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UBC Theses and Dissertations

Variations in the ventilatory and lactate thresholds with prolonged aerobic exercise 1985

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VARIATIONS IN THE VENTILATORY AND LACTATE THRESHOLDS WITH PROLONGED AEROBIC EXERCISE by APOSTOLOS MAVROGIANNIS B.Ph.Ed. N a t i o n a l Academy o f P h y s i c a l E d u c a t i o n , G r e e c e , 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER IN PHYSICAL EDUCATION i n THE FACULTY OF GRADUATE STUDIES P h y s i c a l E d u c a t i o n and R e c r e a t i o n We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE © UNIVERSITY OF BRITISH COLUMBIA Ja n u a r y 1985 A p o s t o l o s M a v r o g i a n n i s , 1985 2? I n 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 o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e 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 a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e h e a d o f my d e p a r t m e n t o r b y h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f • P H Y S I C A L 8 D * J c 4 T / 0 / V Mf> R£C££/\TIQ/S T h e U n i v e r s i t y o f B r i t i s h C o l u m b i a 1956 Main M a l l V a n c o u v e r , C a n a d a V6T 1Y3 D a t e t ) ^ ^ a r y %CL) HPZ i i ABSTRACT The p u r p o s e o f t h i s s t u d y was t o examine the changes i n the v e n t i l a t o r y (VT) and l a c t a t e (LT) t h r e s h o l d s and VO^max f o l l o w i n g p r o l o n g e d a e r o b i c e x e r c i s e . S i x w e l l - t r a i n e d d i s t a n c e r u n n e r s (T:age=25.2 y r s , Ht=170.0 cm, Wt=65.0 kg, VC>2max=59.6 ml * k g - l ' m i n - 1 ) and s i x u n t r a i n e d (UT:age=25.3 y r s , Ht=180.3 cm, Wt=79.2 kg, V0 2max=46.8 m l ' k g - 1 * m i n - l ) males were s t u d i e d on two o c c a s i o n s seven days a p a r t . The i n i t i a l e v a l u a t i o n i n v o l v e d a c o n t i n u o u s h o r i z o n t a l t r e a d m i l l t e s t w i t h a s t a r t i n g v e l o c i t y o f 2.22 m " s ~ l , w h i c h was i n c r e a s e d by 0.22 m*s~l each minute u n t i l f a t i g u e . E x p i r e d gases were c o n t i n u o u s l y sampled and a n a l y z e d by a Beckman M e t a b o l i c Measurement C a r t . M e a s u r e m e n t s were p r o c e s s e d by a d a t a a c q u i s i t i o n s y s t e m (HP 3052A), which d e t e r m i n e d r e s p i r a t o r y gas exchange v a r i a b l e s e v e r y 15 s e c o n d s . B l o o d l a c t a t e m easurements were t a k e n v i a an i n d w e l l i n g c a t h e t e r d u r i n g t h e l a s t 10 sec of each minute of work. VT and LT were de t e r m i n e d by v i s u a l i n s p e c t i o n of the e x c e s s CO2 e l i m i n a t i o n and l a c t a t e c u r v e s , r e s p e c t i v e l y . Seven days l a t e r t h e s u b j e c t s r e p e a t e d t h e t r e a d m i l l t e s t p r e c e d e d by a 60 minu t e t r e a d m i l l run a t a h e a r t r a t e c o r - r e s p o n d i n g t o t h e i r LT. The p h y s i o l o g i c a l measurements r e c o r d e d d u r i n g the f i r s t s e s s i o n were r e p e a t e d . There were s i g n i f i c a n t (p<0.10) r e d u c t i o n s i n VC^max, LT, VT, and t o t a l t r e a d m i l l t i m e on t h e V0 2max t e s t (TTT) i n the T group (59.6 t o 56.9 ml ' k g - 1 ' m i n - 1 , 9.6 t o 9.3 mph , 8.9 t o 8.2 mph , and 925.0 t o 882.5 s e c , r e s p e c t i v e l y ) . V0 2max, LT, VT, and TTT were i i i r e d u c e d i n t h e UT g r o u p (46.8 t o 45.0 m l ' k g - 1 ' r a i n - 1 , 7.7 t o 7.6 raph, 8.0 t o 7.2 mph, and 730.0 t o 652.5 s e c , r e s p e c t i v e l y ) , however, o n l y VT and TTT were reduced s i g n i f i c a n t l y (p<0.10). A l t h o u g h t h e g r o u p s were s i g n i f i c a n t l y d i f f e r e n t (p<0.05) i n the i n i t i a l p h y s i o l o g i c a l measures due t o t r a i n i n g s t a t u s , t h e r e was no change i n t h e r a t e o f d e c l i n e i n VC^max, LT, VT, or TTT when the UT group was compared t o T. As LT and VT are a f f e c t e d by p r o l o n g e d a e r o b i c e x e r c i s e i t i s q u e s t i o n a b l e whether th e s e t h r e s h o l d s can be used w i t h c o n f i d e n c e t o p r e d i c t e n d u r a n c e p e r f o r m a n c e i n e v e n t s up t o 60 min d u r a t i o n f o r w e l l - t r a i n e d and r e c r e a t i o n a l a t h l e t e s . i v TABLE OF CONTENTS A b s t r a c t i i L i s t of T a b l e s v>. L i s t of F i g u r e s . v i Acknowledgment v i i I . INTRODUCTION 1 I I . METHODS 5 I I I . RESULTS 8 IV. DISCUSSION 13 V. REFERENCES 19 APPENDIX A - REVIEW OF LITERATURE 29 I n t r o d u c t i o n 29 Measurement and D e t e r m i n a t i o n of the AT 30 AT and V a r i o u s Modes of E x e r c i s e 41 The R e l a t i o n s h i p between the Onset of M e t a b o l i c A c i d o s i s and H y p e r v e n t i l a t i o n 46 T r a i n i n g and AT 48 AT A l t e r a t i o n s f o l l o w i n g P r o l o n g e d A e r o b i c E x e r c i s e 57 P e r c e i v e d E x e r t i o n R e l a t i v e t o AT 59 AT R e l a t i o n s h i p s w i t h V a r i o u s M e t a b o l i c Parameters 61 AT as a P r e d i c t o r of D i s t a n c e Performance and i t s R e l a t i o n s h i p w i t h Race Pace 63 Heart Rate I n d i c e s and AT 68 AT A l t e r a t i o n s w i t h Changes i n S u b s t r a t e A v a i l a b i l i t y 70 Summary 72 APPENDIX B - MARGINALS 75 APPENDIX C - INDIVIDUAL SUBJECTS PHYSIOLOGICAL DATA 76 APPENDIX D - BLOOD LACTATE VALUES 77 LIST OF TABLES P h y s i c a l C h a r a c t e r i s t i c s of S u b j e c t s P h y s i o l o g i c a l Data of S u b j e c t s v i LIST OF FIGURES 1. L a c t a t e Curve 78 2. Excess C 0 2 Curve 79 3. L a c t a t e and V e n t i l a t o r y T h r e s h o l d V a l u e s 12 v - i i ACKNOWLEDGMENT I would l i k e t o thank the members of my committee, Dr. D. Mc k e n z i e , Dr. J . Taunton, and Dr. K. C o u t t s . I would e s p e c i a l l y l i k e t o t h a n k my a d v i s o r Dr. D. Mckenzie f o r h i s i n v a l u a b l e g u idance and a s s i s t a n c e d u r i n g my f i r s t s t e p s o f r e s e a r c h . Thanks a l s o extended t o J . P o t t s and B. L o r d f o r t h e i r h e l p . F i n a l l y , I w i s h t o acknowledge my g r a t i t u d e t o my p a r e n t s , f o r t h e i r i n e x h a u s t i b l e s u p p o r t . W i t h o u t t h e i r s a c r i f i c e t h i s achievement would not have been p o s s i b l e . For a l l t h e i r s u f f e r i n g I d e d i c a t e t h i s p r o j e c t t o them. I. INTRODUCTION The energy r e q u i r e m e n t s of b r i e f , h i g h - i n t e n s i t y ( a n a e r o b i c ) and p r o l o n g e d , l o w - i n t e n s i t y ( a e r o b i c ) e x e r c i s e a r e w e l l u n d e r s t o o d ( G o l l n i c k and Hermansen 1973, A r m s t r o n g 1976, H o l l o s z l y 1975). C o n t r o v e r s y e x i s t s , however, i n e x p l a i n i n g the phenomenon of t r a n s i t i o n from a e r o b i c t o a n a e r o b i c m e t a b o l i s m d u r i n g p r o l o n g e d i n t e n s e p h y s i c a l a c t i v i t y . T h i s phenomenon was f i r s t i n v e s t i g a t e d by Wasserman e t a l . ( 1 9 6 4 , 1 9 7 3 ) ; they o b s e r v e d i n c r e a s e s i n both b l o o d l a c t a t e and r e s p i r a t o r y e x c h a n g e v a r i a b l e s above r e s t i n g l e v e l s d u r i n g i n c r e m e n t a l e x e r c i s e t o f a t i g u e . They d e f i n e d the l e v e l of work o r oxygen c o n s u m p t i o n j u s t below t h a t a t which m e t a b o l i c a c i d o s i s and the a s s o c i a t e d changes i n gas exchange o c c u r as the " a n a e r o b i c t h r e s h o l d " . I n v e s t i g a t o r s have e i t h e r i n v a s i v e l y d e t e r m i n e d t h e a n a e r o b i c t h r e s h o l d w i t h s e r i a l b l o o d l a c t a t e s ( M c L e l l a n e t a l . 1981, Simon e t a l . 1982, Y o s h i d a e t a l . 1981) o r non- i n v a s i v e l y w i t h such v a r i a b l e s as , V C O 2, R, FEO2 a n d F E C 0 2 (Wasserman e t a l . 1973, Simon e t a l . 1982, Rupp 1981), V g / V C 0 2 , v E / v 0 2 ( M c L e l l a n e t a l . 1981, D a v i s e t a l . 1983, C a i o z z o e t a l . 1982), 0 2 P (Sankar e t a l . 1978), and exces s CO2 ( V o l k o v e t a l . 1975, Rhodes and M c k e n z i e 1 9 8 4 ) , d u r i n g i n c r e m e n t a l e x e r c i s e t o f a t i g u e . The a n a e r o b i c t h r e s h o l d was d e f i n e d as the n o n l i n e a r i n c r e a s e i n the above d e s i g n a t e d v a r i a b l e s p l o t t e d o v e r t i m e d u r i n g p r o g r e s s i v e i n c r e a s e s i n w o r k l o a d . 1 However, K i n d e r m a n e t a l . ( 1 9 7 9 ) and S k i n n e r and M c L e l l a n (1980) have r e c o r d e d two "breakaway" p o i n t s ; the f i r s t , c o r - r e s p o n d i n g t o 2 mM/1 l a c t a t e and t o t h e f i r s t s i g n i f i c a n t n o n l i n e a r i n c r e a s e of Vg and R was termed a e r o b i c t h r e s h o l d . The second, c o r r e s p o n d i n g t o t h e s t e e p p a r t o f e x p o n e n t i a l i n c r e a s e i n l a c t a t e c o n c e n t r a t i o n of 4 mM/1 l a c t a t e was termed a n a e r o b i c t h r e s h o l d . The c o r r e l a t i o n between the gas exchange measurement and the venous b l o o d l a c t a t e measurement of the a n a e r o b i c t h r e s h o l d was found t o be h i g h l y s i g n i f i c a n t , r=0.95 ( D a v i s e t a l . , 1 9 7 6 ) . These two measurements were f o u n d to be v e r y r e p r o d u c i b l e (Sucec e t a l . , 1982). The a s s o c i a t i o n between the "breakaway" p o i n t s i n v e n t i l a t o r y and b l o o d l a c t a t e v a r i a b l e s was b e l i e v e d t o be due t o t h e r e l e a s e of H + which i n c r e a s e s COg d e l i v e r y t o the l u n g s and, s u b s e q u e n t l y , s t i m u l a t i n g t h e a b r u p t i n c r e a s e i n v e n t i l a t i o n (Wasserraan e t a l . 1973, Whipp and D a v i s 1 9 7 9 ) . However, s e v e r a l r e s e a r c h e r s have demonstrated t h a t t h e s e a b r u p t changes i n b o t h v e n t i l a t i o n and b l o o d l a c t a t e d u r i n g i n c r e m e n t a l e x e r c i s e a r e n o t c a u s a l b u t r a t h e r c o i n c i d e n t a l ( H a g b e r g e t a l . 1982, F a r r e l l e t a l . 1983, M o r r i s o n e t a l . 1 9 8 3 ) . R e c e n t l y , i n v e s t i g a t o r s r e a l i z i n g t h e o v e r s i m p l i f i c a t i o n o f t h e p h y s i o l o g i c a l e v e n t s r e p r e s e n t e d by t h e a n a e r o b i c t h r e s h o l d t e rmed t h e t h r e s h o l d d e t e r m i n e d by gas e x c h a n g e measurements as the v e n t i l a t o r y t h r e s h o l d (Hagberg et a l . 1982, Reybrouck e t a l . 1982, 1983), w h i l e t h a t determined by l a c t a t e measurements as the l a c t a t e t h r e s h o l d ( I v y e t a l . 1980, 1981, Gilman and Lemon 1982, DePasquale e t a l . 1983). R e s e a r c h has shown t h a t s u c c e s s i n d i s t a n c e r u n n i n g i s i n f l u e n c e d by s u c h f a c t o r s as VC^max, r u n n i n g economy, muscle f i b e r c o m p o s i t i o n , s u b s t r a t e a v a i l a b i l i t y , o n s e t o f plasma l a c t a t e , and a n a e r o b i c t h r e s h o l d ( C o s t i l l e t a l . 1971, 1976, B ergstrom e t a l . 1967, D a n i e l s 1974, Rusko e t a l . 1978, Wyndham e t a l . 1969, F a r r e l l e t a l . 1979). The importance and a p p l i c a t i o n of the l a t t e r i n d i s t a n c e r u n n i n g i s c o n s i d e r a b l e ; t h e a t h l e t e who knows h i s a n a e r o b i c t h r e s h o l d i s a b l e t o choose a r u n n i n g pace at which he e x e r c i s e s a e r o b i c a l l y w i t h o u t d e l v i n g i n t o a n a e r o b i c m e t a b o l i s m and, c o n s e q u e n t l y , a v o i d i n g f a t i g u e and the t e r m i n a t i o n of e x e r c i s e due t o l a c t a t e a c - c u m u l a t i o n (Rhodes and M c K e n z i e , 1 9 8 4 ) . O t h e r p e r t i n e n t a p p l i c a t i o n s of the a n a e r o b i c t h r e s h o l d i n c l u d e : 1) e x e r c i s e p r e s c r i p t i o n (Dwyer and Bybee, 1983) , 2) c h a r a c t e r i z i n g endurance a t h l e t e s (Rusko et a l . , 1 9 8 0 ) , and 3) p r e d i c t i n g e n d u r a n c e p e r f o r m a n c e ( S j o d i n and J a c o b s 1981, Tanaka e t a l . 1983, Rhodes and McKenzie 1984) . While r u n n i n g a t a n a e r o b i c t h r e s h o l d speed an e q u i l i b r i u m e x i s t s between the amount of oxygen t r a n s p o r t e d t o and t h a t needed by t h e t i s s u e s ; t h e o r e t i c a l l y , the e x e r c i s e can l a s t i n d e f i n i t e l y . However, f a c t o r s such as e l e v a t i o n of t e m p e r a t u r e , e l e c t r o l y t e and f l u i d u n b a l a n c e , d e p l e t i o n of g l y c o g e n s t o r e s , and the s h i f t of m u s c l e f i b e r s r e c r u i t e d f r o m s l o w t w i t c h (ST) t o f a s t t w i t c h ( F T ) c a u s e t h e a t h l e t e t o e x p e r i e n c e f a t i g u e . One a s s u m p t i o n i n u s i n g t h e a n a e r o b i c t h r e s h o l d t o p r e d i c t endurance performance was t h a t t h i s v a r i a b l e does not change thr o u g h o u t the e v e n t . However, i t i s q u e s t i o n a b l e whether the a n a e r o b i c t h r e s h o l d s t a y s unchanged i n the c o u r s e of p r o l o n g e d a e r o b i c e x e r c i s e so t h a t i t can be used w i t h a c c u r a c y f o r time p r e d i c t i o n . Indeed, W i s w e l l e t a l . (1980) r e p o r t e d a 10.7% d e c r e a s e o f t h e a n a e r o b i c t h r e s h o l d and 8.4% d e c r e a s e i n VO^max f o l l o w i n g 2 hours of e x h a u s t i v e r u n n i n g i n m a r a t h o n r u n n e r s ( a v e r a g e V02max=57.3 m l / k g / m i n ) . The s i g n i f i c a n t l y l o w e r R t h a t was f o u n d p o s t e x e r c i s e i n t h i s s t u d y i n d i c a t e d a change i n the type of f u e l s u b s t r a t e u t i l i z e d and the l o w e r i n g of the a n a e r o b i c t h r e s h o l d was a t t r i b u t e d t o the r e d u c t i o n of muscle g l y c o g e n . The above s t u d y i n v e s t i g a t e d the f a t e of the a n a e r o b i c t h r e s h o l d a f t e r a v e r y p r o l o n g e d a e r o b i c e x e r c i s e which caused d e p l e t i o n of muscle g l y c o g e n s t o r a g e . The l i t e r a t u r e r e v e a l s a l a c k of i n f o r m a t i o n about the s t a t e of the a n a e r o b i c t h r e s h o l d i n l e s s p r o l o n g e d a e r o b i c e x e r c i s e where t h e i n d i v i d u a l s a r e not g l y c o g e n d e p l e t e d . Thus t h e p u r p o s e o f t h i s s t u d y was t o d e t e r m i n e the e f f e c t of one hour of a e r o b i c e x e r c i s e on t h e v e n t i l a t o r y and l a c t a t e i n f l e c t i o n p o i n t s and VG^max of u n t r a i n e d s u b j e c t s and t r a i n e d r u n n e r s . I I . METHODS S u b j e c t s . S i x w e l l - t r a i n e d d i s t a n c e r u n n e r s and s i x u n t r a i n e d m a l e s v o l u n t e e r e d f o r t h e s t u d y . The p r o c e d u r e s and t e s t s were e x p l a i n e d and inf o r m e d consent was o b t a i n e d . The s e l e c t i o n o f s u b j e c t s was s u c h t h a t the r u n n e r s had been t r a i n e d and competed i n road r a c e s from 10km up t o the marathon f o r more t h a n 4 y e a r s , w h i l e t h e u n t r a i n e d were not i n v o l v e d i n any r e g u l a r a c t i v i t i e s . They were i n s t r u c t e d t o consume a mixed d i e t f o r 3 da y s p r i o r t o the t e s t i n g day and, i n a d d i t i o n , t h e r u n n e r s m o d i f i e d t h e i r t r a i n i n g . T h i s p r o c e d u r e has shown t o r e s u l t i n s i m i l a r p r e t e s t muscle g l y c o g e n c o n c e n t r a t i o n s ( M i l l e r e t a l . , 1983). They were a l s o asked t o r e f r a i n from e a t i n g o r d r i n k i n g 2 h o u r s b e f o r e t h e i r s c h e d u l e d t e s t i n g time and from t r a i n i n g on t h e i r t e s t i n g day. Pr o c e d u r e • Data c o l l e c t i o n took p l a c e on two s e s s i o n s a p p r o x i - m a t e l y 7 da y s a p a r t . T h i s time p e r i o d was chosen t o a v o i d f l u c t u a t i o n s i n both body w e i g h t and p h y s i c a l c o n d i t i o n i n g of the s u b j e c t s . The e v a l u a t i o n of the p h y s i o l o g i c a l c h a r a c t e r - i s t i c s of the s u b j e c t s i n v o l v e d a c o n t i n u o u s h o r i z o n t a l t r e a d m i l l t e s t w i t h a s t a r t i n g v e l o c i t y o f 2.22 m*s - 1. F o l l o w i n g a 5- m i n u t e warm-up, t h e v e l o c i t y was i n c r e a s e d by 0.22 m*s~l each minute u n t i l v o l i t i o n a l f a t i g u e . E x p i r e d g a s e s were c o n t i n u o u s l y s a m p l e d and a n a l y z e d by a Beckman M e t a b o l i c C a r t . M e a s u r e m e n t s were p r o c e s s e d by a d a t a a c q u i s i t i o n system ( H e w l e t t Packard 3052 A ) , which d e t e r m i n e d r e s p i r a t o r y 5 gas e x c h a n g e v a r i a b l e s e v e r y 15 s e c o n d s . M a x i m a l o x y g e n c o n s u m p t i o n was d e t e r m i n e d by a v e r a g i n g t h e f o u r h i g h e s t c o n s e c u t i v e 15-second v a l u e s . H e a r t r a t e was c o n t i n u o u s l y m o n i t o r e d by d i r e c t l e a d ECG ( A v i o n i c s E l e c t r o c a r d i o g r a p h 4000) . B l o o d l a c t a t e measurements were taken from each s u b j e c t by p l a c i n g , u n d e r s t e r i l e t e c h n i q u e , a 20 g c a t h e t e r (32 mm) i n t h e c e p h a l i c v e i n . T h i s a p p r o a c h a l l o w e d a r a p i d and easy s a m p l i n g of venous b l o o d w i t h o u t i n t e r f e r i n g w i t h t h e r u n n i n g t e c h n i q u e o f t h e s u b j e c t s . The b l o o d samples were taken d u r i n g the l a s t 10 seconds of each minute of work. The b l o o d samples were c e n t r i f u g e d and the serum was f r o z e n . The serum was l a t e r a n a l y z e d f o r l a c t a t e v i a an a u t o m a t e d e l e c t r o c h e m i c a l t e c h n i q u e ( K o n t r o n 640; R a c i n e e t a l . 1975, G u i l l o t e t a l . 1976). Bl o o d l a c t a t e v a l u e s were p l o t t e d v e r s u s t r e a d m i l l speed. The l a c t a t e t h r e s h o l d was d e t e r m i n e d by v i s u a l i n s p e c t i o n o f t h e l a c t a t e c u r v e ; t h e f i r s t "breakaway" p o i n t was the i n d i c a t o r of the l a c t a t e t h r e s h o l d ( f i g . 1) and was e s t a b l i s h e d i n d e p e n d e n t l y by two r e s e a r c h e r s . S i m i l a r l y , by examining the e x c e s s CO2 e l i m i n a t i o n c u r v e s f o r each s u b j e c t the v e n t i l a t o r y t h r e s h o l d was d e t e r m i n e d ( V o l k o v e t a l . 1975, Rhodes and M c K e n z i e 1984) ( f i g . 2 ) . The r e l i a b i l i t y o f t h e s e methods have been r e p o r t e d e l s e w h e r e ( S u c e c e t a l . 1982, Goodman 1982) . D u r i n g the second s e s s i o n the s u b j e c t s r a n f o r 60 minutes on the t r e a d m i l l a t a h e a r t r a t e c o r r e s p o n d i n g t o t h e i r l a c t a t e t h r e s h o l d . T h i s h e a r t r a t e was a t t a i n e d w i t h i n 10 minutes of work. I t was m o n i t o r e d every 5 minutes and when i t exceeded the l a c t a t e t h r e s h o l d v a l u e , the t r e a d m i l l speed was r e d u c e d , a c c o r d i n g l y . The s u b j e c t s were a l l o w e d t o d r i n k w a t e r . Room temperature was m a i n t a i n e d a t 23°C. F o l l o w i n g the 60-minute run the t r e a d m i l l was stopped f o r 2-10 minutes t o a p p l y t h e gas c o l l e c t i o n a p p a r a t u s and t o a l l o w any e l e v a t i o n i n b l o o d l a c t a t e t o r e t u r n t o n o r m a l . The s u b j e c t s t h e n r e p e a t e d the i n i t i a l t e s t t o e x h a u s t i o n . The p h y s i o l o g i c a l parameters measured d u r i n g the f i r s t s e s s i o n were r e - e v a l u a t e d . S t a t i s t i c a l A n a l y s i s . The s t a t i s t i c a l s i g n i f i c a n c e of the d a t a was e v a l u a t e d u s i n g t h r e e two-way MANOVA d e s i g n s . The c h o s e n l e v e l o f s i g n i f i c a n c e was p<0.05. M u l t i p l e comparisons u s i n g S c h e f f e ' s method were f u r t h e r a p p l i e d t o d e t e c t s i g n i f i c a n t d i f f e r e n c e s between pre and p o s t v a l u e s . The 10 p e r c e n t l e v e l of s i g n i f i c a n c e was used f o r t h e s e comparisons ( S c h e f f e \ 1959). 8 I I I . RESULTS P h y s i c a l c h a r a c t e r i s t i c s of the s u b j e c t s a re p r e s e n t e d i n T a ble 1. TABLE 1. Physical C h a r a c t e r i s t i c s of Subjects (Means + SD) Measures T r a i n e d (n=6) Untrained (n=6) Age ( y e a r ) H e i g h t (cm) Weight (kg) V0 2max ( m l ' k g - 1 m i n - ! ) 25.2+2 .0 170.0+5.4 65.0+3 .9 59.6+2.7 25.3+3.1 180.5+10.1 79.2+10.0* 46.8+3.2* * S i g n i f i c a n t d i f f e r e n c e s between groups a t p<0.05 The s t a t i s t i c a l d i f f e r e n c e s i n V02max between groups r e f l e c t e d t h e i r t r a i n i n g s t a t u s . I n a d d i t i o n , t h e t r a i n e d r u n n e r s weighed s i g n i f i c a n t l y l e s s than the u n t r a i n e d s u b j e c t s . The p h y s i o l o g i c a l d a t a i s summarized i n Table 2. V02max av e r a g e d 59.6+2.7 and 46.8+3.2 m l ' k g - 1 * m i n - 1 f o r the t r a i n e d r u n n e r s and u n t r a i n e d i n d i v i d u a l s , r e s p e c t i v e l y . These v a l u e s were reduced t o 56 .9+2 .8 and 45 .0+2 .6 ml * k g - 1 ' m i n - 1 , r e s p e c t i v e l y , f o l l o w i n g t h e o n e - h o u r t r e a d m i l l r u n . However, o n l y t h e t r a i n e d r u n n e r s ' r e d u c t i o n was s i g n i f i c a n t (p<0.10). The l a c t a t e t h r e s h o l d was f o u n d t o o c c u r a t 9.6 + 0.8 and 7.7+0.5 mph f o r the t r a i n e d and u n t r a i n e d s u b j e c t s , r e s - p e c t i v e l y . The 60-min run caused r e d u c t i o n s i n both of the s e t h r e s h o l d s t o 9.3+0.7 mph ( t r a i n e d ) and 7.6+0.3 mph ( u n t r a i n e d ) , but o n l y the t r a i n e d s u b j e c t s ' v a l u e was s i g n i f i c a n t l y (p<0.10) d i f f e r e n t ( f i g . 3 ) . The p r o l o n g e d a e r o b i c e x e r c i s e d i d not change s i g n i f i c a n t l y t h e p e r c e n t a g e of 0 2 consumption c o r - responding t o the l a c t a t e t h r e s h o l d ; T r a i n e d : 81.5+9.3 v e r s u s 82.7+8.9 (%VC>2max) and U n t r a i n e d : 80.2+6.5 v e r s u s 82.2+4.8 ( % V 0 2 m a x ) . The v e n t i l a t o r y t h r e s h o l d was r e c o r d e d a t 8.9+0.8 mph ( t r a i n e d ) and 8.0+0.6 mph ( u n t r a i n e d ) . The 60-min run s i g n i f i - c a n t l y (p<0.10) s h i f t e d these v a l u e s t o 8.2+0.6 mph ( t r a i n e d ) and 7.2+0.5 mph ( u n t r a i n e d ) ( f i g . 3 ) . As i n the case of the l a c t a t e t h r e s h o l d , the percentage of O2 consumption c o r r e s p o n d i n g t o the v e n t i l a t o r y t h r e s h o l d d i d not change s i g n i f i c a n t l y i n b o t h g r o u p s ; T r a i n e d : 76.1+8.6 v e r s u s 73.4+8.7 (XVO^max) and U n t r a i n e d : 81.5+7.6 v e r s u s 78.5+6.5 ( % V 0 2 m a x ) . Furthermore, i t was observed t h a t a l t h o u g h the l a c t a t e t h r e s h o l d (%VQ2max) tended t o i n c r e a s e f o l l o w i n g the 60-min r u n , the v e n t i l a t o r y t h r e s h o l d (XVO^max) moved i n the o p p o s i t e d i r e c t i o n . The t o t a l t r e a d m i l l t i m e (TTT) on the V0 2max t e s t was s i g n i f i c a n t l y (p<0.10) r e d u c e d i n both t r a i n e d (925.0+61.9 v e r s u s 882.5+77.3 sec) and u n t r a i n e d (730.0+52.5 v e r s u s 652.5+75.7 sec) s u b j e c t s . No s i g n i f i c a n t changes were observed i n the h e a r t r a t e s at the time the l a c t a t e t h r e s h o l d o c c u r r e d ; T r a i n e d : 166.5+8.3 v e r s u s 167.3+9.0 ( b / m i n ) and U n t r a i n e d : 167.3+8.3 v e r s u s 167.0+11.1 (b/min). The r e s p i r a t o r y q u o t i e n t c o r r e s p o n d i n g t o the l a c t a t e t h r e s h o l d was s i g n i f i c a n t l y (p<0.10) reduced i n both t r a i n e d (0.99+0.06 v e r s u s 0.95+0.03) and u n t r a i n e d (1.04+0.03 v e r s u s 0.96+0.04) s u b j e c t s . The v e n t i l a t o r y and l a c t a t e t h r e s h o l d s ( e x p r e s s e d i n %V0 2max). c o r r e l a t e d v e r y low; rf=0.42 and ruT=0.54. F i n a l l y , no s i g n i f i c a n t i n t e r a c t i o n s were o b t a i n e d i n any of the v a r i a b l e s measured. Thus we c o n c l u d e t h a t t r a i n i n g s t a t u s seemed t o have no e f f e c t on t h e c h a n g e s o b s e r v e d . However, by v i s u a l l y e x a m i n i n g t h e d a t a we s p e c u l a t e d t h a t we m i g h t o b t a i n u n e q u a l c h a n g e s i n some of the v a r i a b l e s . Indeed, by u s i n g S c h e f f e " t e s t s , i n two of the v a r i a b l e s ( l a c t a t e t h r e s h o l d , V02tnax) t h e g r o u p s d i d n o t show e q u a l c h a n g e s between p r e - p o s t , a l t h o u g h the o v e r a l l i n t e r a c t i o n was non- s i g n i f i c a n t . 11 TABLE 2 . P h y s i o l o g i c a l Data of Subjects (Means+SD) T r a i n e d (n=6) U n t r a i n e d (n=6) Measures Pre P o s t Pre P o s t LT (mph) 9.6+0.8 9.3+0.7* 7.7+0.5 7.6+0.3 • LT (%V0 2max) 81.5+9.3 82.7+8.9 80.2+6.5 82.2+4.8 VT (mph) 8.9+0 .8 8.2+0.6* 8.0+0 .6 7.2+0.5* • VT (%V0 2max) 76.1+8.6 73.4+8.7 81.5+7.6 78.5+6.5 • V0 2max ( m l * k g - l * m i n 59.6+2 .7 56.9+2.8* 46.8+3.2 45.0+2.6 - 1) TTT ( s e c ) 925.0+61.9 882.5+77.3* 730.0+52.5 652^75.7* HR LT (b/min) 166.5+8.3 167.3+9.0 167.3+8.3 167.0+11.1 RLT 0.99+0.06 0.95+0.03* 1.04+0.03 0.96jO.O4* LT : L a c t a t e t h r e s h o l d YT : V e n t i l a t o r y t h r e s h o l d V0 2max : Maximum 0 2 consumption TTT : T o t a l t r e a d m i l l time on the V0 2max t e s t HRLT ' Heart r a t e a t the l a c t a t e t h r e s h o l d RLX • R e s p i r a t o r y q u o t i e n t a t the l a c t a t e t h r e s h o l d * S i g n i f i c a n t d i f f e r e n c e s between p r e - p o s t a t p<0.10 FIGURE 3. Lactate (LT) and ventilatory (VT) threshold values before and after 60 mln of exercise.Trained ( ) versus untrained ( ). The asterisk indicates significant differences between prepost at p<0.05. IV. DISCUSSION The s u b j e c t s examined i n t h i s s tudy c o n s t i t u t e two h e t e r o - geneous groups; w e l l - t r a i n e d endurance a t h l e t e s and u n t r a i n e d • i n d i v i d u a l s . D i f f e r e n c e s i n VC^max, l a c t a t e and v e n t i l a t o r y t h r e s h o l d a r e a t t r i b u t e d t o t h e t r a i n i n g s t a t u s . P r e v i o u s e v i d e n c e (Dunwoody and Rhodes 1981, Rhodes and McKenzie 1984, V o l k o v e t a l . 1975, M a c D o u g a l l 1977) s u p p o r t s o u r f i n d i n g t h a t t r a i n e d i n d i v i d u a l s have h i g h e r VC^max, l a c t a t e and v e n t i l a t o r y t h r e s h o l d s than u n t r a i n e d i n d i v i d u a l s . No s i g n i f i c a n t d i f f e r e n c e s were f o u n d , however, on the t h r e s h o l d s between the two groups when they were e x p r e s s e d as a p e r c e n t a g e o f • V02max. T h i s f i n d i n g i s i n agreement w i t h Parkhouse e t a l . ( 1 9 8 2 ) . As i t was e x p e c t e d , the w e l l - t r a i n e d s u b j e c t s l a s t e d a much l o n g e r t i m e on t h e VC^max t e s t t h a n t h e u n t r a i n e d s u b j e c t s . F i n a l l y , t h e h e a r t r a t e s c o r r e s p o n d i n g t o t h e l a c t a t e t h r e s h o l d were n o t s i g n i f i c a n t l y d i f f e r e n t between the g r o u p s . Parkhouse et a l . (1982) r e p o r t e d s i m i l a r v a l u e s f o r h e a r t r a t e s c o r r e s p o n d i n g t o the v e n t i l a t o r y t h r e s h o l d i n t h r e e groups w i t h d i f f e r e n t f i t n e s s l e v e l s . I v y e t a l . ( 1 9 8 1 ) , K o w a l c h u k and Hughson ( 1 9 8 1 ) , and Hughes e t a l . (1982) have shown t h a t s u b s t r a t e a v a i l a b i l i t y a f f e c t s t h e l a c t a t e and v e n t i l a t o r y t h r e s h o l d . Thus i t was of h i g h i m p o r t a n c e t o c o n s i d e r a s p e c i a l t r a i n i n g and d i e t m o d i f i c a t i o n p r i o r t o t h e t e s t i n g . We f e e l c o n f i d e n t t h a t the p r o c e d u r e we f o l l o w e d r e s u l t e d i n s i m i l a r p r e t e s t muscle g l y c o g e n c o n c e n t r a t i o n s ( M i l l e r e t a l . , 1983). In a d d i t i o n , 13 t h e i n t e n s i t y and d u r a t i o n o f o u r e x e r c i s e p r o t o c o l were such t h a t i t e x c l u d e d a s i g n i f i c a n t muscle g l y c o g e n d e p l e t i o n which would cause f a t i g u e ; i n e x h a u s t i v e r u n s o f 72.5 min a t 8 0% o f V02max ( C o s t i l l e t a l . , 1971-b), 69.4 min a t 80% V0 2max ( C o s t i l l e t a l . , 1971-c) , and 83 min a t 86% of V02max (Sherman e t a l . , 1981) m u s c l e g l y c o g e n d e p l e t i o n has n o t been i m p l i c a t e d as the cause of the f a t i g u e . C o n s e q u e n t l y , the r e s u l t s o b t a i n e d i n t h i s s t u d y a r e h o t a t t r i b u t e d t o the d e p l e t i o n of muscle g l y c o g e n s t o r e s . Keeping the l a b o r a t o r y a t c o n s t a n t t e m p e r a t u r e a v o i d e d e n v i r o n m e n t a l induced v a r i a t i o n s i n t h e m e t a b o l i c r e s p o n s e t o e x e r c i s e which has been shown t o a f f e c t the l a c t a t e t h r e s h o l d ( Gilman and Lemon, 1982). F o l l o w i n g t h e 60-min r u n t h e t r a i n e d s u b j e c t s showed s i g n i f i c a n t r e d u c t i o n s i n VC^max, l a c t a t e and v e n t i l a t o r y t h r e s h o l d , and t o t a l t r e a d m i l l time on the VC^max t e s t ; 4.5%, 3.1%, 7.9%, and 4.6%, r e s p e c t i v e l y . W i s w e l l e t a l . ( 1 9 8 0 ) , r e p o r t e d an 8.4% and 10.7% r e d u c t i o n s i n VC^max and v e n t i l a t o r y t h r e s h o l d , r e s p e c t i v e l y , f o l l o w i n g 2 h o u r s o f e x h a u s t i v e r u n n i n g i n m a r a t h o n r u n n e r s w i t h a s i m i l a r f i t n e s s l e v e l (V02max = 57.3 ml * k g - 1 " m i n - 1 ) as our t r a i n e d group. The h i g h i n t e n s i t y and the l o n g d u r a t i o n of the e x e r c i s e i n t h a t s t u d y and , p a r t i c u l a r l y , the s i g n i f i c a n t l y lower R t h a t was found p o s t - e x e r c i s e i n d i c a t e d a change i n the type of f u e l s u b s t r a t e u t i l i z e d . C o n s e q u e n t l y , t h e l o w e r i n g o f t h e v e n t i l a t o r y t h r e s h o l d was a t t r i b u t e d t o the r e d u c t i o n of muscle g l y c o g e n . V02max, l a c t a t e and v e n t i l a t o r y t h r e s h o l d , and t o t a l t r e a d m i l l t i m e on t h e VC^max t e s t were a l s o d e c r e a s e d i n the u n t r a i n e d s u b j e c t s by 3.8%, 1.3%, 10.0%, and 10.6%, r e s - p e c t i v e l y . However, o n l y the l a s t two v a r i a b l e s were s i g n - i f i c a n t l y d i f f e r e n t . Due t o l a c k o f p e r t i n e n t i n f o r m a t i o n i n t he l i t e r a t u r e we cannot compare t h e s e f i n d i n g s w i t h o t h e r s t u d i e s . In b o t h g r o u p s , t h e l a c t a t e and v e n t i l a t o r y t h r e s h o l d s e x p r e s s e d i n %V02max, as w e l l a s , the h e a r t r a t e c o r r e s p o n d i n g t o the l a c t a t e t h r e s h o l d showed no s i g n i f i c a n t changes f o l l o w i n g the 60-min r u n . F o r t h e r e a s o n s we p r o p o s e d above we do n o t b e l i e v e t h a t t h o s e c h a n g e s o b t a i n e d f o l l o w i n g t h e 60-min r u n a r e a t t r i b u t e d t o the muscle g l y c o g e n d e p l e t i o n . Our s p e c u l a t i o n i s f u r t h e r s u p p o r t e d by t h e p o s t - R v a l u e s we o b t a i n e d ; i f t h e s u b j e c t s were g l y c o g e n d e p l e t e d t h e i r R a t the l a c t a t e t h r e s h o l d would have e x p e c t e d t o be c l o s e t o 0.70, c o n t r a r y t o 0.95(T) and 0.96(UT) t h a t were found p o s t - e x e r c i s e . The o n l y e x p l a n a t i o n t h a t we can o f f e r f o r t h o s e r e d u c t i o n s i n t h e t h r e s h o l d s , i s t h e c o m b i n e d e f f e c t s o f t h e f o l l o w i n g f a c t o r s : 1) e l e v a t i o n o f body t e m p e r a t u r e w h i c h , p o s s i b l y i n f l u e n c e d m i n u t e v e n t i l a t i o n ( S u t t o n and Jo n e s , 1979); 2) e l e c t r o l y t e and f l u i d unbalance as brought about w i t h p r o l o n g e d e x e r c i s e ( C o s t i l l e t a l . 1970, Wyndham and Strydom 1968); 3) t h e s h i f t - o f m u s c l e f i b e r s r e c r u i t e d f r o m s l o w t w i t c h (ST) t o f a s t t w i t c h (FT) (Brooks and Fahey, 1984); 4) neuro- muscular f a t i g u e caused by a f a i l u r e i n n e u r a l t r a n s m i s s i o n ( M c A r d l e e t a l . 1981); and 5) a r e d u c t i o n i n e f f i c i e n c y o f r u n n i n g . As was shown by the i n t e r a c t i o n s , the r e d u c t i o n s o b s e r v e d i n a l l of the v a r i a b l e s m e asured seem t o be u n a f f e c t e d by the t r a i n i n g s t a t u s . The use o f e x c e s s CO2 and l a c t a t e measurements f o r the d e t e r m i n a t i o n of v e n t i l a t o r y and l a c t a t e t h r e s h o l d s , r e s p e c t i v e l y , was shown t o be v a l i d as w e l l as r e l i a b l e methods ( V o l k o v e t a l . 1975, Rhodes and M c K e n z i e 1984, S u c e c e t a l . 1982, Ivy e t a l . 1981, Kumagai e t a l . 1982). S t u d i e s have r e v e a l e d t h a t the i n v a s i v e and n o n - i n v a s i v e methods o f d e t e r m i n i n g the t h r e s h o l d of a n a e r o b i c m e t a b o l i s m c o r r e l a t e h i g h l y between them ( I v y e t a l . 1981, Kumagai e t a l . 1982, Y o s h i d a e t a l . 1981, C a i o z z o e t a l . 1982, D a v i s e t a l . 1976). These papers suggest t h a t both t h r e s h o l d s almost c o i n c i d e . Other a u t h o r s (Hughes e t a l . 1982, D e n i s e t a l . 1 9 8 2 ) , h o w e v e r , r e p o r t e d l o w e r r e l a t i o n s h i p s , w h i l e Simon et a l . (1983-a) and G u t i n e t a l . (1980) r e p o r t e d t h a t t h e v e n t i l a t o r y t h r e s h o l d o c c u r r e d b e f o r e t h e l a c t a t e t h r e s h o l d . In the p r e s e n t s t u d y , we o b s e r v e d v e r y l o w c o r r e l a t i o n s b e tween t h e two t h r e s h o l d s ( e x p r e s s e d i n %V02max); rx=0.42 and ruT=0.54. F u r t h e r m o r e , the a s s o c i a t e d changes i n gas e x c h a n g e o c c u r r e d b e f o r e a marked i n c r e a s e i n p l a s m a l a c t a t e i n t h r e e o f s i x t r a i n e d s u b j e c t s , w h i l e the o p p o s i t e was observed i n t h r e e of s i x u n t r a i n e d s u b j e c t s . T h i s was an u n a n t i c i p a t e d f i n d i n g b e c a u s e the m a j o r i t y of s t u d i e s i n the l i t e r a t u r e r e v e a l a c o i n c i d e n c e o f t h e two "breakaway" p o i n t s . Based on our f i n d i n g t h a t the v e n t i l a t o r y t h r e s h o l d may o c c u r b e f o r e the l a c t a t e t h r e s h o l d , we q u e s t i o n the concept t h a t i n c r e a s e s i n b l o o d l a c t a t e l e a d t o the v e n t i - l a t o r y changes as i t was h y p o t h e s i z e d by Wasserman e t a l . (1973) , Whipp and D a v i s ( 1 9 7 9 ) . F u r t h e r m o r e , l o o k i n g a t t h e e f f e c t t h e 60-min r u n had on t h e s e t h r e s h o l d s , we o b s e r v e d t h a t the d e c r e a s e i n the v e n t i l a t o r y t h r e s h o l d was g r e a t e r t h a n t h e d e c r e a s e i n t h e l a c t a t e t h r e s h o l d ( e x p r e s s e d i n mph) i n b o t h g r o u p s . T h i s f i n d i n g s u g g e s t s , once more, t h a t b l o o d l a c t a t e a c c u m u l a t i o n i s n o t r e s p o n s i b l e f o r t h e i n c r e a s e i n v e n t i l a t i o n . T h i s c o n c l u s i o n i s a l s o s u p p o r t e d by t h e o b s e r v a t i o n t h a t t h e l a c t a t e t h r e s h o l d (%V02fnax) tended t o i n c r e a s e f o l l o w i n g t h e 60-min r u n , w h i l e t h e v e n t i l a t o r y t h r e s h o l d (%V02max) moved i n the o p p o s i t e d i r e c t i o n . I n v e s t i g a t o r s (Rhodes and M c K e n z i e 1984, S j o d i n and Jacobs 1981, F a r r e l l e t a l . 1979) have c o r r e l a t e d the a n a e r o b i c t h r e s h o l d ( u s i n g e i t h e r the i n v a s i v e or n o n - i n v a s i v e method) v e r y h i g h l y w i t h m a r a t h o n r u n n i n g p e r f o r m a n c e . I n t h o s e s t u d i e s i t was t h e o r i z e d t h a t m a r a t h o n e r s are a b l e t o run t h r o u g h o u t the r a c e a t t h a t c r i t i c a l p o i n t b e f o r e a n a e r o b i c m e t a b o l i s m s t a r t s ; i t was assumed t h a t t h e c r i t i c a l p o i n t s t a y s u n a l t e r e d u n t i l the end of the r a c e and, c o n s e q u e n t l y , i t i s p o s s i b l e t o p r e d i c t e n d u r a n c e p e r f o r m a n c e w i t h h i g h a c c u r a c y , t a k e n i n t o a c c o u n t t h a t a l l o t h e r f a c t o r s w h i c h a f f e c t perfomance have t o be o p t i m a l . In a d d i t i o n , L a F o n t a i n e e t a l . ( 1 9 8 1 ) , F a r r e l e t a l . ( 1 9 7 9 ) , and Kumagai e t a l . (1982) have a l s o c o r r e l a t e d t h e a n a e r o b i c t h r e s h o l d v e r y h i g h l y w i t h p e r f o r m a c e a t v a r i o u s s h o r t e r r a c e s f r o m 2 up t o 10 m i l e s . However, based on the f i n d i n g s of the p r e s e n t s t u d y , we q u e s t i o n the v a l i d i t y of u s i n g the v e n t i l a t o r y and l a c t a t e t h r e s h o l d s i n p r e d i c t i n g e n d u r a n c e p e r f o r m a n c e i n e v e n t s up t o 60 min d u r a t i o n f o r w e l l - t r a i n e d a t h l e t e s . We a l s o c o n c l u d e t h e same f o r r e c r e a t i o n a l a t h l e t e s , a l t h o u g h we were u n a b l e t o show s i g n i f i c a n t r e d u c t i o n s i n the l a c t a t e t h r e s h o l d and VC^max o f o u r u n t r a i n e d s u b j e c t s ; t h i s would appear t o be due t o the s m a l l sample s i z e . O t h e r f a c t o r s , s u c h as V02max, r u n n i n g economy, muscle f i b e r c o m p o s i t i o n , and s u b s t r a t e a v a i l a b i l i t y may a l s o be of importance i n p r e d i c t i n g endurance performance i n e v e n t s up t o 60 min d u r a t i o n . V . REFERENCES Armstrong, Robert B. 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A n a e r o b i c t h r e s h o l d s and m a x i m a l o x y g e n c o n s u m p t i o n r a t e s as p r e d i c t o r s of c r o s s c o u n t r y r u n n i n g p e r f o r m a n c e . Med. S c i . S p o r t s Ex. 1 2 ( 2 ) , 87, 1980, ( a b s t r a c t ) . 27 V o l k o v N.I., S h i r k o v e t s E.A., and B o r i l k e v i c h V.E. Assessment of A e r o b i c and A n a e r o b i c 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 R u n n i n g T e s t s . E u r . J . A p p l . P h y s i o l . 34, 121-130, 1975. Wasserman K. B r e a t h i n g d u r i n g e x e r c i s e . N. E n g l . J . Med. 298, 780-785, 1978. Wasserman K., M c l l r o y M. D e t e c t i n g the T h r e s h o l d of A n a e r o b i c M e t a b o l i s m i n C a r d i a c P a t i e n t s D u r i n g E x e r c i s e . Amer. J . C a r d i o l o g y . 14, 844-852, 1964. Wasserman K., Whipp B . J . , and D a v i s J.A. R e s p i r a t o r y P h y s i o l o g y o f e x e r c i s e : M e t a b o l i s m , gas exchange and v e n t i l a t o r y c o n t r o l . In Widdicombe J.G. ( e d ) . I n t e r n a t i o n a l Review o f P h y s i o l o g y . R e s p i r a t o r y P h y s i o l o g y I I I , B a l t i m o r e : U n i v e r s i t y Park P r e s s , pp.: 144-211, 1981. Wasserman K., Whipp B . J . , K o y a l S.N., and Beaver W.L. A n a e r o b i c t h r e s h o l d and r e s p i r a t o r y gas exchange d u r i n g e x e r c i s e . J . A p p l . P h y s i o l . 3 5 ( 2 ) : 236-243, 1973. Weiser P.C., N o r r o n . C.H., and Krogh L.A. A n a e r o b i c t h r e s h o l d and t h e r u n n i n g speed f o r 3.2 Km. Med S c i . S p o r t s . 10, 43, 1978, ( a b s t r a c t ) . Whipp B . J . , D a v i s -3.A. P e r i p h e r a l chemoreceptors and e x e r c i s e hyperpnea. Med. S c i . S p o r t s . 11: 204-212,,1979. W i l m o r e J.H. A c u t e and c h r o n i c p h y s i o l o g i c a l r e s p o n s e s t o e x e r c i s e . I n : E x e r c i s e i n C a r d i o v a s c u l a r H e a l t h and D i s e a s e , e d i t e d by E.A. Amsterdam, J.H. W i l m o r e , and A.N. DeMaria. New York: Y o r k e , 1977, p.53-69. W i s w e l l R.A., G i r a n t o l a R.N., B u l b u l i a n R. , Simard C. The e f f e c t o f two hours of r u n n i n g on a n a e r o b i c t h r e s h o l d . Med. S c i . S p o r t s Ex. 1 2 ( 2 ) , 86, 1980, ( a b s t r a c t ) . W i s w e l l R.A., G i r a n d o l a R.N., D e V r i e s H.A. Comparison of a n a e r o b i c t h r e s h o l d on b i c y c l e and t r e a d m i l l . Med. S c i . S p o r t s . 1 1 ( 1 ) , 88, 1979, ( a b s t r a c t ) . W i t h e r s R.T., Sherman W.M., M i l l e r J.M., and C o s t i l l D.L. S p e c i - f i c i t y o f t h e a n a e r o b i c t h r e s h o l d i n endurance t r a i n e d c y c l i s t s and r u n n e r s . E u r . J . A p p l . P h y s i o l . 47: 93-104, 1981. Wyndham C.H. and S t r y d o m N.B. The d a n g e r o f an i n a d e q u a t e water i n t a k e d u r i n g marathon r u n n i n g . S. A f r i c a n Med. J . 42:893-896, 1969. Wyndham C.H., S t r y d o m N.B., Van R e n s b u r g A.Y., and Benade A . J . S . P h y s i o l o g i c a l r e q u i r e m e n t s f o r w o r l d - c l a s s p e r f o r m a n c e i n e n d u r a n c e r u n n i n g . S. A f r . Med. J . 43: 996-1002, 1969. Y o s h i d a T., N a g a t a A., Muro M., T a k e u c h i N., and Suda Y. The v a l i d i t y o f a n a e r o b i c t h r e s h o l d d e t e r m i n a t i o n by a Douglas bag method compared w i t h a r t e r i a l b l o o d l a c t a t e c o n c e n t r a t i o n . E u r . J . A p p l . P h y s i o l . 46: 423-430, 1981. Y o s h i d a T., Suda Y., and T a k e u c h i N. E n d u r a n c e t r a i n i n g r e g i m e n b a s e d upon a r t e r i a l b l o o d l a c t a t e : E f f e c t s on a n a e r o b i c t h r e s h o l d . E u r . J . A p p l . P h y s i o l . 49: 223-230, 1982. APPENDIX A - REVIEW OF LITERATURE Introduction A l t h o u g h the concept of the a n a e r o b i c t h r e s h o l d o r i g i n a t e d twenty y e a r s ago (Wasserman e t a l . , 1964), i t remains a con- t e m p o r a r y i s s u e w i t h p r a c t i c a l a p p l i c a t i o n t o s p o r t s and c l i n i c a l e x e r c i s e p h y s i o l o g y . D i f f e r e n t t e r m i n o l o g y i s now used t o c h a r a c t e r i z e t he changes i n b l o o d l a c t a t e c o n c e n t r a t i o n and v e n t i l a t o r y gas e x c h a n g e t h a t o c c u r w i t h i n c r e m e n t a l e x e r c i s e i n t e n s i t i e s . The i n i t i a l n o n - l i n e a r i n c r e a s e i n or ex c e s s CO2, r e l a t i v e t o oxygen consumption, i s termed the v e n t i l a t o r y t h r e s h o l d ; the "breakaway" p o i n t f o r b l o o d l a c t a t e v e r s u s e x e r c i s e i n t e n s i t y has been d e f i n e d as the l a c t a t e i n f l e c t i o n p o i n t . B a s i c s c i e n t i s t s do not agree on the p h y s i o l o g i c a l e v e n t s s u r r o u n d i n g t h e s e t h r e s h o l d s . A h i g h c o r r e l a t i o n b e t ween t h e a l t e r a t i o n s i n gas e x c h a n g e and a c o n t i n u o u s r i s e i n l a c t a t e v a l u e s has been r e p o r t e d ( D a v i s e t a l . 1976, Y o s h i d a e t a l . 1981). Hagberg et a l . (1982) , Heigenhauser e t a l . ( 1 9 8 3 ) , and Hughes e t a l . ( 1 9 8 2) have d e m o n s t r a t e d an u n c o u p l i n g o f t h e v e n t i l a t o r y t h r e s h o l d and l a c t a t e i n f l e c t i o n p o i n t . Thus a l t h o u g h the mechanisms c o n t r o l l i n g t h e s e c o n t r o v e r s i a l e v e n t s have not been e l u c i d a t e d e q u i v o c a l l y they would appear to be r e l a t e d t o a c i d - b a s e b a l a n c e (Wasserman e t a l . 1973, 1981). T h i s has a d i r e c t p r a c t i c a l a p p l i c a t i o n t o the e x e r c i s i n g i n d i v i d u a l s i n terms of performance and muscle f a t i g u e . 29 3 0 T h i s paper r e p r e s e n t s a c u r r e n t r e v i e w of the i n f o r m a t i o n and mechanisms of the a n a e r o b i c t h r e s h o l d and i t s a p p l i c a t i o n t o s p o r t s c i e n c e . Measurement and Determination of the Anaerobic Threshold Wasserman e t a l . (1973) determined the n o n i n v a s i v e i n d i c a t o r s of the onset o f a n a e r o b i c m e t a b o l i s m . E i g h t y - f i v e n o r m a l s u b j e c t s between 17 and 91 y e a r s of age were g i v e n i n c r e m e n t a l e x e r c i s e t e s t s on the b i c y c l e e r g o m e t e r w i t h i n c r e m e n t s o f 15W e v e r y minute w h i l e changes i n gas exchange were examined. The a n a e r o b i c t h r e s h o l d c o u l d be i d e n t i f i e d by t h e p o i n t o f : 1) n o n l i n e a r i n c r e a s e i n Vg 2) n o n l i n e a r i n c r e a s e i n V C O 2 3) an i n c r e a s e i n e n d - t i d a l 0 2 w i t h o u t a c o r r e s p o n d i n g d e c r e a s e i n e n d - t i d a l C 0 2 , and 4) an i n c r e a s e i n R. V o l k o v e t a l . (1975) i n v e s t i g a t e d measurements of ex c e s s C 0 2 p l o t t e d v e r s u s i n c r e m e n t a l r u n n i n g speeds on a h o r i z o n t a l t r e a d m i l l of f o u r h i g h l y e x p e r i e n c e d m i d d l e - d i s t a n c e r u n n e r s . Excess C 0 2 was measured by sa m p l i n g the e x p i r e d a i r t h r o u g h o u t t h e t e s t s where e x c e s s C 0 2 was : E x c C 0 2 (ml/kg/min)= VC0 2- Rarest X V 0 2 . By p l o t t i n g the v a l u e s of E x c C 0 2 i n s e m i l o g a r i t h m i c s c a l e a g a i n s t c o r r e s p o n d i n g r u n n i n g s p e e d s i t was p o s s i b l e t o d e t e r m i n e t h e r u n n i n g s p e e d c o r r e s p o n d i n g t o t h r e s h o l d o f a n a e r o b i c m e t a b o l i s m (VXAM)» c h a r a c t e r i z e d by m e t a b o l i c a c i d o s i s and i n c r e a s e i n a r t e r i a l b l o o d l a c t a t e . They o b s e r v e d t h a t a t l o w s p e e d s n o t e x c e e d i n g V^^M» E x c C 0 2 changed o n l y s l i g h t l y . However, when r u n n i n g speed exceeded V^AM» E x c C 0 2 e x h i b i t e d a r a p i d e x p o n e n t i a l i n c r e a s e . The r u n n i n g s p e e d c o r r e s p o n d i n g t o t h e "b r e a k a w a y " p o i n t gave t h e v a l u e o f VTAM> f°r which a s y s t e m a t i c i n c r e a s e of a n a e r o b i c m e t a b o l i s m began. A d d i t i o n a l l y , they n o t i c e d t h a t s u b j e c t s w i t h d i f f e r e n t l e v e l s o f t r a i n i n g e x h i b i t e d c o n s i d e r a b l e d i f f e r e n c e s i n t h e speed a t which ExcC02 began t o show a r a p i d e x p o n e n t i a l i n c r e a s e ; the b e s t t r a i n e d a t h l e t e met the "breakaway" p o i n t a t a s i g n i f i c a n t l y h i g h e r speed than d i d the l e a s t t r a i n e d a t h l e t e . Sankar e t a l . ( 1 9 7 8 ) examined d e t e r m i n a t i o n of a n a e r o b i c t h r e s h o l d by oxygen p u l s e . T h i r t y - f o u r male f i r e f i g h t e r s , aged 19-31 were used f o r the s t u d y . They chose t h o s e s u b j e c t s w i t h V02max of < 3.75 1/min because they observed no p l a t e a u o f o x y g e n p u l s e i n s i m i l a r s u b j e c t s w i t h v e r y h i g h VC^max. The s u b j e c t s underwent i n c r e m e n t a l t r e a d m i l l e x e r c i s e w h i l e b l o o d l a c t a t e s and o t h e r c a r d i o r e s p i r a t o r y v a r i a b l e s were measured a t the f o u r t h minute of s t e a d y - s t a t e work c o n t i n u i n g t o a p p r o x i m a t e l y 80% of VC^max. The oxygen p u l s e i n c r e a s e d l i n e a r l y t o a p p r o x i m a t e l y 7 0 % o f VC^max o r a t l a c t i c a c i d of a p p r o x i m a t e l y 30 mg/dl and p l a t e a u x a t a p p r o x i m a t e l y 18 • • • m l / b e a t a f t e r t h a t . . Between 6 0 - 7 0 % o f V0 2max, V E , VCO2, R, HR, PETO2, and l a c t a t e i n c r e a s e d o u t o f p r o p o r t i o n t o • VO2 i n d i c a t i n g the onset of m e t a b o l i c a c i d o s i s . The i n v e s t i g a t o r s c o n c l u d e d t h a t c u r v i l i n e a r p l a t e a u i n g of ox y g e n p u l s e c o u l d be t h e i n d e x o f t h e m e t a b o l i c a c i d o s i s , and t h e l e v e l i n g of oxygen p u l s e i s a measure of a p p r o a c h i n g VC^max. A c c o r d i n g t o Wasserman e t a l . ( 1 9 6 4 , 1973, 1978) t h e a n a e r o b i c t h r e s h o l d c o i n c i d e s w i t h t h e f i r s t i n c r e a s e i n l a c t a t e l e v e l , t o a p p r o x i m a t e l y 2 mmol/1. However, Kinderman e t a l . (1979) showed t h a t work l o a d i n t e n s i t i e s above t h e a n a e r o b i c t h r e s h o l d d e f i n e d by Wasserman e t a l . ( 1964, 1973, 1978), can be m a i n t a i n e d w i t h s l i g h t l y e l e v a t e d l a c t a t e l e v e l s f o r p r o l o n g e d p e r i o d s o f t i m e . Seven c r o s s - c o u n t r y s k i e r s were used i n t h a t s t u d y . A f t e r t h e i r maximal w o r k i n g c a p a c i t y ( h e a r t r a t e , V O 2 , p e r f o r m a n c e , l a c t a t e ) was d e t e r m i n e d by r u n n i n g on t h e t r e a d m i l l , t r e a d m i l l s p e e d , o x y g e n i n t a k e and h e a r t r a t e s a t l a c t a t e l e v e l s of 4 mmol/1 were d e t e r m i n e d by i n t e r p o l a t i o n . The s u b j e c t s then underwent two a d d i t i o n a l e x e r c i s e s , e a c h w i t h a d u r a t i o n of 30 min. The h e a r t r a t e d e termined f o r 4 mmol/1 l a c t a t e (174 b/min) was k e p t c o n s t a n t f o r t h e d u r a t i o n o f t h e f i r s t e x e r c i s e w h i l e the t r e a d m i l l speed d e t e r m i n e d f o r the same l a c t a t e c o n c e n t r a t i o n r e m a i n e d unchanged d u r i n g the second e x e r c i s e . In o r d e r f o r the h e a r t r a t e d e t e r m i n e d f o r 4 mmol/1 l a c t a t e t o be k e p t c o n s t a n t f o r 30 min d u r a t i o n , t h e t r e a d m i l l speed had t o be reduced c o n t i n u o u s l y . The a r t e r i a l l a c t a t e c o n c e n t r a t i o n d i s p l a y e d an a p p r o x i m a t e l y t w o f o l d r i s e when compared t o 4 mmol/1 up t o 10 min and a f t e r t h a t was c o n t i n u o u s l y reduced as a r e s u l t o f t h e r e d u c t i o n of the t r e a d m i l l speed. When the e x e r c i s e l a s t i n g 30 min was performed w i t h a c o n s t a n t r u n n i n g s p e e d as d e t e r m i n e d f o r 4 mmol/1 l a c t a t e , the h e a r t r a t e r o s e and the a r t e r i a l l a c t a t e c o n c e n t r a t i o n was n e a r l y 4 mmol/1 d u r i n g the whole e x e r c i s e . F i n a l l y , the a u t h o r s suggested new c o n c e p t s of t h r e s h o l d s , as f o l l o w s : I . A e r o b i c t h r e s h o l d : a p p r o x i m a t e l y 2 mmol/1 l a c t a t e - f i r s t s i g n i f i c a n t e l e v a t i o n of l a c t a t e l e v e l , n o n l i n e a r i n c r e a s e of Vg, RQ. I I . 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 : a p p r o x i m a t e l y 2 t o 4 mmol/1 l a c t a t e . I I I . A n a e r o b i c t h r e s h o l d : a p p r o x i m a t e l y 4 mmol/1 l a c t a t e - s t e e p p a r t of e x p o n e n t i a l i n c r e a s e i n l a c t a t e c o n c e n t r a t i o n . M c L e l l a n e t a l . (1981) do not agree w i t h the above d e s i g n a t e d l a c t a t e l e v e l s of 2 and 4 mmol/1 f o r the a e r o b i c and a n a e r o b i c t h r e s h o l d , r e s p e c t i v e l y . They d e s i g n e d a s t u d y i n w h i c h they i n v e s t i g a t e d the e f f e c t of work l o a d d u r a t i o n on i n d i r e c t and d i r e c t d e t e r m i n a t i o n s o f the a e r o b i c and a n a e r o b i c t h r e s - h o l d s . S i x s u b j e c t s underwent c y c l e e r g o m e t e r t e s t s w h i l e the work l o a d was i n c r e a s e 15W each 1 o r 2 min and 30W each 3 o r 4 min. The f i r s t and second "breakaway" p o i n t s i n t h e p l o t o f VE v e r s u s VO2 were u s e d as an i n d i r e c t method f o r the d e t e r m i n a t i o n of the a e r o b i c and a n a e r o b i c t h r e s h o l d s , w h i l e t h e work l o a d a t an i n i t i a l r i s e i n l a c t a t e and the onset of the r a p i d r i s e i n l a c t a t e was used as a d i r e c t method. The f i n d i n g s showed t h a t r e l a t i v e a e r o b i c and a n a e r o b i c t h r e s h o l d v a l u e s were s i g n i f i c a n t l y h i g h e r f o r the 4 v e r s u s 1 min t e s t ( 6 0.13 v s . 5 2 . 0 3 % V 0 2 m a x , and 85.09 v s . 77.52% V 0 2 m a x, f o r a e r o b i c and a n a e r o b i c t h r e s h o l d , r e s p e c t i v e l y ) . L a c t i c a c i d a t a e r o b i c t h r e s h o l d was s i g n i f i c a n t l y h i g h e r f o r t h e 3 v e r s u s 1 rain t e s t b u t t h e r e was no d i f f e r e n c e i n l a c t a t e l e v e l s a t a n a e r o b i c t h r e s h o l d . In a d d i t i o n , VO2 a s s o c i a t e d w i t h t h e s e l a c t a t e v a l u e s was f o u n d t o be d i f f e r e n t f r o m those a t a e r o b i c and a n a e r o b i c t h r e s h o l d d etermined i n d i r e c t l y . B a s e d on t h e s e f i n d i n g s t h e i n v e s t i g a t o r s c o n c l u d e d t h a t a l t h o u g h l a c t a t e l e v e l s of 2 and 4 mmol/1 ar e u s u a l l y found a t a e r o b i c and a n a e r o b i c t h r e s h o l d , r e s p e c t i v e l y , t h e y a r e a r b i t r a r y and do n o t a l w a y s a p p l y . R e l a t i v e a e r o b i c and a n a e r o b i c t h r e s h o l d v a l u e s may v a r y s i g n i f i c a n t l y d e p e n d i n g on the t e s t p r o t o c o l . D a v i s e t a l . ( 1 9 8 3 ) e x a m i n e d whether the gas exchange a n a e r o b i c t h r e s h o l d o c c u r s a t a f i x e d b l o o d l a c t a t e c o n c e n t r a t i o n o f 2 o r 4 mM. T w e l v e males and two females (mean age=22.3 y e a r s ) u n d e r w e n t i n c r e m e n t a l c y c l e e r g o m e t e r t e s t s w h i l e gas exchange and l a c t a t e measurements were t a k e n . The a n a e r o b i c t h r e s h o l d was c h o s e n u s i n g f o u r c r i t e r i a : 1) s y s t e m a t i c • • • • i n c r e a s e i n V g / V 0 2 , w i t h o u t a c o n c o m i t a n t i n c r e a s e i n VE/VC 0 2 , 2) s y s t e m a t i c i n c r e a s e i n b l o o d l a c t a t e , 3) 2 mM l a c t a t e , and 4) 4mM l a c t a t e c o n c e n t r a t i o n s . S u b s e q u e n t l y they compared the VO2 v a l u e s f o r each c r i t e r i o n among a l l s u b j e c t s . T h e i r • • • f i n d i n g s showed t h a t t h e mean v a l u e of VO2 f o r the VE / V O 2 c r i t e r i o n was 1.819 1/min, f o r the second c r i t e r i o n was 1.863 1/min, f o r t h e t h i r d 2.099 1/min, and f o r the f o u r t h 2.847 1/min. The l a s t two v a l u e s d i f f e r e d s i g n i f i c a n t l y f r o m t h e VE/V 0 2 a n a e r o b i c t h r e s h o l d r e s u l t , as w e l l as between them. In a d d i t i o n , t h e m a x i m a l p e r c e n t d i f f e r e n c e s f r o m t h e gas e x c h a n g e a n a e r o b i c t h r e s h o l d were 17, 4 1 , and 87 compared t o the second, t h i r d , and f o u r t h c r i t e r i o n , r e s p e c t i v e l y . These o b s e r v a t i o n s l e d t h e i n v e s t i g a t o r s t o c o n c l u d e t h a t the a n a e r o b i c t h r e s h o l d d i s c e r n e d f r o m gas e x c h a n g e o r t h e l a c t a t e break p o i n t does not c o r r e s p o n d w i t h a f i x e d , a b s o l u t e l a c t a t e c o n c e n t r a t i o n of 2 o r 4 mM. Simon e t a l . (1982) d e s i g n e d an experiment t o i n v e s t i g a t e whether the i n v a s i v e a n a e r o b i c t h r e s h o l d (AT^) and n o n i n v a s i v e a n a e r o b i c t h r e s h o l d (ATn) o c c u r t o g e t h e r i n b o t h t r a i n e d and u n t r a i n e d s e d e n t a r y men. The AT^ was d e t e r m i n e d from a marked i n c r e a s e i n plasma l a c t a t e and the ATn from a n o n l i n e a r i n c r e a s e i n Vg d u r i n g i n c r e m e n t a l l e g c y c l i n g t e s t s . The f i n d i n g s showed t h a t the t r a i n e d s u b j e c t s ' AT-̂  (68.8% VC^max) and ATn (65.8% VC^max) d i d not d i f f e r s i g n i f i c a n t l y . A d d i t i o n a l o b s e r v a t i o n s showed t h a t t h e t r a i n e d s u b j e c t s ' mean peak l a c t a t e c o n c e n t r a t i o n (10.5 mM) d i d not d i f f e r s i g n i f i c a n t l y from the u n t r a i n e d s u b j e c t s ' mean peak l a c t a t e c o n c e n t r a t i o n (11.5 mM). However, the mean time of appearance of the peak l a c t a t e c o n c e n t r a t i o n d u r i n g p a s s i v e r e c o v e r y o c c u r r e d s i g n i f i - c a n t l y e a r l i e r f o r t h e t r a i n e d (1.8 min) compared t o t h e u n t r a i n e d (4.3 m i n ) . T h i s o b s e r v a t i o n l e d the i n v e s t i g a t o r s t o s u g g e s t t h a t t h e r e may be a s l o w e r l a c t a t e t r a n s l o c a t i o n from muscle t o b l o o d i n t h e u n t r a i n e d compared t o t r a i n e d i n d i v i d u a l s . Rupp ( 1 9 8 1 ) i n v e s t i g a t e d w h e t h e r 4 d i f f e r e n t methods f o r the d e t e r m i n a t i o n of the a n a e r o b i c t h r e s h o l d a r e s i m i l a r . Twenty men and women s e r v e d as s u b j e c t s f o r the s t u d y and they underwent a maximal i n c r e m e n t a l b i c y c l e ergometer e x e r c i s e . The methods t e s t e d were : Method 1(M^ - n o n l i n e a r i n c r e a s e i n V E and V C O 2 ) method 2 ( M 2 - i n c r e a s e i n F E 0 2 w i t h o u t a d e c r e a s e i n F E C 0 2 ) , method 3 (M3 - second n o n l i n e a r i n c r e a s e i n V g ) , and method 4 (M4 - a d e c r e a s e i n F E C 0 2 as work i n t e n s i t y i n c r e a s e d ) . T h e i r f i n d i n g s showed t h e f o l l o w i n g : 1) M3 and M4 (32 and 31 V 0 2 m l / k g ) were s i g n i f i c a n t l y d i f f e r e n t f r o m M1 and M 2 (20.7 and 19.7 V 0 2 m l / k g ) . 2) No s i g n i f i c a n t d i f f e r e n c e between males and females (26.4 and 25.2 V 0 2 m l / k g ) . 3) The h e a r t r a t e a t w h i c h M^ and M 2 o c c u r r e d (130.5 and 126.7 b/min) was s i g n i f i c a n t l y d i f f e r e n t f r o m h e a r t r a t e o f M3 and M4 (164.7 and 159.2 b / m i n ) . 4) No s i g n i f i c a n t d i f f e r e n c e b e tween h e a r t r a t e o f M^ and M 2 o r between M3 and M 4 . 5) The h e a r t r a t e of females (151.3 b/min) was s i g n i - f i c a n t l y d i f f e r e n t than males (139.2 b/min) a c r o s s a l l methods. 6) Ui and M 2 (53.6 and 5 1 . 9 % V 0 2 m a x ) were s i g n i f i c a n t l y d i f f e r e n t than M 3 and M 4 (84 and 81.3% V 0 2 m a x ) . 7) No s i g n - i f i c a n t d i f f e r e n c e i n % V 0 2max between M-[ and M 2 o r between M3 and M 4. 8) F e m a l e s (71.2 % V 0 2max were s i g n i f i c a n t l y d i f f e r e n t t h a n m a l e s ( 6 4 . 2 % V 0 2 m a x ) a c r o s s a l l m e t h o d s . Based on t h e s e o b s e r v a t i o n s t h e a u t h o r ' s c o n c l u s i o n s were: 1) M i and M 2 measure t h e same a n a e r o b i c t h r e s h o l d , 2) M3 and M4 measure t h e same a n a e r o b i c t h r e s h o l d , 3) a d i s t i n c t i o n e x i s t s b e t ween , M 2 and M3 , M4 ( V 0 2 m l / k g , h e a r t r a t e , and % V 0 2 m a x ) , 4) a n a e r o b i c t h r e s h o l d h e a r t r a t e s f o r women a r e h i g h e r t h a n t h o s e o f men, and 5 ) a n a e r o b i c t h r e s h o l d o c c u r s a t a h i g h e r % V0 2max i n females than males. Sucec ( 1 9 8 1 ) d e s i g n e d an experiment t o examine t h e v a l i d i t y and r e l i a b i l i t y o f an i n c r e m e n t a l h o r i z o n t a l p r o t o c o l f o r the c o n c u r r e n t d e t e r m i n a t i o n of V0 2max and a n a e r o b i c t h r e s h o l d i n males and f e m a l e s . Twelve male and t w e l v e female d i s t a n c e r u n n e r s were u s e d f o r t h e s t u d y . The means of V0 2max f o r t h e h o r i z o n t a l t r e a d m i l l p r o t o c o l were f o u n d t o be e q u a l t o t h e p a i r e d mean V0 2max s c o r e s from an i n c l i n e d t r e a d m i l l t e s t f o r both s e x e s . The d e t e r m i n a t i o n of a n a e r o b i c t h r e s h o l d from the h o r i z o n t a l t r e a d m i l l p r o t o c o l was found t o be v a l i d and r e l i a b l e f o r both the males (r = 0 . 8 6 ) and females ( r = 0 . 9 3 ) . The males' V 0 2 J a t a n a e r o b i c t h r e s h o l d was 3.28 1/rnin o r 48.0 • m l / k g / m i n w h i l e the f e m a l e s ' V 0 2 a t a n a e r o b i c t h r e s h o l d was s i g n i f i c a n t l y lower 2.33 1/min o r 40.6 m l / k g / m i n . However, when t h e a n a e r o b i c t h r e s h o l d was e x p r e s s e d as a p e r c e n t a g e of t h e i r V0 2max, no s i g n i f i c a n t d i f f e r e n c e was found between t h e m a l e s ' and f e m a l e s ' , 7 2 . 3 % and 7 3 . 2 % , r e s p e c t i v e l y . The a u t h o r c o n c l u d e d t h a t h o r i z o n t a l t r e a d m i l l p r o t o c o l w i l l • p r o d u c e v a l i d and r e l i a b l e V0 2max and a n a e r o b i c t h r e s h o l d v a l u e s s i m i l a r t o v a l u e s made d u r i n g i n c l i n e d t r e a d m i l l p r o t o c o l f o r d i s t a n c e r u n n e r s of b o t h s e x e s . In a d d i t i o n , males have a h i g h e r a n a e r o b i c t h r e s h o l d when e x p r e s s e d i n 1/min or ml/kg/min, t h a n f e m a l e s , b u t when a n a e r o b i c t h r e s h o l d i s e x p r e s s e d as a % of V02max i t i s independent of s e x . C a i o z z o e t a l . ( 1 9 8 2 ) e x a m i n i n g 16 s u b j e c t s 20 t o 31 y e a r s o f age showed t h a t t h e most s e n s i t i v e and r e l i a b l e v e n t i l a t o r y i n d e x f o r d e t e c t i o n of the a n a e r o b i c t h r e s h o l d • • • • • • among i n d i c e s such as , VCO2, R, and V E / V 0 2 , was the V E / V 0 2 . ^ E / v 0 2 had t h e h i g h e s t c o r r e l a t i o n among a l l t h e i n d i c e s t e s t e d w i t h the b l o o d l a c t a t e a n a e r o b i c t h r e s h o l d ( r = 0 . 9 3 ) . The Vg / V 0 2 i n d e x a l s o showed the h i g h e s t t e s t - r e t e s t c o r r e l a t i o n f o r the d e t e c t i o n \of the a n a e r o b i c t h r e s h o l d ( r = 0 . 9 3 ) . These c o r r e l a t i o n s a r e i n c l o s e f i t w i t h f i n d i n g s from D a v i s e t a l . (1976, 1979) and Su c e c e t a l . ( 1 9 8 2 ) , w h i l e Hughes e t a l . ( 1 9 8 2 ) and D e n i s e t a l . ( 1 9 8 2 ) r e p o r t e d a c o r r e l a t i o n o f o n l y 0.71 and 0.77, r e s p e c t i v e l y , b etween v e n t i l a t o r y and l a c t a t e t h r e s h o l d s . G l a d d e n e t a l . ( 1 9 8 3 ) d e s i g n e d a s t u d y t o examine the agreement between gas exchange and l a c t a t e a n a e r o b i c t h r e s h o l d d e t e r m i n a t i o n s among i n d e p e n d e n t i n v e s t i g a t o r s . S i x t e e n s u b j e c t s underwent i n c r e m e n t a l c y c l e e r g o m e t e r t e s t s w h i l e gas e x c h a n g e and l a c t a t e m easurements were t a k e n , and the v a l u e s were p l o t t e d v e r s u s t i m e . S u b s e q u e n t l y , t h e s e p l o t s were s e n t t o 9 i n d e p e n d e n t i n v e s t i g a t o r s who were asked t o dete r m i n e the a n a e r o b i c t h r e s h o l d . Agreement among t h e i n - de p e n d e n t l y d e t e r m i n e d a n a e r o b i c t h r e s h o l d v a l u e s ( v e n t i l a t o r y v e r s u s l a c t a t e ) was v e r y poor w i t h c o r r e l a t i o n c o e f f i c i e n t s r a n g i n g f r o m 0.16 t o 0.82, w i t h a median v a l u e o f 0.46. For t h e v e n t i l a t o r y t h r e s h o l d , t h e r r a n g e d f r o m 0.37 t o 0.96 w i t h a median of 0.66, w h i l e f o r the l a c t a t e t h r e s h o l d , the r ranged from 0.59 t o 0.97 w i t h a median of 0.72. Based on t h e s e r e s u l t s the a u t h o r s suggested t h a t independent e v a l u a - t i o n s o f gas e x c h a n g e and l a c t a t e a n a e r o b i c t h r e s h o l d have l e s s agreement than p r e v i o u s l y r e p o r t e d . In a d d i t i o n , agreement among independent i n v e s t i g a t o r s f o r a g i v e n a n a e r o b i c t h r e s h o l d method i s l e s s than t h a t p r e v i o u s l y r e p o r t e d f o r i n v e s t i g a t o r s w i t h i n a g i v e n l a b o r a t o r y . D e t e r m i n a t i o n o f a n a e r o b i c t h r e s h o l d by a Douglas bag method was found t o be as v a l i d as w i t h a r t e r i a l b l o o d l a c t a t e a n a e r o b i c t h r e s h o l d measurements ( Y o s h i d a e t a l . , 1 9 8 1 ) . By e x a m i n i n g 10 male c o l l e g e - a g e d s u b j e c t s t h e y o b s e r v e d • • • t h a t VC>2%, V02max, , h e a r t r a t e , and R a t a n a e r o b i c t h r e s h o l d d i d not d i f f e r s i g n i f i c a n t l y when me a s u r e d e i t h e r w i t h gas exchange o r l a c t a t e measurements. F u r t h e r m o r e , they r e c o r d e d a c o r r e l a t i o n c o e f f i c i e n t of r=0.86 between l a c t a t e t h r e s h o l d and gas exchange t h r e s h o l d when e x p r e s s e d i n VG>2 v a l u e s ( 1 / m i n ) . C o n c o n i e t a l . (1982) d e s i g n e d a n o n i n v a s i v e f i e l d t e s t t o d e t e r m i n e t h e a n a e r o b i c t h r e s h o l d . They e x a m i n e d 210 r u n n e r s who r u n c o n t i n u o u s l y on t h e t r a c k from an i n i t i a l v e l o c i t y of 12-14 km/h up t o su b m a x i m a l v e l o c i t i e s v a r y i n g a c c o r d i n g t o t h e r u n n e r s ' c a p a b i l i t y w h i l e h e a r t r a t e s were r e c o r d e d and p l o t t e d v e r s u s r u n n i n g s p e e d s . The v e l o c i t y a t which the l i n e a r i t y o f r u n n i n g s p e e d - h e a r t r a t e r e l a t i o n s h i p was l o s t was c a l l e d d e f l e c t i o n v e l o c i t y ( V ^ ) . I t was shown t h a t the c o r r e l a t e d v e r y h i g h l y (r=0.99) w i t h the a n a e r o b i c t h r e s h o l d d e t e r m i n e d by b l o o d l a c t a t e m e a s u r e m e n t s , w h i l e t h e r e p r o d u c i b i l i t y o f t h e d e t e r m i n a t i o n was a l s o found t o be h i g h l y s i g n i f i c a n t ( r = 0 . 9 9 ) . F u r t h e r m o r e , they r e c o r d e d v e r y h i g h c o r r e l a t i o n s b e t ween and c o m p e t i t i v e r u n n i n g speeds, an r=0.93 i n 5000M, r=0.95 i n the marathon, and r=0.99 i n 1-hr r a c e s . These f i n d i n g s h i g h l y demonstrate the f e a s i b i l i t y of measuring t h e a n a e r o b i c t h r e s h o l d by u s i n g n o n i n v a s i v e r u n n i n g s p e e d - h e a r t r a t e r e l a t i o n s h i p s , an a p p r o a c h which can be c a r r i e d out i n the f i e l d . M o r i t a n i e t a l . (1980) showed t h a t s u r f a c e e l e c t r o m y o g r a p h y i s a v a l i d n o n i n v a s i v e method f o r the d e t e r m i n a t i o n o f a n a e r o b i c t h r e s h o l d . E i g h t e e n males (25.3 y e a r s ) and e i g h t e e n females (20.9 y e a r s ) underwent i n c r e m e n t a l c y c l e e x e r c i s e w h i l e s u r f a c e e l e c t r o d e s were a p p l i e d on t h e i r q u a d r i c e p s m u s c l e . The a n a e r o b i c t h r e s h o l d was det e r m i n e d by the n o n l i n e a r i n c r e a s e i n the electromyogram, i . e . , the p o i n t a t which t h r e e c o n s e c u t i v e electromyogram v a l u e s d e v i a t e d above one s t a n d a r d e r r o r o f e s t i m a t e f r o m t h e l i n e a r r e g r e s s i o n e q u a t i o n . T h i s method was t e s t e d f o r i t s v a l i d i t y by c o r r e l a t i n g the VO2 v a l u e s a t the a n a e r o b i c t h r e s h o l d as d e r i v e d by the electromyogram-work p l o t s w i t h t h o s e d e r i v e d f r o m gas e x c h a n g e m e a s u r e m e n t s . The f i n d i n g s showed h i g h l y s i g n i f i c a n t c o r r e l a t i o n s b e t ween t h e two methods f o r m a l e s ( r = 0 . 9 6 ) , f e m a l e s ( r = 0 . 8 9 ) and the p o o l e d d a t a ( r = 0 . 9 7 ) . F u r t h e r s t u d i e s by M o r i t a n i e t a l . ( 1 9 8 2 ) showed t h a t a n a l y s i s of m y o l e c t r i c s i g n a l s may p r o v i d e a n o n i n v a s i v e measure of l a c t a t e t h r e s h o l d . O r r e t a l . (1980) examined whether the s u b j e c t i v e e v a l u a t i o n ( S E ) o f a n a e r o b i c t h r e s h o l d b a s e d on t h e V E / V 0 2 c r i t e r i a and u s i n g a 15 sec s a m p l i n g p e r i o d c o r r e l a t e w i t h a c o m p u t e r i z e d a l g o r i t h m t e c h n i q u e ( C E ) u s i n g m u l t i p l e l i n e a r r e g r e s s i o n s . A 2 ( C E - 2 ) and 3 ( C E - 3 ) r e g r e s s i o n model f i t t e d t o t h e d a t a d e t e r m i n e d on the b a s i s of the s m a l l e s t p o o l e d r e s i d u a l sum of s quares were used f o r the c o m p a r i s o n . Ten s u b j e c t s were u s e d f o r t h e s t u d y whose a n a e r o b i c t h r e s h o l d was d e t e r m i n e d by i n c r e m e n t a l work t e s t s . The f i n d i n g s showed t h a t a n a e r o b i c t h r e s h o l d i n % VC^max was h i g h e r f o r the CE-2 (72.6) d e t e r m i n a t i o n than f o r the S E (63.6) and the CE-3 ( 5 8 . 9 ) d e t e r m i n a t i o n s . S E and C E - 2 c o r r e l a t e d s i g n i f i c a n t l y ( r = 0 . 8 2 ) as w e l l as S E and CE-3 (r=0.65). However, no s i g n i f i c a n t c o r r e l a t i o n was f o u n d between C E - 2 and C E - 3 ( r = 0 . 5 1 ) . The r e s e a r c h e r s c o n c l u d e d t h a t t h e method u s e d t o d e t e r m i n e t h e p o i n t o f "breakaway" can s i g n i f i c a n t l y a f f e c t the v a l u e used f o r a n a e r o b i c t h r e s h o l d . Anaerobic Threshold and Various Modes of Exercise D a v i s e t a l . ( 1 9 7 6 ) i n v e s t i g a t e d t h e c o m p a r a b i l i t y of the a n a e r o b i c t h r e s h o l d among t h r e e modes o f e x e r c i s e (arm c r a n k i n g , l e g c y c l i n g , and t r e a d m i l l w a l k - r u n n i n g ) w i t h d u p l i c a t e d e t e r m i n a t i o n s o b t a i n e d from 30 male s u b j e c t s . The a n a e r o b i c t h r e s h o l d f o r arm c r a n k i n g , l e g c y c l i n g , and t r e a d m i l l w a l k i n g - r u n n i n g o c c u r r e d a t 4 6 . 5 , 63.8, and 58.6% of VC^max, r e s - p e c t i v e l y . No s i g n i f i c a n t d i f f e r e n c e was f o u n d between t h e a n a e r o b i c t h r e s h o l d mean v a l u e s f o r l e g c y c l i n g and t r e a d m i l l w a l k i n g - r u n n i n g w h i l e the mean a n a e r o b i c t h r e s h o l d f o r arm c r a n k i n g was s i g n i f i c a n t l y lower than l e g c y c l i n g o r t r e a d m i l l w a l k i n g - r u n n i n g . A n a e r o b i c t h r e s h o l d d u r i n g one- v e r s u s two-legged c y c l i n g was e x a m i n e d by S t a m f o r d e t a l . ( 1 9 7 8 ) . They f o u n d t h a t a n a e r o b i c t h r e s h o l d approximated 48% of VC^max f o r bo t h one- and two-legged c y c l i n g . A c c o r d i n g t o the a u t h o r s , t h i s f i n d i n g i n d i c a t e d t h a t the s i z e of the t o t a l e x e r c i s i n g muscle mass does n o t i n f l u e n c e a n a e r o b i c t h r e s h o l d when e x p r e s s e d on a r e l a t i v e b a s i s , b u t , r a t h e r , the mode of e x e r c i s e i s p r o b a b l y the p r i m a r y i n f l u e n c i n g f a c t o r as i t i s shown by the f i n d i n g s of the p r e v i o u s s t u d y by D a v i s e t a l . ( 1 9 7 6 ) . P a y n e and Lemon ( 1 9 8 2 ) compared a n a e r o b i c t h r e s h o l d d u r i n g t r e a d m i l l r u n n i n g and t e t h e r e d swimming. S i x male c o m p e t i t i v e swimmers were u s e d f o r t h e s t u d y and l a c t a t e and gas exchange measurements were t a k e n . The r e s u l t s showed t h a t : 1) T r e a d m i l l r u n n i n g was s i g n i f i c a n t l y g r e a t e r than t e t h e r e d swimming f o r a n a e r o b i c t h r e s h o l d : % o f t r e a d m i l l V0 2max (73.0 v e r s u s 5 0 . 4 ) , 2) a n o n - s i g n i f i c a n t d i f f e r e n c e was found f o r 5 min p o s t e x e r c i s e l a c t a t e v a l u e s (11.87 v e r s u s 11.31 mmol/1) and a n a e r o b i c t h r e s h o l d : % mode s p e c i f i c V02max (73.0 v e r s u s 6 5 . 9 ) , and 3) t r e a d m i l l l a c t a t e t h r e s h o l d and a n a e r o b i c t h r e s h o l d (75.4 v e r s u s 71.7) were n o n - s i g n i f i c a n t . 1 Based on the s e f i n d i n g s the a u t h o r s suggested t h a t s p e c i f i c arm t r a i n i n g r e s u l t s i n an a n a e r o b i c t h r e s h o l d (% mode s p e c i f i c V02max) d u r i n g t e t h e r e d swimming t h a t i t i s not d i f f e r e n t from t r e a d m i l l r u n n i n g . Hagerman and M i c k e l s o n (1980) examined a n a e r o b i c t h r e s h o l d among c o m p e t i t i v e oarsmen by u s i n g a r o w i n g e r g o m e t e r and a m o t o r - d r i v e n t r e a d m i l l . T h i r t y - t h r e e c a n d i d a t e s f o r the U.S. N a t i o n a l Men's Rowing Team s e r v e d as s u b j e c t s whose a n a e r o b i c t h r e s h o l d s were de t e r m i n e d by gas exchange measurements on i n c r e m e n t a l e x e r c i s e s i n the rowing ergometer and i n t h e t r e a d m i l l . The f i n d i n g s i n d i c a t e d t h a t the a n a e r o b i c t h r e s h o l d f o r t h e r o w i n g e x e r c i s e o c c u r r e d a t 8 2 % o f VO^max ( a t an average power o u t p u t of 1748 kg-m*min~l), w h i l e the a n a e r o b i c t h r e s h o l d f o r the t r e a d m i l l e x e r c i s e o c c u r r e d a t 72% of V0 2max ( a t an a v e r a g e power o u t p u t o f 780 k g - m * m i n - i ) . However, • V02max v a l u e s d i d not d i f f e r s i g n i f i c a n t l y f o r the two modes of e x e r c i s e . The i n v e s t i g a t o r s a t t r i b u t e d the 10% d i f f e r e n c e i n a n a e r o b i c t h r e s h o l d between the two e x e r c i s e s t o the s p e c i - f i c i t y of t r a i n i n g and t o a d a p t a b i l i t y and t h e y s u g g e s t e d t h e u se o f t a s k s p e c i f i c i t y t e s t i n g f o r r e l i a b l e e v a l u a t i o n of an a t h l e t e ' s p h y s i o l o g i c a l c a p a c i t y . W i s w e l l e t a t . ( 1 9 7 9 ) compared a n a e r o b i c t h r e s h o l d on b i c y l e ergometer and t r e a d m i l l . T h i r t y males, 18 t o 25 y e a r s of age were u s e d as s u b j e c t s . U s i n g gas exchange measure- ments they determined the a n a e r o b i c t h r e s h o l d f o r b i c y c l i n g and t r e a d m i l l r u n n i n g w h i c h o c c u r r e d a t 69.4% and 74.5% of V02max, r e s p e c t i v e l y . These v a l u e s were e q u i v a l e n t of 2.58 and 2.90 1/min, r e s p e c t i v e l y , when e x p r e s s e d i n a b s o l u t e terms. T h e i r s t a t i s t i c a l a n a l y s i s showed a s i g n i f i c a n t d i f f e r e n c e between a n a e r o b i c t h r e s h o l d on b i c y c l e and t r e a d m i l l . I n a d d i t i o n , t h e y o b s e r v e d a s i g n i f i c a n t r e l a t i o n s h i p between a n a e r o b i c t h r e s h o l d (VO2 i n 1/min) and V0 2max ( r b i k e = 0 . 7 9 , r t r e a d m i l l : = 0 » 7 6 ) . However, when a n a e r o b i c t h r e s h o l d was e x p r e s s e d as % VG^max, r e l a t i o n s h i p s f o r a n a e r o b i c t h r e s h o l d a n d VC^max were f o u n d t o be n o n - s i g n i f i c a n t ( r b i k e = 0.4, r t r e a d m i l l = 0 • 1 0 ) • Based on t h e s e f i n d i n g s the a u t h o r s c o n c l u d e d t h a t a n a e r o b i c t h r e s h o l d may be e x e r c i s e m o d a l i t y dependent. B a l l e t a l . ( 1 9 8 1 ) i n v e s t i g a t e d the change i n the p a t t e r n o f v e n t i l a t i o n ( v T , f ) d u r i n g p r o g r e s s i v e work above and b e l o w a n a e r o b i c t h r e s h o l d and t h e i n f l u e n c e o f d i f f e r e n t m u s c l e g r o u p s (arm v e r s u s l e g ) i n a f f e c t i n g the r e s p o n s e . Seven male and s i x f e m a l e c o l l e g e - a g e d s u b j e c t s u n d e r w e n t p r o g r e s s i v e l e g and arm ergometer t e s t s u n t i l f a t i g u e , w h i l e gas exchange measurements were t a k e n . The f i n d i n g s showed t h a t f o r b o t h arm and l e g ergometry, the n o n l i n e a r i n c r e a s e i n above a n a e r o b i c t h r e s h o l d was c o i n c i d e n t w i t h a n o n l i n e a r i n c r e a s e i n f and a p l a t e a u i n g of Vf f o r l e g e x e r c i s e , the s l o p e o f and f v e r s u s time i n c r e a s e d from 2.75 and 0.75 below t h e a n a e r o b i c t h r e s h o l d t o 10.0 and 4.14 above t h e a n a e r o b i c t h r e s h o l d , r e s p e c t i v e l y , w h i l e f o r arm e x e r c i s e , t h e s e s l o p e c h a n g e s f o r VE and f were 2.60 and 1.16 below the a n a e r o b i c t h r e s h o l d and 10.3 and 4.88 above the a n a e r o b i c t h r e s h o l d . F u r t h e r m o r e , i t was found t h a t p l a t e a u e d a t a s i g n i f i c a n t l y l o w e r volume d u r i n g arm e x e r c i s e a l t h o u g h no s i g n i f i c a n t d i f f e r e n c e s were n o t e d i n maximum f . The a u t h o r s c o n c l u d e d t h a t the lower a n a e r o b i c t h r e s h o l d d u r i n g arm e x e r c i s e compared t o l e g e x e r c i s e and t h e p l a t e a u of V f a t a n a e r o b i c t h r e s h o l d d u r i n g b o t h f o r m s o f e x e r c i s e , s u g g e s t s a r e l a t i o n s h i p between h y p o c a p n i a and the Vf p l a t e a u . The s p e c i f i c i t y of the a n a e r o b i c t h r e s h o l d was examined by W i t h e r s e t a l . ( 1 9 8 1 ) i n 10 e n d u r a n c e - t r a i n e d c y c l i s t s and 10 e n d u r a n c e - t r a i n e d r u n n e r s . When a n a e r o b i c t h r e s h o l d was e x p r e s s e d i n r e l a t i v e terms (%V02max) they o b s e r v e d no s i g n i f i c a n t d i f f e r e n c e s between t h e c y c l i s t s ( 6 6 . 3 % ) and ru n n e r s (61.2%) on the b i c y c l e ergometer o r the r u n n e r s (77.3%) and c y c l i s t s (74.3%) on the t r e a d m i l l . However, when a n a e r o b i c t h r e s h o l d was e x p r e s s e d i n a b s o l u t e terms the c y c l i s t s demon- s t r a t e d s i g n i f i c a n t l y g r e a t e r a n a e r o b i c t h r e s h o l d s t h a n t h e r u n n e r s ( 3 .0 v e r s u s 2.56 1/min) on t h e b i c y c l e ergometer, w h i l e the r u n n e r s demonstrated s i g n i f i c a n t l y h i g h e r a n a e r o b i c t h r e s h o l d s t h a n t h e c y c l i s t s ( 52.7 v e r s u s 46.8 ml/kg/min) on the t r e a d m i l l . The i n v e s t i g a t o r s a t t r i b u t e d the ten d e n c y f o r t h e b e t t e r a n a e r o b i c t h r e s h o l d s t o be r e c o r d e d by the group t e s t e d on t h e a c t i v i t y f o r w h i c h i t t r a i n e d t o t h e s p e c i f i c l o c a l m u s c u l a r a d a p t a t i o n s t o c y c l i n g and r u n n i n g . The Relationship Between the Onset of Metabolic Acidosis and Hyperventilation S t u d i e s have shown t h a t v e n t i l a t i o n and b l o o d l a c t i c a c i d d i s p l a y s i m i l a r a b r u p t i n c r e a s e s d u r i n g an i n c r e m e n t a l e x e r c i s e t e s t t o f a t i g u e . R e s e a r c h e r s have s p e c u l a t e d t h a t t h e s e s i m i l a r i t i e s i n o c c u r e n c e a t t h e "b r e a k a w a y " p o i n t between v e n t i l a t i o n and b l o o d l a c t a t e may be due t o the r e l e a s e of H + which i n c r e a s e s CO2 d e l i v e r y t o the l u n g s and, s u b s e q u e n t l y , s t i m u l a t e v e n t i l a t i o n (Wasserman e t a l . 1973, Whipp and D a v i s 1979). Hagberg e t a l . (1982) d e s i g n e d a st u d y where they c o u l d t e s t t h e a f o r e m e n t i o n e d s p e c u l a t i o n . They e x a m i n e d f o u r M c A r d l e ' s d i s e a s e p a t i e n t s who, due t o the l a c k of myophos- p h o r y l a s e , a r e i n c a p a b l e o f m u s c l e g l y c o g e n o l y s i s . T h e i r v e n t i l a t o r y t h r e s h o l d o c c u r r e d a t 81% of VO^max. They o b s e r v e d t h a t b l o o d l a c t i c a c i d d i d n o t r i s e above r e s t i n g v a l u e s and v e n o u s pH d i d not de c r e a s e but r a t h e r i n c r e a s e d . These o b s e r v a t i o n s suggested t h a t h y p e r v e n t i l a t i o n d u r i n g e x e r c i s e i s not c a u s a l l y r e l a t e d w i t h the m e t a b o l i c a c i d o s i s . F a r r e l e t a l . ( 1 9 8 3 ) e x a m i n e d 8 m a l e s who u n d e r w e n t c y c l e ergometer t e s t s on two s e p a r a t e o c c a s i o n s ; the c o n t r o l and t h e e x p e r i m e n t a l t r e a t m e n t . I n t h e c o n t r o l t r e a t m e n t the s u b j e c t s p e d a l e d f o r 4 min a t 0 w o r k - l o a d and t h e r e a f t e r , a t a w o r k - l o a d which was i n c r e a s i n g 135 kpm e v e r y min u n t i l f a t i g u e , w h i l e l a c t a t e measurements were t a k e n p r i o r t o t h e t e s t and a t t h e end of each w o r k - l o a d . V e n t i l a t o r y measurements were a l s o m o n i t o r e d a t each w o r k - l o a d . In the e x p e r i m e n t a l t r e a t m e n t , t h e s u b j e c t s p e r f o r m e d t h e same t e s t as i n the c o n t r o l t r e a t m e n t , a f t e r they f i r s t performed two 3-min work b o u t s a t 1300-2000 kp/min on t h e c y c l e ergometer i n o r d e r i t o p r e m a t u r e l y r a i s e b l o o d l a c t a t e l e v e l s and l o w e r b l o o d pH. They o b s e r v e d t h a t the onset of h y p e r v e n t i l a t i o n o c c u r r e d a t the same VO2 i n both t r e a t m e n t s ( c o n t r o l = 2 . 3 2 , e x p e r i m e n t a l 2.15 1/min) a l t h o u g h a t t h i s p o i n t , b l o o d l a c t a t e was s i g n i f i - c a n t l y e l e v a t e d ( c o n t r o l = l . 9 9 , e x p e r i m e n t a l = 1 0 . 3 0 mM) and b l o o d pH s i g n i f i c a n t l y d e p r e s s e d ( c o n t r o l = 7.352, e x p e r i m e n - t a l i s e ? ) d u r i n g the e x p e r i m e n t a l t r e a t m e n t . These o b s e r v a t i o n s l e d t h e i n v e s t i g a t o r s t o c o n c l u d e t h a t t h e r i s e i n b l o o d l a c t a t e and d e c l i n e i n b l o o d pH w i t h the onset of h y p e r v e n t i l a t i o n a r e c o i n c i d e n t a l r a t h e r than c a u s a l . M o r r i s o n e t a l . (1983) i n v e s t i g a t e d the e f f e c t of a l k a l i n e i n f u s i o n on the a n a e r o b i c t h r e s h o l d . S i x males (mean VC>2max=4.01 1/min) u n d e r w e n t i n c r e m e n t a l c y c l e e r g o m e t e r t e s t s u n t i l f a t i g u e . B l o o d pH a t maximum power o u t p u t was 7.24, and plasma b i c a r b o n a t e 18.1 mmol/1. In a r e p e a t t e s t on a n o t h e r o c c a s i o n , 4.2% NaHC03 was i n f u s e d i n t r a v e n o u s l y a t a r a t e which k e p t b l o o d pH and b i c a r b o n a t e a t r e s t i n g l e v e l s . Con- s e q u e n t l y , b l o o d pH (7.36) and b i c a r b o n a t e (27.0 mmol) were s i g n i f i c a n t l y h i g h e r u n d e r n e u t r a l c o n d i t i o n s t h a t t h o s e under a c i d e m i c c o n d i t i o n s , w h i l e VC^max d i d not d i f f e r s i g n - i f i c a n t l y i n t h e two c o n d i t i o n s . V e n t i l a t o r y " b r e a k a w a y " was a l s o f o u n d t o be n o t s i g n i f i c a n t l y d i f f e r e n t f o r t h e n e u t r a l ( 7 9 . 1 % VC^max) and a c i d e m i c (76.8% VC^max) c o n d i t i o n . f V e n t i l a t i o n a t 100% V02max was a l s o s i m i l a r f o r a c i d e m i c (150 1/min) and n e u t r a l (154 1/min) c o n d i t i o n , as w e l l as peak b l o o d l a c t a t e f o r a c i d e m i c (10.4 mmol/1) and n e u t r a l (10.9 mmol/1). However, peak CO2 o u t p u t was s i g n i f i c a n t l y d i f f e r e n t f o r a c i d e m i c (4.58 1/min) and n e u t r a l (5.10 1/min) c o n d i t i o n . These f i n d i n g s l e d the i n v e s t i g a t o r s t o c o n c l u d e t h a t the v e n t i l a t o r y "breakaway" i s u n a f f e c t e d when a c i d o s i s i s c o r r e c t e d w i t h NaHC03, and they suggested t h a t n o n - c h e m i c a l s t i m u l i c o n t r i b u t e t o w a r d t h e i n c r e a s e i n v e n t i l a t i o n a t the a n a e r o b i c t h r e s h o l d . The g e n e r a l c o n c l u s i o n o f t h e a f o r e m e n t i o n e d s t u d i e s , t h a t the i n c r e a s e i n l a c t a t e c o n c e n t r a t i o n i s not r e s p o n s i b l e f o r the i n c r e a s e i n v e n t i l a t i o n d u r i n g an i n c r e m e n t a l e x e r c i s e , i s a l s o c o n f i r m e d w i t h s t u d i e s by D a v i s and Gass ( 1 9 8 1 ) , Ivy e t a l . ( 1 9 8 1 ) , and G u t i n e t a l . ( 1 9 8 0 ) . Of s p e c i a l i n t e r e s t i s the f i n d i n g of G u t i n e t a l . (1980) and Simon e t a l . (1983-a) t h a t the v e n t i l a t o r y " b r e a k p o i n t " o c c u r r e d b e f o r e t h e l a c t a t e " b r e a k p o i n t . " Training and Anaerobic Threshold C o s t i l l e t a l . (1973) and D a n i e l s (1974) have r e p o r t e d t h a t i n d i v i d u a l s w i t h s i m i l a r V02max v a l u e s p e r f o r m q u i t e d i f f e r e n t l y i n an endurance c o m p e t i t i o n . In a d d i t i o n , A s t r a n d and Rodahl (1977) and Wilmore (1977) p o i n t out t h a t a t h l e t e s may c o n t i n u e t o i m p r o v e t h e i r p e r f o r m a n c e a l t h o u g h t h e i r V02max r e a c h e s a p l a t e a u . These o b s e r v a t i o n s i n d i c a t e t h a t o t h e r f a c t o r s than VO^max may a l s o a f f e c t endurance per f o r m a n c e . D a v i s e t a l . (1979) d e s i g n e d an experiment where they i n v e s t i g a t e d one s u c h f a c t o r , t h e a n a e r o b i c t h r e s h o l d . Nine middle-aged men performed c y c l e endurance t r a i n i n g 5 days p e r week e a c h f o r 45 min per e x e r c i s e s e s s i o n f o r 9 weeks. For the f i r s t 4 weeks of t r a i n i n g the s u b j e c t s e x e r c i s e d a t a t a r g e t h e a r t r a t e d e s i g n e d t o c o r r e s p o n d t o a VC^max 50% of the way between • t h e a n a e r o b i c t h r e s h o l d and VC^max. F o r the l a s t 5 weeks of t r a i n i n g t h i s v a l u e was i n c r e a s e d t o 70%. A f t e r t r a i n i n g , the a n a e r o b i c t h r e s h o l d i n c r e a s e d s i g n i f i c a n t l y by 44%, e x p r e s s e d as a b s o l u t e VO2, and by 15%, e x p r e s s e d r e l a t i v e t o V0 2max. Ready and Quinney (1982) examined a l t e r a t i o n s i n a n a e r o b i c t h r e s h o l d as the r e s u l t of endurance t r a i n i n g and d e t r a i n i n g i n 21 m a l e s , 25 y e a r s o f age. The t r a i n i n g c o n s i s t e d of c y c l i n g on t h e e r g o m e t e r a t 80% o f VC^max f o r 30 min f o u r t i m e s per week f o r 9 weeks. T r a i n i n g r e s u l t e d i n 70.4% and 19.4% i n c r e a s e s i n a n a e r o b i c t h r e s h o l d e x p r e s s e d as a b s o l u t e (1/min) and r e l a t i v e (%V02max) terms, r e s p e c t i v e l y . However, the change i n r e l a t i v e a n a e r o b i c t h r e s h o l d was not s t a t i s t i c a l l y s i g n i f i c a n t . F o l l o w i n g 9 weeks of d e t r a i n i n g 37.1% of the i n c r e a s e i n a b s o l u t e a n a e r o b i c t h r e s h o l d was remained. A l t h o u g h t h e d e c r e a s e i n a n a e r o b i c t h r e s h o l d was s u b s t a n t i a l 6 weeks a f t e r t r a i n i n g , the f i n a l v a l u e remained s i g n i f i c a n t l y e l e v a t e d above t h e p r e - t e s t measurement. The a u t h o r s c o n c l u d e d t h a t 9 weeks of t r a i n i n g i s s u f f i c i e n t time t o cause s i g n i f i c a n t c h a n g e s i n a n a e r o b i c t h r e s h o l d and t h e l o s s o f a n a e r o b i c t h r e s h o l d due t o d e t r a i n i n g appears t o be s i m i l a r t o changes i n V0 2max. The e f f e c t o f e n d u r a n c e t r a i n i n g a t an i n t e n s i t y c o r - r e s p o n d i n g t o 4 mmol/1 a r t e r i a l b l o o d l a c t a t e c o n c e n t r a t i o n was e x a m i n e d by Y o s h i d a e t a l . ( 1 9 8 2 ) . Seven male c o l l e g e s t u d e n t s underwent c y c l e e r g o m e t e r t r a i n i n g f o r 15 min on 3 da y s p e r week f o r 8 weeks, a t an i n t e n s i t y c o r r e s p o n d i n g t o 4 mmol/1 a r t e r i a l b l o o d l a c t a t e d e termined d u r i n g an i n c r e - m e n t a l e x e r c i s e t e s t . T h i s t r a i n i n g r e s u l t e d i n s i g n i f i c a n t i n c r e a s e i n a b s o l u t e a n a e r o b i c t h r e s h o l d ( 3 7 % ) , i n the onset o f r e s p i r a t o r y c o m p e n s a t i o n o f m e t a b o l i c a c i d o s i s ( 1 7 % ) , and V02max ( 1 4 % ) . F u r t h e r m o r e , t h e y o b s e r v e d s i g n i f i c a n t d e c r e a s e s i n submaximal VO2 ( 4 % ) , Vg ( 1 5 % ) , h e a r t r a t e (10%), R ( 5 % ) , and l a c t a t e ( 2 3 % ) . Based on th e s e f i n d i n g s t he i n v e s t i - g a t o r s s u g g e s t e d t h a t t he endurance t r a i n i n g i n t e n s i t y c o r - r e s p o n d i n g t o 4 mmol/1 a r t e r i a l l a c t a t e , as s u g g e s t e d by K i n d e r m a n e t a l . ( 1 9 7 9 ) , would be one of the most e f f e c t i v e methods f o r endurance t r a i n i n g . D enis e t a l . (1982) i n v e s t i g a t e d t he e f f e c t of 40 weeks of e n d u r a n c e t r a i n i n g on t h e a n a e r o b i c t h r e s h o l d i n f i v e s u b j e c t s , 35 y e a r s o f a g e . The s u b j e c t s underwent b i c y c l e ergometer e x e r c i s e l a s t e d 60 min p e r day 3 day s a week a t an i n t e n s i t y c o r r e s p o n d i n g t o 80-85% of V02max. T h i s t r a i n i n g r e s u l t e d i n i n c r e a s e s i n t h e v e n t i l a t o r y t h r e s h o l d (10%), l a c t a t e t h r e s h o l d ( 1 1 % ) , a n a e r o b i c t h r e s h o l d a t 4 mmol/1 l a c t a t e ( 1 8 % ) , m a x i m a l work l o a d ( 2 2 % ) , and net e f f i c i e n c y ( 1 4 % ) . However, no s i g n i f i c a n t i n c r e a s e was o b s e r v e d i n V02max. F u r t h e r m o r e , i t was shown t h a t a l t h o u g h the i n c r e a s e i n maximal work l o a d was s i g n i f i c a n t f r o m t h e 1 0 t h week o f t r a i n i n g , t h e i n c r e a s e i n a n a e r o b i c t h r e s h o l d s appeared a t the 20t h week. S j o d i n e t a l . ( 1 9 8 2 ) e x a m i n e d m u s c l e enzyme a c t i v i t y changes o c c u r r i n g w i t h an added t r a i n i n g o f 20 min r u n n i n g a t a v e l o c i t y where VQBLA o c c u r r e d (4 mmol/1 l a c t a t e ) once a week f o r 14 weeks t o the r e g u l a r program of e i g h t w e l l - t r a i n e d m i d d l e and l o n g d i s t a n c e male r u n n e r s . They obse r v e d a s i g n i f i - c a n t i n c r e a s e i n VQBLA (from 4.69 t o 4.89 m x s ~ l ) , s i g n i f i c a n t d e c r e a s e i n p h o s p h o f r u c t o c i n a s e ( f r o m 7.65 t o 5.35 m o l e s x g - l x m i n - ! x io~®) , w h i l e the a c t i v i t i e s of l a c t a t e de- hydrogenase and c i t r a t e s y n t h a s e were u n c h a n g e d . However, a s i g n i f i c a n t d e c r e a s e i n PFK/CS a c t i v i t y r a t i o from 1.42 t o 0.90 moles x g ~ l x m i n - ! x i o~4 w a s o b s e r v e d . The VO^max of the r u n n e r s d i d n o t i n c r e a s e s i g n i f i c a n t l y o v e r t h e 14 weeks. These o b s e r v a t i o n s l e d the i n v e s t i g a t o r s t o c o n c l u d e t h a t the t r a i n i n g i n t e n s i t y c o r r e s p o n d i n g t o VQBLA w i l l i n c r e a s e VQBLA and w i l l r e s u l t i n l o c a l m e t a b o l i c a d a p t a t i o n s i n the a c t i v e s k e l e t a l m u s c l e s o f w e l l - t r a i n e d r u n n e r s w i t h o u t a s i g n i f i c a n t change i n VC^max. A l t e r a t i o n s i n m u s c l e m e t a b o l i t e s and b l o o d l a c t a t e i n work above and below the a n a e r o b i c t h r e s h o l d were i n v e s t i g a t e d by Green e t a l . ( 1 9 8 0 ) . F i v e a c t i v e c o l l e g e s t u d e n t s s e r v e d as s u b j e c t s f o r t h e s t u d y and t h e y e x e r c i s e d a t c o n s t a n t w o r k - l o a d on d i f f e r e n t o c c a s i o n s a t VO2 v a l u e s c o r r e s p o n d i n g t o 50, 70, 107 and 117% of V 0 2 a t a n a e r o b i c t h r e s h o l d . When t h e s u b j e c t s e x e r c i s e d b e l o w t h e VO2 a n a e r o b i c t h r e s h o l d , no change was found i n a n a e r o b i c t h r e s h o l d , c r e a t i n e , l a c t a t e , g l u c o s e - 6 - P o r c i t r a t e w h i l e a 20% r e d u c t i o n i n c r e a t i n e p h o s p h a t e was o b s e r v e d . A t 107% V 0 2 a n a e r o b i c t h r e s h o l d , c r e a t i n e p h o s p h a t e was r e d u c e d ( 1 2 . 2 t o 9.6 mmol"kg - 1 wet wt) and l a c t a t e was i n c r e a s e d ( 3 . 1 t o 7.7 mmol * k g - l ) . At 117% VO2 a n a e r o b i c t h r e s h o l d , c r e a t i n e phosphate was dec r e a s e d even f u r t h e r ( t o 5 . 2 mmol*kg~l) , l a c t a t e i n c r e a s e d ( t o 16.7 mmol'kg- 1), as w e l l as g l u c o s e - 6 - P (0.37 t o 0.83 m m o l ' k g - 1 ) , and c r e a t i n e (13.8 t o 18.6 m m o l ' k g - 1 ) . B l o o d l a c t a t e i n c r e a s e s were o n l y o b s e r v e d i n work above t h e VO2 a n a e r o b i c t h r e s h o l d , and t h e b l o o d c o n c e n t r a t i o n s were c o n s i s t e n t l y b e l o w t h e m u s c l e c o n c e n t r a t i o n s . The l a t t e r became more e x a g g e r a t e d the h i g h e r the VO2 a n a e r o b i c t h r e s h o l d . H e n r i t z e e t a l . (1982) i n v e s t i g a t e d the e f f e c t s of t r a i n i n g above and below the onset of b l o o d l a c t a t e a c c u m u l a t i o n on c a r d i o v a s c u l a r and body c o m p o s i t i o n p a r a m e t e r s i n c o l l e g e women. The s u b j e c t s who t r a i n e d 5 days p e r week f o r 12 weeks were d i v i d e d i n two grou p s , above-OBLA and below-OBLA. A f t e r the t r a i n i n g p e r i o d i t was observed t h a t o n l y the above-OBLA group showed a s i g n i f i c a n t i n c r e a s e i n V02max (6%) and VO2-OBLA ( 4 8 - 5 0 % ) . I t was f u r t h e r observed t h a t w h i l e both the above-OBLA and below-OBLA g r o u p s showed s i g n i f i c a n t i n c r e a s e s i n V O 2 - 0BLA/V02raax p r e - p o s t t r a i n i n g the below-OBLA group demonstrated o n l y a 16% i n c r e a s e w h i l e t h e above-OBLA g r o u p i n c r e a s e d by 4 2 % . Body c o m p o s i t i o n p a r a m e t e r s r e m a i n e d u n c h a n g e d . The i n v e s t i g a t o r s c o n c l u d e d t h a t OBLA may be a c r i t i c a l t r a i n i n g i n t e n s i t y f o r e l i c i t i n g changes i n VC^max and VO2-OBLA, and t h a t l a r g e i m p r o v e m e n t s i n V02max may not be r e q u i r e d f o r l a r g e improvements i n VO2-OBLA. R o b i n s o n and S u c e c ( 1 9 8 0 ) e x a m i n e d t h e r e l a t i o n s h i p of t r a i n i n g i n t e n s i t y and a n a e r o b i c t h r e s h o l d t o e n d u r a n c e performance as measured by a 15 min r u n . Twenty-one n o r m a l l y a c t i v e males, 22.3 y e a r s of age were d i v i d e d i n t o d i s t a n c e , i n t e r v a l and c o n t r o l g r o u p s . The t r a i n i n g program l a s t e d 12 weeks and each group was t r a i n i n g as f o l l o w s : 1) D i s t a n c e (D) - r u n n i n g c o n t i n u o u s l y f o r 30 min f o r a mean f r e q u e n c y o f 2.8 t i m e s p e r week ( c a . 85% V02max) and a mean speed of 217 m/min. 2) I n t e r v a l ( I ) - r u n n i n g i n t e r v a l s of 100m, 200m, 300m a t a t i m e work t o r e s t r a t i o of 1:3 f o r 30 min f o r a mean f r e q u e n c y o f 2.9 t i m e s per week ( c a . 125% V02max) and a mean speed of 323 m/min. 3) C o n t r o l (C) - c o n t i n u e d t h e same a c t i v i t y p a t t e r n d u r i n g the t r a i n i n g p e r i o d . The f i n d i n g s showed t h a t : 1) the mean V0 2max s c o r e s i n c r e a s e d 8.9% (3.73 t o 4.06 1/min) f o r D group and o n l y 3.1% (3.80 t o 3.9o 1/min) and 3.2% (3.30 t o 3.41 1/min) f o r I and C g r o u p s , r e s p e c t i v e l y . 2) The a n a e r o b i c t h r e s h o l d changes r e s u l t e d i n mean i n c r e a s e s of 15.6% (2.35 t o 2.72 1/min) f o r VO2 a t a n a e r o b i c t h r e s h o l d f o r D group, 11.3% (2.55 t o 2.84 1/min) f o r I group and 6.5% (2.08 t o 2.81 1/min) f o r C group. 3) i n c r e a s e s i n a n a e r o b i c t h r e s h o l d when e x p r e s s e d i n r e l a t i v e t e r m s (%V02max) were 6.2% f o r D group (63.1 t o 67.0 % ) , 8.1% f o r I g r o u p (67.8 t o 7 3 . 3 % ) , and 3.0% f o r C group (63.3 t o 6 5 . 2 % ) . 4) endurance performance i n c r e a s e d 1 9.3% f o r D g r o u p (2.95 t o 3.5 km), 12.8% f o r I g r o u p (3.07 t o 3.47 km), and 1.3% f o r C group (2.97 t o 3.0 km). The c o r r e l a t i o n c o e f f i c i e n t s f o r the change • • • i n V02max and a n a e r o b i c t h r e s h o l d (VO2 and %V02max) w i t h changes i n endurance performance were 0.14, -0.61, and -0.35, r e s p e c t i v e l y . Based on t h e s e o b s e r v a t i o n s the a u t h o r s c o n c l u d e d • t h a t b o t h m o d e r a t e ( c a . 85% VO^max) and i n t e n s i v e ( c a . 125% • V02max) t r a i n i n g i n c r e a s e s a n a e r o b i c t h r e s h o l d and endurance performance, ant t h a t a n a e r o b i c t h r e s h o l d changes a r e c l o s e l y r e l a t e d t o endurance performance changes than VO2 changes. M e t a b o l i c and performance r e s p o n s e s t o a n a e r o b i c t h r e s h o l d and h i g h i n t e n s i t y t r a i n i n g were s t u d i e d by R i v e r a e t a l . ( 1 9 8 0 ) . Twenty-four female swimmers, 12-19 y e a r s of age were s u b j e c t e d t o s i x weeks of i n t e r v a l t r a i n i n g w h i l e t h e y were d i v i d e d i n two groups as f o l l o w s : Group I - h i g h i n t e n s i t y t r a i n i n g ( 8 4 . 1 1 % o f s u b j e c t s ' b e s t p e r f o r m a n c e t i m e ) . Group I I - t r a i n i n g a t the a n a e r o b i c t h r e s h o l d (an i n t e n s i t y which e l i c i t e d an a c c u m u l a t i o n of 4 mmol/1 l a c t a t e ) . Maximal a e r o b i c c a p a c i t y , m a x i m a l a l a c t a c i d c a p a c i t y , and m a x i m a l l a c t a c i d c a p a c i t y were d e t e r m i n e d f r o m a t e t h e r e d swimming t e s t , w h i l e 100 and 400 meters timed swim were a l s o performed from each s u b j e c t . The f i n d i n g s showed t h a t both groups had s i g n i f i c a n t i n c r e a s e s i n m a x i m a l a e r o b i c c a p a c i t y , m a x i m a l a l a c t a c i d c a p a c i t y , and maximal l a c t a c i d c a p a c i t y . However, the Group I demonstrated s i g n i f i c a n t l y g r e a t e r g a i n s over the Group I I : maximal a e r o b i c c a p a c i t y 11.42 v e r s u s 3.08 c a l / k g * m i n , m a x i m a l a l a c t a c i d c a p a c i t y 13.10 v e r s u s 2.62 c a l / k g , and maximal l a c t a c i d c a p a c i t y 11.42 v e r s u s 8.73 c a l / k g . With r e g a r d s t o perf o r m a n c e , both g r o u p s i m p r o v e d , w i t h t h e Group I I i m p r o v i n g a t a f a s t e r r a t e t h a n Group I i n 100 m (2.07 v e r s u s 1.63 sec) and 400 m (8.18 v e r s u s 4.63 s e c ) . The a u t h o r s ' c o n c l u s i o n from t h i s s t u d y was t h a t Group I t r a i n i n g had a more p r o f o u n d e f f e c t on the m e t a b o l i c r e s p o n s e s , but Group I I was more e f f e c t i v e on the performance t e s t s . G i b b o n s e t a l . ( 1 9 8 1 ) e x a m i n e d t h e e f f e c t o f v a r i o u s t r a i n i n g i n t e n s i t i e s on a n a e r o b i c t h r e s h o l d , a n a e r o b i c power and V02max i n 29 young (mean age = 19.8 y e a r s ) l o w f i t (mean • V02max = 35 m l / k g / m i n ) f e m a l e s . The s u b j e c t s were d i v i d e d i n t h r e e g r o u p s , Group I ( a n a e r o b i c t h r e s h o l d h e a r t r a t e ) , Group I I ( a n a e r o b i c t h r e s h o l d h e a r t r a t e p l u s 40% of a n a e r o b i c t h r e s h o l d h e a r t r a t e ) , and Group I I I ( a n a e r o b i c t h r e s h o l d h e a r t r a t e m i n u s 40% o f a n a e r o b i c t h r e s h o l d h e a r t r a t e ) . They t r a i n e d f o r 8 weeks on t r e a d m i l l s a t i n d i v i d u a l t r a i n i n g h e a r t r a t e s (+ 5 b/min). A f t e r the t r a i n i n g p e r i o d the t h r e e groups i n c r e a s e d s i g n i f i c a n t l y i n a n a e r o b i c t h r e s h o l d , a n a e r o b i c power and VC^max f r o m p r e - t o p o s t - t e s t . No s i g n i f i c a n t d i f f e r e n c e was found between gr o u p s . The a u t h o r s c o n c l u d e d t h a t a n a e r o b i c t h r e s h o l d , a n a e r o b i c power, and VC^max a r e a l l t r a i n a b l e w i t h i n the i n t e n s i t y l e v e l s which were i n v e s t i g a t e d and t h e y recommended t h a t l o w - f i t f e m a l e s s h o u l d t r a i n a t a l e v e l 40% below t h e i r a n a e r o b i c t h r e s h o l d . The e f f e c t o f i n t e n s i t y and q u a n t i t y o f e x e r c i s e on the a e r o b i c (2 mmol/1 l a c t a t e ) and a n a e r o b i c (4 mmol/1 l a c t a t e ) t h r e s h o l d s were i n v e s t i g a t e d by L a F o n t a i n e e t a l . ( 1 9 8 2 ) . F o r t y m o d e r a t e l y f i t ( a n a e r o b i c t h r e s h o l d s o f 5 5 % t o 70% of V02max) males were used f o r the s t u d y . The s u b j e c t s t r a i n e d a t e i t h e r low ( a n a e r o b i c t h r e s h o l d minus 20 b/min) , medium ( a e r o b i c t h r e s h o l d ) , o r h i g h i n t e n s i t y ( a n a e r o b i c t h r e s h o l d ) and e i t h e r low (15 m i l e s p e r week) o r h i g h (30 m i l e s p e r week) q u a n t i t y f o r t e n weeks. T r a i n i n g o c c u r r e d f i v e days per week and i n t e n s i t y was m o n i t o r e d d a i l y . A f t e r the t r a i n i n g p e r i o d t h e i n v e s t i g a t o r s found: 1) the low i n t e n s i t y groups d i d not i n c r e a s e t h e i r a e r o b i c o r a n a e r o b i c t h r e s h o l d s , 2) t h e g r o u p s t r a i n i n g a t medium and h i g h i n t e n s i t y i n c r e a s e d t h e i r a e r o b i c t h r e s h o l d s s i g n i f i c a n t l y more t h a n t h e g r o u p s t r a i n i n g a t low i n t e n s i t y , and 3) t h e g r o u p s t r a i n i n g a t medium i n t e n s i t y - h i g h q u a n t i t y and a t h i g h i n t e n s i t y - l o w q u a n t i t y i n c r e a s e d t h e i r a n a e r o b i c t h r e s h o l d s i g n i f i c a n t l y more t h a n t h e o t h e r g r o u p s . V02max d i d not change i n the s u b j e c t s t e s t e d . A c c o r d i n g t o t h e a u t h o r s t h e s e f i n d i n g s i n d i c a t e d i n i n t e n s i t y t h r e s h o l d f o r i n c r e a s e s i n the a e r o b i c t h r e s h o l d . Howard e t a l . (1982) examined m i t o c h o n d r i a l volume changes i n d i f f e r e n t muscle f i b e r t y p e s due t o t r a i n i n g a t the a n a e r o b i c t h r e s h o l d . F i v e u n t r a i n e d s u b j e c t s u n d e r w e n t 6 weeks o f b i c y c l e ergometer t r a i n i n g 5 t i m e s a week f o r 30 min a t an i n t e n s i t y o f 6 0 - 8 2 % o f t h e i r i n d i v i d u a l V0 2max, e l i c i t i n g a b l o o d l a c t a t e c o n c e n t r a t i o n o f 4 mmol/1. T h i s t r a i n i n g r e s u l t e d i n s i g n i f i c a n t i n c r e a s e s i n m a x i m a l power ( 1 2 % ) , • VC^max ( 1 3 % ) , power a t a b l o o d l a c t a t e c o n c e n t r a t i o n of 4 mmol/1 ( 1 8 % ) , volume d e n s i t y of m i t o c h o n d r i a i n v a s t u s l a t e r a l i s m u s c l e ( 4 0 % ) , and t h e number o f c a p i l l a r i e s p e r number of muscle f i b e r ( 2 1 % ) . Type I I B f i b e r s demonstrated the l a r g e s t i n c r e a s e s i n m i t o c h o n d r i a l volume ( f r o m 2.47% t o 4 . 0 7 % ) , f o l l o w e d by the Type I I A f i b e r s ( f r o m 4.47% t o 6.60%) and the Type I f i b e r s ( f r o m 6.21% t o 7.13%). These o b s e r v a t i o n s l e d t h e i n v e s t i g a t o r s t o c o n c l u d e t h a t u n t r a i n e d s u b j e c t s e x e r c i s i n g a t a n a e r o b i c t h r e s h o l d show a s i g n i f i c a n t i n c r e a s e i n a e r o b i c c a p a c i t y and an even g r e a t e r i n c r e a s e i n m u s c l e m i t o c h o n d r i a l volume, e s p e c i a l l y i n Type I I f i b e r s . Anaerobic Threshold Alterations Following Prolonged Aerobic Exercise W i s w e l l e t a l . ( 1 9 8 0 ) e x a m i n e d w h e t h e r l o w e r i n g t h e muscle g l y c o g e n a f f e c t s the a n a e r o b i c t h r e s h o l d . S i x marathon r u n n e r s (mean V02max =57.26 m l / k g / m i n ) were s u b j e c t e d t o a V02max t e s t on a b i c y c l e e r g o m e t e r . A f t e r the t e s t the s u b j e c t s r e s t e d f o r 20 min and t h e n t h e y r a n f o r 2 h o u r s i n m a x i m a l e f f o r t ( c o v e r i n g 14-17 m i l e s ) . When the run was completed they r e s t e d f o r a n o t h e r 20 min and r e p e a t e d t h e • V 0 2 m a x t e s t . A n a e r o b i c t h r e s h o l d was o b t a i n e d by u s i n g gas • • • exchange measurements (Vg, Vg / V 0 2 and F E O 2 ) and b l o o d l a c t a t e s were t a k e n a t 4 min a f t e r e x e r c i s e . The f i n d i n g s showed an 8.4% r e d u c t i o n i n VO^max (from 4.5 t o 4.12 1/min) accompanied w i t h a r e d u c t i o n i n a n a e r o b i c t h r e s h o l d of 10.7% when e x p r e s s e d i n a b s o l u t e t e r m s ( f r o m 3.65 t o 3.26 1/min) o r 10.4% when e x p r e s s e d i n r e l a t i v e terms (from 81.3% t o 72 . 0 % ) . A d e c r e a s e o f 4 5 % was a l s o o b s e r v e d i n p o s t - e x e r c i s e maximum l a c t a t e . F u r t h e r m o r e , r e s p i r a t o r y e x c h a n g e r a t i o was s i g n i f i c a n t l y r e d u c e d a t any g i v e n VO^max d u r i n g t h e s e c o n d t e s t . The i n v e s t i g a t o r s s p e c u l a t e d t h a t t h i s m i g h t be t h e r e s u l t o f a change i n t y p e o f f u e l s u b s t r a t e u t i l i z e d a f t e r the r u n . A n o n - s i g n i f i c a n t r e l a t i o n s h i p between the dec r e a s e i n p o s t - e x e r c i s e l a c t a t e and t h e d e c r e a s e i n a n a e r o b i c t h r e s h o l d was f o u n d . The i n v e s t i g a t o r s c o n c l u d e d t h a t t h e i n c r e a s e i n a n a e r o b i c t h r e s h o l d t h a t o c c u r s w i t h endurance t r a i n i n g may be brought about a t l e a s t i n p a r t by i n c r e a s i n g m u s c l e g l y c o g e n l e v e l s . Sucec e t a l . (1980) i n v e s t i g a t e d the e f f e c t of u l t r a m a r a t h o n performance on maximal a e r o b i c power and a n a e r o b i c t h r e s h o l d . F i v e u l t r a m a r a t h o n r u n n e r s , f i v e u l t r a m a r a t h o n w a l k e r s and 5 c o n t r o l r u n n e r s s e r v e d as s u b j e c t s whose VO^max and a n a e r o b i c t h r e s h o l d were t e s t e d p r i o r t o (9-4 days) and f o l l o w i n g (2-6 days) a 100-mile t r a c k r a c e . F o r t h e f i v e d a y s f o l l o w i n g the r a c e j o i n t and muscle s o r e n e s s was r e c o r d e d u s i n g Henry's 9 p o i n t P a i n S c a l e . The u l t r a m a r a t h o n r u n n e r s c o v e r e d a mean d i s t a n c e of 108.7 km (16.77 h o u r s ) , w h i l e the u l t r a m a r a t h o n w a l k e r s c o v e r e d a mean d i s t a n c e o f 100.9 km (16.38 h o u r s ) . F o l l o w i n g the r a c e the r u n n e r s ' VC^max was d e c r e a s e d by 5.4% ( f r o m 4.24 t o 4.01 1 / m i n ) , w h i l e t h e w a l k e r s ' V02max d i d not d e c r e a s e s i g n i f i c a n t l y ( f r o m 3.23 t o 3.17 1 / m i n ) . The a n a e r o b i c t h r e s h o l d was d e c r e a s e d f o r both r u n n e r s and w a l k e r s , 7.3% (from 2.86 t o 2.63 1/min) and 8.0% ( f r o m 1.92 t o 1.78 1 / m i n ) , r e s p e c t i v e l y . I t was a l s o o b s e r v e d a g e n e r a l i z e d , m o d e r a t e l y i n t e n s i v e j o i n t and m u s c l e s o r e n e s s t h r o u g h o u t t h e l o w e r and m i d - r e g i o n s o f t h e body w h i c h p e r s i s t e d f o r 2 t o more than 5 days f o l l o w i n g the r a c e . The i n v e s t i g a t o r s c o n c l u d e d t h a t mechanisms u n d e r l y i n g p o s t e x e r c i s e s o r e n e s s a r e r e l a t e d t o t h e d e c r e m e n t s s e e n i n the p o s t V02max and a n a e r o b i c t h r e s h o l d v a l u e s . Perceived Exertion Relative to Anaerobic Threshold Simon e t a l . (1983-b) examined p e r c e i v e d e x e r t i o n r e l a t i v e t o a n a e r o b i c t h r e s h o l d i n s i x h i g h l y t r a i n e d and s i x s e d e n t a r y u n t r a i n e d men. B o r g S c a l e r a t i n g s o f p e r c e i v e d e x e r t i o n , l a c t a t e , and gas exchange measurements were t a k e n t h r o u g h o u t an i n c r e m e n t a l c y c l e e r g o m e t e r t e s t . V02max and a n a e r o b i c t h r e s h o l d f o r the t r a i n e d group averaged 63.8 m l / k g / m i n and 6 0 . 6 % VO^max, w h i l e t h o s e o f t h e u n t r a i n e d group averaged 35.5 ral/kg/min and 45.1% VO^max, r e s p e c t i v e l y . The t r a i n e d s u b j e c t s ' p e r c e i v e d e x e r t i o n a t the a n a e r o b i c t h r e s h o l d (13.5) was s i g n i f i c a n t l y g r e a t e r than t h a t of the u n t r a i n e d s u b j e c t s ' ( 1 0 . 5 ) . However, the mean p e r c e i v e d e x e r t i o n c o r r e s p o n d i n g t o a l a c t a t e c o n c e n t r a t i o n of 4 mmol/1 i n the t r a i n e d (16.2) and u n t r a i n e d (15.4) were s i m i l a r which o c c u r r e d a t 8 5 % and 8 0 . 1 % V0 2max, r e s p e c t i v e l y . I t was a l s o o b s e r v e d t h a t the c o r r e l a t i o n between p e r c e i v e d e x e r t i o n and % VC^max f o r both groups combined was 0.94, w h i l e f o r p e r c e i v e d e x e r t i o n and % a n a e r o b i c t h r e s h o l d was s i g n i f i c a n t l y l o wer and c o r r e l a t e d a t 0.87. The i n v e s t i g a t o r s c o n c l u d e d t h a t 1) t r a i n e d s u b j e c t s r a t e t h e e f f o r t o f work a t t h e a n a e r o b i c t h r e s h o l d t o be g r e a t e r than u n t r a i n e d s u b j e c t s but b o t h groups r a t e i t s i m i l a r l y a t a l a c t a t e c o n c e n t r a t i o n o f 4 mmol/1, and 2) p e r c e i v e d e x e r t i o n i s more h i g h l y r e l a t e d t o % VO^max than % a n a e r o b i c t h r e s h o l d . D r e s s e n d o r f e r e t a l . (1981) examining 110 n o n - a t h l e t i c men, 30 t o 61 y e a r s of age r e p o r t e d a r a t i n g o f p e r c e i v e d e x e r t i o n o f 14 +_ 2 ("somewhat h a r d " t o "hard") a t the time the a n a e r o b i c t h r e s h o l d o c c u r r e d . 61 Anaerobic Threshold R e l a t i o n s h i p s With Various Metabolic Parameters Green e t a l . (1979) i n v e s t i g a t e d whether the v a r i a b i l i t y i n a n a e r o b i c t h r e s h o l d which e x i s t s between i n d i v i d u a l s may be e x p l a i n e d by muscle f i b e r t y pe and c o m p o s i t i o n . Examining 10 a c t i v e c o l l e g e m a l e s (mean V02max=53.9 ml/kg/min) they found t h a t t h e i r muscle f i b e r t y pe d i s t r i b u t i o n s were 4 6 . 3 , 44.3 and 8.9% f o r type I , I I A , and I I B , r e s p e c t i v e l y , w h i l e t h e i r a n a e r o b i c t h r e s h o l d o c c u r r e d a t 75% V0 2max. C o r r e l a t i o n c o e f f i c i e n t s between the f i b e r t y pe d i s t r i b u t i o n s and a n a e r o b i c t h r e s h o l d were found t o be n o n - s i g n i f i c a n t and ranged between -0.11 and 0.30. No s i g n i f i c a n t d i f f e r e n c e was a l s o f o u n d when f i b e r type was e x p r e s s e d as a p e r c e n t of c r o s s s e c t i o n a l a r e a (r=-0.44 t o 0.37) or when SDH a c t i v i t y was u s e d . The i n v e s t i g a t o r s c o n c l u d e d t h a t the muscle c h a r a c t e r i s t i c s s t u d i e d do not i n f l u e n c e t h e o n s e t o f a n a e r o b i o s i s as r e p r e s e n t e d by the a n a e r o b i c t h r e s h o l d . " Rusko e t a l . (1980) examined a n a e r o b i c t h r e s h o l d , s k e l e t a l muscle enzymes and f i b e r c o m p o s i t i o n i n 15 young (mean age=17.6 y e a r s ) female c r o s s - c o u n t r y s k i e r s . T h e i r a n a e r o b i c t h r e s h o l d a v e r a g e d 40.9 m l / k g / m i n o r 86% of V0 2max. I t was observed t h a t V02max c o r r e l a t e d s i g n i f i c a n t l y (r=0.60) w i t h a n a e r o b i c t h r e s h o l d , e x p r e s s e d i n ml/kg/min ( a b s o l u t e ) and n o n - s i g n i f i c a n t l y when e x p r e s s e d i n % VO^max ( r e l a t i v e ) . The % ST f i b e r s showed no s i g n i f i c a n t c o r r e l a t i o n w i t h r e l a t i v e a n a e r o b i c t h r e s h o l d . SDH c o r r e l a t e d s i g n i f i c a n t l y w i t h r e l a t i v e a n a e r o b i c t h r e s h o l d (r=0.63) and c i t r a t e s y n t h a s e w i t h a n a e r o b i c t h r e s h o l d e x p r e s s e d i n ml/kg/min (r=0.58). The age o f t h e s u b j e c t s c o r r e l a t e d p o s i t i v e l y w i t h r e l a t i v e a n a e r o b i c t h r e s h o l d ( r = 0 . 5 4 ) . A c c o r d i n g t o t h e a u t h o r s t h e s e r e s u l t s s u p p o r t t h e h y p o t h e s i s t h a t a n a e r o b i c t h r e s h o l d i s r e l a t e d t o o x i d a t i v e c a p a c i t y of muscle. The r e l a t i o n s h i p between a n a e r o b i c t h r e s h o l d and oxygen t r a n s p o r t was i n v e s t i g a t e d i n 32 b i a t h l e t s 18.7 y e a r s o f age ( R u s k o and P a h k i l a , 1 9 8 0 ) . The s u b j e c t s had a V02max and a n a e r o b i c t h r e s h o l d o f 62 m l / k g / m i n and 49 m l / k g / m i n (78% VC^max) , r e s p e c t i v e l y . I t was obser v e d t h a t h e a r t volume (x = 383 ml/m 2) and hematocht (x = 46.9%) c o r r e l a t e d s i g n i f i c a n t l y w i t h VC^max and a n a e r o b i c t h r e s h o l d . The i n v e s t i g a t o r s c o n c l u d e d t h a t d e t e r m i n a n t s o f o x y g e n t r a n s p o r t may have i n f l u e n c e on the onset of m e t a b o l i c a c i d o s i s . Komi e t a l . (1981) examining 9 s u b j e c t s r e p o r t e d a s i g n i - f i c a n t r e l a t i o n s h i p between %ST muscle f i b e r s and V Q B L A (r=0.78), and b e t w e e n a v e r a g e m e c h a n i c a l power o u t p u t a t V Q B L A A N C L V Q B L A ( r = 0 . 9 0 ) , w h i l e t h e m e c h a n i c a l work was not r e l a t e d s i g n i f i c a n t l y t o V Q B L A * Ivy e t a l . (1980) s t u d y i n g 13 male s u b j e c t s found s i g n i f i c a n t r e l a t i o n s h i p s b e t ween t h e c a p a c i t y o f m u s c l e homogenates t o o x i d i z e p y r u v a t e and a b s o l u t e (r=0.94) o r r e l a t i v e (r=0.83) l a c t a t e t h r e s h o l d s ; between %ST m u s c l e f i b e r s and a b s o l u t e (r=0.74) and r e l a t i v e (r=0.70) l a c t a t e t h r e s h o l d s ; and between V02max' and a b s o l u t e l a c t a t e t h r e s h o l d (r=0.91). S j o d i n e t a l . ( 1 9 8 1 ) e x a m i n e d 19 male marathoners and r e p o r t e d a r e l a t i o n s h i p between V Q B L A a n d L D H a n d PFK/CS r a t i o of r=-0.46 and -0.68, r e s p e c t i v e l y . %ST muscle f i b e r s and c a p i l l a r y d e n s i t y c o r r e l a t i o n s w i t h V Q B L A were r=0.62 and r=0.58, r e s p e c t i v e l y . F u r t h e r m o r e , i t was shown t h a t PFK/CS r a t i o t o g e t h e r w i t h c a p i l l a r y d e n s i t y a ccounted f o r 61% of the v a r i a n c e i n V Q B L A * T e s c h e t a l . ( 1 9 8 1 ) r e p o r t e d t h a t 16 m a l e s showed a s i g n i f i c a n t c o r r e l a t i o n between O B L A (%V02max) and %ST a r e a . However, no c o r r e l a t i o n was f o u n d between 0 2 c o n s u m p t i o n a t O B L A and %ST a r e a . F u r t h e r m o r e , i t was shown t h a t %ST a r e a p l u s c a p i l l a r y d e n s i t y accounted f o r 92% o f the v a r i a n c e i n O B L A (r = 0 . 9 6 ) . When V0 2max was added as a n o t h e r v a r i a b l e the c o r r e l a t i o n was o n l y s l i g h t l y h i g h e r (r=0.98). The i n v e s t i - g a t o r s s u g g ested t h a t b o t h i n h e r e n t and a d a p t a t i v e q u a l i t i e s of the e x e r c i s i n g muscle a r e of s i g n i f i c a n c e f o r t h e o n s e t of b l o o d l a c t a t e a c c u m u l a t i o n . Anaerobic Threshold as a Predictor of Distance Performance and i t s Relationship with Race Pace W e i s e r e t a l . ( 1 9 7 8 ) i n v e s t i g a t e d the r e l a t i o n s h i p of a n a e r o b i c t h r e s h o l d and r a c e p a c e of 3.2 km i n 7 men and 5 women j o g g e r s . The s u b j e c t s underwent an i n c r e m e n t a l t e s t where i t was o b s e r v e d t h a t e i g h t of them showed two a b r u p t changes i n the V E / V 0 2 r a t i o , the f i r s t o c c u r r e d a t 73% V0 2max and t h e s e c o n d a t 87% V0 2max. F o u r s u b j e c t s showed o n l y t h e f i r s t a b r u p t change a t 78% VC^max. From a 3.2 km time t r i a l , the r u n n i n g speed f o r e a c h 400 m o f t h e m i d d l e 2.4 km was averaged. The s u b j e c t s who showed two a n a e r o b i c t h r e s h o l d changes r a n a t the second one, w h i l e those w i t h one a n a e r o b i c t h r e s h o l d change r a n a t t h a t s p e e d . I t was observ e d t h a t r u n n i n g speed was s i g n i f i c a n t l y c o r r e l a t e d w i t h the t r e a d m i l l s p e e d a t t h e c r i t i c a l a n a e r o b i c t h r e s h o l d (r=0.92) and w i t h • VC^max (r=0.86) , w h i l e the c r i t i c a l a n a e r o b i c t h r e s h o l d e x p r e s s e d as %V02max was not s i g n i f i c a n t l y c o r r e l a t e d w i t h VC^max (r=0.19). Based on t h e s e o b s e r v a t i o n s the i n v e s t i g a t o r s s u g g ested t h a t a p e r s o n ' s r u n n i n g s p e e d f o r 3.2 km c l o s e l y a p p r o x i m a t e s t h a t pace above which an e x p o n e n t i a l i n c r e a s e i n h y p e r v e n t i l a t i o n o c c u r s as pace i s i n c r e a s e d . T h o r l a n d e t a l . ( 1 9 8 0 ) s t u d i e d r e l a t i o n s h i p s between c r o s s c o u n t r y (5000m) r u n n i n g times and m e t a b o l i c r e s p o n s e s d u r i n g t r e a d m i l l r u n n i n g i n t e n female (18.8 t o 28.2 y e a r s ) c o l l e g i a t e c r o s s - c o u n t r y c o m p e t i t o r s . They o b s e r v e d t h a t the a n a e r o b i c t h r e s h o l d was t h e b e s t p r e d i c t o r of c r o s s - c o u n t r y run time and t h i s r e l a t i o n s h i p was d e s c r i b e d by the f o l l o w i n g e q u a t i o n : B e s t t i m e ( s e c ) = 2091.23 - (19.363 x a n a e r o b i c t h r e s h o l d ) . A n a e r o b i c t h r e s h o l d v a l u e s a c c o u n t e d f o r 7 1 % of t h e v a r i a n c e (r=0.84) i n the r u n n i n g p e r f o r m a n c e s , w h i l e • V02max v a l u e s e i t h e r s i n g u l a r l y (r=0.78) o r i n c o m b i n a t i o n w i t h a n a e r o b i c t h r e s h o l d (r=0.81) was not as a c c u r a t e a p r e d i c t o r of r u n n i n g t i m e s . The r e l a t i o n s h i p b e t ween a n a e r o b i c t h r e s h o l d and VO2 a t s e l f - p a c e d r u n n i n g was i n v e s t i g a t e d by Dwyer e t a l . (1982) i n 16 women. The v e l o c i t y of i n d i v i d u a l 15 min s e l f - p a c e d r u n n i n g was dete r m i n e d on a t r a c k and thes e v e l o c i t i e s were then used i n 8 min t r e a d m i l l runs t o o b t a i n VO2 a t a s e l f - p a c e d r u n n i n g pace. These d a t a were compared t o VO^max and a n a e r o b i c t h r e s h o l d o b t a i n e d i n i n c r e m e n t a l t r e a d m i l l runs t o f a t i g u e . The V0 2max was 47.5 ml/kg/min and a n a e r o b i c t h r e s h o l d a v e r - aged 34.7 m l / k g / m i n o r 7 3 . 2 % VO^max. I t was observ e d t h a t i n s e l f - p a c e d r u n n i n g and a n a e r o b i c t h r e s h o l d c o r r e l a t e d h i g h l y ( r = 0 . 8 7 ) . The i n v e s t i g a t o r s c o n c l u d e d t h a t women run s l i g h t l y above a n a e r o b i c t h r e s h o l d when they run a t what they p e r c e i v e t o be a c o m f o r t a b l e pace f o r a e r o b i c t r a i n i n g . G r e e n e t a l . ( 1 9 8 1 ) e x a m i n i n g 18 h i g h l y t r a i n e d male a d o l e s c e n t and a d u l t d i s t a n c e r u n n e r s o b s e r v e d t h a t one and two m i l e t r a c k t i m e s were i n v e r s e l y r e l a t e d t o a n a e r o b i c t h r e s h o l d and VO^max. I t was a l s o suggested by the a u t h o r s t h a t a n a e r o b i c t h r e s h o l d may p l a t e a u w i t h t r a i n i n g and w i t h age l i k e VC^max. Kumagai e t a l . ( 1 9 8 2 ) e x a m i n e d r e l a t i o n s h i p s between a n a e r o b i c t h r e s h o l d and p e r f o r m a n c e s i n 5km, 10km, and 10 m i l e r a c e s i n 17 e n d u r a n c e r u n n e r s (16-18 y e a r s o f a g e ) . A n a e r o b i c t h r e s h o l d averaged 51.0 ml/kg/min and VC^max averaged 64.1 m l / k g / m i n . They o b s e r v e d t h a t c o r r e l a t i o n s b e t w e e n • V02max and performances i n 5km, 10km, and 10 m i l e r a c e s were not h i g h ( r = - 0 . 6 4 , r=-0.67, r=-0.57, r e s p e c t i v e l y ) , w h i l e those between a n a e r o b i c t h r e s h o l d and performances were v e r y h i g h ( r = - 0 . 9 4 , r = - 0 . 8 3 , r = - 0 . 8 3 , r e s p e c t i v e l y ) . A n a e r o b i c t h r e s h o l d a ccounted f o r 83.9%, 70.4%, and 69.7% of the v a r i a n c e i n t he 5 km, 10 km, and 10 m i l e p e r f o r m a n c e s , r e s p e c t i v e l y . T a n a k a e t a l . ( 1 9 8 3 ) compared t h e c o n t r i b u t i o n of the a n a e r o b i c t h r e s h o l d and OBLA t o e n d u r a n c e p e r f o r m a n c e i n e l e v e n non-endurance t r a i n e d a c t i v e males, aged 22-28 y e a r s . They obse r v e d t h a t a n a e r o b i c t h r e s h o l d ( e x p r e s s e d i n ml/kg/min) c o r r e l a t e d h i g h e r w i t h 1500-m min run performance (r=-0.81) t h a n d i d V0 2max ( r = - 0 . 7 7 ) and OBLA ( r = - 0 . 6 0 ) , as w e l l as work r a t e a t a n a e r o b i c t h r e s h o l d (r=-0.77) w i t h p e r f o r m a n c e v e r s u s work r a t e a t OBLA ( r = - 0 . 7 0 ) . A n a e r o b i c t h r e s h o l d , work r a t e a t a n a e r o b i c t h r e s h o l d , OBLA, and work r a t e a t OBLA acc o u n t e d 67, 60, 37 and 50% of the v a r i a n c e i n endurance p e r f o r m a n c e , r e s p e c t i v e l y . When h e a r t r a t e a t a n a e r o b i c t h r e s h o l d was c o m b i n e d t o a n a e r o b i c t h r e s h o l d as a n o t h e r p r e d i c t o r , the v a r i a n c e of t h e s e two v a r i a b l e s t o e n d u r a n c e performance i n c r e a s e d t o 84%. R e y b r o u c k e t a l . ( 1 9 8 3 ) examined r e l a t i o n s h i p s between v e n t i l a t o r y t h r e s h o l d f o r s h o r t - t e r m e x e r c i s e ( d e f i n e d as the work r a t e o r V 0 2 i m m e d i a t e l y below the work r a t e a t which v e n t i l a t i o n i n c r e a s e d d i s p r o p o r t i o n a t e l y r e l a t i v e t o work r a t e o r V 0 2 ) and v e n t i l a t o r y t h r e s h o l d f o r l o n g - t e r m e x e r c i s e • ( d e f i n e d as the work r a t e o r V 0 2 i m m e d i a t e l y below the work r a t e a t which v e n t i l a t i o n c o n t i n u e d t o i n c r e a s e w i t h t i m e r a t h e r than a t t a i n a s t e a d y s t a t e ) w i t h endurance performance (12-min run) i n 8 males. They observed t h a t 12-min run showed t h e h i g h e s t c o r r e l a t i o n w i t h t h e v e n t i l a t o r y t h r e s h o l d f o r l o n g - t e r m e x e r c i s e (r=0.82) i n comparison t o the v e n t i l a t o r y t h r e s h o l d f o r s h o r t - t e r m e x e r c i s e ( r = 0 . 7 3 ) . They c o n c l u d e d t h a t t h e v e n t i l a t o r y t h r e s h o l d f o r l o n g - t e r m e x e r c i s e i s a more s p e c i f i c measure t o p r e d i c t endurance performance. S j o d i n and J a c o b s (1981) examining 18 male marathoners r e p o r t e d a v e r y h i g h c o r r e l a t i o n (r=0.96) between V Q B L A A N D marathon r u n n i n g v e l o c i t y . F u r t h e r m o r e , i t was shown t h a t V Q B L A a c c o u n t e d f o r 92% of the v a r i a n c e i n marathon r u n n i n g v e l o c i t y , w h i l e V Q B L A t o g e t h e r w i t h t r a i n i n g volume p r i o r t o the marathon accounted f o r 96% of t h i s v a r i a n c e . F a r r e l e t a l . ( 1 9 7 9 ) showed t h a t V Q B L A w a s roost c l o s e l y r e l a t e d (r^.0.91) t o p e r f o r m a n c e (3.2km, 9.7km, 15km, 19.3km, and m a r a t h o n r a c e s ) than d i d %ST muscle f i b e r s (r>0.47), VC^max ( r M ) . 8 3 ) , r u n n i n g economy ( r ^ 0 . 4 9 ) , and V 0 2 c o r r e s p o n d i n g t o the OBLA (r>0.91). They a l s o o b s e r v e d t h a t the h i g h r e l a t i o n - s h i p between V Q B L A a n d r a c e pace i s independent of the c o m p e t i t i v e l e v e l of the r u n n e r . L a F o n t a i n e e t a l . (1981) s t u d i e d the r e l a t i o n s h i p between maximal s t e a d y s t a t e ( d e f i n e d as t h e o x y g e n u p t a k e , h e a r t r a t e and/or t r e a d m i l l v e l o c i t y a t which plasma l a c t a t e concen- t r a t i o n was 2.2 mmol/1 of plasma) and v a r i o u s r u n n i n g e v e n t s . They o b s e r v e d t h a t r u n n i n g p a c e s f o r t h e 402,3m, 3.22km, 8.05km, 16.09km, and 20km d i s t a n c s c o r r e l a t e d h i g h l y w i t h the t r e a d m i l l pace a t maximal s t e a d y s t a t e (r=0.84 t o 0.995). Rhodes and McKe n z i e (1984) d e s i g n e d a st u d y t o examine the r e l a t i o n s h i p between p r e d i c t e d marathon t i m e s ( c a l c u l a t e d from the r u n n i n g v e l o c i t y a t the t h r e s h o l d of a n a e r o b i c meta- b o l i s m - V T A M ) a n c i a c t u a l p e r f o r m a n c e t i m e s , i n a marathon. They e x a m i n e d e i g h t e e n male marathon r u n n e r s whose V-pAM w a s d e t e r m i n e d by e x c e s s CO2 e l i m i n a t i o n c u r v e s as d e s c r i b e d by V o l k o v e t a l . ( 1 9 7 5 ) . From the V T A M v a l u e s they e s t i m a t e d the p r e d i c t e d t i m e s f o r t h e m a r a t h o n and c o r r e l a t e d t h e s e w i t h the a c t u a l t i m e s t a k e n from a marathon r a c e . They found a h i g h l y s i g n i f i c a n t c o r r e l a t i o n (r=0.94) between the p r e d i c t e d and a c t u a l m a r a t h o n t i m e s , and t h e y s u g g e s t e d t h a t , w i t h o t h e r f a c t o r s b e i n g o p t i m a l , V-p A M may be a good p r e d i c t o r f o r marathon performance. Heart Rate Indices and Anaerobic Threshold D r e s s e n d o r f e r e t a l . ( 1 9 8 1 ) e x a m i n i n g 110 n o n a t h l e t i c men, 30 t o 61 y e a r s of age, o b s e r v e d t h a t t h e h e a r t r a t e s a t a n a e r o b i c t h r e s h o l d were s i g n i f i c a n t l y h i g h e r than 85% of a c t u a l maximum r a t e (152 b/min) o r 85% of the a g e - p r e d i c t e d (220 minus age) maximum h e a r t r a t e (151 b / m i n ) . However, h e a r t r a t e s a t a n a e r o b i c t h r e s h o l d were n o t s i g n i f i c a n t l y d i f f e r e n t from 80% of maximum h e a r t r a t e r e s e r v e (154 b/min) as c a l c u l a t e d by the K a r v o n e n e q u a t i o n . I n 78 o f t h e 110 s u b j e c t s ( 7 1 % ) , h e a r t r a t e a t a n a e r o b i c t h r e s h o l d was h i g h e r than 85% of maximum h e a r t r a t e . P a t t o n e t a l . (1979) examined 5 r u n n e r s and 6 non-runners and f o u n d t h a t t h e r u n n e r s ' a n a e r o b i c t h r e s h o l d o c c u r r e d a t h i g h e r a b s o l u t e and r e l a t i v e l e v e l s a t VO^max. However, the h e a r t r a t e a t a n a e r o b i c t h r e s h o l d f o r b o t h g r o u p s was not s i g n i f i c a n t l y d i f f e r e n t , runners=181 b/min, non-runners= 185 b/min. The i n v e s t i g a t o r s c o n c l u d e d t h a t r e g a r d l e s s o f an i n d i v i d u a l ' s f i t n e s s l e v e l a b s o l u t e h e a r t r a t e measures p r o v i d e a good i n d i c a t i o n of work l e v e l r e q u i r e d f o r a n a e r o b i c t h r e s h o l d . Dwyer and Bybee (1983) i n v e s t i g a t e d the h e a r t r a t e response and p e r c e n t maximum h e a r t r a t e o f a n a e r o b i c t h r e s h o l d i n 20 young f e m a l e s . The s u b j e c t s ' a n a e r o b i c t h r e s h o l d , VC^max and maximum h e a r t r a t e were det e r m i n e d d u r i n g an i n c r e m e n t a l c y c l e e x e r c i s e t o f a t i g u e , w h i l e the h e a r t r a t e a t a n a e r o b i c t h r e s h o l d was d e t e r m i n e d by r e g r e s s i n g h e a r t r a t e on VO2 u s i n g i n d i v i d u a l r e g r e s s i o n e q u a t i o n s . The mean v a l u e f o r • a n a e r o b i c t h r e s h o l d was 70.1% VC^max w i t h c o r r e s p o n d i n g h e a r t r a t e o f 158.4 b/min ( 8 6 . 3 % o f maximum h e a r t r a t e ) . They o b s e r v e d t h a t a l l s u b j e c t s were b e l o w a n a e r o b i c t h r e s h o l d a t 70% of maximum h e a r t r a t e . However, a zone of non-uniform work s t r e s s w i t h r e s p e c t t o a n a e r o b i c t h r e s h o l d was observ e d between 75-90% of maximum h e a r t r a t e (58-75% VC^max). W i t h i n t h i s zone a h i g h l y v a r i a b l e number o f s u b j e c t s e x e r c i s e d above t h e i r a n a e r o b i c t h r e s h o l d a t any s p e c i f i c p e r c e n t a t maximum h e a r t r a t e . F u r t h e r m o r e , t h e low c o r r e l a t i o n o f r=0.60 t h a t was f o u n d b e tween % o f maximum h e a r t r a t e of a n a e r o b i c t h r e s h o l d and %V02max of a n a e r o b i c t h r e s h o l d d i d a l l o w , a c c o r d i n g t o the a u t h o r s , the t r a n s l a t i o n of a n a e r o b i c t h r e s h o l d t o a p e r c e n t maximum h e a r t r a t e o r a b s o l u t e h e a r t r a t e f i g u r e f o r t r a i n i n g p r e s c r i p t i o n . The i n v e s t i g a t o r s c o n c l u d e d t h a t s t a n d a r d v a l u e s f o r % maximum h e a r t r a t e a t a n a e r o b i c t h r e s h o l d , g r o u p e d by age o r s e x , s h o u l d n o t be a p p l i e d t o i n d i v i d u a l s due t o the wide range among homogeneous s u b j e c t s i n r e l a t i v e h e a r t r a t e a t the a n a e r o b i c t h r e s h o l d . P a r k h o u s e e t a l . ( 1982) e x a m i n e d t h i r t y - t h r e e men, 17 t o 28 y e a r s of age who were d i v i d e d i n t o 3 groups; 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 . They obse r v e d t h a t the h e a r t r a t e s a t a n a e r o b i c t h r e s h o l d f o r t h e 3 g r o u p s were a l m o s t i d e n t i c a l ( 1 6 3 . 9 , 164.4, and 167.0 b / m i n ) , as w e l l as the pe r c e n t a g e of maximum h e a r t r a t e a t a n a e r o b i c t h r e s h o l d (82, 84, and 8 6 ) . I n a d d i t i o n , 67% of a l l s u b j e c t s had a h e a r t r a t e a t a n a e r o b i c t h r e s h o l d above 80% of maximum h e a r t r a t e . The i n v e s t i g a t o r s c o n c l u d e d t h a t % o f maximum h e a r t r a t e may be u s e d f o r e x e r c i s e p r e s c r i p t i o n , h o w e v e r, t r a i n i n g a t 8 0 % o f maximum h e a r t r a t e may be t o o low a s t i m u l u s f o r maximal a e r o b i c / a n a e r o b i c improvement. Anaerobic Threshold A l t e r a t i o n s with Changes i n Substrate A v a i l a b i l i t y I v y e t a l . ( 1 9 8 1 ) i n v e s t i g a t e d t h e l a c t a t e t h r e s h o l d of 9 a c t i v e s u b j e c t s d u r i n g c y c l e ergometer e x e r c i s e s u n d e r c o n t r o l , h i g h b l o o d g l u c o s e , and h i g h b l o o d f r e e f a t t y a c i d c o n d i t i o n s . D u r i n g the g l u c o s e t r i a l b l o o d l a c t a t e was g r e a t e r t h a n c o n t r o l a t a l l w o r k - l o a d s . C o r r e c t e d b l o o d l a c t a t e v a l u e s ( b l o o d l a c t a t e - p r e - e x e r c i s e v a l u e = change i n b l o o d l a c t a t e ) were the same f o r c o n t r o l and g l u c o s e t r i a l s . I t was o b s e r v e d t h a t t h e l a c t a t e t h r e s h o l d was not d i f f e r e n t f o r t h e two t r e a t m e n t s ( c o n t r o l = 5 3 . 9 % VO^max; g l u c o s e = 52 . 7 % VO^max). However, f r e e f a t t y a c i d c o n d i t i o n caused a r e d u c t i o n i n b o t h b l o o d l a c t a t e and change i n b l o o d l a c t a t e • a t a l l w o r k - l o a d s a l t h o u g h VO2 was t h e same as c o n t r o l . The f r e e f a t t y a c i d c o n d i t i o n a l s o c a u s e d a s h i f t i n t h e l a c t a t e t h r e s h o l d (59.8% VO^max). Based on t h e s e o b s e r v a t i o n s the i n v e s t i g a t o r s c o n c l u d e d t h a t t h e l a c t a t e t h r e s h o l d c a n be a l t e r e d by changing s u b s t r a t e a v a i l a b i l i t y . Kowalchuk and Hughson (1981) showed t h a t 5 days of d i e t a r y m a n i p u l a t i o n a f f e c t s t h e a n a e r o b i c t h r e s h o l d d e t e r m i n e d by gas exchange measurements. F i v e female s u b j e c t s were t e s t e d under h i g h c a r b o h y d r a t e d i e t ( H ) , low c a r b o h y d r a t e d i e t ( L ) and a normal mixed d i e t (M). The s i g n i f i c a n t l y lower R t h a t was found f o r L than t h a t f o r H and M, c e r t i f i e d the changes i n the r e l a t i v e p r o p o r t i o n of c a r b o h y d r a t e and f a t m e t a b o l i z e d d u r i n g e x e r c i s e . The plasma l a c t a t e l e v e l s were lower d u r i n g L and h i g h e r d u r i n g H. However, VC^max was s i g n i f i c a n t l y h i g h e r f o l l o w i n g H (2535 ml/min) than f o l l o w i n g L (2305 ml/min) . Fu r t h e r m o r e , the Vg / V C 0 2 was h i g h e r i n L throughout the e x e r c i s e , w h i l e the oxygen uptake c o r r e s p o n d i n g t o the a n a e r o b i c t h r e s h o l d was h i g h e r i n H (1595 ml/min) and lower i n L (1310 m l / m i n ) . These o b s e r v a t i o n s l e d t h e i n v e s t i g a t o r s t o c o n c l u d e t h a t d i e t a r y m a n i p u l a t i o n a l t e r s the v e n t i l a t o r y response t o p r o - g r e s s i v e e x e r c i s e . Hughes e t a l . ( 1 9 8 2 ) s t u d y i n g 9 males observed t h a t the a n a e r o b i c t h r e s h o l d was a f f e c t e d by t h e g l y c o g e n s t a t e o f the s u b j e c t s . When the s u b j e c t s were under a g l y c o g e n - d e p l e t e d s t a t e the v e n t i l a t o r y t h r e s h o l d was s h i f t e d t o a l e s s e r work r a t e , w h i l e t h e l a c t a t e t h r e s h o l d t o a g r e a t e r work r a t e r e l a t i v e t o a normal g l y c o g e n s t a t e . Summary The a n a e r o b i c t h r e s h o l d i s d e t e r m i n e d by 1) l a c t a t e measurements, 2) gas exchange measurements, 3) e l e c t r o m y o g r a p h y , and 4) f i e l d t e s t s . These methods appear t o c o r r e l a t e h i g h l y among them, however, the d e t e r m i n a t i o n of a n a e r o b i c t h r e s h o l d i s v e r y s u b j e c t i v e ; i n d e p e n d e n t i n v e s t i g a t o r s may o b t a i n d i f f e r e n t a n a e r o b i c t h r e s h o l d s . The v e n t i l a t o r y measurements • • • • which de t e r m i n e the a n a e r o b i c t h r e s h o l d a r e Vg, V C O 2, V E / V 0 2 , • • • • • V E / V C 0 2 , R, F E 0 2 , F E C 0 2 , 0 2 P , and exce s s C 0 2 . V E / V 0 2 , V E, and t h e e x c e s s CO2 methods seem t o be t h e most v a l i d and r e l i a b l e . R e c e n t l y , i n v e s t i g a t o r s d i s c e r n two " b r e a k a w a y " p o i n t s ; t h e f i r s t c o r r e s p o n d i n g t o a p p r o x i m a t e l y 2 mmol/1 l a c t a t e ( a e r o b i c t h r e s h o l d ) and t h e s e c o n d c o r r e s p o n d i n g t o a p p r o x i m a t e l y 4 mmol/1 l a c t a t e ( a n a e r o b i c t h r e s h o l d ) . New terms of t h r e s h o l d s have a l s o been i n t r o d u c e d ; the t h r e s h o l d d e t e r m i n e d by gas exchange measurements i s c a l l e d v e n t i l a t o r y , w h i l e t h a t d e t e r m i n e d by l a c t a t e measurements i s c a l l e d l a c t a t e t h r e s h o l d . A n a e r o b i c t h r e s h o l d i s e x e r c i s e m o d a l i t y d e p e n d e n t ; a t h l e t e s tend t o show a h i g h e r a n a e r o b i c t h r e s h o l d when they a r e t e s t e d a t the a c t i v i t y f o r which they t r a i n . T h i s r e f l e c t s the s p e c i f i c i t y of t r a i n i n g and a d a p t a t i o n . The b e l i e f t h a t the i n c r e a s e i n b l o o d l a c t a t e c o n c e n t r a t i o n was r e s p o n s i b l e f o r the a b r u p t i n c r e a s e i n v e n t i l a t i o n d u r i n g an i n c r e m e n t a l e x e r c i s e does not h o l d t r u e any l o n g e r . I t was shown t h a t t h e s e a b r u p t changes are not c a u s a l but r a t h e r o n l y c o i n c i d e n t a l . P a r t o f t h e i m p r o v e m e n t i n e n d u r a n c e p e r f o r m a n c e i s a t t r i b u t e d t o the i n c r e a s e of a n a e r o b i c t h r e s h o l d a f t e r s p e c i f i c t r a i n i n g . There i s disagreement among i n v e s t i g a t o r s c o n c e r n i n g t h e m a g n i t u d e o f i m p r o v e m e n t o f t h e a n a e r o b i c t h r e s h o l d , p r o b a b l y b e c a u s e o f d i f f e r e n t t r a i n i n g p r o t o c o l s used and d i f f e r e n t f i t n e s s l e v e l s o f s u b j e c t s . i t seems, h o w e v e r , t h a t a t r a i n i n g i n t e n s i t y c o r r e s p o n d i n g t o a p p r o x i m a t e l y 4 mmol/1 l a c t a t e i s the most e f f e c t i v e i n e l i c i t i n g the maximum improvement. A n a e r o b i c t h r e s h o l d d e c r e a s e s a f t e r p r o l o n g e d a e r o b i c e x e r c i s e ; i t i s a l s o a f f e c t e d by s u b s t r a t e a v a i l a b i l i t y . T h e r e i s a r e l a t i o n s h i p b e t ween VC^max, SDH, c i t r a t e s y n t h a s e , h e a r t volume, h e m a t o c r i t , hemoglobin, and %ST f i b e r s w i t h a n a e r o b i c t h r e s h o l d . A n a e r o b i c t h r e s h o l d d e t e r m i n e s the pace which i n d i v i d u a l s can run a e r o b i c a l l y f o r a l o n g d i s t a n c e . Knowing the a n a e r o b i c t h r e s h o l d a l l o w s an a p p r o x i m a t i o n of performance i n p r o l o n g e d a e r o b i c a c t i v i t i e s . H e a r t r a t e can be a good i n d i c a t o r o f t h e a n a e r o b i c t h r e s h o l d , r e g a r d l e s s o f s e x , age, and f i t n e s s l e v e l s o f i n d i v i d u a l s . A n a e r o b i c t h r e s h o l d i s a c o n t r o v e r s i a l i s s u e i n t h e a r e a of e x e r c i s e p h y s i o l o g y . U n d o u b t e d l y , t h e r e i s a need f o r more i n f o r m a t i o n t o be o b t a i n e d i n t h i s a r e a which w i l l l e a d i n t o c l a r i f i c a t i o n of the phenomenon of t r a n s i t i o n from a e r o b i c t o a n a e r o b i c m e t a b o l i s m . APPENDIX B - MARGINALS FACTOR LEVEL VARIATE COUNT MEAN STD DEV STATUS TRAINED UNTRAINED PREPOST PRE POST LT . 12 LT(%V0 2max) 12 VT . 12 VT(%V0 2max) 12 V0 2max 12 TTT 12 HR L T 12 RLT 12 LT . 12 LT(%V0 2max) 12 VT . 12 YT(%V0 2max) 12 V0 2max 12 TTT 12 HR L T 12 R L T 12 LT . 12 LT(%V0 2max) 12 VT . 12 YT(%V0 2max) 12 V0 2max 12 TTT 12 HR L T 12 R L T 12 LT . 12 LT(%V0 2max) 12 VT . 12 YT(%V0 2max) 12 V0 2max 12 TTT 12 HR L T 12 R L T 12 9.5 0.8 82.1 8.8 8.5 0.8 74.8 8.4 58.3 3.0 903.7 70.4 166.9 8.3 0.97 0.05 7.6 0.4 81.3 5.6 7.6 0.7 80.0 7.0 45.9 2.9 691.2 74.2 167.2 9.4 1.00 0.06 8.6 1.2 80.9 7.7 8.5 0.9 78.8 8.3 53.2 7.3 827.5 115.6 166.9 7.9 1.02 0.06 8.5 1.1 82.5 6.9 7.7 0.8 76.0 7.8 51.0 6.7 767.5 140.5 167.2 9.7 0.96 0.04 APPENDIX C-INDIVIDUAL SUBJECTS PHYSIOLOGICAL DATA LT .LT VT .VT VOgmax TTT H R u RLT (mph) (XVO^max) (mph) (%VQr>max) (ml.kg" 1.min- 1) (sec) (b/min) TRAINED-PRE VALUES 1 10.0 79.91 7.5 61.76 61.73 990 175 1.03 2 10.0 87.01 10.0 87.01 59.54 900 166 0.94 3 10.0 78.51 9.0 74.71 57.85 915 176 1.05 4 8.0 67.11 8.5 73.03 56.62 840 156 1.05 5 9.5 81.50 9.5 81.50 58.00 900 158 0.98 6 10.0 95.23 9.0 78.87 63.89 1005 168 0.89 TRAINED-POST VALUES 1 9.5 78.64 7.5 63.97 57.40 945 169 0.98 2 10.0 83.20 8.0 68.18 60.66 945 167 0.99 3 9.5 81.96 9.0 77.00 58.22 855 179 0.99 4 8.0 70.19 7.5 67.80 53.94 795 158 0.95 5 9.0 84.26 8.0 75.38 53.19 795 156 0.93 6 10.0 97.76 9.0 88.21 58.00 960 175 0.90 UNTRAINED-PRE VALUES 7 7.5 83.13 8.5 87.09 41.30 690 176 1.07 8 7.5 72.05 7.0 67.09 46.73 720 155 1.01 9 8.0 75.06 8.5 80.78 49.00 825 169 1.06 10 7.0 76.99 8.5 87.49 46.20 735 175 1.00 11 8.5 88.61 8.0 80.90 50.84 735 169 1.10 12 7.5 85.59 7.5 85.59 46.69 675 160 1.05 UNTRAINED-POST VALUES 7 7.5 83.95 7.5 83.95 41.88 630 170 0.99 8 7.5 77.09 7.0 72.18 47.05 690 163 0.93 9 8.0 78.98 7.0 68.52 45.80 780 164 0.99 10 7.0 80.84 7.0 80.84 46.40 630 186 0.92 11 8.0 81.85 8.0 81.85 47.34 630 152 0.94 12 7.5 90.82 6.5 83.86 41.51 555 167 1.03 77 APPENDIX D - BLOOD LACTATE VALUES (mph): 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 TRAINED-PRE VALUES 1 2.1 2.1 2.6 2.3 2.9 3.9 4.9 4.9 8.1 7.6 2 3 4 3.3 3.3 2.9 2.9 5 1.7 1.4 TRAINED-POST VALUES 1 1.3 1.2 1.5 2.0 2.8 4.3 4.4 5.4 6.9 10.0 2 1.1 1.1 0.9 1.1 1.3 1.8 2.3 3.0 3.8 3 1.6 1.2 2.0 2.2 2.7 4.0 4.8 6.6 4 1.2 1.1 2.1 1.4 1.4 1.7 2.1 2.7 5.8 4.6 5.7 5 1.5 0.9 1.4 1.1 1.4 2.2 2.9 3.5 4.6 6 1.2 1.2 1.4 2.0 2.2 4.0 4.8 7.1 9.3 15.6 1.0 1.0 1.3 1.4 1.4 2.2 2.1 2.2 5.2 1.1 2.3 2.1 2.8 3.3 4.1 5.2 4.9 7.2 3.0 3.6 3.2 3.8 5.2 6.7 1.2 1.1 1.6 1.5 3.3 2.6 3.2 6.7 8.5 2.7 2.1 2.1 2.8 2.7 3.6 6.3 7.1 9.4 UNTRAINED-PRE VALUES 7 2.9 2.9 3.7 4.1 5.1 5.0 6.1 6.3 7.9 8 3.6 2.7 3.3 3.1 4.9 6.7 8.2 13.8 9 1.3 1.1 1.9 2.0 3.5 4.7 6.0 8.9 10.6 10 1.9 2.1 2.3 3.0 3.1 3.7 5.0 6.2 6.4 8.5 11 4.5 4.1 5.4 4.7 6.4 6.1 7.9 10.0 10.2 13.1 12 4.0 3.9 4.6 6.0 4.8 7.3 10.0 UNTRAINED-POST VALUES 7 1.4 1.7 1.7 2.0 2.5 3.9 4.5 8 1.3 2.0 1.6 2.2 3.0 4.0 6.1 8.8 11.4 9 0.9 0.9 0.9 1.4 1.4 2.1 3.1 4.2 6.4 9.5 10 1.7 1.7 2.1 2.8 4.2 4.7 6.6 8.7 11.3 11 1.4 1.5 1.8 2.2 2.5 4.1 4.1 4.9 5.7 12 6.3 5.8 6.2 6.9 8.5 10.5 11.1 a FIGURE 1. Lactate curve for one subject shows a velocity of 10.0 mph at the lactate threshold. 79 FIGURE 2. Excess C0 2 curve f o r one subject shows a v e l o c i t y 7.0 mph at the v e n t i l a t o r y threshold.

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