37 76.9 70.2 37.00 55.20 4.50 167 1 44.0 1 23 73.6 86.2 33.12 49.20 4.00 1 84 1 46.0 1 28 69.5 79.3 32.76 42. 1 0 4.00 175 1 04.6 1 07 61.1 59.7 30.57 72.70 4.00 1 60 1 25.3 108 67.5 78.3 32.03 51 .60 4.00 1 64 115.7 1 1 7 71.3 70.5 36.09 56. 1 0 4.00 184 156.0 135 73.3 84.7 27.23 61 .40 4.00 1 57 136.6 1 1 8 75. 1 87.0 30.60 50.80 4.00 1 50 147.0 94 62.6 98.0 30.97 57.80 4.00 1 55 1 28.0 1 40 90.3 82.5 58 APPENDIX C - RELIABILITY STUDY P a i r e d t - t e s t s were performed on A e r T ( l ) and AerT(2) using BMD program p3d. R e s u l t s showed a t e s t / r e - t e s t r e l i a b i l i t y of r = .967 between the f i v e s u b j e c t s . Raw Data Subjects AerTHR 1 AerTHR 2 (bpm) (bpm) 1 140 146 2 151 157 3 130 135 4 118 128 5 112 108 r = .97 59 APPENDIX D - SAMPLE OF COMPUTER GENERATED MEAN TRAINING HEART RATE * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * HEART RATE MONITOR PROGRAM * * J . M. BUCHANAN FITNESS AND RESEARCH CENTER* * SCHOOL OF PHYSICAL EDUCATION * * DEPT OF SPORT SCIENCES * * UNIVERSITY OF B.C. * * VANCOUVER, B.C. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * T I M E 1 S E C O N O £ 1 MEAN it:in I 00 15 30 45 HEART RATE 0 1 97 103 106 1 102 1 1 104 110 113 116 1 111 2 1 122 127 129 130 1 127 3 1 131 135 133 137 1 134 4 1 136 137 137 . 136 1 137 5 1 140 1 4 1 1 4 1 1 4 1 1 141 • 6 1 141 141 142 14 5. 1 142 7 1 146 145 145 145 1 145 6 1 147 147 146 145 1 146 9 1 143 143 143 142 1 143 10 1 142 140 142 142 1 142 11 1 142 142 142 143 . 1 142 12 1 141 141 142 142 1 142 13 1 143 145 145 144 1 144 14 1 142 141 139 138 1 14 C 5 ! 138 136 137 137  36 1 16 1 140 140 140 139 1 140 1 17 1 138 138 139 140 1 139 16 1 141 141 143 1 4 4 1 142 19 1 143 147 146 143 1 14 5 1 20 1 140 138 135 132 1 136 1 21 1 129 128 123 • 126 1 128 ! 22 1 . 128 129 129 129 1 129 1 23 1 133 134 136 139  35 1 24' 1 141 142 144 147 1 144 1 25 1 149 147 144 145 1 146 1 26 1 150 146 139 1 36  3 1 27 1 121 141 139 135 1 134 1 28 1 136 139 139 141 1 . 139 1 29 1 143 143 137 139 1 141 VOLTS X 55 - HP 60 APPENDIX E - SAMPLE OF COMPUTER GENERATED PLOT OF TRAINING HEART RATE ******************************************* * . SAKE: * * AGE: 53 YEARS * * SPORT: C a r c i a c Rehab * * DATE: JUNE 27,1982 * * UPPER LIMIT: 200-AGE-147 * * LOWER LIMIT: ' 170-AGE-117 * ******************************************* i i E A P T FATE VE TIME GRAPH 220 200 .H! ICC 14 0 120 IOC SO 6 0 10 + 4 6 8 10 12 14 16 16 20 22 24 26 26 2 01 1£L 160 ****** ** JtiM 12 0- 10,0' 60 60 C 2 4 6 8 10 12 14 16 18 20 22 24 26 23 30 TIME (min) 61 APPENDIX F - SAMPLE OF COMPUTER GENERATED PLOT OF MINUTE VENTILATION AiMAiJHJdJC ' i ' t iRi-JShULij CuHvl-J ve ( S T H L I ) VS T IMb ( n i n ) & o P C L l ) (mph) V e ( S i ' F D ) 64. 00 57.60 51.20 44.80 38.40 32. 00 25.60 19. 20 12.80 6.40 o.oo- I I I 0 1 2 3 4 5 6 7 3 9 10 1 1 12 1 3 3 4 1 5 If, 17 IS 19 20 3 4 5 6 7 -8 3 10 11 12 13 T IME ( m i n u t e s ) 3 P E X L ) ( n p h ) 62 APPENDIX G ~ SAMPLE OF COMPUTER GENERATED PLOT OF EXCESS CARBON DIOXIDE AnAtPOaiC liir-EtillOLlj CURVE E x c e s s C02 (ml/kg) vs U M t (min) i S r E E L (iron) Excess C02 (ul /ko) 14.00+ 12.604 11.20 9.8 0 8.404 7.00 5.60' 4.20' 2.80 1.40 0.00 i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f 0 1 2 3 4 5 6 7 8 9 10 11 12 13 ] 4 JS 16 ]7 18 19 2U 3 4 5 6 7 a <i 10 11 . 12 13 TIME (minutes) SPEED (rotih) 63 APPENDIX H - SAMPLE OF COMPUTER GENERATED PLOT OF RESPIRATORY EXCHANGE RATIO ~ ~ r . E . F . 1. 60 1.44 1.2 3 l . i ; 0. 96 C.SO 0.64 :.48 0.32 C. 16 0.00 A N A E R O B I C T H R E S H O L D C U R V E R . E . R . V E T I N E ( r a i n ) & EPiEC ( r p h ) * * * * * 1 2 3 4 5 6 7 6 3 4 5 6 9 10 11 12 13 14 15 16 17 18 19 20 7 6 9 10 11 12 'ilKE ( n i n u t e s ) S P E E D (ir.ch) 64 A P P E N D I X I - S A M P L E O F I N F O R M E D C O N S E N T F O R M PROTOCOL AND CONSENT FORM TITLE: HEART RATE AND ANAEROBIC THRESHCOLD IN EXERCISING CARDIAC PATIENTS THIS STUDY INVOLVES TWO PROCEDURES WHICH WILL BE DONE ON TWO SEPARATE OCCASIONS. THE INITIAL TEST WILL BE DONE AS PART OF YOUR USUAL EXERCISE PROGRAM DURING THE REGULAR CARDIAC REHAB- ILITATION EXERCISE SESSION. YOUR HEART RATE WILL BE MONITORED BY ATTACHING A SERIES OF ELECTRODES \J) TO YOUR CHEST AND HAVING YOU WEAR A SMALL BATTERY OPERATED RECORDING DEVICE. THIS WILL TAPE YOUR HEART RATE RESPONSE TO YOUR STANDARD EXERCISE ROUTINE. THERE IS NO DISCOMFORT AND YOU WILL NOT EVEN BE AWARE OF THE UNIT ONCE YOU ARE EXERCISING. THE TREADMILL EVALUATION WILL TAKE PLACE IN THE J.M. BUCHANAN FITNESS AND RESEARCH CENTRE ON THE U.B.C. CAMPUS. YOU WILL BE ASKED TO RUN ON A TREADMILL WITH A PROGRESSIVE INCREASE IN SPEED UNTIL YOU ARE UNABLE TO CONTINUE. YOUR HEART RATE WILL BE CON- TINUOUSLY MONITORED AND YOU WILL BE ASKED TO BREATHE THROUGH A MOUTHPIECE SO THAT YOUR EXPIRED AIR CAN BE COLLECTED AND ANALYZED. FROM THIS INFORMATION WE CAN CALCULATE YOUR ANAEROBIC THRESHOLD. THE RISKS OF THE TREADMILL RUN ARE MINIMAL, BUT IF ANY PROBLEMS DO ARISE THE LABORATORY DOES HAVE ALL NECESSARY MEDICAL EQUIP- MENT FOR TREATMENT OF EMERGENCIES AND THE TEST IS MONITORED BY A PHYSICIAN. ALL DATA WILL BE TREATED IN CONFIDENCE. IN REPORTING THE RE- SULTS, NAMES OF THE SUBJECTS WILL NOT BE USED. WE WILL BE HAPPY TO ANSWER ANY ENQUIRIES CONCERNING THE PROCEDURES OR THE STUDY IN GENERAL 1 CONSENT TO PARTICIPATE IN THIS RESEARCH PROJECT. 1 UNDERSTAND THAT I MAY WITHDRAW FROM THE STUDY AT ANY TIME WITHOUT PREJUDICE TO FUTURE CARE. (Signature) (Witness) (Date) Investigators: D.C. McKenzie L. Goodman 66 APPENDIX K - STEPWISE COREL-ATION MATRIX %V02maxAerT Vtam -age %HRmaxAerTHR AerTHR V02max -.11 . 79n HRmax -.20 .51 THR 1 3 0 %HRmaxTHR .16 Vtam # 4 6 _ n (P < .01) • (P < .05)

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