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The effect of electrical stimulation and isokinetic exercise on muscular power of the quadriceps Nobbs, Leslie Ann 1982

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THE EFFECT OF ELECTRICAL STIMULATION AND ISOKINETIC EXERCISE: ON MUSCULAR POWER OF THE QUADRICEPS by LESLIE ANN NOBBS B.P.E., U n i v e r s i t y o f B r i t i s h C o lumbia, 1979 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PHYSICAL EDUCATION i n THE FACULTY OF GRADUATE STUDIES S c h o o l Of 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 the r e q u i r e d s t a n d a r d s THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1982 (c) L e s l i e Ann Nobbs, 1982 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 advanced degree 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 and s t u d y . I f u r t h e r a gree 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 head o f my department o r by 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 . Department o f 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 The 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 2075 Wesbrook P l a c e V ancouver, Canada V6T 1W5 Date A p r i l 5, 1982 DE-6 (2/79) ABSTRACT Power and strength t r a i n i n g , using conventional techniques, has been studied by several researchers. Investigations into the use of d i f f e r e n t t r a i n i n g methods and t h e i r e f f e c t on power and strength development are continually being studied and re-assessed. Recently, the use of faradic or e l e c t r i c a l stimulation has become an i n t e r e s t i n g alternative method, although much controversy surrounds t h i s technique. It has been reported by Johnson et a l . (1977) and Kots (1977) that faradic stimulation i s used with success as part of a strengthening program by e l i t e Soviet athletes. The combined ef f e c t s of a program consisting of exercise as well as e l e c t r i c a l stimulation was undertaken to determine the muscular power and strength potentials. The main objective of t h i s study was to compare power and strength changes between equated groups employing the following t r a i n i n g techniques: e l e c t r i c a l stimulation plus i s o k i n e t i c exercise, i s o k i n e t i c exercise and e l e c t r i c a l stimulation, respectively. Twenty-seven, moderately trained, female subjects, nine per group, were tested on three separate occasions. During the f i r s t session, height, weight, l e f t and right quadriceps power evaluation, time to peak tension of the muscle contraction at the four v e l o c i t i e s :(30, "100'/: 180 arid'iO. degrees per second) and two thigh g i r t h measurements were determined. The three groups were equated for power afte r the pretest was conducted. The second and t h i r d t e s t i n g s e s s i o n s a s s e s s e d the power and time t o peak t e n s i o n o f the non-dominant l e g a t the f o u r v e l o c i t i e s and p a t e l l a r and g l u t e a l t h i g h g i r t h s . A s i g n i f i c a n t d i f f e r e n c e f o r power was found between the pre and p o s t t e s t s and the pre and mid t e s t s f o r t h e combined groups d u r i n g the s i x week p e r i o d o f t r a i n i n g . A l t h o u g h no d i f f e r e n c e was found between each o f the t h r e e groups, the r e s u l t s ^ i n d i c a t e d t h a t programs i n v o l v i n g e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r c i s e , i s o k i n e t i c e x e r c i s e and e l e c t r i c a l s t i m u l a t i o n o n l y , a r e p o t e n t i a l l y e f f e c t i v e i n i m p r o v i n g m u s c u l a r power and s t r e n g t h i n normal s u b j e c t s . The st u d y r e v e a l e d t h a t one method was n o t s u p e r i o r t o a n o t h e r a f t e r s i x weeks o f t r a i n i n g . There was s i g n i f i c a n t power d i f f e r e n c e s between the pre and p o s t t e s t s and pre and mid t e s t s a t the slow i s o k i n e t i c speeds o f 30° and 0° per second. S i n c e the t r a i n i n g was conducted a t the speeds o f 30° and 0° ( i s o m e t r i c ) p e r second, the slow t e s t i n g speeds r e f l e c t e d n e u r a l a d a p t a t i o n and mus c u l a r r e c r u i t m e n t when the s p e c i f i c i t y o f t r a i n i n g t h e o r y i s c o n s i d e r e d . These f i n d i n g s i m p l y t h a t power and s t r e n g t h t r a i n i n g b e n e f i t s a re l i m i t e d t o speeds used d u r i n g t r a i n i n g . D u r i n g t h e s i x week t r a i n i n g p e r i o d , t ime t o peak.maximal t o r q u e and h y p e r t r o p h y o f the q u a d r i c e p s muscle group d i d n o t a l t e r s i g n i f i c a n t l y when e x a m i n i n g the means o f a l l t h r e e groups. i v ACKNOWLEDGEMENT The a u t h o r would l i k e t o thank t h o s e who a s s i s t e d h e r i n c o m p l e t i n g t h i s t h e s i s : committee c h a i r m a n , Dr. E. Rhodes, and committee members, Dr. D. McKenzie, Dr. J . Taunton and Mr. R. M a t t i s o n , f o r t h e i r v a l u a b l e guidance and p a t i e n c e . I would a l s o l i k e t o e x p r e s s a p p r e c i a t i o n t o M i s s H. S o u t h a r d , S c h o o l o f R e h a b i l i t a t i o n M e d i c i n e , f o r use o f t h e e l e c t r i c a l s t i m u l a t o r . V T A B L E OF CO N T E N T S Page A B S T R A C T i i ACKNOWLEDGEMENT i v L I S T OF T A B L E S v i i L I S T OF F I G U R E S v i i i Chapter 1. I N T R O D U C T I O N 1 S I G N I F I C A N C E : O F THE'-STUDY. 6 H Y P O T H E S E S 7 . D E L I M I T A T I O N S 9 L I M I T A T I O N S 1 0 D E F I N I T I O N S 1 0 2. R E V I E W OF L I T E R A T U R E 1 3 I S O K I N E T I C T R A I N I N G 1 3 E L E C T R I C A L S T I M U L A T I O N 2 1 SUMMARY ...... 3 0 : .. 3. METHODS AND P R O C E D U R E S 3 3 S U B J E C T S 3 3 T I M E A N D D U R A T I O N OF T H E ST U D Y 3 3 T E S T I N G P R O T O C O L 3 4 T R A I N I N G P R O C E D U R E S 3 5 E X P E R I M E N T A L D E S I G N A N D D A T A A N A L Y S I S .... 3 8 4. R E S U L T S A N D D I S C U S S I O N 4 0 R E S U L T S 4 0 D I S C U S S I O N 5 3 V i Page 5. SUMMARY AND CONCLUSIONS 61 SUMMARY •:• 68 CONCLUSIONS 70 RECOMMENDATIONS FOR FURTHER RESEARCH .... 71 BIBLIOGRAPHY ' 7 3 APPENDIX A 77 APPENDIX B: . 85 APPENDIX C 90 v i i LIST OF TABLES TABLE PAGE I P h y s i c a l C h a r a c t e r i s t i c s o f S u b j e c t s . 43 I I Comparison o f Power Between E l e c t r i c a l S t i m u l a t i o n and I s o k i n e t i c E x e r c i s e (ES + I E ) , I s o k i n e t i c E x e r c i s e (IE) and E l e c t r i c a l S t i m u l a t i o n (ES) Groups 44 I l i a M u l t i v a r i a t e A n a l y s i s o f V a r i a n c e f o r Power Parameter 45 I l l b M u l t i v a r i a t e A n a l y s i s o f V a r i a n c e f o r Power Parameter 46 IV Comparison o f M i d and P o s t Power G a i n s 47 V Summary o f Hypotheses T e s t i n g 52 v i i i LIST OF FIGURES • FIGURE PAGE I P r e , Mid and P o s t Power Measurements a t 30° x s " 1 48 I I P r e , M i d and P o s t Power Measurements a t 100° x s " 1 49 I I I P r e , Mid and P o s t Power Measurements a t 180° x s _ 1 50 IV P r e , Mid and P o s t Power Measurements a t 0° x s " 1 51 1 CHAPTER I INTRODUCTION Exercise t r a i n i n g u t i l i z i n g either i s o t o n i c , isometric or i s o k i n e t i c techniques i s generally considered the most important means of developing power and strengthening muscles. Recently, inte r e s t has developed i n the use of tetanic e l e c t r i c a l stimulation, although i t i s a somewhat controversial alternative to improving muscular strength and power. Isokinetic exercise controls angular v e l o c i t y and allows for maximal accomodating resistance throughout the f u l l range of limb motion. Isokinetic resistance t r a i n i n g procedures are s i g n i f i c a n t l y better i n bringing about changes i n muscular strength, power, body composition and motor performance tasks than are standard, weight t r a i n i n g procedures (Pipes and Wilmore, 1975). Pipes and Wilmore (1975) stated that i s o k i n e t i c t r a i n i n g achieves greater gains i n muscular strength and power not only in exercise patterns that are s i m i l a r to the t r a i n i n g a c t i v i t y but also at limb speeds. that are'.typical of .those found:" i n a t h l e t i c and sports a c t i v i t i e s when t r a i n i n g at a s p e c i f i c speed. Lesmes et a l . (1978) demonstrated that i s o k i n e t i c t r a i n i n g v e l o c i t y i s an important consideration i n improving peak torque. Due to the greatly decreased time required for developing power and strength, i s o k i n e t i c exercise has been suggested for use i n r e h a b i l i t a t i o n and a t h l e t i c t r a i n i n g over isotonic or isometric exercises (Moffroid et a l . 1972). 2 The purpose of e l e c t r i c a l stimulation i s to produce a maximal muscular contraction, as sim i l a r to a normal maximal voluntary contraction, by stimulating a l l the motor units (Astrand, 1977). Kots (1977) theorized that under normal conditions, a maximal voluntary contraction i s ten to t h i r t y percent lower i n strength than an involuntary contraction that can be obtained with e l e c t r i c a l stimulation because of a force d e f i c i t . The force d e f i c i t can be explained by the fact that the current i s able to r e c r u i t more peripheral motor units than an i n d i v i d u a l can with a maximal voluntary contraction. Much controversy s t i l l e x ists over the use of e l e c t r i c a l stimulation as an adjunct to enhancing muscular strength and power. However, recent improvements i n equipment and techniques have made e l e c t r i c a l stimulation a more viable stengthening mode through research. Nowakowska (1962) and Ikai et a l . (1967, 1969), claimed that faradic stimulation increases muscular strength, endurance, working capacity and e x c i t a b i l i t y of the muscle groups trained. But Massey et a l . (1965) indicated that the conditioning of -muscle by means of e l e c t r i c a l stimulation was not as e f f e c t i v e for increasing strength than were t r a d i t i o n a l , .isometric and isot o n i c , methods of exercise. In another study by Munsat (1976), e l e c t r i c a l stimulation applied for long durations (days or weeks) appears to a l t e r the pattern of a c t i v i t y of muscle to increase the size of fast 3 g l y c o l y t i c and slow oxidative f i b e r s . His study suggests that the neural component of the motor unit may be acting i n a passive manner as a conduit for central nervous system information. Although e l e c t r i c a l stimulation for short periods of time i s not l i k e l y to cause h i s t o l o g i c a l and biochemical changes of muscle, these changes were not investigated i n t h i s study. The t r a d i t i o n a l use of electro-stimulation has been for muscle re-education, supplementing exercise. However, Johnson et a l . (1977) states that i t i s only i n recent years that faradic stimulation has been used as part of a strength t r a i n i n g program by e l i t e Russian athletes. This was p a r t i c u l a r l y evident when i t was reported that they had used the "Russian technique" of electro-stimulation to hypertrophy selected normal muscles i n athletes competing i n the 1972 Olympic Games. It has been observed that along with increased power and strength of large muscle groups, the time to accomplish these gains was s i g n i f i c a n t l y shorter as compared with the time required for increases to occur with normal weight t r a i n i n g programs (Kots, 1977). However, these reports are questionable because the Russian c l i n i c a l studies have not been published i n North America. Williams (1976), Johnson et a l . (1977) and Halbach. and Straus (1980) reported that e l e c t r i c a l stimulation increases g i r t h and strength of the quadriceps femoris muscle group. Some of the s p e c i f i c claims made by Kots (1977), with respect to e l e c t r i c a l stimulation, were that improvements i n strength, v e l o c i t y and endurance t r a i n i n g could be achieved. Johnson and 4 co-workers (1977) , u s i n g f a r a d i c s t i m u l a t i o n as t h e o n l y t r e a t -ment mode, found s i g n i f i c a n t s t r e n g t h g a i n s among p a t i e n t s h a v i n g m i l d and se v e r e c h o n d r o m a l a c i a , r e s p e c t i v e l y . There was a much g r e a t e r improvement i n the se v e r e group, as compared t o t h e m i l d c h o n d r o m a l a c i a group. T h i s i s n o t t o t a l l y due t o a s p e c i f i c b e n e f i t o f f a r a d i s m i n t h i s d i s o r d e r . R a t h e r , t h e g r e a t e r improvement o f the severe group p r o b a b l y r e f l e c t s t h e more p r o f o u n d q u a d r i c e p s a t r o p h y p r e s e n t i n i t i a l l y . When muscle i s e x e r c i s e d s t r e n u o u s l y a t a maximum work i n t e n s i t y i t adapts t o the s t r e s s by h y p e r t r o p h y i n g and enhanc-i n g i t s a b i l i t y t o ge n e r a t e f o r c e ( t e n s i o n ) . G o l l n i c k (1980) found t h a t i n h i g h i n t e n s i t y e x e r c i s e , b o t h t y p e s o f motor u n i t s ( f a s t g l y c o l y t i c o r type l i b f i b e r s and slow o x i d a t i v e o r type I f i b e r s ) may c o n t r i b u t e t o the e f f o r t , and such e x e r -c i s e may t r a i n b o t h f i b e r t y p e s . H i g h speed by i t s e l f does n o t appear t o a c t i v a t e t h e fafst t w i t c h motor u n i t s . The main p o i n t i s t h a t i t does n o t appear t o be p h y s i o l o g i c a l l y p o s s i b l e t o a c t i v a t e o n l y f a s t t w i t c h u n i t s d u r i n g power a c t i v i t i e s o r s t i m u l a t i o n s e s s i o n s by "jumping o v e r " t h e slow t w i t c h u n i t s . However, e l e c t r i c a l s t i m u l a t i o n o f normal f a s t g l y c o l y t i c and slow o x i d a t i v e muscles have i n d i c a t e d a tendency f o r slow o x i d a t i v e muscle t o . i n c r e a s e c o n t r a c t i o n speed when c h r o n i c a l l y s t i m u l a t e d w i t h i m p u l s e p a t t e r n s s i m i l a r t o f a s t g l y c o l y t i c m u s c l e s , w h i l e the o p p o s i t e o c c u r s i n f a s t g l y c o l y t i c muscle s t i m u l a t e d w i t h i m p u l s e p a t t e r n s o f slow o x i d a t i v e muscle ( I a n u z z o , 1976). Support f o r the motor i m p u l s e t h e o r y has come from e x p e r i m e n t s t h a t have imposed d i f f e r e n t p a t t e r n s o f 5 s t i m u l a t i o n on f a s t g l y c o l y t i c and slow o x i d a t i v e muscles ( I a n u z z o , 1976). Ianuzzo (1976) s t a t e s t h a t t h e time t a k e n t o r e a c h peak c o n t r a c t i o n changes w i t h e l e c t r i c a l s t i m u l a t i o n such t h a t slow o x i d a t i v e muscles i n c r e a s e c o n t r a c t i o n speed when c h r o n i c a l l y s t i m u l a t e d w i t h i m p u l s e p a t t e r n s s i m i l a r t o f a s t g l y c o l y t i c muscle s t i m u l i . K o t s 1 (1977) f i n d i n g s a l s o s u p p o r t the r e s e a r c h o f Ia n u z z o . K o t s (1977) f u r t h e r e x p l a i n e d t h a t the r e c r u i t m e n t o r d e r o f muscle f i b e r s w i t h h i s e l e c t r i c a l s t i m u l a t o r , was l a r g e r ( f a s t g l y c o l y t i c ) f i b e r s f i r s t f o l l o w e d by s m a l l e r (slow o x i d a t i v e ) f i b e r s , w hich i s o p p o s i t e t o the "normal" v o l u n t a r y c o n t r a c t i o n sequence. W i l l i a m s (1976) found t h a t e l e c t r i c a l s t i m u l a t i o n combined w i t h a c t i v e m u s c u l a r c o n t r a c t i o n was s u p e r i o r t o e x e r c i s e s a l o n e i n r e s t o r i n g t h e f u n c t i o n o f the knee j o i n t . However, C u r r i e r e t a l . (1970) d i s c o v e r e d t h a t e l e c t r i c a l s t i m u l a t i o n combined w i t h maximum i s o m e t r i c c o n t r a c t i o n s had no g r e a t e r e f f e c t on en h a n c i n g s t r e n g t h t h a n d i d c o n v e n t i o n a l s t a t i c e x e r c i s e . H a l b a c h and S t r a u s (1980) found t h a t b o t h i s o k i n e t i c s and e l e c t r o - m y o s t i m u l a t i o n i n c r e a s e d muscle power o f t h e knee e x t e n s o r muscles i n h e a l t h y s u b j e c t s . T h e r e f o r e , a c o n t r o v e r s y e x i s t s about t h e combined e f f e c t o f e l e c t r i c a l s t i m u l a t i o n and e x e r c i s e f o r d e v e l o p i n g m u s c u l a r s t r e n g t h and power. At p r e s e n t , r e h a b i l i t a t i o n f o r i n c r e a s i n g power and s t r e n g t h o f muscle groups i s b a s i c a l l y done w i t h i s o m e t r i c , i s o t o n i c and i s o k i n e t i c e x e r c i s e s t h a t u s u a l l y 6 involve eight to ten weeks (Johnson et a l . 1977). Since e l e c t r i c a l stimulation reduces the time to accomplish muscle power and strength gains, a reduction in time output would bene-f i t the athlete. Although recent work has broadened the understanding of the e f f e c t s of i s o k i n e t i c exercise and electro-stimulation of the quadriceps on producing muscular power and strength, there remains a need to compare the effectiveness of these techniques c l i n i c a l l y i n r e h a b i l i t a t i n g and t r a i n i n g muscles. The purpose of t h i s study, employing the quadriceps muscle group, i s to determine whether a t r a i n i n g regimen consisting of e l e c t r i c a l stimulation applied concurrently with maximum, is o k i n e t i c muscular contractions increases power more than does an exercise program consisting of only i s o k i n e t i c contractions, or a program of only e l e c t r i c a l stimulation. Significance of the Study To date, research involving muscle power t r a i n i n g has not elucidated whether a regime consisting of e l e c t r i c a l stimulation applied concurrently with maximum i s o k i n e t i c muscular contrac-tions increases power more than does an exercise program con-s i s t i n g of maximum i s o k i n e t i c contractions or a program of e l e c t r i c a l stimulation, respectively. This study intends to examine the value of such programs and extend the knowledge of e l e c t r i c a l stimulation for future t r a i n i n g of muscle power and r e h a b i l i t a t i o n of musculature after injury. 7 Hypotheses Group I - E l e c t r i c a l Stimulation and Isokinetic Exercise (ES + IE) Group II - Isokinetic Exercise (IE) Group III - E l e c t r i c a l Stimulation (ES) Following a six week t r a i n i n g program: 1. Power Measured at 0° per second (isometric), 30° per second, 100° per second and 180° per second for each of the three groups, respectively. The increase in muscular power produced by ES + IE ^ > the increase in muscular power produced by IE, which i s > the increase i n muscular power produced by ES (ES + IE>IE>ES). Rationale: The increase i n power produced by e l e c t r i c a l stimulation i s primarily caused by increased recruitment of peripheral nerves (motor units) and also caused by i n -creased cross-sectional area of muscle. Peripheral r e c r u i t -ment i s an important contributing power factor, as both f i b e r types are innervated within the stimulated muscle. Dynamic i s o k i n e t i c exercise provides a greater form of resistance than s t a t i c , e l e c t r i c a l stimulation contractions. This implies that i s o k i n e t i c exercise increases power more than e l e c t r i c a l stimulation alone. In addition, i s o k i n e t i c t r a i n i n g procedures are s i g n i f i c a n t l y better i n bringing about changes i n muscular power than are standard r e s i s -tance t r a i n i n g methods. Since additional muscle fi b e r s are recruited to increase power with e l e c t r i c a l stimulation and i s o k i n e t i c e x e r c i s e t r a i n i n g , t h e r e s h o u l d be power g a i n s e v i d e n t when i s o m e t r i c a l l y c o n t r a c t i n g (0° per second) and a t slow (30° per second) and f a s t (100° and 180° per second) speeds o f movement. Time t o peak t e n s i o n Measured a t 0° per second ( i s o m e t r i c c o n t r a c t i o n ) 30° p e r second, 100° per second and 180° per second f o r each o f the t h r e e groups, r e s p e c t i v e l y . Time t o peak t e n s i o n produced by ES + IE <C t h e time t o peak t e n s i o n produced by IE which i s < t h e time t o peak t e n s i o n produced by ES (ES + IE < IE < E S ) . R a t i o n a l e : The i n c r e a s e i n c o n t r a c t i o n v e l o c i t y (decrease i n c o n t r a c t i o n time) d u r i n g e l e c t r i c a l s t i m u l a t i o n i s a t t r i b u t e d t o a change i n the f i r i n g r a t e o f f a s t t w i t c h and slow t w i t c h f i b e r s . Because slow t w i t c h motor u n i t s r e q u i r e t w i c e the time t o r e a c h peak t e n s i o n as f a s t t w i t c h motor u n i t s , i t i s p o s s i b l e f o r the f a s t t w i t c h u n i t s t o be a c t i v a t e d l a t e r but s t i l l r e a c h peak t e n s i o n i n time t o make major c o n t r i b u t i o n s t o the e f f o r t . The f a s t t w i t c h f i b e r s r e a c t t o a h i g h e r f i r i n g f r e q u e n c y s i g -n a l than t h o s e which i n n e r v a t e slow t w i t c h f i b e r s . How-e v e r , when slow t w i t c h f i b e r s a r e c h r o n i c a l l y s t i m u l a t e d w i t h i m p u l s e p a t t e r n s s i m i l a r t o f a s t muscle s t i m u l i t h e slow t w i t c h f i b e r s i n c r e a s e c o n t r a c t i o n speed. So, b o t h f a s t t w i t c h and slow t w i t c h f i b e r s speed up t h e i r v e l o c i t y . T h i s e x p l a i n s why t h e r e i s - a n i n c r e a s e d a b i l i t y t o r e a c h peak c o n t r a c t i o n t ime f o r a muscle when an a c t i o n p o t e n t i a l 9 i s produced. I s o k i n e t i c e x e r c i s e i n c r e a s e s m u s c u l a r power, and s i n c e power t r a i n i n g i s based on s h o r t , h i g h i n t e n s i t y -work bouts then f a s t and slow t w i t c h f i b e r s a r e r e c r u i t e d f o r performance. S i n c e b o t h f i b e r t y p e s i n c r e a s e t h e i r v e l o c i t y w i t h e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r c i s e t r a i n i n g , t h e r e s h o u l d be a d e c r e a s e d time t o peak t e n s i o n when i s o m e t r i c a l l y c o n t r a c t i n g (0° per second) and a t slow (30° per second) and f a s t (100° and 180° per second) speeds o f movement. 3. T h i g h c i r c u m f e r e n c e The t h i g h c i r c u m f e r e n c e produced by ES + IE >^ t h e t h i g h c i r c u m f e r e n c e produced by IE whi c h i s > t h e t h i g h c i r c u m -f e r e n c e produced by ES (ES + IE > IE > E S ) . R a t i o n a l e : The muscle h y p e r t r o p h y t h a t r e s u l t s from r e -s i s t a n c e t r a i n i n g programs i s due t o an i n c r e a s e i n t h e c r o s s - s e c t i o n a l a r e a o f i n d i v i d u a l muscle f i b e r s . Body c o m p o s i t i o n changes f o l l o w i n g a r e s i s t a n c e t r a i n i n g program c o n s i s t o f a l o s s o f r e l a t i v e body f a t and a g a i n i n muscle mass. T h e r e f o r e , t h e c o m b i n a t i o n o f e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r c i s e s h o u l d produce an i n c r e a s e i n t h i g h c i r c u m f e r e n c e due t o h y p e r t r o p h y o f t h e q u a d r i c e p s . D e l i m i t a t i o n s 1. I n f e r e n c e s from t h i s s t u d y a r e l i m i t e d t o m o d e r a t e l y a c t i v e female s u b j e c t s , ages 19 t o 27 y e a r s , w i t h n o r m a l l y i n n e r -v a t e d s k e l e t a l muscle. 10 2. The e f f e c t s o f e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r -c i s e a r e a s s e s s e d o v e r a s i x week p e r i o d . 3. The s u b j e c t s are f r e e t o engage i n d a i l y a c t i v i t i e s but t h e y must not be on an a t h l e t i c team o r p a r t i c i p a t e i n s t r e n u o u s p h y s i c a l a c t i v i t y . L i m i t a t i o n s 1. S u p e r f i c i a l muscles are s t i m u l a t e d t o a g r e a t e r degree t h a n deep muscles and t h u s , e q u a l i n c r e a s e s i n s t r e n g t h o f the. q u a d r i c e p s a r e not p o s s i b l e u s i n g e l e c t r i c a l s t i m u l a t i o n . 2. Each s u b j e c t ' s t o l e r a n c e l e v e l t o e l e c t r i c a l s t i m u l a t i o n i s d i f f e r e n t due t o the v a r i a t i o n s i n s k i n r e s i s t a n c e and p a i n t h r e s h o l d s . D e f i n i t i o n s C o n t r a c t i o n v e l o c i t y - the speed a t w h i c h a muscle can c o n t r a c t o r d e v e l o p t e n s i o n as i t s h o r t e n s . E l e c t r i c a l s t i m u l a t i o n - t h e e l e c t r i c a l s t i m u l a t i o n t o be used i n the s t u d y i s a f a r a d i c c u r r e n t . The c u r r e n t i s produced by a f a r a d i c c o i l w h i c h c o n s i s t s o f a r i s e and f a l l o f u n i d i r e c t i o n a l c u r r e n t i m p u l s e s . The e s s e n t i a l f e a t u r e s a r e t h a t t h e s t i m u l i , w i t h a d u r a t i o n o f .1-1 m i l l i -second, are r e p e a t e d 50-100 t i m e s per second. The r a p i d r e c u r r e n c e o f t h e s e i m p u l s e s h o l d s a normal muscle i n 11 continued tetanic contraction u n t i l the current i s terminated. Fast twitch f i b e r s - white, type l i b muscle fi b e r s having a high anaerobic c a p a b i l i t y (glycolytic) and re-cruited during power exercises. Muscle power - the rate of work; the c a p a b i l i t y for which maxi-mum muscle tension i s developed i n a b r i e f time span. Exercises for power are designed to increase strength of muscles. Performance of muscular work i s expressed as work per unit of time. Power i s expressed as Newton-meters per second i n t h i s study. Muscle strength - the force that a muscle or muscle groups can exert against a resistance i n one maximal e f f o r t . Muscle hypertrophy - acquired increase i n the size of a normally developed t i s s u e . Newton-meters per second - a measure of power; that i s , a load of work i s the product of force and distance. Performance of work i s -2 expressed as IN = 1 k g x m x s = the force which gives the mass of 1 k g -2 an acceleration of lm x s . The unit for force i s N (Newton) and the unit for distance i s m (meter); there-fore, the unit for work i n a given 12 p e r i o d o f t ime i s N-m per second (Appendix C ) . T h i g h g i r t h - The d i s t a n c e around th e t h i g h a t the p o i n t o f g r e a t e r muscle mass. Time t o peak t e n s i o n - t h e p e r i o d o f time i t t a k e s from the i n i t i a l f o r c e e x e r t e d by a c o n t r a c t i n g muscle t o the maximal f o r c e e x e r t e d by t h e c o n t r a c t i n g muscle. Torque - a power o r s t r e n g t h f o r c e t h r o u g h a range o f m o t i o n . Slow t w i t c h f i b e r s - r e d , t ype I muscle f i b e r s h a v i n g an a e r o b i c c a p a c i t y ( o x i d a t i v e ) and r e c r u i t e d d u r i n g l o n g - t e r m endurance t y p e s o f a c t i v i t i e s . Speed s e l e c t i o n - (degrees per second) the speed o r v e l o c i t y a t w hich l i m b movement can be c o n t r o l l e d o v e r the f u l l range o f motion on i s o k i n e t i c e q u i p -ment . 13:: CHAPTER II REVIEW OF LITERATURE "" A" .library search revealed a lack of l i t e r a t u r e concerning the e f f e c t s of e l e c t r i c a l stimulation on the development of muscular strength and power i n normally innervated human skele t a l muscle. Two areas of l i t e r a t u r e which are es s e n t i a l in understanding t h i s study w i l l be examined. The two areas are: i s o k i n e t i c t r a i n i n g and e l e c t r i c a l stimulation. Isokinetic Training Athletes and non-athletes have always been interested i n techniques to increase strength and power of muscles. Iso-k i n e t i c programs have been suggested for use i n r e h a b i l i t a t i o n and a t h l e t i c t r a i n i n g due to the greatly decreased time required for developing muscular power and strength, and the absence of injury. Isokinetic t r a i n i n g i s r e l a t i v e l y new and has not been the subject of many studies. Therefore, much controversy e x i s t s regarding the etiology of i s o k i n e t i c strength gains, and i n addition, what combination of method and protocol provide the most e f f i c i e n t power gains. However, i s o k i n e t i c t r a i n i n g i s a viable technique for obtaining substantial strength gains based on the few studies conducted so far (Pipes and Wilmore, 1975; Moffroid, 1969 and T h i s t l e et a l . , 1967). Isokinetic or accommodating resistance exercise i s a new dimension i n the f i e l d of resistance exercise and muscle evaluation. The underlying p r i n c i p l e i s motion at a constant. 14 speed. This prevents acceleration, which re s u l t s i n increased resistance. The resistance developed i s i n proportion to the exerted muscle force. Isokinetic exercise not only controls the angular v e l o c i t y but i t allows for maximal resistance throughout the f u l l range of limb motion. In theory, i s o k i n e t i c exercises should lead to the great-est improvement i n muscular performance. As mentioned - • e a r l i e r , the i s o k i n e t i c p r i n c i p l e permits development of maximal muscular tension throughout the f u l l range of j o i n t movement. In other words, a greater number of motor units are activated,(Rosentsweig and Hinson, 1972). As a r e s u l t , a greater work load than was previously possible can be placed on the muscles being exercised (Hislop and Perrine, 1967). One of the most important features of i s o k i n e t i c t r a i n i n g as related to muscular t r a i n i n g or therapeutic exercise, since in most sports a c t i v i t i e s and progressive stages of r e h a b i l -i t a t i o n , muscular force i s applied during movement at varying speeds. The rela t i o n s h i p between muscular force and speed of movement becomes evident i n the force-velocity curve. Moffroid and Whipple (19 70) demonstrated that the force-v e l o c i t y curve can be shifted upward and to the r i g h t a f t e r a fast speed (108° per second) t r a i n i n g routine was completed. Training at fast speeds of movement produced increases i n strength at a l l speeds of contraction at and below the t r a i n i n speed. Whereas slow speed (36° per second) t r a i n i n g produced the greatest increase i n strength only at slow speeds of -• - .• 15 movement. In another s t u d y , P i p e s and Wilmore (1975) i n v e s t i g a t e d two d i f f e r e n t t r a i n i n g s p e e d s . T r a i n i n g was conducted t h r e e days per week f o r e i g h t weeks. The slow speed ( 2 4 ° per second) group d i d e i g h t r e p e t i t i o n s d u r i n g each o f t h r e e s e t s , w h i l e the f a s t speed (136° per second) group d i d f i f t e e n r e p e t i t i o n s d u r i n g each o f the t h r e e s e t s . The f i n d i n g s o f P i p e s and Wilmore (1975) demonstrated t h a t t r a i n i n g a t a f a s t speed i n c r e a s e d s t r e n g t h a t bo th f a s t and slow speeds of movement. However, t r a i n i n g a t a slow speed produced i n c r e a s e s i n s t r e n g t h o n l y a t slow speeds o f movement. In two subsequent s t u d i e s , T h i s t l e e t a l . (1967) and M o f f r o i d e t a l . (1969) found t h a t h i g h power ( f a s t v e l o c i t y , low load) e x e r c i s e produced an i n c r e a s e i n muscular f o r c e a t a l l speeds of c o n -t r a c t i o n a t and below the t r a i n i n g speed . T h i s t l e e t a l . (1967) p r o v i d e d a compar ison of i s o k i n e t i c , i s o t o n i c and i s o m e t r i c programs. The s u b j e c t s i n t h i s s tudy were p a t i e n t s w i t h v a r y i n g degrees o f r e h a b i l i t a t i v e p r o b l e m s . The t r a i n i n g f r e q u e n c y and d u r a t i o n were f o u r days per week f o r e i g h t weeks. In t h i s c a s e , i t was c o n c l u d e d t h a t the i s o k i n e t i c program was c l e a r l y s u p e r i o r to the o t h e r programs i n bo th s t r e n g t h and endurance g a i n s . In P i p e s and W i l m o r e ' s (1975) compara t ive s tudy o f i s o -k i n e t i c v e r s u s i s o t o n i c s t r e n g t h t r a i n i n g , i t was shown t h a t the i s o k i n e t i c r e s i s t a n c e programs are s i g n i f i c a n t l y b e t t e r i n b r i n g i n g about changes i n muscu la r s t r e n g t h , body c o m p o s i t i o n 16 and s e l e c t e d power t a s k s t h a n a r e s t a n d a r d i s o t o n i c r e s i s t a n c e t r a i n i n g p r o c e d u r e s . These r e s e a r c h e r s a l s o demonstrated t h a t i s o k i n e t i c t r a i n i n g a c h i e v e s g r e a t e r g a i n s i n m u s c u l a r s t r e n g t h not o n l y i n e x e r c i s e p a t t e r n s t h a t a r e s i m i l a r t o the t r a i n i n g a c t i v i t y but a l s o a t l i m b speeds t h a t a r e t y p i c a l o f t h o s e found i n a t h l e t i c and s p o r t s a c t i v i t i e s as e v i d e n c e d by sub-s t a n t i a l improvements i n the power.performance t a s k s . A l t h o u g h th e c o n t r a c t i l e p r o p e r t i e s o f s k e l e t a l muscle appear t o be u n a l t e r e d by r e s i s t a n c e t r a i n i n g , major changes do o c c u r w i t h t r a i n i n g i n the m e t a b o l i c p o t e n t i a l o f t h e muscle and t h e i n d i v i d u a l f i b e r s . G o l l n i c k (1980) s t a t e d t h a t i n t h e s l ow t w i t c h f i b e r s the most d r a m a t i c e v i d e n c e o f m e t a b o l i c a d a p t a t i o n i s the i n c r e a s e d c o n c e n t r a t i o n o f m i t o c h o n d r i a and t h e enzymes f o r o x i d a t i v e m e t a b o l i s m w i t h endurance t r a i n i n g . The i n c r e a s e d o x i d a t i v e p o t e n t i a l o f muscle w i t h t r a i n i n g would appear t o i n c r e a s e i t s c a p a c i t y f o r u s i n g i t s energy r e s e r v e s -b o t h t h o s e s t o r e d i n t r a c e l l u l a r l y and t h o s e t r a n s p o r t e d t o i t by t h e b l o o d - t h r o u g h o x i d a t i o n t o carbon d i o x i d e and w a t e r . I n t h e case o f c a r b o h y d r a t e s , t h i s p r o c e s s y i e l d s l a r g e energy s u p p l i e s from ATP than when l a c t a t e i s produced by t h e a n a e r o b i c pathway. The i n c r e a s e d a e r o b i c c a p a c i t y would i n c r e a s e the muscle's a b i l i t y t o use f a t t y a c i d s p r o v i d e d t o i t by t h e b l o o d . The c o m b i n a t i o n o f t h e s e p r o c e s s e s would e x e r t a g l y c o g e n - s p a r i n g e f f e c t on the muscle and r e s u l t i n g r e a t e r endurance c a p a c i t y , because t h e r e i s a r e l a t i o n s h i p between the d e p l e t i o n o f i n t r a c e l l u l a r g l y c o g e n r e s e r v e s o f muscle and the t e r m i n a t i o n o f m o d e r a t e l y severe- e x e r c i s e . 17 The influence of t r a i n i n g on the anaerobic capacity of s k e l e t a l muscle i s not as clear as that of the aerobic capacity. However, the fast twitch f i b e r s have a fast speed of contrac-tion but they rapidly fatigue as they exhaust t h e i r i n t e r n a l supply of glycogen. Associated with the fast twitch f i b e r s ' low oxidative capacity i s a poor blood supply, which f a i l s to provide these f i b e r s with the additional glucose required to maintain contraction. It has been asserted by Pipes and Wilmore (1975) that fast or slow t r a i n i n g causes sele c t i v e recruitment of fast and slow twitch motor units, respectively. However, the fore-going i s not i n agreement with a considerably body of s c i e n t i f i c evidence. MacDougall et a l . (1980b) and Prince et a l . (1976) showed that bodybuilders and power l i f t e r s have enlarged fast twitch as well as slow twitch f i b e r s . Further, conventional slow v e l o c i t y weight t r a i n i n g and slow i s o k i n e t i c t r a i n i n g causes hypertrophy of both f i b e r types (MacDougall et a l . 1980a). In fact, the fast twitch f i b e r s are enlarged to a greater extent than the slow twitch f i b e r s in the bodybuilders and power l i f t e r s ; s i m i l a r l y , slow v e l o c i t y t r a i n i n g causes greater hypertrophy of the fast twitch f i b e r s (MacDougall et a l . 1980a and Thorstensson et a l . 1976). This does not mean that the fast twitch motor units were recruited more but may indicate that fast twitch f i b e r s are more adaptable i n r e l a t i o n to hypertrophy. Electromyographic studies undertaken by Desmedt and Godaux (1979) and Maton (1980) indicate that provided the degree of voluntary e f f o r t i s maximal, the motor unit a c t i v a t i o n 18 i s s i m i l a r r e g a r d l e s s o f the v e l o c i t y o f c o n t r a c t i o n . G o l l n i c k e t a l . (1974) and Warmolts and E n g e l (1972) have shown t h a t f a s t t w i t c h motor u n i t s are a c t i v a t e d d u r i n g i s o m e t r i c c o n -t r a c t i o n s . In a d d i t i o n , a p o s i t i v e c o r r e l a t i o n between i s o -m e t r i c s t r e n g t h and the percen tage o f f a s t t w i t c h f i b e r s w i t h i n a muscle has been demonstra ted by Tesch and K a r l s s o n (1978). T h e r e f o r e , i t can be c o n c l u d e d t h a t t h e r e i s no b a s i s f o r the c l a i m t h a t s low t w i t c h motor u n i t s a re p r e f e r e n t i a l l y r e c r u i t e d d u r i n g maximal slow v e l o c i t y c o n t r a c t i o n s . The m i s l e a d i n g n o t i o n may have a r i s e n from the assumpt ion t h a t f a s t t w i t c h muscle f i b e r s c o u l d o n l y be i n v o l v e d i n f a s t c o n t r a c t i o n s ; however, f a s t t w i t c h f i b e r s are a l s o d e s i g n e d to c o n t r i b u t e f o r c e , r e g a r d l e s s o f v e l o c i t y . A l s o , slow t w i t c h motor u n i t s can c o n t r i b u t e f o r c e to v e r y r a p i d c o n t r a c t i o n s . As f a r as the s p e c i f i c i t y o f a t r a i n i n g e f f e c t i s c o n -c e r n e d , the f a c t t h a t the nervous c o n t r o l p l a y s a d e c i s i v e r o l e f o r the development o f s t r e n g t h i s impor tan t ( E c c l e s , 1973) . The s p e c i f i t y i s r e l a t e d to the o r g a n i z a t i o n o f movements by n e u r a l a d a p t a t i o n - r a t h e r than to s e l e c t i v e r e c r u i t m e n t o f motor u n i t t y p e s (Desmedt and Godaux, 1979) . The c e n t r a l n e r -vous system c o n t i n u o u s l y r e c e i v e s messages from p e r i p h e r a l r e c e p t o r s about j o i n t p o s i t i o n s , muscle l e n g t h and t e n s i o n , movements, envi ronment and so o n . When a c a l l f o r a movement i s r e p o r t e d to the b r a i n , the nervous system has a l l the n e c e s s a r y r e q u i r e m e n t s f o r e x e c u t i o n and c o n t r o l o f the move-ment. T h e r e f o r e , the s t r e n g t h t r a i n i n g program d e s i g n e d f o r "speed" and "power" a t h l e t e s s h o u l d i n c l u d e f a s t movements to 19 t r a i n the nervous system and slow movements t o t r a i n t h e m u s c l e s . In o t h e r words, the a t h l e t e s h o u l d t r a i n t h e muscles and l e a r n t o e x e c u t e the d e s i r e d movements t h r o u g h n e u r a l c o n t r o l . Commonly a s s o c i a t e d w i t h s t r e n g t h e n i n g programs i s muscle s o r e n e s s . F r e q u e n t l y , i n r e s i s t a n c e t r a i n i n g programs t h e r e i s an i n i t i a l l o s s o f s t r e n g t h due t o muscle s o r e n e s s as e v i d e n c e d by T a l a g (1973). A t p r e s e n t t h e r e a r e t h r e e d i f f e r e n t e x p l a n -a t i o n s f o r t h e problem o f d e l a y e d muscle s o r e n e s s a c c o r d i n g t o Abraham (1977). The " t o r n t i s s u e " h y p o t h e s i s s u g g e s t s t h a t t h e p a i n r e s u l t s from s t r u c t u r a l damage i n t h e muscle. A l t e r n a t -i v e l y , the spasm t h e o r y proposes t h a t t h e d e l a y e d s o r e n e s s i s caused by t o n i c spasms i n l o c a l i z e d motor u n i t s . The h y p o t h e s i s t h a t o v e r s t r e t c h i n g , t h e m u s c l e s ' e l a s t i c components, i . e . , the c o n n e c t i v e t i s s u e among the f i b e r s and f i b r i l s , e s p e c i a l l y d u r -i n g e c c e n t r i c t y p e s o f work, r e s u l t s i n d e l a y e d p o s t - e x e r c i s e p a i n . Abraham (1977) s t a t e s t h a t by c o r r e l a t i n g t h e appearance o f d e l a y e d s o r e n e s s w i t h breakdown p r o d u c t s from muscle c e l l s and/or c o n n e c t i v e t i s s u e , i t would be p o s s i b l e t o d e t e r m i n e i f the " c o n n e c t i v e t i s s u e damage" t h e o r y e x i s t s . The " c o n n e c t i v e t i s s u e damage" p r o p o s a l can be s t u d i e d by m o n i t o r i n g u r i n a r y h y d r o x y p r o l i n e (OHP) l e v e l s . S i n c e OHP has been shown t o be a s p e c i f i c breakdown p r o d u c t o f c o n n e c t i v e t i s s u e , a s s a y s f o r u r i n a r y OHP would be u s e f u l i n s t u d y i n g c o l l a g e n m e t a b o l i s m . Abraham's (1977) i n v e s t i g a t i v e work r e v e a l e d t h a t s t r e n u -ous e x e r c i s e r e s u l t e d i n i n j u r y t o the c o n n e c t i v e t i s s u e i n and around the muscle. Thus, i t may be t h a t when the l e v e l o f 20 e x e r c i s e became s u f f i c i e n t l y s e v e r e , a r e d u c t i o n i n t h e p h y s i c a l s t r e n g t h o f t h e c o l l a g e n a l l o w e d i t t o be damaged. T h i s t h e o r y would suggest t h a t i n c r e a s e d d e g r a d a t i o n was r e s p o n s i b l e f o r the h i g h e r u r i n a r y OHP l e v e l s . In a d d i t i o n , h y p o x i a i s known t o s t i m u l a t e c o l l a g e n s y n t h e s i s . S i n c e m e c h a n i c a l s t r e s s and l o c a l t i s s u e h y p o x i a may r e s u l t from e x e r c i s e , i t i s c o n c e i v a b l e t h a t t h e i n c r e a s e d OHP e x c r e t i o n s are 5 i n d i c a t i v e o f more r a p i d c o l l a g e n s y n t h e s i s . The answer as t o which mechanism r e s u l t e d i n t h e i n c r e a s e d OHP e x c r e t i o n d u r i n g t h i s i n v e s t i g a t i o n c o u l d not be o b t a i n e d . However, what was c o n c l u d e d from t h e s e r e s u l t s was. t h a t t h e d e l a y e d muscle s o r e n e s s o b s e r v e d a f t e r e x e r c i s e was most l i k e l y c o r r e l a t e d t o a l t e r a t i o n s i n t h e muscle c o n n e c t i v e t i s s u e . On t h e o t h e r hand, T h i s t l e e t a l . (1967) and P i p e s and Wilmore (1975) o b s e r v e d t h a t i s o k i n e t i c t r a i n i n g s u b j e c t s d i d n o t r e p o r t muscle s o r e n e s s . I t i s s u g g ested t h a t i s o k i n e t i c r e s i s t a n c e p r o c e d u r e s employ o n l y p o s i t i v e , c o n c e n t r i c c o n t r a c -t i o n s w i t h l i t t l e o r no r e s i s t a n c e d u r i n g the r e c o v e r y phase o f t h e e x e r c i s e . I t has been demonstrated t h a t the a p p l i c a t i o n o f e c c e n t r i c c o n t r a c t i o n s i n t r a i n i n g has no advantage compared w i t h t h e c o n c e n t r i c . D u r i n g an i s o k i n e t i c c o n t r a c t i o n , the muscle i s n o t l e n g t h e n e d as i n a n e g a t i v e , e c c e n t r i c movement. T h i s e x p l a i n s t h e absence o f c o n n e c t i v e t i s s u e damage and l a c k o f s o r e n e s s a s s o c i a t e d w i t h i s o k i n e t i c t r a i n i n g . I t appears t h a t the s u p e r i o r i t y - o f the i s o k i n e t i c programs i s p r o b a b l y due t o the n a t u r e o f t h e i s o k i n e t i c c o n t r a c t i o n , 21 i . e . , maximal r e s i s t a n c e t h r o u g h th e t o t a l range o f m o t i o n . The a p p a r e n t s u p e r i o r i t y o f the h i g h speed e x e r c i s e o v e r the low speed e x e r c i s e i s p r e s e n t l y u n e x p l a i n a b l e and r e q u i r e s f u r t h e r i n v e s t i g a t i o n . I n v i e w i n g t h e l i m i t e d l i t e r a t u r e on i s o k i n e t i c t r a i n i n g w i t h r e s p e c t t o m u scular power and s t r e n g t h , one would con-c l u d e t h a t i t i s s t i l l a r e l a t i v e l y u n e x p l o r e d t r a i n i n g mode. I t appears t h a t P i p e s and Wilmore (1975) and M o f f r o i d and Whipple's (1970) work have been the most e x t e n s i v e i n terms o f d e v e l o p i n g an i s o k i n e t i c t r a i n i n g regime. E l e c t r i c a l S t i m u l a t i o n The m a j o r i t y o f t h e r e s e a r c h e x a m i n i n g the e f f e c t o f e l e c t r i c a l s t i m u l a t i o n on the development o f m u s c u l a r s t r e n g t h o r power has d e a l t w i t h e i t h e r a n i m a l s t u d i e s o r d e n e r v a t e d muscles o f humans. T r a d i t i o n a l l y , e l e c t r i c a l s t i m u l a t i o n has been used f o r muscle r e - e d u c a t i o n , s u p p l e m e n t i n g e x e r c i s e . F a r a d i c o r e l e c t r i c a l s t i m u l a t i o n i s d e v e l o p e d from a f a r a d i c c o i l and has two e s s e n t i a l f e a t u r e s : t h e s t i m u l i must l a s t f o r a d u r a t i o n o f -.1-1 m i l l i s e c o n d and be r e p e a t e d 50-100 t i m e s per second. C u r r e n t o f t h i s t y p e can s t i m u l a t e the motor n e r v e s and t h e muscle i t s e l f w i t h s u f f i c i e n t c u r r e n t t o e l i c i t a muscle c o n t r a c t i o n . Because the s t i m u l i are r e p e a t e d 50-100 t i m e s per second, th e c o n t r a c t i o n i s t e t a n i c . I f t h i s t y pe o f c o n t r a c t i o n i s m a i n t a i n e d f o r a p e r i o d o f 22 t i m e , muscle f a t i g u e i s produced, so t h e c u r r e n t i s u s u a l l y s urged o r i n t e r r u p t e d t o a l l o w f o r muscle r e l a x a t i o n . When th e c u r r e n t i s s u r g e d the c o n t r a c t i o n i n c r e a s e s and d e c r e a s e s i n s t r e n g t h , s i m i l a r t o a v o l u n t a r y c o n t r a c t i o n ( S c o t t , 1975 and S t i l l w e l l , 1967). The muscle' c o n t r a c t i o n produced by t h i s t y p e o f c u r r e n t has been found t o be s i m i l a r t o a v o l u n t a r y c o n t r a c t i o n ( S c o t t , 1975). S t i l l w e l l (1967) mentioned t h a t e l e c t r i c a l s t i m u l a t i o n comparable t o t h e method used i n t h i s e x periment s t i m u l a t e s s e n s o r y n e r v e s , motor n e r v e s and t h e e n t i r e muscle. E l e c t r i c a l s t i m u l a t i o n t o a muscle causes s i m i l a r v a s c u l a r changes as a s s o c i a t e d w i t h v o l u n t a r y c o n t r a c t i o n . An i n c r e a s e i n the r e q u i r e m e n t f o r n u t r i e n t s o c c u r s , as w e l l as an i n c r e a s e needed f o r removal o f waste p r o d u c t s . S t i l l w e l l (1976:127) s t a t e s : " I f a muscle c o n t r a c t s a s u f f i c i e n t number o f t i m e s a g a i n s t a r e s i s t a n c e o f an adequate l o a d t h e r e i s an i n c r e a s e i n the b u l k o f t h e muscle f i b e r s and the muscle i s s t r e n g t h e n e d . There i s some doubt whether the muscle c o n t r a c t i o n caused by f a r a d i c s t i m u l a t i o n can produce t h e s e e f f e c t s , but presumably i f s u f f i c i e n t c o n t r a c -t i o n s a r e produced a g a i n s t a r e s i s t a n c e o f an adequate l o a d i t s h o u l d be p o s s i b l e t o do so." S t i l l w e l l (1976) was s k e p t i c a l as t o the e f f e c t s o f e l e c t r i c a l s t i m u l a t i o n p e r t a i n i n g t o s t r e n g t h i n c r e m e n t s i n s k e l e t a l muscle. There has been l i t t l e i n f o r m a t i o n g a t h e r e d t o suggest t h a t muscle power can i n c r e a s e by e l e c t r i c a l s t i m u l a t i o n ( N i c o l s , 1976 and S t i l l w e l l , 1967). T h i s i s because the d i s c o m f o r t o f the s t i m u l i i s such t h a t a c o n t r a c -t i o n produced i s r a r e l y more th a n t h i r t y p e r c e n t o f a maximal 23 c o n t r a c t i o n (Nic'ols, 1976). I n the s t u d y conducted by Halb a c h and S t r a u s (1980), as i n d i v i d u a l t r e a t m e n t s e s s i o n s p r o g r e s s e d w i t h e l e c t r o - m y o s t i m u l a t i o n , the maximum amount o f f a r a d i c c u r r e n t t h a t c o u l d be t o l e r a t e d i n c r e a s e d s i g n i f i c a n t l y . How-e v e r , f o l l o w i n g t r e a t m e n t s o f maximum t o l e r a n c e , t h e r e was a de c r e a s e i n t h e amount o f f a r a d i c c u r r e n t t h a t c o u l d be t o l e r -a t e d , due t o t h e r e s u l t a n t muscle s o r e n e s s . R e c e n t l y , new equipment has been i n t r o d u c e d overcoming the u n c o m f o r t a b l e s e n s o r y s t i m u l a t i o n a s s o c i a t e d w i t h e l e c t r i c a l c u r r e n t . I n the s t u d y by Curwin e t a l . (1980) i t was demon-s t r a t e d t h a t m o d u l a t i o n o f s i n u s o i d a l c u r r e n t s used f o r muscle s t i m u l a t i o n produces medium f r e q u e n c y c u r r e n t s c a p a b l e o f b l o c k i n g s u p e r f i c i a l n e rve e n d i n g s . T h i s p e r m i t s t h e more c o m f o r t a b l e use o f h i g h i n t e n s i t i e s . F a r a d i c c u r r e n t s u t i l i z -i n g s p i k e d p u l s e s w i t h a d u r a t i o n o f 50 t o 500 mic r o s e c o n d s and a f a s t r i s e t i me s i m i l a r l y d e c r e a s e r e s i s t a n c e r e d u c i n g s e n s o r y e f f e c t s and a l l o w i n g use o f h i g h i n t e n s i t i e s . Cummings (1980) s t a t e s t h a t t h e c u r r e n t s w i t h a f a s t r i s e t i me a v o i d accommoda-t i o n by the motor n e r v e , p r o d u c i n g r e q u i r e d t e t a n i c c o n t r a c t i o n a t a lo w e r i n t e n s i t y . The use o f e l e c t r i c a l s t i m u l a t i o n as a s t i m u l u s f o r a t r o p h y r e t a r d a t i o n has been s t u d i e d by many i n v e s t i g a t o r s . Guttmann and Guttmann (1942) r e p o r t e d t h a t d e n e r v a t e d r a b b i t muscle a t r o p h i e s l e s s when exposed t o e l e c t r i c a l s t i m u l a t i o n . Osbourne (1951) found a d e c r e a s e i n a t r o p h y i n humans w i t h l e s i o n s o f p e r i p h e r a l n e r v e s a f t e r r e c e i v i n g e l e c t r i c a l s t i m u l a t i o n . 24 J a c k s o n and Seddon (1945) s t u d i e d p a t i e n t s w i t h d e n e r v a t e d muscles o f t h e hand and found t h a t e l e c t r i c a l s t i m u l a t i o n r e t a r d e d a t r o p h y d u r i n g the f i r s t one hundred days o f d e n e r v a -t i o n and s u b s e q u e n t l y , the s t i m u l a t i o n was r e s p o n s i b l e f o r p r e v e n t i n g f u r t h e r a t r o p h y a f t e r t h i s t i m e . Not o n l y can a t r o p h y be c o n t r o l l e d , but o t h e r r e s e a r c h e r s have demonstrated t h a t h y p e r t r o p h y w i t h i n the muscle can be i n f l u e n c e d by e l e c t r i c a l s t i m u l a t i o n . c Osbourne e t a l . (1950) s t i m u l a t e d s u b j e c t s w i t h p o l i o m y e l i t i s u s i n g a s i n u s o i d a l wave f o r t e n minutes a day, and t h e r e s u l t s showed s i g n i f i c a n t i n c r e a s e s i n the c i r c u m f e r e n c e s o f t h e l i m b s . More r e c e n t l i t e r a t u r e by Peckham (1976) i l l u s t r a t e d s i g n i f i c a n t s t r e n g t h g a i n s i n q u a d r a p l e g i c p a t i e n t s when s u b j e c t e d t o e l e c t r i c a l s t i m u l a t i o n . An i n t r a m u s c u l a r e l e c t r o d e was p l a n t e d w i t h i n the muscle n e r v e s which s t i m u l a t e d t h e muscle a t f i f t y p e r c e n t o f i t s maximal f o r c e . The c o n t r a c t i o n was p r i m a r i l y by e x c i t a t i o n o f i n t r a m u s c u l a r n e r v e s and i t was e s t i m a t e d t h a t o n l y f i v e p e r c e n t o f t h e m u scular f o r c e was from d i r e c t muscle s t i m u l a -t i o n . The c u r r e n t remained on f o r 2.5 seconds and o f f f o r the same d u r a t i o n . The hand was i n a l o c k e d p o s i t i o n and f i n g e r f l e x o r s were s t i m u l a t e d f o r two t o t h r e e hours per day f o r t h i r t y weeks. S i g n i f i c a n t s t r e n g t h g a i n s were o b s e r v e d a f t e r o n l y f o u r weeks o f s t i m u l a t i o n . As r e p o r t e d by Johnson e t a l . (1977), the R u s s i a n s a r o u s e d renewed i n t e r e s t by u s i n g e l e c t r i c a l s t i m u l a t i o n t o h y p e r t r o p h y s e l e c t e d normal muscles i n a t h l e t e s competing i n the 1972 25 Olympic Games. The R u s s i a n c l i n i c a l s t u d i e s have not been pub-l i s h e d i n N o r t h America t o d a t e . C o n s e q u e n t l y , l i t t l e i s known about the s t a n d a r d i z a t i o n o r e f f i c i e n c y o f the t e c h n i q u e . I n a C a n a d i a n - S o v i e t exchange symposium, Kot s (1977) o u t -l i n e d t h e " R u s s i a n t e c h n i q u e " and r e s u l t s o f the S o v i e t r e s e a r c h . P r e c i s e d e t a i l s o f t h i s method and d e s c r i p t i o n o f the a p p a r a t u s a r e not a v a i l a b l e . K o t s (1977) u t i l i z e d e l e c t r i c a l muscle s t i m u l a t i o n t o r e h a b i l i t a t e s o f t and h a r d t i s s u e i n j u r i e s , as w e l l as a s t r e n g t h e n i n g mode f o r h e a l t h y m u s c l e s . He a l s o has found t h a t e l e c t r i c a l s t i m u l a t i o n produces b e t t e r r e s u l t s than t r a d i t i o n a l e x e r c i s e regimes a l o n e , and can be s p e c i f i c a l l y used t o i s o l a t e p a r t i c u l a r muscles f o r i n d i v i d u a l s p o r t s . The R u s s i a n e l e c t r i c a l s t i m u l a t o r produced o v e r a l l s t r e n g t h g a i n s t h a t were s i m i l a r , whether t r e a t m e n t s were on a l t e r n a t e days o r f o r an e q u i v a l e n t number o f s e s s i o n s on a d a i l y b a s i s . The i m p o r t a n t f a c t o r s appear t o be the t o t a l number o f t r e a t m e n t s and an adequate r e s t p e r i o d f o l l o w i n g each t r e a t m e n t . The R u s s i a n t e c h n i q u e has demonstrated o p t i m a l s t r e n g t h b e n e f i t s f o l l o w i n g f o u r t o f i v e weeks, o r twenty t o t w e n t y - f i v e t r a i n i n g s e s s i o n s ( K o t s , 1977). As i s t h e case w i t h t r a d i t i o n a l v o l u n t a r y s t r e n g t h t r a i n i n g t e c h n i q u e s , the r a t e o f s t r e n g t h g a i n d e c r e a s e s as the number o f t r e a t m e n t s e s s i o n s i n c r e a s e s . S t r e n g t h i s m a i n t a i n e d a t near maximum f o r t h r e e months and n i n e t y p e r c e n t f o r t e n months. Kot s (1977) a t t r i b u t e s the 26 s t r e n g t h e n i n g e f f e c t t o two f a c t o r s . F i r s t l y , muscle c r o s s -s e c t i o n i s i n c r e a s e d w i t h an a s s o c i a t e d d e c r e a s e i n subcutaneous f a t as measured by u l t r a s o u n d t e c h n i q u e s . S e c o n d l y , t h e r e i s g r e a t e r r e c r u i t m e n t o f p e r i p h e r a l n e r v e s . T h i s a c c o u n t s f o r r e t a i n e d s t r e n g t h a f t e r h y p e r t r o p h y d e c r e a s e s and i s t h e p r i m a r y b e n e f i t o f e l e c t r i c a l s t i m u l a t i o n f o r muscle s t r e n g t h e n i n g . He s t a t e d t h a t a change i n v e l o c i t y o r r a t e o f muscle c o n t r a c t i o n may be a r e s u l t o f p e r c e n t f a s t - t w i t c h f i b e r s t o p e r c e n t o f s l o w - t w i t c h f i b e r s r e m a i n i n g the same but the q u a l i t y o f r e c r u i t -ment may t e n d t o be more s p e c i f i c t o the f a s t - t w i t c h f i b e r s , even though b o t h f i b e r t y p e s i n c r e a s e t h e i r v e l o c i t y . Johnson e t a l . (1977) found t h a t e l e c t r i c a l s t i m u l a t i o n was b e n e f i c i a l i n i m p r o v i n g s t r e n g t h and muscle s i z e u s i n g the R u s s i a n regimen d u r i n g r e h a b i l i t a t i o n . They s t u d i e d f i f t y p a t i e n t s s u f f e r i n g c h o n d r o m a l a c i a p a t e l l a , each p a t i e n t was measured f o r l e g s t r e n g t h and t h i g h g i r t h i n i t i a l l y and a f t e r twenty s e s s i o n s o f f a r a d i c s t i m u l a t i o n . The t r e a t m e n t con-s i s t e d o f t e n maximum t e t a n i c c o n t r a c t i o n s w i t h a f i f t y second r e s t p e r i o d between each c o n t r a c t i o n . The S o v i e t t e c h n i q u e i s c a p a b l e o f p r o d u c i n g a medium f r e q u e n c y c u r r e n t o f s u f f i c i e n t i n t e n s i t y t o a c t i v a t e a l l a v a i l a b l e motor u n i t s a t maximal t e t a n u s f r e q u e n c y , but a t t h e same time m i n i m i z e s the s k i n s e n s o r y d i s c o m f o r t . The c o n t r a c t i o n s were i s o m e t r i c i n n a t u r e w i t h the knee a t f i v e degrees o f f l e x i o n . The r e s u l t s showed a 25.3 p e r c e n t i n c r e a s e i n q u a d r i c e p s s t r e n g t h i n t h e m i l d c h o n d r o m a l a c i a group and a 36.2 p e r c e n t i n c r e a s e i n t h e se v e r e c h o n d r o m a l a c i a group. There was a l s o a s i m i l a r i n c r e a s e i n 27 t h i g h g i r t h o f 4.3 p e r c e n t i n the m i l d group and 6.8 p e r c e n t i n t h e s e v e r e group. Johnson e t a l . (1977) c o n c l u d e d t h a t f a r a d i c s t i m u l a t i o n i s an e f f e c t i v e form o f t h e r a p y f o r c h o n d r o m a l a c i a p a t e l l a and has i t s g r e a t e s t b e n e f i t i n the i n i t i a l s t a g e s , t o p r e v e n t the l o s s o f v o l u n t a r y c o n t r o l o f q u a d r i c e p s c o n t r a c t i o n . Other s t u d i e s have shown t h a t e l e c t r i c a l s t i m u l a t i o n was advantageous i n o b t a i n i n g s t r e n g t h i n c r e m e n t s ( C u r r i e r e t a l . , 1979 and G odfrey e t a l . , 1979). The purpose o f t h e s t u d i e s was t o compare the e f f e c t i v e n e s s o f e l e c t r i c a l s t i m u l a t i o n as a mode o f e x e r c i s e . a n d t r e a t m e n t , r e s p e c t i v e l y . C u r r i e r e t a l . (1979) took two groups o f h e a l t h y s u b j e c t s ; one group performed i s o m e t r i c e x e r c i s e w h i l e s i m u l t a n e o u s l y r e c e i v i n g e l e c t r i c a l s t i m u l a t i o n and the second group engaged i n i s o m e t r i c e x e r c i s e o n l y . The knee e x t e n s o r muscles o f b o t h groups i n c r e a s e d i n s t r e n g t h , however the s t r e n g t h g a i n s f o r b o t h groups were e q u i v a l e n t . I n a comparison s t u d y by Godfrey e t a l . (1979), i t was r e p o r t e d t h a t a program o f e l e c t r i c a l s t i m u l a t i o n i s as e f f e c t i v e as a program o f i s o m e t r i c q u a d r i c e p s s t r e n g t h e n i n g f o r development o f muscle power f o l l o w i n g s u r g e r y o r i n j u r y t o t h e knee. These r e s e a r c h e r s c o n c l u d e d t h a t by u s i n g e l e c t r i c a l s t i m u l a t i o n a p h y s i c a l r e s t o r a t i o n program i s s t a r t e d immedi-a t e l y because o f t h e a b i l i t y t o m a i n t a i n a v o l u n t a r y f u l l c o n t r a c t i o n . I n a r e c e n t s t u d y , H a l b a c h e t a l . (1980) compared e l e c t r i -c a l s t i m u l a t i o n t o i s o k i n e t i c t r a i n i n g i n o r d e r t o i n c r e a s e 28 m u s c u l a r power. I t was demonstrated t h a t b o t h i s o k i n e t i c s and e l e c t r i c a l s t i m u l a t i o n i n c r e a s e muscle power o f h e a l t h y knee e x t e n s o r m u s c l e s , however the i s o k i n e t i c s p r o v e d t o be s u p e r i o r i n i n c r e a s i n g power as compared t o e l e c t r i c a l s t i m u l a t i o n . I t was c o n c l u d e d t h a t more s t u d y needs t o be u n d e r t a k e n w i t h e l e c t r i c a l s t i m u l a t i o n and i t s e f f e c t on i n c r e a s i n g power, p a r t i c u l a r l y when the s u b j e c t can t o l e r a t e o v e r t w e n t y - f i v e m i l l i a m p e r e s . S e v e r a l a u t h o r s (Curwin e t a l . , 1980 and S t a n i s h e t a l . , 1980) have shown t h a t p a t i e n t s u n d e r g o i n g muscle s t i m u l a t i o n as p a r t o f t h e i r r e h a b i l i t a t i o n program d i d n o t have a d e c r e a s e i n m y o f i b r i l l a r ATPase a c t i v i t y , as d e t e r m i n e d by muscle b i o p s i e s , n o r m a l l y a s s o c i a t e d w i t h an i m m o b i l i z a t i o n p e r i o d . I t was c o n c l u d e d t h a t e l e c t r i c a l s t i m u l a t i o n was a b l e t o p r e -v e n t th e d e c r e a s e i n m y o f i b r i l l a r ATPase and a t r o p h y t h a t accompanies i m m o b i l i z a t i o n , but t h e f i n d i n g s do not n e c e s s a r i l y l e a d t o t h e c o n c l u s i o n t h a t t h e use o f e l e c t r i c a l s t i m u l a t i o n f o r the improvement o f muscle f u n c t i o n i s s u p e r i o r t o conven-t i o n a l t r a i n i n g programs o r p h y s i o t h e r a p y t e c h n i q u e s . I t can be employed as a means o f m a i n t a i n i n g m y o f i b r i l l a r ATPase l e v e l s o f t h e q u a d r i c e p s group w h i l e the knee j o i n t i s i m m o b i l i z e d . E r i k s s o n e t a l . (1979) worked w i t h p a t i e n t s i n a s i m i l a r s t u d y c o n c e r n i n g enzymes c o n n e c t e d w i t h muscle a c t i v i t y . They examined the e f f e c t s t h a t p o s t - s u r g i c a l i m m o b i l i z a t i o n had upon s u c c i n a t e d dehydrogenase (SDH) a c t i v i t y . T h i s p a r t i c u l a r 29 enzyme was s i n g l e d out because i t has been found t o be w e l l c o r r e l a t e d w i t h the a b i l i t y o f muscle t o p e r f o r m everyday t a s k s and s t r e n u o u s s p o r t s . The r e s u l t s showed t h a t t h e p a t i e n t s who r e c e i v e d e l e c t r i c a l s t i m u l a t i o n had l e s s muscle a t r o p h y and b e t t e r muscle f u n c t i o n t h a n d i d the p a t i e n t group t h a t d i d i s o m e t r i c t r a i n i n g . When the b i o c h e m i c a l a n a l y s i s o f the muscle b i o p s y was c a r r i e d o u t i t was found t h a t t h e i n c r e a s e i n SDH i n the s t i m u l a t e d group was s i g n i f i c a n t and the d e c r e a s e i n SDH i n t h e i s o m e t r i c a l l y t r a i n e d group was a l s o s i g n i f i c a n t . E r i k s s o n e t a l . (1981) i n a subsequent s t u d y e v a l u a t e d t h e a c u t e and a d a p t i v e e f f e c t s o f e l e c t r i c a l s t i m u l a t i o n o f t h e q u a d r i c e p s muscle on h e a l t h y human s k e l e t a l muscle. The a c u t e e f f e c t s , such as d e p l e t i o n o f phosphagen and g l y c o g e n s t o r e s and f o r m a t i o n o f l a c t a t e as w e l l as d e c r e a s e s i n c e r t a i n enzyme a c t i v i t i e s , we're s i m i l a r t o t h o s e found f o r i n t e n s e m u s c u l a r e x e r c i s e . I n t e r m i t t e n t e l e c t r i c a l s t i m u l a t i o n f o r f o u r t o f i v e weeks d i d not cause any s i g n i f i c a n t changes i n enzyme a c t i v i t i e s , muscle f i b e r c h a r a c t e r i s t i c s , o r m i t o c h o n d r i a l p r o p e r t i e s . The f i n d i n g s i n d i c a t e d t h a t a f o u r week p e r i o d o f e l e c t r i c a l s t i m u l a t i o n r e s u l t e d i n improvements o f muscle s t r e n g t h comparable t o t h e r e s u l t s o f a c o r r e s p o n d i n g program o f v o l u n t a r y t r a i n i n g . The e l e c t r i c a l l y s t i m u l a t e d l e g had t h e g r e a t e s t i n c r e a s e i n s t r e n g t h a t s m a l l j o i n t ' a n g l e s , whereas the v o l u n t a r y t r a i n e d l e g seemed l e s s s p e c i f i c i n t h i s r e s p e c t . An o p p o s i t e p a t t e r n was o b s e r v e d when the t r a i n i n g r e s p onse was compared i n r e l a t i o n t o speed o f c o n t r a c t i o n . I n 30 t h i s c a s e , the v o l u n t a r i l y t r a i n e d l e g showed the l a r g e s t i n c r e m e n t s i n s t r e n g t h a t the speed c o r r e s p o n d i n g t o t h a t used i n t r a i n i n g , whereas the e l e c t r i c a l l y s t i m u l a t e d l e g appeared l e s s speed s p e c i f i c . So, the e f f e c t s o f e l e c t r i c a l s t i m u l a t i o n appeared more " p o s i t i o n - s p e c i f i c " and l e s s " s p e e d - s p e c i f i c " t han t h o s e o f v o l u n t a r y t r a i n i n g w i t h slow i s o k i n e t i c c o n t r a c -t i o n s . The f i n d i n g s o f G o l d b e r g e t a l . (1975) a r e s u p p o r t e d by E r i k s s o n ' s e t a l . (1981) r e s e a r c h . S p e c i f i c i t y o f t r a i n i n g i s i m p o r t a n t and s h o u l d be c o n s i d e r e d when d e v e l o p i n g a r e s i s -t a n c e t r a i n i n g program, whether i t be f o r improvement o f a t h l e t i c performance o r muscle f u n c t i o n a f t e r trauma. Ianuzzo (1976) e x p l a i n s v e l o c i t y t r a i n i n g t h r o u g h the use o f e l e c t r i c a l s t i m u l a t i o n . H i s work on c o n t r a c t i l e c h a r a c t e r -i s t i c s found t h a t i n mammalian s k e l e t a l muscles the time r e q u i r e d t o r e a c h peak t e n s i o n was d e t e r m i n e d t o be two t o f o u r t i m e s q u i c k e r i n f a s t - t w i t c h f i b e r s t h a n s l o w - t w i t c h f i b e r s . I a nuzzo (1976) s t a t e s t h a t t h i s peak time r e a c t i o n has been shown t o change w i t h e l e c t r i c a l s t i m u l a t i o n such t h a t slow muscles i n c r e a s e c o n t r a c t i o n speed when c h r o n i c a l l y s t i m u l a t e d w i t h i m p u l s e p a t t e r n s s i m i l a r t o f a s t muscle s t i m u l i . Summary I s o k i n e t i c t r a i n i n g i s a r e l a t i v e l y new t e c h n i q u e f o r d e v e l o p i n g m u s c u l a r power and s t r e n g t h . I s o k i n e t i c r e s i s t a n c e t r a i n i n g p r o c e d u r e s a r e s i g n i f i c a n t l y b e t t e r i n b r i n g i n g about 31 changes i n m u s c u l a r s t r e n g t h , body c o m p o s i t i o n , and power t a s k s w i t h l i t t l e m u s c ular s o r e n e s s t h a n are s t a n d a r d w e i g h t t r a i n i n g p r o c e d u r e s ( P i p e s and Wilmore, 1975). The l i m i t e d amount o f r e s e a r c h p u b l i s h e d i n t h i s a r e a has demonstrated s e v e r a l i m p o r t a n t f i n d i n g s w i t h normal s u b j e c t s . F i r s t l y , i s o k i n e t i c e x e r c i s e i s an e f f e c t i v e means w i t h w h i c h t o i n c r e a s e m u s c u l a r tone t h r o u g h o u t an a r c o f m o t i o n . I t has been shown t o i n c r e a s e t h e work a muscle can do more so t h a n does i s o m e t r i c o r i s o t o n i c e x e r c i s e . F i n a l l y , power and s t r e n g t h r e s p o n s e s a r e s p e c i f i c t o t h e j o i n t a n g l e and v e l o c i t y a t w h i c h t h e muscle group i s t r a i n e d ( M o f f r o i d e t a l . , 1969 and P i p e s and Wilmore, 1975). E l e c t r i c a l s t i m u l a t i o n t e c h n i q u e s have been e f f e c t i v e as a form o f t h e r a p y i n r e s t o r i n g muscle s i z e and s t r e n g t h o f the i n j u r e d o r d e n e r v a t e d l i m b d u r i n g r e h a b i l i t a t i o n . The use o f e l e c t r i c a l s t i m u l a t i o n f o r the purpose o f i m p r o v i n g normal muscular s t r e n g t h has n o t been an i m p o r t a n t c o n c e r n i n rehab-i l i t a t i o n . However, a t h l e t i c t r a i n i n g p r e s e n t s a s i t u a t i o n beyond s i m p l e c r e h a b i l i t a t i o n . L a t e l y , e l e c t r i c a l s t i m u l a t i o n has become a complement and even a s u b s t i t u t e f o r the o r d i n a r y s t r e n g t h t r a i n i n g program o f many a t h l e t e s i n v o l v e d i n s t r e n g t h and power e v e n t s ( K o t s , 1977). On the o t h e r hand, t h e r e has been no c o n c l u s i v e r e s e a r c h t o i n d i c a t e t h a t e l e c t r i c a l s t i m u -l a t i o n has p o s i t i v e e f f e c t s on muscle t i s s u e . T h e r e f o r e , by u s i n g e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c t r a i n i n g s i m u l t a n e o u s l y as a p h y s i c a l r e s t o r a t i o n program and/or 32 s t r e n g t h e n i n g regime, i t c o u l d be s u b s t i t u t e d f o r c o n v e n t i o n a l and time-consuming r e h a b i l i t a t i v e and t r a i n i n g t e c h n i q u e s . S i n c e e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r c i s e r educes the time t o a c c o m p l i s h muscle s t r e n g t h and power g a i n s , a r e d u c t i o n i n time o u t p u t would b e n e f i t the a t h l e t e i n p a r t i c u -l a r , w i t h h i s c o m p e t i t i v e c h a r a c t e r and t i g h t t r a i n i n g r o u t i n e , as w e l l as t h e r e c o v e r i n g p a t i e n t . 33 CHAPTER I I I METHODS AND PROCEDURES S u b j e c t s Twenty-seven f e m a l e , U n i v e r s i t y o f B r i t i s h Columbia s t u d e n t s , between the ages o f 19 t o 27 y e a r s , p a r t i c i p a t e d i n t h i s s t u d y . The s u b j e c t s were measured f o r power a t 30° p e r second speed i n b o t h q u a d r i c e p s muscle groups. The purpose o f t h i s i n i t i a l measurement:",was t o equate th e t h r e e groups f o r power and t o d e t e r m i n e t h e non-dominant muscle group, w h i c h was t h e p r e f e r r e d q u a d r i c e p s group f o r t h e s t u d y . The s u b j e c t s were ranked . o n e ^ t o n t w e n t y ^ s e v e n j f x o m H i g h e s t rto : o l o w e s t q u a d r i c e p s 1 power. S u b j e c t s , i n o r d e r o f power r a n k i n g , were p l a c e d i n t o the t h r e e t r a i n i n g groups o f n i n e s u b j e c t s p e r group. T h i s t e c h n i q u e f o r a c h i e v i n g c o n s t a n c y between the t h r e e groups i s termed "matching by e q u a t i n g subjects 1- 1'. The s u b j e c t s were n o t on an a t h l e t i c team o r p a r t i c i p a t i n g i n s t r e n u o u s c p h y s i c a l a c t i v i t y o r muscle s t r e n g t h e n i n g regimes. S u b j e c t s were a l s o s c r e e n e d f o r p a t e l l a r f e m o r a l j o i n t d i s o r d e r s , i n t e r n a l derangement o f the knee, h i s t o r y o f knee s u r g e r y and any g e n e r a l d i s e a s e o r p a t h o l o g y c o n t r a i n d i c a t i n g s t r e n g t h t r a i n i n g o f the q u a d r i c e p s . Time and D u r a t i o n o f . t h e Study There.were e i g h t e e n t r a i n i n g s e s s i o n s f o r each group, h e l d t h r e e t i m e s p e r week (Monday, Wednesday, F r i d a y ) f o r 34 s i x weeks. The p r e t e s t was c a r r i e d o u t , b e f o r e any t r a i n i n g , on the i n i t i a l v i s i t d u r i n g the f i r s t week o f the s t u d y . The m i d t e s t was s u b s t i t u t e d f o r the t r a i n i n g s e s s i o n h e l d a t the end o f the f o u r t h week. The e i g h t h week, a f t e r s i x weeks o f t r a i n i n g , c o n s i s t e d o f the p o s t t e s t . S u b j e c t s were encouraged t o p e r f o r m m a x i m a l l y d u r i n g the t h r e e t e s t i n g s e s s i o n s . T e s t i n g P r o t o c o l The Cybex I I I s o k i n e t i c dynamometer was used f o r t e s t i n g q u a d r i c e p s power and s t r e n g t h . The f o r c e was r e c o r d e d i n f o o t pounds and c a l c u l a t e d t o Newton-meters p e r second (N-m • s "*") . The s u b j e c t s were t e s t e d i n t h e e x e r c i s e p o s i t i o n w i t h the knee moving f r e e l y a g a i n s t the Cybex arm, t h r o u g h a 90° t o 0° knee a n g l e (0° = s t r a i g h t l e g ) . The t e s t used f o r measuring m u s c u l a r s t r e n g t h , power and j o i n t i n t e g r i t y was t h e p r e f e r r e d p r o t o c o l as o u t l i n e d i n t h e Cybex I I T e s t i n g P r o t o c o l Manual (Cybex D i v i s i o n ) . T h i s method uses a t e s t i n g speed o f 30° pe r second and a paper speed o f 5 m i l l i m e t e r s p e r second. Two a d d i t i o n a l f a s t speeds, 100° and 180° p e r second, and an i s o m e t r i c measurement, were u t i l i z e d t o determinerpower. The t e s t c a l l e d f o r t h r e e sub-maximal t r i a l s a t 30° per second t o f a m i l i a r i z e the s u b j e c t w i t h r e q u i r e d movement and then t h r e e t e s t c u r v e s were r e c o r d e d , w i t h t h e h i g h e s t t o r q u e r e a d i n g b e i n g a c c e p t e d as the measure o f maximum power. D u r i n g the p r e t e s t , each s u b j e c t had b o t h l e g s measured f o r maximal q u a d r i c e p s power t o determine w h i c h was t h e weaker 35 or non-dominant limb. Once the non-dominant leg was known then the remaining pretest variables, time to peak tension, thigh circumference, weight, height and age, were measured. The c o n t r a l a t e r a l or non-stimulated leg w i l l be assessed again on completion of the study to determine i f cross-education of the central nervous system or physical a c t i v i t y outside of the study influenced the power gains of the'rtraining limb. The thigh g i r t h was calculated by use of a Wyteface s t e e l tape at one centimeter d i s t a l to gluteal l i n e and twenty centimeters superior to the base of the p a t e l l a . The subject stood erect with feet s l i g h t l y apart, while the two circumference measurements were taken on the horizontal plane. Each s i t e was measured twice and the two average values were recorded for the non-dominant leg. After the pretest measurements were complete and the subjects were assigned to the three groups, the two groups receiving e l e c t r i c a l stimulation (ES + IE and ES) were given one introductory session with the stimulator. The introduction was used to explain b r i e f l y the nature of the t r a i n i n g and sesnsations to be experienced. Training Procedures The three groups were t r a i n i n g on a Cybex II Isokinetic Dynamometer i n the exercise p o s i t i o n : s i t t i n g , thighs f u l l y supported-.:-onca quadricepsibencfr, -i back supported-,with hips at 90°, use of thigh b e l t , and lower leg s t a b i l i z e d by the Cybex 36 l e v e r arm. The non-dominant l e g r e c e i v e d t h e t r a i n i n g i n each group. The e l e c t r i c a l s t i m u l a t i o n group (ES) r e c e i v e d f a r a d i c s t i m u l a t i o n from t h e M u l t i t o n e M u l t i f a r a d i c U n i t (Model F283). T h i s u n i t was chosen because o f i t s a v a i l a b i l i t y and c a p a b i l i t y o f p r o d u c i n g the d e s i r e d p r o l o n g e d t e t a n i c c o n t r a c t i o n n e c e s s a r y f o r t h i s t e c h n i q u e . The e l e c t r i c a l s t i m u l a t o r has a maximum c u r r e n t o f 198 m i l l i a m p e r e s . R e c t a n g u l a r wave s t i m u l i were used t o e l i c i t a t e t a n i c r e s p o n s e . The r e c t a n g u l a r waveform p r o v i d e d maximum a c t i v a t i o n o f t h e motor u n i t s and brou g h t about g r e a t e r t e n s i o n t h a n v o l u n t a r y e f f o r t a l o n e (Johnson e t a l . , 1977). S u b j e c t s were e x p e c t e d t o t o l e r a t e 10-20 m i l l i a m p e r e s o f f a r a d i c c u r r e n t . The s u b j e c t s r e c e i v e d a t e n second c o n t r a c t i o n a t a f r e q u e n c y o f s i x t y c y c l e s p e r second w i t h a f i f t y second r e s t p e r i o d and t e n r e p e t i t i o n s p e r t r e a t -ment. The i n t e n s i t y was a d j u s t e d a c c o r d i n g t o each s u b j e c t ' s v a r i a b l e t o l e r a n c e under t h e t e s t e r ' s s u p e r v i s i o n . T h i s was r e p e a t e d : t h r e e t i m e s p e r week f o r s i x weeks. A monopolar method u s i n g a medium s i z e a c t i v e e l e c t r o d e (9 x 14 cm) was r p l a c e d o ver t h e f e m o r a l nerve t r u n k p r o x i m a l l y and a l a r g e s i z e d i s p e r s i v e e l e c t r o d e ('S' shaped p a t t e r n ) was p l a c e d o v e r the motor p o i n t s o f the v a s t u s m e d i a l i s , r e c t u s f e m o r i s and v a s t u s l a t e r a l i s . The shape o f the l a t t e r e l e c t r o d e was t o produce a c o n t r a c t i o n o f t h e whole q u a d r i c e p s group and t o ensure i n -c l u s i o n o f the deeper v a s t u s i n t e r m e d i u s . D u r i n g t h e a c t u a l s t i m u l a t i o n p e r i o d the s u b j e c t was urged t o t a k e t h e maximal c u r r e n t t o l e r a b l e . 37 The subjects were treated i n the exercise p o s i t i o n , however the knee was supported at 45° fl e x i o n (Halbach and Straus, 1980), and preventedirfrom further extension by the Cybex II lever arm. The use of the Cybex II at zero v e l o c i t y , as used i n isometric t e s t i n g , provided an accomodating resistance to any force exerted by the quadriceps, without j o i n t movement. This provided the subject with v i s i b l e feedback of attained torque for motivation during each t r a i n i n g session. The i s o k i n e t i c exercise group (IE), using the same exercise p o s i t i o n , were instructed to maximally extend the knee against the Cybex arm from 90° to 0°. The workouts consisted of six maximal contractions per set at a slow speed/high resistance setting of 30° per second; t h i s procedure was repeated three times. The e l e c t r i c a l stimulation plus i s o k i n e t i c exercise group (ES + IE) performed the same exercise routine as the IE group, but i n addition, the subjects received e l e c t r i c a l stimulation concurrently with each v o l i t i o n a l maximum i s o k i n e t i c contraction. The e l e c t r i c a l stimulation protocol was the same as that for the ES group. The faradic current was applied for three seconds which was the approximate duration of each v o l i t i o n a l maximum is o k i n e t i c contraction. The tester turned the faradic current to the subject's maximum tolerance ^simultaneously as she extended her knee, using maximum e f f o r t , from 90° to 0° on the Cybex II bench. At approximately 2 0°, p r i o r to complete extension, the tester turned the faradic current down to zero 38 i n t e n s i t y . This procedure was repeated six times for three sets. Experimental Design and Data Analysis This study adopted an experimental method using equated groups with a pretest, midtest and posttest design. The de-pendent variables were leg power and time to peak tension measured at 0°, 30°, 100° and 180° per second, and thigh circumference measured at p a t e l l a r and gluteal s i t e s . The experimental design used i n t h i s study was a repeated measures design on the second and t h i r d factors, with the three groups, ES + IE, IE and ES, being the three levels of the independent variable. The data was analyzed using a multivariate analysis of variance. This was accomplished using the computer program BMD P4V: General Univariate and Multivariate Anova (Davidson and Toporek, 1981) at the computing centre of the University of B r i t i s h Columbia. The P4V i s a general purpose analysis of variance and covariance program. It handles both univariate and multivariate analyses. Both univariate and multivariate tests are given for repeated measurement of several d i f f e r e n t dependent variables. Each variable was tested at an alpha 1 l e v e l of 0.05. A s i g n i f i c a n t o v e r a l l multivariate F (p<0.05) was followed by pairwise comparison of groups (nonorthogonal) to get a between groups multivariate F, i n conjunction with the univariate 39 F's f o r each dependent v a r i a b l e . Each s i g n i f i c a n t v a r i a b l e was t e s t e d a t an a l p h a l e v e l o f p < 0 . 0 1 o r p<0.05, w i t h Tukey's m u l t i p l e comparison t e s t o f means, as t h i s was the c r i t e r i o n measure f o r acceptance o r r e j e c t i o n o f the n u l l h y p o t h e s i s . 40 CHAPTER IV RESULTS AND DISCUSSION Results The twenty-seven subjects were tested according to the testing protocols and t h e i r physical c h a r a c t e r i s t i c s are summarized i n Table I. The power measurements are represented in Table I I , while the time to peak tension and thigh g i r t h parameters are represented i n Appendix A (Tables I I I , IV, V, VI). The r e s u l t s of the s t a t i s t i c a l analysis for the power measurement are displayed i n Tables I l i a and I l l b . Appendix A (Tables.Ia, lb and II) i l l u s t r a t e s the s t a t i s t i c a l analysis for the remaining power variables, time to peak tension and thigh g i r t h parameters. A multivariate s t a t i s t i c a l analysis revealed s i g n i f i c a n t differences on several power, time to peak tension and thigh g i r t h measurements. As well, a univariate s t a t i s t i c a l analysis of the three parameters was performed as part of the multivariate s t a t i s t i c a l program. The multivariate s t a t i s t i c a l analysis was followed up by pairwise comparison to obtain the univariate analyses and p r o b a b i l i t i e s for each groupwise contrast. The power, time to peak tension and thigh g i r t h analyses that did not contribute to the relevancy of the study are represented i n Appendix A (Tables I to VI). The power, time to peak tension and thigh 41 g i r t h a n a l y s e s t h a t e x e m p l i f i e d s i g n i f i c a n c e , and s u b s e q u e n t l y , were impor tan t t o the h y p o t h e s e s , were f o l l o w e d through w i t h a p o s t hoc c o m p a r i s o n . T u k e y ' s m u l t i p l e compar ison o f means t e s t was used t o determine the l o c a t i o n o f s i g n i f i c a n c e . The f o l l o w i n g u n i v a r i a t e v a l u e s f o r power were found not to be s t a t i s t i c a l l y s i g n i f i c a n t as shown i n T a b l e I l i a and Appendix A (Table I I ) : t h e r e was n o n s i g n i f i c a n t power d i f f e r e n c e s between each o f the t h r e e g r o u p s ; no s i g n i f i c a n t p o w e r : d i f f e r e n c e s f o r i n t e r a c t i o n s ( t e s t s x g r o u p s , t e s t s x s p e e d s , speeds x groups and t e s t s x speeds x g r o u p s ) ; a n d , no s i g n i f i c a n t power d i f f e r e n c e s f o r p a i r w i s e compar isons c o u l d be i d e n t i f i e d . Appendix A (Table IV) r e v e a l e d t h a t s e v e r a l o f the u n i v a r i a t e v a l u e s f o r t ime to peak t e n s i o n were not s i g n i f i c a n t . There was no s i g n i f i c a n t d i f f e r e n c e s between the g r o u p s ; f n o s i g n i f i c a n t t ime t o peak d i f f e r e n c e s between the t e s t s were p r e v a l e n t ; and , no s i g n i f i c a n t t ime t o peak d i f f e r e n c e s f o r i n t e r a c t i o n s ( t e s t s x g r o u p s , speeds x g r o u p s , t e s t s x speeds and t e s t s x speeds x groups) e x i s t e d . The u n i v a r i a t e v a l u e f o r the t h i g h g i r t h a n a l y s i s .'(Appendix A - T a b l e VI) d i s p l a y e d no s i g n i f i c a n t p a t e l l a r g i r t h d i f f e r e n c e s between the g r o u p s , t e s t s or i n t e r a c t i o n ( t e s t s x x g r o u p s ) . T u k e y ' s p o s t hoc compar ison o f means r e v e a l e d s i g n i f i c a n t d i f f e r e n c e s ( p < C 0 . 0 1 and 0.05) on s e v e r a l power, t ime to peak t e n s i o n and t h i g h g i r t h p a r a m e t e r s . The p o s t hoc t rea tment of theopower d a t a e s t a b l i s h e d t h a t the pre t o mid and pre t o p o s t t e s t s and 30° and 0° pe r second speeds were s t a t i s t i c a l l y 42 s i g n i f i c a n t , as e v i d e n t i n T a b l e s I l i a and I l l b . W h i l e the p o s t hoc comparison o f t h e t i m e t o peak t e n s i o n parameter i n Appendix A (Table IV) i d e n t i f i e d the f o u r speeds (30°, 100°, 180° and 0° per second) as b e i n g s i g n i f i c a n t . Tukey's comparison of means a l s o r e v e a l e d , from the two t h i g h g i r t h measurements ( p a t e l l a r and g l u t e a l ) , t h a t o n l y the g l u t e a l t h i g h g i r t h i n Appendix A (Table VI) was s t a t i s t i c a l l y s i g n i f i c a n t between the ES + IE and ES groups. T a b l e V summarizes the r e s u l t s o f the hypotheses t e s t i n g . TABLE I PHYSICAL CHARACTERISTICS OF SUBJECTS PARAMETER * * ES + IE GROUP IE GROUP' ES GROUP AGE (years) X 21.22 S.D. + 2.11 22.67 + 3.12 20.89 + 1.54 WEIGHT (kgs) 55.44 + 5.17 57.98 + 6.64 58.58 + 6.77 HEIGHT (cm) 163.38 + 6 .12 165.10 + 7.26 167.78 + 7.08 PRETEST EQUATING (N-m per second) 70.08 + 12.52 70.68 + 10.63 69.90 + 13.59 NUMBER IN EACH GROUP *ES + IE - E l e c t r i c a l Stimulation and Isokinetic Exercise Group IE - Isokinetic Exercise Group ES - E l e c t r i c a l Stimulation Group TABLE II COMPARISON OF POWER BETWEEN  ELECTRICAL STIMULATION AND ISOKINETIC EXERCISE (ES + IE), ISOKINETIC EXERCISE (IE) AND ELECTRICAL STIMULATION (ES) GROUPS PARAMETER ES + IE GROUP IE GROUP ES GROUP POWER PRE MID POST PRE MID POST PRE :MID POST 30° x s 1 X 70.08* .;78.84 S.D. +12.52 +15.15 100° x s 1 180° x s" 1 0 x s 201.60 +37.83 234.95 +68.09 119.48 +30.00 200.27 + 3 3..75: 227.04 +42.00 132.21 +29.18 82.88 +16;29 204.80 +39.25 250.08 +46.85 139.68 +28.81 -70.6 8 +10.63 170.67 +38.29 214.56 +52.15 106.82 +22.32 76. 80 + 9.14 191.16 +35.51 242.51 +53.47 123.55 +31.56 82.88 + 8.30 216.80 +59.65 280.32 +98.07 134.39 +33.69 69.90 +13.59 174.01 +37.42 220.87 +39.28 110.29 +33.69 75.16 + 6.37 184.49 +24.70 253.93 +62.76 139.94 +47.59 77.56 +10.40 189.29 +22.89 224.16 +45.43 142.38 +42.90 * Newton-meters per second TABLE I l i a in ^ MULTIVARIATE ANALYSIS OF VARIANCE FOR POWER PARAMETER DEPENDENT VARIABLE BETWEEN GROUPS PROBABILITY <P<) BETWEEN TESTS PROB. INTERACTION T X G PROBABILITY BETWEEN SPEEDS PROB. INTERACTION S X G PROBABILITY INTERACTION T X S PROBABILITY INTERACTION T X S X G PROBABILITY POWER 0.8678 0.0004 0.1350 0.0000 0.5450 0. 4952 0.04 90 UNIVARIATE F VALUE 0.14 9.18 1.85 311.28 0.84 0.90 1.83 POST HOC ANALYSIS: (TUKEY) i ;01^ERE-R©ST .05 PRE-MID .01 NO S I G . 46 TABLE I I l b MULTIVARIATE ANALYSIS OF VARIANCE FOR POWER PARAMETER DEPENDENT VARIABLE POWER SPEED 3 0 ° x s 1 MULTIVARIATE F TUKEY'S POST HOC ANALYSIS: BETWEEN GROUPS PROBABILITY (P<) 0.8132 0.21 BETWEEN TESTS PROBABILITY 0.0000 24.53 .01 PRE-POST .05 PRE-MID INTERACTION T X G PROBABILITY 0.6219 0.66 SPEED 0 ° x s 1 MULTIVARIATE F TUKEY'S POST HOC ANALYSIS: 0.7813 0.25 0.0000 19.25 01 PRE-POST 05 PRE-MID 0.5689 0.74 SPEED 1 0 0 ° x s 1 MULTIVARIATE F TUKEY'S POST HOC ANALYSIS: 0.4209 0.90 0.0169 4 . 45 NO SIG. 0.1875 1.61 SPEED 1 8 0 ° x s 1 MULTIVARIATE F 0. 8352 0.18 0.0826 2.63 0.0987 2.08 TABLE IV COMPARISON OF MID AND POST POWER GAINS MID GAINS (Mid Test - Pre Test) POST GAINS (Post Test - Pre Test) GROUPS 30 100 180 30 100 180 (degrees 0 per sec.) ES + IE X 8.76 -1.33 -7.91 12.93 * S.D.+ 6.73 +24.97 +40.75 +9.97 12.80 3.20 15.13 20.20 + 6.25 +25.40 +48.63 +16.06 IE 6.12 20.49 27.95 16.72 + 8.8 0 +26.. 82 +33.35. +26.61 12.20 + 7.37 46.13 +65.38 65.76 +105.35 27.57 +27.10 ES 5.26 10.48 33.06 29.65 +11.52 +36.07 +67.62 ' +29.94 7.66 +12.11 15.28 +38.16 3.29 +39.86 32.09 +31.81 * Newton-meters p e r second 48 FIGURE I POWER (N-m-s ) PRE, MID AND POST POWER MEASUREMENTS AT 30° x s " i 88-86-84-8 2 -80-78-76-74-7 2 -70-1 ES + I E I E O ES A l I l PRE I l l MID TESTS I l l POST FIGURE II PRE, MID AND POST POWER MEASUREMENTS AT 100° x s 1 POWER (N-m-s ) 225-220-215-210-205-200-195-190-185-180-175-ES + IE IE O ES A l I l PRE l l l MID l I l POST TESTS T E S T S 51'' FIGURE IV PRE, MID AND POST POWER MEASUREMENTS AT 0 ° x s 1 POWER , (N-m-s ) 150-145-140-135-130-125-120-115-110-105-100-ES + IE IE O ES A l l l PRE l I I MTD TESTS I I I POST 52 T A B L E V SUMMARY OF H Y P O T H E S E S T E S T I N G D E P E N D E N T V A R I A B L E S P R O P O S E D : G R O U P R E L A T I O N S H I P S R E S U L T S 1. POWER (N-m • s ) a t 30, 100, 180 and 0 degrees p e r second, r e s p e c t i v e l y E S + I E > I E > E S N O N S U P P O R T E D T I M E TO P E A K T E N S I O N (seconds) a t 30, 100, 18 0 and 0 degrees p e r second, r e s p e c t i v e l y E S + I E < I E < E S N O N S U P P O R T E D 3. T H I G H G I R T H ( c e n t i -meters) a t p a t e l l a r and g l u t e a l s i t e s E S + I E > I E > E S N O N S U P P O R T E D 53 Discussion The main objective of t h i s study was to compare the e f f e c t of s p e c i f i c t r a i n i n g regimens (ES + IE, IE and ES) on the power of the quadriceps muscle group at v e l o c i t i e s of 30°, 100°, 180° and 0° per second. It was also the intention of t h i s research to compare the e f f e c t of t r a i n i n g on the v e l o c i t y of muscle contraction and muscle hypertrophy. The comparision was designed to determine i f there exists a difference i n muscle power and time to peak tension variables at the four v e l o c i t i e s i n these three groups. There was a s i g n i f i c a n t difference between the pretest and midtest, as well as between the pretest and posttest with respect to the power measurement when a l l three groups were combined. As represented i n Tables ITIa, I l l b .(between tests) and IV (mid and post gains), the three groups improved muscular power during the six week t r a i n i n g period, although there was no p a r t i c u l a r group which had the greatest power gains. The significance between the tests indicated that i t i s possible to improve muscular power and strength, but which i s the best t r a i n i n g method remains questionable. It was postulated that the ES + IE and IE groups were responsible for the improvement i n muscular power, more so than the ES group. The increases i n muscular power and strength may have resulted: ; /f rom^the-:is<bkineticrresistive vtrdining:;.alone . This finding i s i n p a r t i a l agreement with the research of Halbach. and Straus (1980) and Eriksson et a l . (1981) with respect to improvements i n muscle power and strength i n healthy q u a d r i c e p s muscle. H a l b a c h and S t r a u s (1980) and E r i k s s o n e t a l . (1981) demonstrated t h a t v o l u n t a r y i s o k i n e t i c e x e r c i s e and e l e c t r i c a l s t i m u l a t i o n i n c r e a s e muscle power and s t r e n g t h , however the i s o k i n e t i c s p r o v e d t o be s u p e r i o r f o r i n c r e a s i n g power as compared t o e l e c t r i c a l s t i m u l a t i o n . The i s o k i n e t i c -r e s i s t a n c e programs are s i g n i f i c a n t l y b e t t e r i n b r i n g i n g about changes i n m u s c u l a r s t r e n g t h and s e l e c t e d power t a s k s t h a n i s o m e t r i c o r i s o t o n i c programs, as shown by P i p e s and Wilmore (1975); M o f f r o i d (1969) and T h i s t l e e t a l . (1967). To d a t e , i t has n o t been shown t h a t a combined e f f e c t o f s t i m u l a t i o n and e x e r c i s e can i n c r e a s e m u scular power and s t r e n g t h . (?:«?.•. . C o n s e q u e n t l y , t h e r e may be no summation e f f e c t o f power a s s o c i a t e d w i t h e l e c t r i c a l s t i m u l a t i o n , when g i v e n . c o n c u r r e n t l y w i t h i s o k i n e t i c e x e r c i s e . M u scle power d i d not demonstrate a s i g n i f i c a n t d i f f e r e n c e between each of the t h r e e groups a f t e r r e c e i v i n g e i g h t e e n t r a i n i n g s e s s i o n s . K o t s (1977) s t a t e s t h a t t h e o p t i m a l e f f e c t on power and s t r e n g t h o c c u r s between twenty and t w e n t y - f i v e sessions w i t h ! : p s t i m u l a t i o n ? ^ r W h e r e a s f Haibach»and;>Straus-:;;C19.8 0) and E r i k s s o n e t a l . (1981) o b t a i n e d r e s u l t s a f t e r f i f t e e n and twenty t r a i n i n g s e s s i o n s , r e s p e c t i v e l y . P e r h a p s , i f the t r e a t m e n t groups had r e c e i v e d s e v e r a l more s e s s i o n s , a sig.-^i r : ' . c r n i f l e a n t m u s c u l a r power e f f e c t may have o c c u r e d . G e n e r a l l y , t h e g r e a t e r the f r e q u e n c y o f t h e t r a i n i n g program, the g r e a t e r w i l l be the improvements. There was a s i g n i f i c a n t d i f f e r e n c e i n power between the v e l o c i t i e s o f 30°, 100°, 180° and 0° per s e c o n d . As the v e l o c i t y o f the c o n t r a c t i o n i n c r e a s e s , the f o r c e t h a t can b e . g e n e r a t e d d e c r e a s e s , d e s p i t e maximal e f f o r t . A s s o c i a t e d w i t h i n c r e a s e d v e l o c i t i e s i s a p r o p o r t i o n a t e i n c r e a s e i n Newton-meters per s e c o n d . Newton-meters d e c r e a s e w i t h an i n c r e a s e i n i s o k i n e t i c v e l o c i t y , however when t ime (seconds) i s i n t r o d u c e d t h e r e i s a m u l t i p l i c a t i o n f a c t o r w i t h Newton-meters a t the f a s t speeds (100° and 180° per s e c o n d ) . T h i s was c o n f i r m e d as the slow v e l o c i t y i n c r e a s e d t o a f a s t v e l o c i t y on the i s o k i n e t i c dynamometer, the Newton-meters i n c r e a s e d . The p o s t hoc a n a l y s i s r e v e a l e d t h a t power was s i g n i f i c a n t l y d i f f e r e n t between tite-> f o u r speeds (Table I l i a ) , however i t was not an a c c e p t a b l e s i g n i f i c a n t e f f e c t because o f Newton-m e t e r s ' n u m e r i c a l v a r i a t i o n w i t h s p e e d s . The s u b j e c t s i n the ES + IE and IE groups t r a i n e d a t 30° pe r s e c o n d , w h i l e the ' s u b j e c t s i n the ES group t r a i n e d i s o m e t r i c a l l y . A c c o r d i n g t o P i p e s arid Wilmore (1975) and M o f f r o i d and Whipple (1970), the s p e c i f i c i t y o f t r a i n i n g -t h e o r y was r e s p o n s i b l e f o r the s i g n i f i c a n t power g a i n s a t speeds o f 30° a n d ,0° per s e c o n d . These r e s e a r c h e r s showed t h a t t r a i n i n g a t a s low speed produces i n c r e a s e s i n s t r e n g t h o n l y a t s low speeds o f movement. Whereas, t r a i n i n g a t f a s t speeds o f movement p roduces i n c r e a s e s i n s t r e n g t h a t a l l speeds of c o n t r a c t i o n a t and below the t r a i n i n g s p e e d . T h e r e f o r e , i t i s impor tan t t o r e a l i z e t h a t i t i s p o s s i b l e t o i n c r e a s e low v e l o c i t y s t r e n g t h w i t h s p e c i f i c t r a i n i n g and a l s o , low v e l o c i t y t r a i n i n g has a b e t t e r t r a n s f e r e f f e c t t o low v e l o c i t i e s 56 rather than to high v e l o c i t i e s (Moffroid and Whipple, 1970). Sp e c i f i c slow v e l o c i t y t r a i n i n g regimes were c l e a r l y a p o s i t i v e factor i n developing muscular power i n t h i s study. The three groups produced gains i n power at angular v e l o c i t i e s equal to or slower than the t r a i n i n g v e l o c i t i e s (Table I l l b and Figures I to IV). At the high or fast v e l o c i t i e s no s i g n i f i c a n t changes were observed. It i s not possible to r e c r u i t s i m i l a r motor units that have been trained slowly i n a s i t u a t i o n r e q u i r i h g r f a s t muscle movement (Moffroid and Whipple, 1970). These findings imply that the power t r a i n i n g benefits:- may be limited to the speeds used during t r a i n i n g . This i s of p r a c t i c a l consideration to the athlete as i t suggests that the athlete should t r a i n at speeds approximating or exceeding those used during his or her actual sport. These observations are supported by the findings of Pipes and Wilmore (1975) . Tables IT.Ia and I l l b indicate that power between tests for the combined groups, s p e c i f i c a l l y between the pre and mid tests and between the pre and post tests at the i s o k i n e t i c speed of 30° per second and i s o m e t r i c a l l y , was s i g n i f i c a n t l y d i f f e r e n t . These re s u l t s indicate that by t r a i n i n g at a slow speed (.30° per second) , the same muscle f i b e r s are recruited for power and strength at even slower speeds (0° per second). There i s evidence that slow twitch motor units (MacDougall et a l . , 1980a and Thorstensson et a l . , 1976) are recruited along with the fast twitch motor units (Gollnick et a l . , 1974 57 and Warmolts and E n g e l , 1972), d e s p i t e t h e d i f f e r e n c e s i n con-t r a c t i l e p r o p e r t i e s and energy systems. The slow t w i t c h , t y p e l l f i b e r s have a l o n g time i n t e r v a l between a c t i v a t i o n and r e a c h i n g peak t e n s i o n , i n a d d i t i o n t o h a v i n g a h i g h c a p a c i t y f o r a e r o b i c o r o x i d a t i v e m e t a b o l i s m and a low c a p a c i t y f o r a n a e r o b i c m e t a b o l i s m . C o n v e r s e l y , the f a s t t w i t c h , t y pe l i b f i b e r s a t t a i n peak t e n s i o n r a p i d l y by h a v i n g a low c a p a c i t y f o r a e r o b i c m e t a b o l i s m and a h i g h c a p a c i t y f o r a n a e r o b i c o r g l y c o l y t i c m e t a b o l i s m . MacDougall e t a l . (1980a) have demonstrated t h a t s low v e l o c i t y t r a i n i n g , whether i t i s i s o t o n i c o r i s o k i n e t i c , causes h y p e r t r o p h y o f b o t h f i b e r t y p e s . T h i s does n o t i m p l y t h a t the f a s t t w i t c h motor u n i t s were r e c r u i t e d more but may i n d i c a t e t h a t f a s t t w i t c h f i b e r s aretmore a d a p t a b l e i n r e l a t i o n t o h y p e r t r o p h y . Hence, slow t r a i n i n g a t 30° p e r second and i s o m e t r i c a l l y a c t i v a t e d b o t h slow and f a s t t w i t c h motor u n i t s . C o n s e q u e n t l y , v e l o c i t y - s p e c i f i c a d a p t a t i o n w i t h i n t h e nervous system i s e s t a b l i s h e d . Based on t h e e v i d e n c e p r e s e n t e d by Desmedt and Godaux (1979), t h e b r a i n o r g a n i z e s and i n i t i a t e s f a s t , b a l l i s t i c movements d i f f e r e n t l y than slow movements. The mechanism r e s p o n s i b l e i s p r i m a r i l y n e u r a l o r g a n i z a t i o n o f movements by t h e c e n t r a l nervous system r a t h e r t h a n s e l e c t i v e r e c r u i t m e n t o f motor u n i t t y p e s . The nervous c o n t r o l p l a y s a d e c i s i v e r o l e f o r the d e v e l o p -ment o f power, as f a r as the s p e c i f i c i t y o f a t r a i n i n g e f f e c t i s c o n c e r ned. I t appears as i f power and s t r e n g t h , d e v e l o p e d over a p e r i o d o f t i m e , are m a i n t a i n e d by the same motor u n i t s ( E c c l e s , 1973). An i n c r e a s e i n t h e d e v e l o p e d f o r c e i n t h e 58 same a c t i v i t y means t h a t the same motor u n i t s become engaged w i t h g r e a t e r f r e q u e n c y and t h a t new motor u n i t s are r e c r u i t e d i n a d d i t i o n . Only a t maximal e f f o r t are the motor u n i t s r e p r e p r e s e n t i n g the " l a s t r e s e r v e " thrown i n t o p l a y . E c c l e s (1973) s t a t e d t h a t t h e s e r e s e r v e u n i t s may become more e a s i l y engaged as the r e s u l t o f t r a i n i n g . T h u s , one e x p l a n a t i o n f o r the s p e c i f i c i t y ; ; o f a d a p t a t i o n t o a s p e c i f i c t r a i n i n g program i s t h a t a g i v e n type o f e x e r c i s e r e q u i r e s a s p e c i f i c c o m b i n a t i o n of motor u n i t s t h a t are b e s t adapted f o r t h a t demand. The e x i s t e n c e o f motor u n i t t y p e s i s an example o f b u i l t - i n a d a p t -a t i o n or s p e c i f i c i t y . When a c a l l f o r a movement i s r e p o r t e d to the b r a i n , i t has a l l the n e c e s s a r y requ i rements from the p e r i p h e r a l r e c e p t o r s f o r e x e c u t i o n and c o n t r o l o f the movement. The a t h l e t e t r a i n s the musc les and l e a r n s t o execute s p e c i f i c movements th rough the i n t e r v e n t i o n o f the c e n t r a l nervous sys tem. T h e r e f o r e , the p h y s i o l o g i c a l b a s i s f o r the s p e c i f i c i t y e f f e c t i s e x p l a i n e d by the f a c t t h a t n e u r a l a d a p t a t i o n s p l a y an impor tan t r o l e i n the response to power t r a i n i n g . I t i s i n t e r e s t i n g t o note t h a t w i t h the ES + IE and ES s u b j e c t s , as i n d i v i d u a l t r a i n i n g s e s s i o n s p r o g r e s s e d , the maximum amount o f f a r a d i c c u r r e n t t h a t c o u l d be t o l e r a t e d i n c r e a s e d s i g n i f i c a n t l y (Appendix B - F i g u r e I V ) . F o l l o w i n g t r a i n i n g w i t h maximum t o l e r a n c e , however, t h e r e was g e n e r a l l y a d e c r e a s e i n the amount o f f a r a d i c c u r r e n t a s u b j e c t c o u l d t o l e r a t e , due t o muscle s o r e n e s s . Dur ing s e v e r a l s e s s i o n s i t was r e p o r t e d by s u b j e c t s t h a t p h y s i c a l f a t i g u e was r e s p o n s i b l e f o r -a l i m i t e d t o l e r a n c e . The average dosage o f e l e c t r i c a l 59 s t i m u l a t i o n f o r the ES group d u r i n g the l a t t e r p a r t o f the t r a i n i n g p e r i o d began t o l e v e l o f f as shown i n Appendix B ( F i g u r e I V ) . T h i s was an i n d i c a t i o n t h a t the s u b j e c t s i n the ES group had r eached the maximum amperage t h a t c o u l d be s u s -t a i n e d w i t h o u t u n b e a r a b l e p a i n . The ES + IE group d i d not p l a t e a u a t the same l e v e l as the ES group. I n s t e a d the ES + IE group c o n t i n u e d t o t o l e r a t e a g r e a t e r amperage t h r o u g h o u t the s t u d y . P o s s i b l y , t h e r e a s o n f o r the ES + IE group b e i n g a b l e t o t o l e r a t e a g r e a t e r dosage o f s t i m u l a t i o n , may be a t t r i b u t e d t o t h e i r p a r t i c i p a t i o n i n v o l u n t a r y dynamic c o n t r a c t i o n s w h i l e s i m u l t a n e o u s l y r e c e i v i n g e l e c t r i c a l s t i m u l a t i o n . I t was r e -p o r t e d by T h i s t l e e t a l . (1967) and P i p e s and Wilmore (1975) t h a t i s o k i n e t i c t r a i n i n g d i d not i n d u c e muscle s o r e n e s s . The c o n c e n t r i c c o n t r a c t i o n s o f i s o k i n e t i c movements d u r i n g the r e c o v e r y phase o f e x e r c i s e were an advantage i n l i m i t i n g ^ and p r e v e n t i n g muscle s o r e n e s s w h i l e e l e c t r i c a l s t i m u l a t i o n was a p p l i e d c o n c u r r e n t l y . Whereas the ES group r e p o r t e d f e e l i n g d e l a y e d muscle s o r e n e s s one t o two days a f t e r r e c e i v i n g the s t i m u l a t i o n . Abraham (197 7) c o n c l u d e d t h a t a l t e r a t i o n s i n muscle c o n n e c t i v e t i s s u e were r e s p o n s i b l e f o r d e l a y e d , p o s t -e x e r c i s e muscle s o r e n e s s . When e x e r c i s e became se v e r e enough t o damage t h e c o n n e c t i v e t i s s u e , i t caused an i n c r e a s e d de-g r a d a t i o n o f ' c o l l a g e n . Thus, i n c r e a s e d breakdown o f c o l l a g e n would be e v i d e n t i n the h i g h u r i n a r y h y d r o x y p r o l i n e l e v e l s . T h i s p r o c e s s caused an imbalance i n c o l l a g e n m e t a b o l i s m r e q u i r i n g a compensatory i n c r e a s e i n c o l l a g e n s y n t h e s i s . 60 T h e r e f o r e , t h e r e i s a s t r o n g p o s s i b i l i t y p t h a t s t i m u l a t i o n , p a r t i c u l a r l y i n u n t r a i n e d m u scle, causes e i t h e r muscle c e l l i n j u r y and/or c o n n e c t i v e t i s s u e damage r e s u l t i n g i n l o c a l i z e d soreness.24-48 hours l a t e r . The ES group a l s o c o m p l a i n e d about the p a i n and b u r n i n g s e n s a t i o n a s s o c i a t e d w i t h the e l e c t r i c a l s t i m u l a t i o n more than the ES + IE group. I t appears t h a t e x e r c i s i n g t h e muscle t h r o u g h o u t the f u l l range of motion p r e v e n t e d o r reduced th e u n c o m f o r t a b l e s e n s a t i o n and muscle s o r e n e s s a f f l i a t e d w i t h e l e c t r i c a l s t i m u l a t i o n . I t i s i m p o r t a n t t o note t h a t most o f the s u b j e c t s : were p h y s i c a l l y a c t i v e d u r i n g the s t u d y , however i t was r e v e a l e d t h a t no s i g n i f i c a n t c r o s s - e d u c a t i o n e f f e c t from the non-dominant t r a i n i n g l e g t o the dominant l e g o c c u r r e d (Appendix B - F i g u r e V ) . Power g a i n s i n t h e c o n t r a l a t e r a l l i m b were not e v i d e n t between the p r e and p o s t t e s t s , t h e r e f o r e no p h y s i c a l f a c t o r s o u t s i d e o f the s t u d y i n f l u e n c e d the power i n c r e m e n t s o f the t r a i n e d l e g . Thus, the t r a i n i n g produced e f f e c t s , i f any, on the p e r i p h e r a l motor u n i t s o f the t r a i n e d l i m b and n o t the n e u r a l system o f the o p p o s i t e l i m b . The p r i m a r y h y p o t h e s i s o f the s t u d y s t a t e d t h a t power c o u l d be i n c r e a s e d t o a g r e a t e r degree by u s i n g e l e c t r i c a l s t i m u l a t i o n i n c o m b i n a t i o n w i t h i s o k i n e t i c e x e r c i s e , more so than:1, w i t h i s o k i n e t i c e x e r c i s e o r e l e c t r i c a l s t i m u l a t i o n (ES + IE > I E > ES) . T h i s h y p o t h e s i s was n o t a c c e p t e d . There was ho s i g n i f i c a n t d i f f e r e n c e between the t h r e e groups f o r 61 muscular power gains. However, the rationale stating that increased power res u l t s from a greater recruitment of slow and fast motor units with e l e c t r i c a l stimulation, and when i s o k i n e t i c exercise i s j o i n t l y involved, was p a r t i a l l y evident by reasoning of the s i g n i f i c a n t tests e f f e c t . The fact that the combined groups did improve muscular power and strength h between the t e s t s , -although no one group had greater increases i n power than the others, indicates that t h i s p hysiological rationale? may e x i s t . Perhaps i f the t r a i n i n g sessions had been extended for a longer period of time s i g n i f i c a n t power increments may have, occurred i n the ES + IE group, as they were receiving two types of strength t r a i n i n g modalities. Muscle power i s c l o s e l y related to the cross-sectional area of a muscle. Evidence shows that power t r a i n i n g increases the cross-sectional area of the fast twitch f i b e r s of human muscle (Gollnick, 1980);. Theoretically, the:'-ES + IE group's muscles should have hypertrophied to a larger size and at a faster rate than the IE and ES groups because i t was assumed that more slow and fast motor units were being activated. Time to peak tension, the second dependent variable of t h i s study, was the period of time i t took from the onset, of muscular contraction to the peak maximal muscular contraction. It was hypothesized that the time to peak tension produced by the ES + IE group would be less than the time to peak tension for the IE and ES groups (ES + IE< IE<ES) . However, no s i g -n i f i c a n t difference between the three groups resulted i n a change i n the time to peak muscular tension as shown in 7; >'r>c:::-. 62 Appendix A (Table I V ) . The r a t i o n a l e b e h i n d t h i s t h e o r y s u g g e s t s t h a t the d e c r e a s e i n c o n t r a c t i o n t ime d u r i n g e l e c t r i c a l s t i m u l a t i o n i s a t t r i b u t e d t o a change i n numbers o f f a s t t w i t c h and slow t w i t c h f i b e r s t h a t a re r e c r u i t e d . The q u a l i t y o f r e c r u i t m e n t may t e n d t o be more s p e c i f i c t o f a s t t w i t c h f i b e r s ( K o t s , 1977). However, t h i s was n o t demonstrated i n t h e s t u d y and, i n f a c t , ' G b l l n i c k ( 1 9 8 0 ) has shown t h a t i t i s n o t p o s s i b l e t o a c t i v a t e o n l y f a s t t w i t c h u n i t s d u r i n g e x e r c i s e by "gumping o v e r " the slow t w i t c h u n i t s . The f a s t t w i t c h motor u n i t s , w h i c h c o n t a i n many;' -fibersiiand produce l a r g e amounts o f f o r c e and a r e i n n e r v a t e d by l a r g e motoneurons, a r e a c t i v a t e d o n l y a f t e r t h e slow t w i t c h u n i t s a r e engaged. T h i s p a t t e r n o f motor u n i t r e c r u i t m e n t l e a d s t o an o r d e r l y i n c r e a s e i n the f o r c e d e v e l o p e d by muscle and r e s u l t s i n a smooth c o n t r o l o v er motor a c t i v i t y . C o n v e n t i o n a l slow v e l o c i t y t r a i n i n g and slow i s o k i n e t i c t r a i n i n g causes h y p e r t r o p h y o f b o t h f i b e r t y p e s (MacDougall e t a l . , 1980a). I t has been shown t h a t the f a s t t w i t c h f i b e r s are e n l a r g e d t o a g r e a t e r e x t e n t t h a t the slow t w i t c h f i b e r s I n t h e power movements; s i m i l a r l y , s l ow v e l o c i t y t r a i n i n g causes g r e a t e r h y p e r t r o p h y o f the f a s t t w i t c h f i b e r s (MacDougall e t a l . , 1980a and T h o r s t e n s s o n e t a l . , 1976). T h i s does n o t mean t h a t the f a s t t w i t c h motor u n i t s were r e c r u i t e d more bu t may i n d i c a t e t h a t f a s t t w i t c h f i b e r s a r e more a d a p t a b l e i n r e l a t i o n t o h y p e r t r o p h y . T h e r e f o r e , t h e r e i s no b a s i s f o r t h e c l a i m t h a t s l ow t w i t c h motor u n i t s a re p r e f e r e n t i a l l y r e c r u i t e d d u r i n g 63 maximal slow v e l o c i t y c o n t r a c t i o n s . The m i s c o n c e p t i o n may have a r i s e n from th e a ssumption t h a t f a s t t w i t c h muscle f i b e r s c o u l d o n l y be i n v o l v e d i n f a s t c o n t r a c t i o n s ; however, f a s t t w i t c h f i b e r s a r e a l s o d e s i g n e d t o c o n t r i b u t e f o r c e , r e g a r d l e s s o f v e l o c i t y . S i m i l a r l y , s l ow t w i t c h motor u n i t s can c o n t r i b u t e f o r c e t o v e r y r a p i d c o n t r a c t i o n s (slow t w i t c h f i b e r s can d e v e l o p t h e i r peak f o r c e w i t h i n 0.1 second o r l e s s ) . As i s c l e a r l y e v i d e n t i n Appendix B ( F i g u r e I ) , t r a i n i n g w i t h e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r c i s e produced a speeds e f f e c t w i t h r e s p e c t t o time t o peak t e n s i o n . As e x p e c t e d , th e t ime t o peak t e n s i o n between the f o u r speeds was s i g n i f i c a n t l y d i f f e r e n t . The t ime t o peak t e n s i o n was d i r e c t l y i n f l u e n c e d by t h e t e s t i n g v e l o c i t i e s and n u m e r i c a l v a r i a n c e o f the Newton-meters, r a t h e r t h a n b e i n g i n f l u e n c e d by the t r a i n i n g methods. T h i s c r e a t e d a f a l s e s i g n i f i c a n t e f f e c t between the speeds. To summarize, the time t o peak t e n s i o n d i d n o t s i g n i f i c a n t l y d e c r e a s e o v e r the s i x week t r a i n i n g p e r i o d . The d e c r e a s e i n c o n t r a c t i o n t ime d u r i n g t r a i n i n g i s a t t r i b u t e d t o a change i n t h e f i r i n g r a t e o f f a s t t w i t c h and s low t w i t c h f i b e r s . Both:;r f i b e r t y p e s were h y p o t h e s i z e d t o speed up t h e i r v e l o c i t y , however t h i s was not proven d u r i n g t h e s t u d y . P e r h a p s , the slow and f a s t t w i t c h f i b e r s d i d not adapt t o f a s t e r v e l o c i t y and faster.ocon.trac.tion p a t t e r n s because the t r a i n i n g p e r i o d was n o t o f s u f f i c i e n t d u r a t i o n f o r a t r a i n i n g change t o o c c u r . Thus, a change i n time t o peak t e n s i o n was n o t e v i d e n t a f t e r 64 r e c e i v i n g a program o f e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r c i s e . The t h i r d dependent v a r i a b l e , t h i g h g i r t h ( p a t e l l a r and g l u t e a l ) , was h y p o t h e s i z e d t o be g r e a t e r i n t h e group r e c e i v i n g t h e c o m b i n a t i o n o f s t i m u l a t i o n and e x e r c i s e t h a n th e e x e r c i s e o r e l e c t r i c a l l y s t i m u l a t e d group a f t e r t r a i n i n g f o r s i x weeks (ES + I E > I E > E S ) . A c c o r d i n g t o t h e r e s u l t s , Appendix A (Table V I ) , t h e r e was a s i g n i f i c a n t d i f f e r e n c e between the t h r e e groups f o r g l u t e a l t h i g h g i r t h . The p o s t hoc l o c a t i o n of t h e s i g n i f i c a n c e was d e t e r m i n e d t o be between the ES + IE and ES groups. However, the s i g n i f i c a n c e was n o t r e l a t e d t o a t r a i n i n g change. The f a c t t h a t t h e s e two groups had d i f f e r e n t p r e t e s t g l u t e a l t h i g h measurements was p r o b a b l y because o f t h e i r d i f f e r e n c e i n s i z e (Appendix B - F i g u r e I I I ) . The groups were equated o n l y f o r power and no o t h e r e q u a t i n g f a c t o r s were t a k e n i n t o c o n s i d e r a t i o n . The ES + IE group, as l i s t e d i n T a b l e I , was s m a l l e s t i n s t a t u r e and w e i g h t , c o n v e r s e l y the ES group was the t a l l e s t i n s t a t u r e and h e a v i e s t I n w e i g h t . The d i f f e r e n c e i n s i z e would account f o r t h e v a r i a t i o n i n the mean g a i n v a l u e s , p a r t i c u l a r l y a t t h e g l u t e a l s i t e i n the ES + IE and ES groups. The u n i v a r i a t e a n a l y s i s o f the p a t e l l a r t h i g h g i r t h between the groups was a l s o s i g n i f i c a n t as shown i n Appendix A .(Table V I ) . Tukey's comparison t e s t d i d n o t d i s p l a y s u f f i c i e n t s i g n i f i c a n c e t o cause a d i f f e r e n c e i n t h i g h g i r t h . The l ower l e g c i r c u m f e r e n c e was 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 65 g roups, even though the upper l e g c i r c u m f e r e n c e d i d r e f l e c t a s i z e d i f f e r e n t i a l , d e s p i t e an o b v i o u s s i z e d i s c r e p a n c y between the groups. As shown i n Appendix B ( F i g u r e I I ) , the p a t e l l a r g i r t h measurement i n c r e a s e d f o r t h e ES group, but t h e measurement d e c r e a s e d mid way t h r o u g h the s t u d y and t h e n i n c r e a s e d t o i n i t i a l o r b e t t e r g i r t h s i z e a t t h e p o s t t e s t f o r the ES + IE and IE groups. K o t s (197 7) s t a t e s t h a t a d e c r e a s e i n s u b c u t a n -eous f a t and a c o r r e s p o n d i n g i n c r e a s e i n muscle h y p e r t r o p h y s h o u l d be a p parent a f t e r t e n t r a i n i n g s e s s i o n s . U n f o r t u n a t e l y , t h i s p h y s i o l o g i c a l e f f e c t was n o t e x h i b i t e d i n the s t u d y . Appendix B ( F i g u r e I I I ) i n d i c a t e s t h a t the g l u t e a l measurement i n c r e a s e d s t e a d i l y f o r the ES group, w h i l e the g l u t e a l measurement f o r t h e ES + IE and IE groups i n c r e a s e d up t o the m i d t e s t and then began t o d e c r e a s e s l o w l y . The g l u t e a l measurement was a much b e t t e r i n d i c a t o r o f g i r t h s i z e because t h e r e i s more muscle t i s s u e i n t h i s r e g i o n o f the l e g . A p o s t u l a t e d r e a s o n e x i s t s f o r t h e i n c r e a s e and then sudden de c r e a s e i n t h e l a t t e r two groups' t h i g h g i r t h . The p r i m a r y e x p l a n a t i o n was r e l a t e d t o the f a c t t h a t the two groups were p h y s i c a l l y a c t i v e and therebyl.had w e l l - d e v e l o p e d g l u t e a l muscles t o b e g i n w i t h , so t h a t o n l y a s m a l l change i n h y p e r t r o p h y was p o s s i b l e . I t was h y p o t h e s i z e d t h a t the r e s i s t a n c e t r a i n i n g from the c o m b i n a t i o n o f s t i m u l a t i o n and e x e r c i s e would i n c r e a s e the c r o s s - s e c t i o n a l a r e a o f the i n d i v i d u a l muscle f i b e r s 66 ( E r i k s s o n e t a l . , 1981; Halbach and S t r a u s , 1980 and K o t s , 1977). I t has been shown t h a t body c o m p o s i t i o n changes c o n s i s t o f a d e c r e a s e i n r e l a t i v e body f a t and a g a i n i n muscle mass when f o l l o w i n g a r e g u l a r r o u t i n e o f r e s i s t a n c e t r a i n i n g . S u b s e q u e n t l y , i f the s t u d y had been conducted f o r a l o n g e r p e r i o d o f t ime and had the groups been equated f o r the t h i g h c i r c u m f e r e n c e as w e l l as power, the muscle h y p e r t r o p h y may have been g r e a t e r . In summary, the ES + IE group was h y p o t h e s i z e d t o have the g r e a t e s t improvements i n power, time t o peak t o r q u e and t h i g h g i r t h r e l a t i v e t o t h e IE group, w h i c h was p o s t u l a t e d t o have the n e x t b e s t r e s u l t s , f o l l o w e d by the ES group, w h i c h was t o show the l e a s t improvements. A l t h o u g h v o l u n t a r y i s o -k i n e t i c t r a i n i n g has been used as a s t r e n g t h t r a i n i n g t e c h n i q u e s u c c e s s f u l l y , the use o f e l e c t r i c a l s t i m u l a t i o n as a method of i n c r e a s i n g s t r e n g t h has l o n g been a q u e s t i o n i n the eyes o f v a r i o u s r e s e a r c h e r s . S t i l l w e l l (196 7) had some doubt whether muscle c o n t r a c t i o n s caused by f a r a d i c s t i m u l a t i o n c o u l d produce s t r e n g t h i n c r e a s e s . The f i n d i n g s o f t h i s s t u d y r e f l e c t a t r e n d f o r y i e l d s i n m u s c u l a r power and s t r e n g t h o f t h e t o t a l g r o ups, by u s i n g t h e c o m b i n a t i o n o f e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r c i s e , as w e l l as i s o k i n e t i c e x e r c i s e and e l e c t r i c a l s t i m u l a t i o n , r e s p e c t i v e l y , a f t e r s i x weeks. A l t h o u g h i t was n o t p r o v e n s t a t i s t i c a l l y t h a t power g a i n s were o b t a i n e d between each group. I t s h o u l d be n o t e d t h a t one method o f t r a i n i n g was n o t s i g n i f i c a n t l y b e t t e r t h a n a n o t h e r . T r a i n i n g the t h r e e groups a t s l o w speeds, demonstrated t h a t s p e c i f i c i t y o f v e l o c i t y 67 i s a s s o c i a t e d w i t h power and s t r e n g t h development. N e u r a l a d a p t a t i o n t h r o u g h t r a i n i n g o f the c e n t r a l nervous system p l a y e d an i m p o r t a n t r o l e i n t h e response t o power t r a i n i n g . F u r t h e r s t u d i e s need t o be conducted on l a r g e r groups o f u n t r a i n e d s u b j e c t s f o r l o n g e r d u r a t i o n s u s i n g e l e c t r i c a l s t i m u l a t i o n as a supplement t o i s o k i n e t i c e x e r c i s e , o r even as a s u b s t i t u t e t o c o n v e n t i o n a l s t r e n g t h t r a i n i n g , t o d e t e r m i n e t h e advantages and d i s a d v a n t a g e s o f t h i s t e c h n i q u e f o r power and s t r e n g t h e v e n t s . 6 :8 CHAPTER V SUMMARY AND CONCLUSIONS Summary Power and s t r e n g t h t r a i n i n g , u s i n g c o n v e n t i o n a l t e c h n i q u e s , has been s t u d i e d by s e v e r a l r e s e a r c h e r s ; g e n e r a l l y t h e type of e x e r c i s e performed r e f l e c t s the t r a i n i n g e f f e c t s . I n v e s t -i g a t i o n s i n t o t h e use o f d i f f e r e n t t r a i n i n g methods and t h e i r e f f e c t on power and s t r e n g t h development are c o n t i n u a l l y b e i n g s t u d i e d and r e - a s s e s s e d . R e c e n t l y , the use o f f a r a d i c o r e l e c t r i c a l s t i m u l a t i o n has become an i n t e r e s t i n g a l t e r n a t i v e method, a l t h o u g h much c o n t r o v e r s y s u r r o u n d s t h i s t e c h n i q u e . I t has been r e p o r t e d by Johnson e t a l . (1977) and Kots (1977) t h a t f a r a d i c s t i m u l a t i o n was used w i t h s u c c e s s as p a r t o f a s t r e n g t h e n i n g program by e l i t e S o v i e t a t h l e t e s . The combined e f f e c t s o f a program c o n s i s t i n g o f e x e r c i s e as w e l l as e l e c t r i c a l s t i m u l a t i o n was un d e r t a k e n t o determine the m u s c u l a r power and s t r e n g t h p o t e n t i a l s . The main o b j e c t i v e o f t h i s s t u d y was t o compare power and s t r e n g t h changes between equated groups e m p l o y i n g the f o l l o w i n g t r a i n i n g t e c h n i q u e s : e l e c t r i c a l s t i m -u l a t i o n p l u s i s o k i n e t i c e x e r c i s e , i s o k i n e t i c e x e r c i s e and e l e c t r i c a l s t i m u l a t i o n , r e s p e c t i v e l y . o Twenty-seven, m o d e r a t e l y t r a i n e d , female s u b j e c t s , nine" p e r group, were t e s t e d on t h r e e s e p e r a t e o c c a s i o n s . D u r i n g the f i r s t s e s s i o n , h e i g h t , w e i g h t , l e f t and r i g h t q u a d r i c e p s power e v a l u a t i o n , time t o peak t e n s i o n o f the muscle c o n t r a c t i o n 69; a t the f o u r v e l o c i t i e s and two t h i g h g i r t h measurements were de t e r m i n e d . The t h r e e groups were equated f o r power a f t e r the p r e t e s t was c onducted and t h e r e s u l t s are shown i n T able 1. The second and t h i r d t e s t i n g s e s s i o n s a s s e s s e d the power and time t o peak t e n s i o n o f the non-dominant l e g a t the f o u r v e l -o c i t i e s and p a t e l l a r and g l u t e a l t h i g h g i r t h s . A s i g n i f i c a n t d i f f e r e n c e f o r power was found between the pre and p o s t t e s t s and the p r e and mid t e s t s f o r the combined groups d u r i n g the s i x week p e r i o d o f t r a i n i n g . A l t h o u g h no d i f f e r e n c e was found between each of the t h r e e groups, the r e s u l t s i n d i c a t e d t h a t programs i n v o l v i n g e l e c t r i c a l s t i m u l a t i o n and i s o k i n e t i c e x e r c i s e , i s o k i n e t i c e x e r c i s e and e l e c t r i c a l s t i m u l a t i o n o n l y are p o t e n t i a l l y e f f e c t i v e i n i m p r o v i n g m u s c u l a r power and s t r e n g t h i n h e a l t h y s u b j e c t s . The s t u d y r e v e a l e d t h a t one method was n o t s u p e r i o r t o a n o t h e r a f t e r s i x weeks o f t r a i n i n g . There was s i g n i f i c a n t power d i f f e r e n c e s between the pre and p o s t t e s t s and pre and mid t e s t s a t the slow i s o k i n e t i c speeds o f 30° and 0° per second. S i n c e the t r a i n i n g was con-d u c t e d a t t h e speeds o f 30° and 0° ( i s o m e t r i c ) p e r second, the s l ow t e s t i n g speeds (30° and 0° p e r second) s h o u l d r e f l e c t n e u r a l a d a p t a t i o n and m u s c u l a r r e c r u i t m e n t when the s p e c i f i c i t y o f t r a i n i n g t h e o r y i s c o n s i d e r e d . These f i n d i n g s i m p l y t h a t power and s t r e n g t h t r a i n i n g b e n e f i t s are l i m i t e d t o speeds used d u r i n g t r a i n i n g . 70 The t h i g h g i r t h between the ES + IE and ES groups was s i g n i f i c a n t . T h i s s i g n i f i c a n c e was r e l a t e d to the f a c t t h a t the ES group had s l i g h t h e i g h t and weight advantages as compared to the ES + IE group, which accounted f o r t h e i r g r e a t e r g l u t e a l p r o p o r t i o n s . So, the s i z e d i f f e r e n c e between the groups was presen t a t the s t a r t o f the study, c o n t r i b u t i n g t o f a l s e s t a t i s t i c a l s i g n i f i c a n c e . C o n c l u s i o n s The f o l l o w i n g c o n c l u s i o n s can be reached: (1) ES + IE, IE^and ES used i n the methods of t h i s experiment are p o s s i b l e methods f o r i n c r e a s i n g power and s t r e n g t h "of..healthy quadriceps muscles. (2) One method of t r a i n i n g was not s i g n i f i c a n t l y b e t t e r than another. E l e c t r i c a l s t i m u l a t i o n combined with i s o -k i n e t i c e x e r c i s e , used as a form of power and s t r e n g t h t r a i n i n g , i s not a b e t t e r form of t r a i n i n g than a program of i s o k i n e t i c e x e r c i s e or e l e c t r i c a l s t i m u l a t i o n t r a i n i n g as used i n t h i s experiment over s i x weeks. (3) T r a i n i n g e f f e c t s are s p e c i f i c t o the v e l o c i t y a t which the .exercise i s performed. Power increments i n the ES +• IE, IE and ES groups were l i m i t e d t o the v e l o c i t i e s used d u r i n g t r a i n i n g . 71 (4) Time t o peak m u s c u l a r t e n s i o n does n o t d e c r e a s e w i t h ES + IE t r a i n i n g more th a n the time t o peak t e n s i o n w i t h IE o r ES t r a i n i n g as used i n t h i s s t u d y . (5) G i r t h measurements showed no r e l a t i o n s h i p t o i n c r e a s i n g power i n the q u a d r i c e p s muscle group. (6) P a i n and b u r n i n g s e n s a t i o n s were th e major l i m i t i n g f a c t o r s i n t h e amount o f amperage t h a t -could be t o l e r a t e d w i t h ES + IE and ES. Recommendations f o r F u r t h e r R esearch (1) T r a i n i n g s e s s i o n s o f g r e a t e r f r e q u e n c y and d u r a t i o n would be b e n e f i c i a l i n d e t e r m i n i n g which method, ES + I E , IE o r ES, i s b e t t e r f o r i m p r o v i n g m u s c u l a r power and s t r e n g t h . (2) The use o f s e d e n t a r y s u b j e c t s i n l a r g e r t r a i n i n g groups would ; a s s i s t . .' i n d e t e r m i n i n g w h i c h method i s s u p e r i o r f o r muscle power and s t r e n g t h development. (3) A d d i t i o n a l r e s e a r c h i s needed t o determine whether the t e c h n i q u e s used i n t h i s s t u d y would b e n e f i t p a t i e n t s w i t h a t r o p h i e d muscle and knee j o i n t d i s o r d e r s . R e - e d u c a t i o n f o l l o w i n g weakness caused by trauma o r s u r g e r y , may demonstrate maximal b e n e f i t s u s i n g t h e s e t r a i n i n g methods i n s t e a d o f t r a d i t i o n a l r e -h a b i l i t a t i o n t e c h n i q u e s . 72 (4) More s t u d i e s need to be conducted with ES and i t s e f f e c t on i n c r e a s i n g power, e s p e c i a l l y when the p a r t i c i p a n t can t o l e r a t e a h i g h amperage. (5) C l a r i f i c a t i o n i s needed on the c a p a b i l i t i e s o f the s t i m -u l a t i n g d e v i c e s p r e s e n t l y a v a i l a b l e . 73 BIBLIOGRAPHY Abraham, W.M. 1977. Factors i n delayed muscle soreness. Med. S c i . Sports. 9: 11-2 0. Astrand, P.O. and K. Rodahl. 1977. .Textbook of Work Physiology. Toronto, McGraw-Hill Book Company. Cummings, F. 1980. Physiological basis of e l e c t r i c a l stimulation i n s k e l e t a l muscle.' J. Can. 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INTERACTION S X G ..PROBABILITY 0.0000 104.66 01 INTERACTION T X S PROBABILITY INTERACTION T X S X G PROBABILITY 0.7309 0.60 I E GROUP MULTI. F TUKEY'S POST HOC ANALYSIS: 0.0004 9.11 NO S I G . 0.0000 113.91 01 0.0413 2 . 26 NO SIG. ES GROUP 0.0827 0.0000 0.1250 MULTI. F 2.63 94.39 1.70 TUKEY'S POST HOC ANALYSIS: .01 TABLE l b MULTIVARIATE ANALYSIS OF VARIANCE FOR POWER PARAMETER DEPENDENT VARIABLE POWER BETWEEN GROUPS PROBABILITY' (P<) BETWEEN TESTS PROB. INTERACTION T X G PROBABILITY BETWEEN SPEEDS PROB. INTERACTION S X G PROBABILITY INTERACTION T X S PROBABILITY INTERACTION T X S X G PROBABILITY PRETEST 0.4818 MULTI. F 0.75 TUKEY'S POST HOC AN A L Y S I S : 0.0000 189.52 01 0.6480 0.70 MIDTEST MULTI. F TUKEY'S POST HOC ANALYSIS: 0.9284 0.07 ' 0.0000 0.3191 189.49 1.19 .01 POSTTEST 0.4771 MULTI. F 0.76 TUKEY'S POST HOC ANAL Y S I S : 0.0000 0.1265 145.13 1.73 .01 TABLE I I MULTIVARIATE ANALYSIS OF PAIRWISE COMPARISON FOR POWER VARIABLE DEPENDENT Tx(GRl&2)* Tx(GR2&3) Sx(GRl&3) TxSx(GRl&2) VARIABLE Tx(GRl&3) Sx(GRl&2) Sx(GR2&3) TxSx(GRlS (P<) POWER 0.0448 0.3591 • 0.0938 0.5467 0.4983 0.3983 0.2139 0.2179 UNIVARIATE F VALUE 2.01 1.05 2.49 0.71 0.80 1.00 1.41 1.54 TUKEY'S POST HOC ANALYSIS: *GR1 - ES + I E Group GR2 - IE Group GR3 - ES Group TABLE I I I COMPARISON OF*TIME TO PEAK TENSION BETWEEN  ELECTRICAL STIMULATION AND I S O K I N E T I C EXERCISE (ES + I E ) , ISOKINETIC EXERCISE ( I E ) AND ELECTRICAL STIMULATION (ES) GROUPS PARAMETER ES + I E GROUP I E GROUP ES GROUP TIME TO PEAK TENSION ->r.O -1 30 x s 100° x s " 1 180 xivs n o -1 0 x s PRE MID POST PRE MID POST PRE MID POST X S.D. . 73 + .38 .25 + .07 .40 + .07 2.10 +1.11 .71 + .23 . 32 + .07 .44 + .06 3.24 +1.06 .63 + .22 .34 + .08 .23 + .05 2. 39 +1.18 .48 .71 .55 +.13 +.29 +.11 .29 + .05 .15 + .04 .36 + .07 .23 + .04 . 32 + .04 .24 + .04 3.06 2.46 1.77 +1.46 +1.47 +1.37 .57 + .17 .26 + .09 .13 + .06 3.17 + 1.36 .69 + .26 .33 + 106 .23 + .02 2.38 + 1.16 .61 + .22 .33 + .07 .22 + .04 2.35 + 1.16 * seconds T A B L E I V CM 00 M U L T I V A R I A T E A N A L Y S I S O F V A R I A N C E F O R T I M E T O P E A K T E N S I O N P A R A M E T E R D E P E N D E N T V A R I A B L E B E T W E E N G R O U P S P R O B A B I L I T Y B E T W E E N T E S T S P R O B . (P <) I N T E R A C T I O N T X G P R O B A B I L I T Y B E T W E E N S P E E D S P R O B . I N T E R A C T I O N S X G P R O B A B I L I T Y I N T E R A C T I O N T X S P R O B A B I L I T Y I N T E R A C T I O N T X S X G P R O B A B I L I T Y T I M E T O P E A K T E N S I O N 0 . 5 8 8 5 0 . 1 4 7 0 0 . 2 6 4 8 0 . 0 0 0 0 0 . 9 7 3 8 0 . 0 5 9 3 0 . 0 1 0 1 U N I V A R I A T E F V A L U E 0 . 5 4 2 . 0 0 1 . 3 5 1 6 0 . 2 7 0 . 2 1 2 . 0 8 2 . 3 1 T U K E Y ' S P O S T H O C A N A L Y S I S : . 0 1 N O S I G . TABLE V COMPARISON OF THIGH GIRTHS BETWEEN  ELECTRICAL STIMULATION AND ISOKINETIC EXERCISE (ES + I E ) , ISOKINETIC EXERCISE (IE) AND ELECTRICAL STIMULATION (ES) GROUPS PARAMETER ES + IE GROUP IE GROUP ES GROUP THIGH GIRTH PRE MID POST PATELLAR ; X 50.44 46.97 S.D. + 2.45 +10.76 GLUTEAL. 53.79 + 2.28 54.19 + 2.94 50.42 + 2.60 53. 80 + 2.64 PRE •MID POST 51.71 + 2.38 55.28 + 2.41 51.60 + 2.05 55.65 + 2.03 51.84 + 2.81 55.60 + 3.25 PRE MID POST 53.60 53.74 53.82 + 2.14 + 1.99 + 2.22 57.77 + 2.93 58.25 + 2.48 58.81 + 2.06 * c e n t i m e t e r s 8*4 TABLE VI MULTIVARIATE ANALYSIS OF VARIANCE FOR THIGH GIRTH PARAMETER DEPENDENT VARIABLE BETWEEN GROUPS PROBABILITY (P<) BETWEEN TESTS PROBABILITY INTERACTION T X G PROBABILITY PATELLAR THIGH GIRTH 0.0238 -UNIVARIATE. F' VALUE 4.39 TUKEY'S POST HOC ANALYSIS: NO SIG. 0.3244 1.15 0.4096 1.01 GLUTEAL THIGH GIRTH 0.0052 0.1120 0.6519 UNIVARIATE F VALUE 6.59 2.29 0.62 TUKEY'S POST HOC ANALYSIS: .05 ES+IE-ES APPENDIX ( F i g u r e s 86 FIGURE I TIME TO PEAK TENSION FOR ES + IE, IE AND ES GROUPS AT 30°, 100°, 180° and 0° x s" 1 SPEEDS 3.25 -3.00 -2.75 -2.50 -2.25 -TIME TO 2.00 -PEAK TENSION 1.75 -( sec) 1.50 1.25 -1.00 -75 -50 -25 -DURING PRE, MID AND POST TESTS T-30°.s" 1 100°.s" 1 180°.s - 1 i i i PRE I I I MID TESTS I l l POST FIGURE I I PATELLAR. THIGH GIRTH FOR ES + I E , I E AND ES GROUPS DURING PRE, MID AND POST TESTS PATELLAR THIGH GIRTH (cm) 55-54-5 3-52-51-50-4 9 H 48H 47H 46H 45H i i i PRE I I i MID l l I POST TESTS 88 FIGURE I I I GLUTEAL THIGH GIRTH FOR ES + I E , I E AND ES GROUPS DURING PRE, MID AND POST TESTS GLUTEAL THIGH GIRTH (cm) 60-59-58-57-56-55-54-53-52-51-50-ES + I E # I E O ES A l - l >. I PRE I I I MID l I l POST TESTS 8 9 -FIGURE I V COMPARISON OF MEAN FARADIC CURRENTS THAT COULD BE  TOLERATED WITH ELECTRICAL STIMULATION I N THE ES + I E GROUP AND ES GROUP ES + I E ES 50-45-40-F a r a d i c C u r r e n t f - ' '35-(mAmp) 30-25-20-15-10-ES + ES —I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I ~ ~ 1 2 3 4 J5 6 7 8 9 10 11 : 12 13 14 15 16 it 17 TRAINING SESSIONS 9-0. FIGURE V PRE AND POST COMPARISON OF DOMINANT LEG POWER BETWEEN ES + I E , I E AND ES GROUPS 200-190-180-170-ES + I E I E O ES A 160- A POWER , (N-m-s ) 150-140-130-120-110-100-A 0 PRE i I I POST TESTS 91 : i 1 APPENDIX C (Sample C a l c u l a t i o n ) 92 Sample C a l c u l a t i o n f o r Newton-meters p e r Second Power = f o r c e x d i s t a n c e x time 1 o r Power = Work x time 1 * Power = Newton-meters x second = t o r q u e x * ^ .— x speed ^ radxan t o r q u e = foot-pounds ,7 180° 22 r a d i a n = - = — - l»= —=• TT V speed = v e l o c i t y o f l e v e r arm (degrees p e r second * foot-pounds o f t o r q u e may be c o n v e r t e d t o Newton-meters o f t o r q u e by m u l t i p l y i n g by 1.356 Example: -1 j-, -, , 1.356 r->rvO „~1\ N-m x s = 60 f t - l b x ^j-^ r a d i a n x (30 r x s ) = 60 x .024 x 30 = 43.2 Power - N-m x s 1 = 43.2 

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