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A comparison of torque characteristics produced by the knee flexors and extensors during continuous concentric… Perkins, Christopher David 1992

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A COMPARISON OF TORQUE CHARACTERISTICS PRODUCED BY THE KNEE FLEXORS AND EXTENSORS DURING CONTINUOUS CONCENTRIC AND ECCENTRIC LOADING IN POWER ATHLETES AND AEROBICALLY TRAINED RUNNERS by CHRISTOPHER DAVID PERKINS B.P.E., University of New Brunswick, Fredericton, New Brunswick 198 9 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF PHYSICAL EDUCATION in THE FACULTY OF GRADUATE STUDIES (Department of Physical Education) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September 1992 © Christopher David Perkins, 1992 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of P h y s i c a l E d u c a t i o n The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT It was the purpose of t h i s investigation to evaluate con-tinuous concentric and eccentric i s o k i n e t i c loading of the knee extensors (KE) and flexors (KF) at 90, 135, and 180 deg/sec-1 in power athletes (PA), aerobically trained runners (ATR), and a control group of moderately active individuals (MA). A t o t a l of s i x t y healthy subjects (N= 20/group), aged 18-35 years, were assigned to one of the three groups aft e r p h y s i o l o g i c a l assess-ment consisting of v e r t i c a l jump and maximal oxygen consumption (VO2 max) was performed. Gravity corrected concentric and eccentric average i s o k i n e t i c torque was measured from 75-30° of knee f l e x i o n and knee flexion-extension r a t i o s (KF-E ratios) were calculated. A three-way ANOVA with two repeated measures (angular v e l o c i t y and muscle group) was calculated for each measured contraction type (concentric and ecc e n t r i c ) . A t h i r d three-way ANOVA with two repeated measures (angular v e l o c i t y and contrac-t i o n type) was computed for the analysis of KF-E r a t i o s . Sig-n i f i c a n t findings were further analyzed using Scheffé's post hoc comparisons. F i n a l l y correlations between the a b i l i t y to produce concentric and eccentric torque for the KE and KF and VO2 max, v e r t i c a l jumping a b i l i t y , and sk e l e t a l muscle mass (SMM) were examined using Person Product Moment Correlations. It was found that the power group produced s i g n i f i c a n t l y greater average concentric and eccentric i s o k i n e t i c torque than either the endurance (concentric and eccentric at p< 0.01) or sedentary (concentric at p< 0.05 and eccentric at p< 0.01) groups for both the KE and KF while the l a s t two groups did not s i g n i f i c a n t l y d i f f e r (p> 0.05). For a l l groups i s o k i n e t i c torque produced both e c c e n t r i c a l l y and c o n c e n t r i c a l l y by the KE was s i g n i f i c a n t l y greater at p< 0.001 than that produced by the KF at each angular v e l o c i t y examined. As well, eccentric KF-E r a t i o s were s i g n i f i c a n t l y greater (p< 0.001) than those produced concentrically for each of the three groups for a l l angular v e l o c i t i e s . The power groups had s i g n i f i c a n t l y greater concentric and eccentric KF-E r a t i o s (p< 0.01) than eithe r the endurance or sedentary groups of subjects who did not d i f f e r s i g n i f i c a n t l y . Concentric KF-E r a t i o s s i g n i f i c a n t l y increased with increasing angular v e l o c i t i e s for both the endurance and sedentary groups (p< 0.02) while eccentric r a t i o s did not s i g n i f i c a n t l y change with increasing angular v e l o c i t y i n any of the three groups of subjects. F i n a l l y , there were s i g n i f i c a n t correlations between the a b i l i t y to generate torque both co n c e n t r i c a l l y and eccen-t r i c a l l y by the knee extensors and knee flexors and v e r t i c a l jumping a b i l i t y while VO2 max nor SMM s i g n i f i c a n t l y correlated with v e r t i c a l jumping a b i l i t y . These findings are important when designing i n d i v i d u a l i z e d conditioning and r e h a b i l i t a t i o n programs for athletes who are t r a i n i n g for a c t i v i t i e s which require d i f f e r e n t v e l o c i t i e s of muscular contraction. CONTENTS Page(s) ABSTRACT i i - i i i CONTENTS i v - v i LIST OF TABLES v i i LIST OF FIGURES v i i i ACKNOWLEDGEMENT ix CHAPTER 1 1 - 10 I Introduction 1 - 4 A Imbalance vs Asymmetry 2 - 4 II Statement of the problem 5 - 8 A De f i n i t i o n s 5 - 6 B Delimitations 6 C Limitations 6 - 7 D Assumptions 7 E Hypotheses 8 III Significance of the study 9 - 10 CHAPTER 2 11 - 28 I Lit e r a t u r e Review A Methods of examining muscle strength and function 11 - 14 i Isometric / isoton i c 11 - 12 Page(s) i i Isokinetic 12 - 14 B Analysis of the running motion 14 - 16 C Torque production and muscle f i b r e composition 16 - 19 D Knee flexion-extension assessment 19 - 21 E Faults with previous research 22 - 28 i Exclusive measurement of concentric contractions 22 - 23 i i Hip angle and subject positioning during t e s t i n g 23 - 24 i i i Lack of gravity correction 24 - 25 i v Time to reach pre-set angular v e l o c i t y 25 - 27 V Inclusion of fat mass when torque corrected for body weight... 27 - 28 CHAPTER 3 29 -34 I Procedures 29 - 32 A Methodology 2 9 B Testing Procedures 29 - 32 II Design and Characteristics of the data 33 - 34 CHAPTER 4 35 - 88 I Results 35 - 62 v i Page(s) A Physical C h a r a c t e r i s t i c s 35 - 37 B Physiological C h a r a c t e r i s t i c s 38 - 39 C Anthropometric C h a r a c t e r i s t i c s 40 - 41 D Corrected Concentric Torque 42 - 48 E Corrected Eccentric Torque 49 - 53 F Knee F-E Ratios 54 - 60 G Correlations 61 - 62 II Discussion 63 - 88 A Group Differences 64 - 67 B Concentric and Eccentric Contractions... 67 - 74 C Knee Extensor and Flexor Torque 74 - 79 D KF-E Ratios 80 - 84 E Significance of KF-E Asymmetry 84 - 86 F Goal of Rehabi l i t a t i o n 86 - 87 CHAPTER 5 8 9 - 92 I Summary 8 9 - 9 0 II Conclusions 90 - 91 III Recommendations 91 - 92 REFERENCES 9 3 - 9 9 TABLES Tables Page 4.1 Physical c h a r a c t e r i s t i c s 36 4.2 Physiological c h a r a c t e r i s t i c s 38 4.3 Anthropometric c h a r a c t e r i s t i c s 40 4.4 Corrected concentric torque 45 4.5 Corrected eccentric torque 51 4.6 KF-E r a t i o s 57 4.7 Correlation Matrix 62 FIGURES Figures Page 4.1 Group physical c h a r a c t e r i s t i c s 37 4.2 Group phys i o l o g i c a l c h a r a c t e r i s t i c s 39 4.3 Anthropometric c h a r a c t e r i s t i c s 41 4.4 Corrected concentric torque 4 6 4.5 Muscle Group X Angular v e l o c i t y i n t e r a c t i o n . . 47 4.6 Muscle Group X A t h l e t i c Group i n t e r a c t i o n . .. 48 4.7 Corrected eccentric torque 52 4.8 Muscle Group X A t h l e t i c Group i n t e r a c t i o n . . . . 53 4.9 KF-E r a t i o s 58 4.10 Contraction type X A t h l e t i c Group in t e r a c t i o n 59 4.11 Contraction type X Angular v e l o c i t y i n t e r a c t i o n 60 AKNOWLEDGEMENT The author would l i k e to thank the committee chairman: Dr J.E. Taunton and committee members Dr. D.B. Clement and Dr. E.C. Rhodes for t h e i r support and guidance. Assistance during the phy s i o l o g i c a l t e s t i n g was provided by Mr. Dusan Benicky. A thank you i s not enough when expressing my gratitude toward my parents for t h e i r support during these past few years. F i n a l l y t h i s thesis i s dedicated to my fiancée who has waited p a t i e n t l y during the past three years while I have attempted to achieve a dream. Chapter 1 INTRODUCTION Past i s o k i n e t i c assessment of the knee jo i n t has been performed to investigate several d i f f e r e n t areas of i n t e r e s t to both the f i e l d s of research and r e h a b i l i t a t i o n which include: monitoring progress following the repair or reconstruction of knee ligament(s), the examination of hamstring and quadricep torque curves a f t e r either knee j o i n t or thigh muscle injury, the r e l a t i o n s h i p between muscle strength and muscle f i b r e composition, and knee flexion-extension r a t i o s . It i s t h i s l a s t area, the focus of many studies, which examines the rel a t i o n s h i p between hamstring muscle s t r a i n and knee f l e x o r -extensor (KF-E) imbalance. Although i t i s believed that an abnormal KF-E r a t i o may have some association with such injury (Holmes & Alderink 1984, Bailey & Bremiller 1981, Burkett 1970, Heiser et a l . 1984), d e f i n i t e proof has yet to be established (Nosse 1982). Muscle s t r a i n i n j u r i e s (MSI) have a high rate of incidence i n those sports which require some degree of sprinting, jump-ing, and/or rapid acceleration (Arge 1985, Garrett 1983, Stanton & Purdam 1989). Brubaker & James (1974) as reported by Arge (1985), found that i n runners, 33% of a l l i n j u r i e s were of the MSI variety; a 50% rate of incidence i n those athletes p a r t i c i p a t i n g i n sprint events. One idea which has been offered to explain the abnormal frequency of these i n j u r i e s i s muscle imbalance. The term muscle imbalance (MI) refers to an asymmetrical difference which exists between extremities or between the agonist and antagonist of the same extremity which may include strength, power, power-endurance, or other value when examining the same subject (Grace 1985). This imbalance i s currently measured by evaluating average and/or peak i s o k i n e t i c torque of agonist and antagonist, d i v i d i n g the two measures with the result being the r a t i o . This balance, or lack there of, i s deemed as being i p s i l a t e r a l or contra l a t e r a l (Gilliam et a l . 1979, Heiser et a l . 1984) . IMBALANCE VS ASYMMETRY Previous studies have examined KF-E ratios using many d i f f e r e n t t e s t i n g procedures and groups of subjects. One aspect which has been common to a l l , however, i s the use of the term MI. To date, research examining t h i s r e l a t i o n s h i p has suggested that MI between the KF and KE i s "unhealthy", pos-s i b l y contributing to the occurrence of hamstring MSI (Burkett 1970, Burkett 1976, Cooper & F a i r 1978, Stafford & Granna 1984). The use of t h i s term i n such a manner i s incorrect. One should consider that because the KE and KF are two separate and d i s t i n c t groups of muscle with d i f f e r e n t actions, inner-vations, and are composed of d i f f e r e n t percentages of Type II muscle f i b r e s (Garrett 1983, Polgar 1973), imbalances should exist between these two groups of muscle. Considering the st r u c t u r a l differences between the KE and KF perhaps a more appropriate term to describe an "unhealthy" difference i n torque production i s asymmetry. There are two d i f f e r e n t types of asymmetry: functional and s t r u c t u r a l . Structural asymmetry measures differences which can be associated with physical c h a r a c t e r i s t i c s such as differences i n muscle size, innervation(s), origin(s) and i n s e r t i o n ( s ) , and muscle f i b r e composition. Therefore, struc-t u r a l asymmetry between the KE and KF should be expected. However, gross s t r u c t u r a l asymmetrical differences between legs, such as s i g n i f i c a n t l y d i f f e r e n t thigh circumferences, can be pathological i n nature. The second form of asymmetry i s that of a functional nature. Functional asymmetry examines the d i f f e r e n t aspects of muscle function measured i n a variety of ways regardless of s t r u c t u r a l status which include the coordination of muscular contraction, speed of movement/joint angular v e l o c i t y , and strength. Functional asymmetry either between the KE and KF and/or between the l e f t and right leg can be considered as pre-disposing one to injury. Previous studies have indicated that peak and average torque i s greater for the quadriceps than which the hamstrings are capable of producing at a l l angular v e l o c i t i e s presently avail a b l e for t e s t i n g (Baltzopolous & Brodie 1989, Ghena et a l . 1991, Sanderson et a l . 1984). Thus, i f the KE are s i g n i f i c a n t -l y stronger than the i p s i l a t e r a l KF, any cocontraction of these two muscle groups may result i n the knee flexors being over-powered by the force produced by the knee extensors. Such an occurrence may result in hamstring MSI (Sutton 1984). The l i t e r a t u r e addresses the measurement of i s o k i n e t i c knee fl e x i o n and extension torque from many d i f f e r e n t perspec-t i v e s . In recent years there have been several advances i n the c a p a b i l i t i e s of i s o k i n e t i c dynamometers which have revolution-ized t h i s entire area of research. Studies were once l i m i t e d to i s o k i n e t i c concentric evaluation of muscle, now i s o k i n e t i c eccentric c h a r a c t e r i s t i c s can also be examined. By investigating KF-E torque e c c e n t r i c a l l y , we can further advance our knowledge concerning KF-E torques, t h e i r r a t i o s , and possible r e l a t i o n s h i p to eccentric hamstring MSI. STATEMENT OF THE PROBLEM The purpose of t h i s study was two-fold: 1) to examine the r e l a t i o n s h i p between concentric and eccentric torque as pro-duced by the knee flexors and extensors and t h e i r KF-E r a t i o s i n a manner which best simulated the length-tension r e l a t i o n -ships found during running and 2) to examine the differences i n the a b i l i t y to produce torque between power athletes (PA), ae r o b i c a l l y trained runners (ATR), and a group of moderately active i n d i v i d u a l s (MA). DEFINITIONS For the purpose of c l a r i f i c a t i o n , the following d e f i n i -tions are considered applicable throughout the study. 1) Torque — a turning or rotary force; the product of a force and the perpendicular distance from the l i n e of action of the force to the axis of rotation 2) Average Torque — the average recorded value measured during a t r i a l regardless of i t s p o s i t i o n i n the range of motion 3) Power Subject — any subject who performs a v e r t i c a l jump of 65 cm or greater and does not achieve a value of 60 ml/kg/min on the VO2 max t e s t 4) A e r o b i c a l l y Trained Subject — any subject who performs a « VO2 max test of greater than or equal to 60 ml/kg/min and does not achieve a value of 65 cm on the v e r t i c a l jump test 5) Moderately Active Subject — any subject who cannot perform a v e r t i c a l jump of 65 cm nor can achieve a value of 60 ml/kg/min on the VO2 max test 6) Concentric — muscle contraction which occurs when the involved muscle shortens while contracting 7) Eccentric — muscle contraction which occurs when the involved muscle lengthens while contracting DELIMITATIONS The results of the study were delimited by: 1) Sample size, sex, age, l e v e l of a t h l e t i c status 2) A b i l i t y of the tester to ensure that correct procedures and techniques were employed i n the measurement of ph y s i o l o g i c a l tests, anthropometry, and torque evaluation 3) The s p e c i f i c angles i n the ROM which torque measurements were examined LIMITATIONS The results of t h i s study were l i m i t e d by: 1) Errors of data c o l l e c t i o n by the Beckman Metabolic Measure-ment Cart. This was minimized by c a l i b r a t i n g the Beckman before each aerobic endurance te s t and by standardizing the t e s t i n g procedures and instructions for a l l subjects. 2) Errors of data c o l l e c t i o n by the Kin-Com i s o k i n e t i c dyna-mometer as well as errors that can occur i n the accuracy of reading values o f f the recording chart. These were mini-mized by c a l i b r a t i n g the Kin-Corn before each t e s t i n g session and through the standardization of t e s t i n g proced-ures and instru c t i o n s , 3) A l t e r a t i o n i n subject body po s i t i o n during t e s t i n g which was minimized through the use of s t a b i l i z a t i o n straps. 4) The subject reporting accurately that no previous lower extremity injury had occurred. 5) A b i l i t y of the subjects to perform c o r r e c t l y on the Kin-Com. 6) Any reference between running angular v e l o c i t i e s and those available for t e s t i n g on the Kin-Com remembering that the speed of running has been estimated to occur at 800 deg/ sec"-^ and the maximal speed available for t e s t i n g on the Kin-Com i s 210 deg/sec"^. ASSUMPTIONS The construct of t h i s study included the following assumptions : 1) That the res u l t s of the i s o k i n e t i c torque tests were depend-ant upon the e f f o r t and cooperation of each subject 2) That the measurements recorded were only as accurate as instrumentation allowed HYPOTHESES It was hypothesized that: 1) Torque produced concentrically and e c c e n t r i c a l l y by the knee extensors w i l l be s i g n i f i c a n t l y greater than that produced by the knee flexors for a l l groups at a l l v e l o c i t i e s . 2) PA w i l l produce s i g n i f i c a n t l y greater concentric and eccen-t r i c torque for both the knee flexors and extensors than either the ATR or MA groups at a l l v e l o c i t i e s . 3) PA w i l l have s i g n i f i c a n t l y greater concentric and eccentric KF-E r a t i o s than the MA and ATR groups for each v e l o c i t y of contraction. 4a) For a l l groups at each angular v e l o c i t y , eccentric KF-E ra t i o s w i l l be s i g n i f i c a n t l y greater than concentric r a t i o s . 4b) As angular v e l o c i t y increases concentric r a t i o s w i l l increase while eccentric r a t i o s w i l l remain unchanged for a l l three groups. 5) V e r t i c a l jumping a b i l i t y w i l l s i g n i f i c a n t l y correlate with torque production while V02max and sk e l e t a l muscle mass w i l l not s i g n i f i c a n t l y correlate. SIGNIFICANCE OF THE STUDY Hamstring MSI are notorious for t h e i r slow rate of healing and high incidence of recurrence, thus they can be severely d e b i l i t a t i n g . Knowledge of healthy athlete's KF-E r a t i o s , measured both concentrically and e c c e n t r i c a l l y may be of assistance to several d i f f e r e n t people who a s s i s t i n the t r a i n -ing of athletes. This information could be used as a measuring to o l to determine i f t h e i r athletes are capable of producing and withstanding the forces present associated with t h e i r p a r t i c u l a r event. As well, t h i s knowledge may be useful during the r e h a b i l i t a t i o n of athletes who have experienced hamstring MSI or other injury such as damage to knee ligament(s) where the thigh musculature plays a s i g n i f i c a n t role i n r e h a b i l i t a t i o n . This knowledge, c o l l e c t e d on individuals who have not p r e v i -ously experienced hamstring injury, could be used as a guide-l i n e which aids the physiotherapist i n determining i f the injured athlete i s ready to return to competition without r i s k i n g further injury. Rothstein et a l . (1987) have stated that previous studies performed i n t h i s f i e l d have been f i l l e d with errors which are discovered as more research i s performed, evaluation methods are refined and t e s t equipment i s improved. Due to previous errors further investigation i n t h i s area using s t r i c t test procedures so ' s p r i n t - l i k e ' torques can be measured remembering the l i m i t a t i o n s of the i s o k i n e t i c devices such as the Kin-Com must be performed. Therefore, t h i s study was designed to further examine con-cen t r i c and eccentric torques of the knee flexors and extensors and KF-E r a t i o s i n power athletes, aerobically trained runners, and moderately active individuals over three d i f f e r e n t v e l o c i -t i e s of muscle contraction. Of further interest to t h i s inves-t i g a t i o n was the rel a t i o n s h i p between whole body s k e l e t a l muscle mass, v e r t i c a l jumping a b i l i t y , and VO2 max to torque production. Chapter 2 LITERATURE REVIEW This part of the paper i s divided into f i v e sections: previous methods of examining muscle strength and function, analysis of the running motion, torque production and muscle f i b r e composition, knee flexion-extension assessment, and fau l t s with previous re l a t e d research. METHODS OF EXAMINING MUSCLE STRENGTH AND FUNCTION Past research has i d e n t i f i e d two separate methods of measuring muscle asymmetry: i s o m e t r i c a l l y / i s o t o n i c a l l y and i s o k i n e t i c a l l y . Isometrically / I s o t o n i c a l l y Knee fl e x i o n and extension scores as well as KF-E r a t i o s were i n i t i a l l y performed is o m e t r i c a l l y using a cable t e n s i -ometer before i s o k i n e t i c dynamometers became popular, t h e i r r e s u l t s measured i n 'pounds of force'. As a re s u l t , force for that p a r t i c u l a r group of muscles being examined could be measured at only one s p e c i f i c joint angle. Subjects would exert maximum e f f o r t at a fixed p o s i t i o n within the range of motion, and thus s t a t i c strength could be determined for that p a r t i c u l a r j o i n t angle (Gleim 1978). Force measurements would be taken at other j o i n t angles throughout the range of motion (ROM) i n a sim i l a r manner, but the strength of the muscle group throughout i t s ROM could only be properly calculated by c o r r e l -ating the strength measurement to the precise joint angle at which the measurement was taken (Sutton 1984) . The use of iso t o n i c t e s t i n g to measure the strength of a muscle group has also been employed i n the past. This method of strength t e s t i n g requires the subject to l i f t a predeter-mined weight, usually a certain percentage of the indiv i d u a l ' s body weight. The test would continue with incremental pro-gression u n t i l the subject could no longer perform a complete ROM (Anderson et a l . 1991). The primary l i m i t a t i o n of t h i s method of t e s t i n g i s that the maximum is o t o n i c strength of a muscle group i s only as strong as the force that i t can produce at the weakest point i n i t s ROM. Both the isometric and i s o -tonic methods of evaluating muscle strength are similar i n that they measured force only at one s p e c i f i c j o i n t angle (Sutton 1984). I s o k i n e t i c a l l y With the development of an electromechanical device which kept limb motion at a constant predetermined v e l o c i t y , an alternative method of evaluating muscular strength was made available i n mid 1960's: i s o k i n e t i c s . Since i t s conception, i s o k i n e t i c measurement has proved to be a superior a l t e r n a t i v e to previous methods of muscle assessment (Moffroid et a l . 1969). By applying accommodating resistance to match the strength output of a p a r t i c u l a r muscle group being tested, the i s o k i n e t i c system can objectively evaluate and record the magnitude and pattern of torque generated by a muscle group across a s p e c i f i c j o i n t (Gleim 1978). In so doing, i t also allows an accurate and complete determination of muscle func-t i o n between the i p s i l a t e r a l and c o n t r a l a t e r a l extremities and the agonist and antagonist muscle groups within the same extremity (Grace et a l . 1984). A second benefit of i s o k i n e t i c measurement i s that i t allows the v e l o c i t y of contraction (angular v e l o c i t y of the j o i n t being measured) to be predeter-mined, thus evaluating muscle function at d i f f e r e n t angular v e l o c i t i e s (Sutton 1984). The early years of i s o k i n e t i c t e s t i n g made use of the CYBEX and then the CYBEX II i s o k i n e t i c dynamometers. These machines are capable of measuring peak torque and the angle at which i t occurs during the ROM, torque produced at s p e c i f i c angles, t o t a l work performed during a contraction, the average power of a contraction, and torque acceleration energy. A l l measurements can be examined at angular v e l o c i t i e s ranging from 0 to 300 deg/sec"^ (Burdett & VanSwearingen 1987). Both, however, are capable of only evaluating i s o k i n e t i c muscular contractions c o n c e n t r i c a l l y . During the past decade there has been further advancement in the a b i l i t y to perform functional muscle t e s t i n g . Isokinetic machines which are capable of evaluating a muscle e c c e n t r i c a l l y i n addition to concentric examination have been developed. The k i n e t i c communicator (Kin-Com), one such instrument, i s a h y d r a u l i c a l l y driven, microcomputer-controlled device designed to measure torque and work during eccentric and concentric i s o k i n e t i c loading. The device's controlled modes of exercise include i s o k i n e t i c , isotonic, and passive joint movement. When a subject performs a movement on the Kin-Com, the dynamometer provides resistance v i a a rotating transducer arm. The Kin-Com and i t s on-line microsystem computer are capable of recording concentric and eccentric torque and work at v e l o c i t i e s of movement from 0 to 210 deg/sec"-^ (Kin-Com, Med-Ex Diagnostics of Canada, Inc., 51 Leeder Ave., Coquitlam, B.C., V3K 3V5). ANALYSIS OF THE RUNNING MOTION As mentioned e a r l i e r , hamstring muscle s t r a i n has been found to be a common injury occurring to spr i n t e r s . Before we can associate any cause of such injury to the frequency, we must f i r s t discuss the running motion. In reviewing the role of the KF and KE i n the running motion, t h e i r function i s to alte r n a t e l y act as both a prime mover and a s t a b i l i z e r (Burkett 1976) . The primary role of the KF i s to contract e c c e n t r i c a l l y during the l a t t e r p o s i t i o n of the swing phase, decelerating the lower leg and thigh u n t i l the leg swing i s halted at a point approximately 30° from terminal extension (Stanton & Purdam 1989, Sutton 1984). It i s during t h i s late swing phase, while the KF are e c c e n t r i c a l l y contracting, that Sutton (1984) suggests as one of the points during running that hamstring MSI i s l i k e l y to occur. Stanton & Purdam (1989) quote Wood as reporting peak torque values of 150 Nm at the knee and 250 Nm at the hip during t h i s phase of running. Torques such as these are known to l i m i t how late i n recovery that the KF can decelerate the leg, making them prone to s t r a i n (Stanton & Purdam 1989). Ghena et a l . (1991) and Klopfer & Greij (1988) have stated that the KF are, on average, weaker than the KE. Because t h i s cocontraction has opposing forces the weaker muscle(s) must 'give'; thus r e s u l t i n g i n MSI i f s u f f i c i e n t asymmetry between these two groups of muscles e x i s t s . A further c h a r a c t e r i s t i c of the knee flexors i s that, l i k e most b i a r t i c u l a r muscles, they have no i n t r i n s i c mechanism to l o c a l i z e t h e i r contraction to only one j o i n t . It i s therefore possible for them to exceed t h e i r capacity to stretch; the resu l t being MSI. Other studies have also reported the consequence(s) of such an asymmetry e x i s t i n g between the KF and KE (Arge 1985, Sanderson et a l 1984, Sutton 1984). Arge (1985) stated that i f the strength of the KF i s low i n comparison to the KE, the force of contraction may be i n s u f f i c i e n t to counteract the force of knee extension i n the swing phase of gait or to pro-vide adequate hip extension i n the stance phase. This would re s u l t i n an overstretch injury or MSI to the hamstring unit. Burkett (1970) suggested that asymmetry between these two groups of muscles, the KE and KF, was a causative factor i n hamstring MSI. He also stated, however, that not everyone who possesses a muscle asymmetry w i l l experience a hamstring MSI. Unfortunately, one of the l i m i t a t i o n s when t r y i n g to rel a t e the re s u l t s of i s o k i n e t i c t e s t i n g to actual movement i s that one assumes that muscle contracts at the same v e l o c i t y as the limb, a second being that i s o k i n e t i c dynamometers are not yet capable of measuring torque at those angular v e l o c i t i e s which occur during a t h l e t i c a c t i v i t y . Klopfer & G r e i j (1988) quote others as reporting that various functional and sporting a c t i v i t i e s have angular v e l o c i t i e s estimated to range from 700-2000 deg/sec"-'-: s p r i n t i n g having angular v e l o c i t i e s of approx-imately 800-1000 deg/sec"-^ while walking has been reported to occur at 233 deg/sec"^ (Stafford & Granna 1984). TORQUE PRODUCTION AND MUSCLE FIBRE COMPOSITION In examining torque produced by the knee flexors and extensors during i s o k i n e t i c t e s t i n g many studies have also examined the composition of muscle f i b r e type i n t h e i r subjects to see i f relationships between these two variables (torque and muscle f i b r e type) e x i s t . This research has shown that athletes such as weight l i f t e r s , sprinters, and jumpers; those who perform fast contractions with high tensions, have a greater percentage of fast twitch. Type Il/non-oxidative as compared to slow twitch. Type I/oxidative muscle f i b r e s i n the same leg muscle ( C o s t i l l et a l . 1976, Melichna et a l , 1989, Thorstensson et a l . 1976b). Thorstensson et a l . (1976b) i n examining active maies found a c o r r e l a t i o n of r= 0.50 between muscle performance as measured by i s o k i n e t i c concentric contractions at f i v e d i f f e r -ent angular v e l o c i t i e s and Type II muscle f i b r e . They also found that motor units demonstrating higher tension outputs and shorter contraction times were shown to contain muscle f i b r e that could be c l a s s i f i e d as Type II with t h e i r histochemical techniques. They concluded that a high percentage of Type II muscle f i b r e i s one prerequisite for performing fast contract-ions with si m i l a r tension outputs. In 1977, Thorstensson and colleagues reported i n t h e i r review of the l i t e r a t u r e that endurance event athletes have a predominance of Type I muscle f i b r e and that VO2 max has been shown to be p o s i t i v e l y correlated with the percentage of Type I f i b r e . They also mentioned that with endurance t r a i n i n g the aerobic pot e n t i a l and the r e l a t i v e area of Type I fi b r e s have been reported to increase, predominantly re c r u i t e d during con-tr a c t i o n s of low tension outputs. Type II f i b r e s , however, have a metabolic p r o f i l e that favors anaerobic energy production and appear to only be re c r u i t e d when high tension and/or v e l o c i t y are required. Examining sprinters, jumpers, downhill skiers, race walkers, orienteers, and a group of sedentary men, they found that: 1) s k e l e t a l muscle of endurance trained athletes possessed a predominance of Type I fi b r e s 2) peak torque per Kg of body weight of endurance athletes were sim i l a r to those of sedentary men 3) a higher percentage of Type II f i b r e s i n s p r i n t -ers/jumpers (X=61%) as compared to sedentary (X=56%) and endurance athletes (X^-^nge^ 33-41%) . They concluded that the percent d i s t r i b u t i o n of muscle f i b r e type i s g e n e t i c a l l y determined as shown by Gollnick et a l . (1973) and Thorstensson et a l . (197 6a) and that Type II f i b r e s are of s i g n i f i c a n c e for high force production during high speeds of movement. Thus, one would expect that among e l i t e athletes i n high power events such as s p r i n t i n g and jumping, "natural s e l e c t i o n " would have l e f t only those with a high proportion of Type II fibres capable of competing at high s k i l l l e v e l s . Thorstensson et a l . (1976a) performed an eight week t r a i n -ing study which resulted i n a s i g n i f i c a n t increase i n isometric dynamic strength. By comparing pre-post muscle biopsies of the vastus l a t e r a l i s , they found that the percent d i s t r i b u t i o n of Type I and Type II muscle fibres were not altered which was i n accordance with other t r a i n i n g studies performed on animals (Edgerton 1969) and i n humans (Gollnick et a l . 1973). It was noticed however, that the r e l a t i v e volume of f i b r e types i n muscle was altered by a change i n the Type I-Type II area r a t i o s which increased with t h i s strength t r a i n i n g protocol. Such a discovery indicates that selected hypertrophy of Type II f i b r e s can occur with t r a i n i n g . Thus although the number of f i b r e s does not s i g n i f i c a n t l y change, the s i z e of those f i b r e s already present increases i n response to t r a i n i n g s t i m u l i . They concluded that the r e s u l t s support the idea that f i b r e d i s t r i b u t i o n i s governed lar g e l y by genetic factors. C o s t i l l et a l . (1976) also support t h i s l i n e of thought. In t h e i r discussion they described an e a r l i e r study performed by Gollnick et a l . (1973) which reported that f i b r e d i s t r i b u -t i o n remained unchanged i n adult males following a f i v e month t r a i n i n g program which involved the pedalling of a b i c y c l e ergometer f o r one hour/day, f o u r times/week at an i n t e n s i t y o f 75-90% o f t h e i r maximal a e r o b i c c a p a c i t y . However t h e o x i d a t i v e c a p a c i t i e s o f b o t h f i b r e t y p e s i n c r e a s e d . C o s t i l l e t a l . sug-g e s t e d t h a t 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 are d e v e l o p e d e a r l y i n l i f e t h r o u g h g e n e t i c s and o n l y t h e m e t a b o l i c q u a l i t i e s o f muscle f i b r e s adapt t o e x e r c i s e . M e l i c h n a e t a l . (1989) a l s o r e p o r t e d a p o s i t i v e r e l a t i o n -s h i p between VO2 max, t h e p e r c e n t a g e o f Type I f i b r e s , and t h e a c t i v i t i e s o f m i t o c h o n d r i a l enzymes. Other t e s t s have shown a r e l a t i o n s h i p w i t h Type I I muscle f i b r e s and performance a c t i v -i t i e s t h a t i n c l u d e v e r t i c a l jumping a b i l i t y and q u a d r i c e p s t r e n g t h (Vandewalle e t a l . 1987). The V a n d e w a l l e e t a l . s t u d y showed t h a t t h o s e i n d i v i d u a l s who p a r t i c i p a t e d i n s p r i n t and power a c t i v i t i e s p e r f o r m e d b e s t i n v e r t i c a l jumping when com-p a r e d t o endurance and r e c r e a t i o n a l a t h l e t e s . KNEE FLEXION-EXTENSION ASSESSMENT The concept t h a t a t h l e t e s , who p a r t i c i p a t e i n s p o r t s which a r e deemed t o be o f h i g h r i s k , a c h i e v i n g and m a i n t a i n i n g a d e s i r a b l e KF-E r a t i o t o p r e v e n t p o s s i b l e h a m s t r i n g MSI has been debated i n t h e l i t e r a t u r e f o r t h e p a s t two decades ( A r v i d s s o n e t a l . 1981, B u r k e t t 1970, G i l l i a m e t a l . 1979, Grace e t a l . 1984, H e i s e r e t a l . 1984, Holmes & A l d e r i n k 1984, Oberg e t a l . 1986, Sanderson e t a l . 1984, Scudder 1980, Wyatt & Edwards 1981). I t was K l e i n & A l l m a n i n 1969 who f i r s t r e p o r t e d a c o n c e n t r i c KF-E r a t i o o f 0.60 or 60% a t a t e s t i n g v e l o c i t y o f 60 deg/sec"-'-. C o p l i n i n 1971, as r e p o r t e d by s e v e r a l a u t h o r s . was the f i r s t to recommend that a r a t i o of 60% e x i s t between the knee extensors and flexors to prevent possible MSI involving the hamstrings suggesting that such a r a t i o would minimize the amount of stress placed on the knee. Unfortunately i t was not mentioned as to how these data were co l l e c t e d . The concentric KF-E r a t i o has been reported to vary from 39 to 85% (Cooper & F a i r 1978, Ghena et a l . 1991, G i l l i a m et a l . 1979, Grace et a l . 1984, Heiser et a l . 1984, Holmes & Alderink 1984, Moffroid et a l . 1969, Oberg et a l . 1986, Sanderson et a l . 1984, Smith et a l . 1981, Watkins & Harris 1983). Sanderson and colleagues (1984) and Scudder (1980) were unable to confirm s i m i l a r results as those studies mentioned previously. Scudder found and reported a concentric r a t i o of 62% even when increasing angular v e l o c i t i e s were used with nonathletic subjects. Sanderson et a l . reported concentric r a t i o s averaging around 44% using 60 and 180 deg/sec"-"- as angular v e l o c i t i e s i n 18-25 year old male and female non-a t h l e t i c subjects. It i s Sanderson et a l . who suggested that the difference found between t h e i r work and that performed previously i s that while the others did not take in to account the weight of the lower leg, for the effect(s) of gravity, t h e i r study did. They also found that when the ratios that were measured during t h e i r study were l e f t uncorrected for gravity the torque readings obtained resembled those of previous studies. That i s , increasing concentric KF-E ratios with increasing v e l o c i t i e s . When a g r a v i t a t i o n a l correction factor was calculated l i t t l e difference existed between torques at the d i f f e r e n t speeds. In a more recent study Ghena et a l . (1991) examined the torque c h a r a c t e r i s t i c s of the knee extensors and flexors during concentric and eccentric loading in 100 male university v a r s i t y athletes (18-25 y r s ) . Of these subjects, 60 were involved i n sprint-type a c t i v i t i e s . Measuring concentrically at 60, 120, 300, and 450 deg/sec"-'- and e c c e n t r i c a l l y at 60 and 120 deg/ sec"-"- t h e i r r e s u l t s indicated: 1) concentric KF and KE torque decreased with increasing angular v e l o c i t y , the KF decreasing at a slower rate while eccentric torque increased 2) concentric KF-E r a t i o s increased as angular v e l o c i t y increased while eccentric r a t i o s remained unchanged 3) eccentric r a t i o s were greater than concentric ones at the same v e l o c i t i e s FAULTS WITH PREVIOUS RELATED RESEARCH The problem with previous research i s that several proce-dural and t h e o r e t i c a l errors have been revealed as t h i s area expands and t e s t i n g equipment i s improve. These include: 1) exclusive measurement of concentric contractions 2) hip angle and subject p o s i t i o n during t e s t i n g 3) lack of gravity correction 4) time to reach pre-set angular v e l o c i t y 5) in c l u s i o n of fat mass when examining torque per kilogram of body weight Exclusive measurement of concentric contractions To date, the majority of experiments have examined only the concentric c a p a b i l i t i e s of the KF, KE, and t h e i r r a t i o s ; t r y i n g to relate these measures to the frequency and incidence of hamstring MSI. Although i s o k i n e t i c dynamometers which have the a b i l i t y to measure eccentric muscular contraction such as the Kin-Com have existed for the past h a l f decade, research has s t i l l been performed concentrically when examining F-E r a t i o s of the knee. Such isol a t e d research does not a i d i n the under-standing of eccentric i s o k i n e t i c c h a r a c t e r i s t i c s of the knee flexors and extensors which previously has been stated as an area of possible weakness predisposing hamstring MSI, es p e c i a l -l y i n spr i n t e r s . Kramer & MacDermid (1989) have examined the eccentric c h a r a c t e r i s t i c s of the knee extensors i n previously uninjured young females, Ghena et a l . (1991) have measured torque produced both concentrically and e c c e n t r i c a l l y of the knee flexors and extensors i n male university athletes, and Klopfer & Greij (1988) i n previously uninjured untrained males and females, but such investigation i s rare. Hip angle and subject positioning during t e s t i n g Previous studies have examined t h e i r subjects i n a supine only p o s i t i o n for both KF and KE torque measurements. To make examination of subjects as sport s p e c i f i c as possible then po s i t i o n i n g during data c o l l e c t i o n must allow the examined muscle (s) to perform as they would during a t h l e t i c competition. Worrell et a l . (1990) examined i s o k i n e t i c torque produced by the KF i n both supine and prone test positions. They found average torque to be greater i n the prone t e s t i n g p o s i t i o n than when t r i a l s were performed supine and that eccentric torque was greater than concentric torque i n the prone t r i a l s . They concluded that the prone po s i t i o n allows maximal force develop-ment of the KF while maintaining muscle length-tension r e l a -tionships s i m i l a r to what occurs during running. They also stated that such a t e s t i n g p o s i t i o n should be used when evalu-ating KF torque for a c t i v i t y . It was also mentioned that during s p r i n t i n g the KF are contracting c o n c e n t r i c a l l y and e c c e n t r i c a l l y at both the knee and hip jo i n t s and i t appears that t h i s s i t u a t i o n can clos e l y be simulated i n prone t e s t i n g . Also with the area of subject po s i t i o n i n g i s the degree of hip f l e x i o n which i s maintained during data c o l l e c t i o n . Worrell, Perrin & Denegar (1989) reported that close examin-ation of KF and KE role during a t h l e t i c p a r t i c i p a t i o n indicates i t s strength i s more appropriately assessed from a supine p o s i t i o n of 10° of hip f l e x i o n . They quote Mann (1982) as saying that the knee flexor p o s i t i o n during a t h l e t i c p a r t i c -ipation i s best assessed with hip f l e x i o n of 0-10°. Lack of gravity correction Correcting for gravity i s another important oversight by many previous researchers. Knowing that during knee extension in a supine test p o s i t i o n not only must force be exerted to propel the transducer arm, but i s also used i n the r a i s i n g and supporting of the lower leg throughout the entire range of motion one must correct for t h i s action. I f not corrected for then the torque recorded i s not a v a l i d measure. The same can also be said during the knee fl e x i o n phase. A correction factor must be calculated into the value obtained during t h i s part of the test because the weight of the lower leg i n extension i s drawn to the ground na t u r a l l y by gravity. This assistance i n the propulsion of the lower leg i n knee fl e x i o n enhances those torque measurements obtained for the KF and hinders those results of the KE. With prone t e s t i n g of the KF then gravity problems are the same as i n supine KE t e s t i n g . Such correction factors have been reported by Hart et a l . (1984) and Sanderson et a l . (1984), both c i t i n g methods used by Winter et a l . (1981). However, Nelson & Duncan (1983) have suggested a correctional factor for f l e x i o n and extension at the knee which i s less costly and has the same r e l i a b i l i t y as those suggested by Winter. Newer i s o k i n e t i c dynamometers such as the Kin-Com have b u i l t into t h e i r software gravity correct-ion equations, thus allowing instantaneous corrections to be computed. Time to reach pre-set angular v e l o c i t y Isokinetic assessment of KF-E torque has, i n the past, not considered the influence of acceleration i n the c o l l e c t e d data. Kannus (1991) reported that previous i s o k i n e t i c evaluation of peak torque i s affected by the time i t takes the pre-set angular v e l o c i t y to be reached thus causing a f a l s e change i n the angle at which peak torque occurs. The limb to be tested must f i r s t achieve the v e l o c i t y that has been predetermined before true re s u l t s can be measured. The greater the angular v e l o c i t y of the test, the longer i t takes for the limb to at t a i n terminal v e l o c i t y (Kannus 1991, Jensen et a l . 1991). Kannus (1991) stated that with i s o k i n e t i c t e s t i n g people who posses high l e v e l s of strength and power c h a r a c t e r i s t i c s , such as e l i t e athletes, may be able to work e f f e c t i v e l y at extreme knee angles. He further stated that they are better able to achieve a maximal e f f o r t much quicker a f t e r beginning movement and are capable of maintaining t h i s high l e v e l of e f f o r t u n t i l the end of the ROM thus changing the shape of the measured torque curve. He suggested that t h i s a b i l i t y i s due to an athlete's superior reaction time and neural control of the contracting muscles as compared to nonathletic indi v i d u a l s or people with knee joint injury . Piette et a l . (1986) found that during concentric knee extensor contractions torque was s i g n i f i c a n t l y increased during the f i r s t 15° at 180 deg/sec"-'-and the f i r s t 5° at 30 deg/sec"^ when 0, 50, and 100% maximal voluntary isometric contractions (MVIC's) were used as pre-load forces. In t h e i r review of the l i t e r a t u r e Jensen et a l . (1991) reported that one of the features of the Kin-Com i s s t a t i c pre-loading which requires the subject to f i r s t apply an operator-selected force to the transducer arm before motion i s allowed. Referring to Gransberg & Knuttson (1983), they suggested that s t a t i c pre-loading could be used as a method of allowing a more accurate measurement of maximal dynamic muscle performance at the beginning of motion. Piette et a l . (1986) examined d i f -ferent pre-loading lev e l s at two speeds: 30 and 180 deg/sec"-'-. It was Jensen et a l . (1991) who stated that such an increase i n the torque produced during the early phase of the t e s t i n g range as a resu l t of pre-loading w i l l affect the whole-curve analysis by increasing the area under the torque curve. To further investigate the effects of pre-loading, Jensen et a l . (1991) examined concentric and eccentric KE performance using two s t a t i c pre-load l e v e l s . Using a tes t ROM from 100-30° of knee f l e x i o n and pre-load force of 50N and 75% of MVIC, they found when the 75% MVIC pre-load was used quicker tension development and greater torque was produced for the f i r s t 15° concentrically and for the f i r s t 20° e c c e n t r i c a l l y than what was measured using the 50N pre-load force. Once predetermined angular v e l o c i t y was attained no s i g n i f i c a n t differences between the two pre-load lev e l s were found to e x i s t . They also reported that the i n i t i a l higher l e v e l of tension development allows the muscle to quickly work closer to i t s maximal l e v e l of f i b r e recruitment and thus an increase i n the average torque and concluded that by using a percentage of each subjects MVIC as a pre-load force, more accurate t e s t i n g can take place and a more gradual r i s e to peak torque with high pre-load lev e l s can occur. Inclusion of fat mass when torque corrected for body weight When previous studies examined the influence of body weight per kilogram on the amount of torque that was able to be produced by the KF and KE they did not account for the amount of adipose tissue, bone, and skin adding to the weight of each subject. A more appropriate method would be to measure the mass of s k e l e t a l muscle of each i n d i v i d u a l and r e l a t e t h i s lean body mass to the amount of torque that could be produced. Muscle, not adipose i s responsible for producing forces which allow motion and therefore, should be measured so that such invest i g a t i o n can be performed. A noninvasive method of c a l c u l a t i n g muscle mass was devel-oped by Martin et a l . (1990) . They suggested that a method of measuring s k e l e t a l muscle would be useful when examining e l i t e -l e v e l athletes since athletes of d i f f e r e n t sports may vary between muscle mass and fat mass. In the examination of twelve male cadavers (aged 50-94), they performed the following anthropometric measurements: s k i n f o l d t h i c k n e s s a t t r i c e p s , s u b s c a p u l a r , b i c e p s , a n t e r i o r t h i g h , and m e d i a l c a l f and c i r c u m f e r e n c e measurements t a k e n on t h e fore a r m , arm, t h i g h , and m e d i a l c a l f . Limb g i r t h s were t h e n c o r r e c t e d f o r s k i n f o l d t h i c k n e s s u s i n g t h e c i r c u l a r model o f t h e l i m b c r o s s - s e c t i o n and l i m b muscle g i r t h s e s t i m a t e d . They t h e n d i s s e c t e d and weighed a l l s k e l e t a l muscle, f r e e o f s k i n , a d i p o s e t i s s u e , bone, o r organs f i n d i n g s i m p l e g i r t h c o r r e l a t i o n c o e f f i c i e n t s o f r= 0.824-0.942. When c o r r e c t e d f o r t h e s k i n f o l d measurement t h e s e i n c r e a s e d t o r= 0.896-0.990. They d e t e r m i n e d t h a t from t h e s e r e s u l t s t h a t t h e two b e s t p r e d i c t o r s o f muscle mass were fo r e a r m c i r c u m f e r e n c e (r^= 0.93) and m i d - t h i g h c i r c u m f e r e n c e (r^= 0.89) whi c h were i n c r e a s e d when s k i n f o l d - c o r r e c t e d c i r c u m f e r e n c e s were used. They d e c i d e d t h a t i n o r d e r t o reduce s a m p l i n g e r r o r a t h i r d v a r i a b l e s h o u l d e n t e r t h e i r p r e d i c t i o n e q u a t i o n , c o r r e c t -ed c a l f g i r t h and t h u s d e v e l o p e d t h e f o l l o w i n g e q u a t i o n : MM= STAT (0.0553 CTG^ + 0.0987 F<^ + 0.0331 CCG^) - 2445 where MM i s t h e t o t a l s k e l e t a l muscle mass ( g ) , STAT i s s t a t u r e (cm), CTG i s t h i g h c i r c u m f e r e n c e c o r r e c t e d f o r t h e a n t e r i o r t h i g h s k i n f o l d t h i c k n e s s (cm), FG i s t h e u n c o r r e c t e d f o r e a r m c i r c u m f e r e n c e , and CCG i s c a l f c i r c u m f e r e n c e c o r r e c t e d f o r t h e m e d i a l c a l f s k i n f o l d t h i c k n e s s (cm). Chapter 3 PROCEDURES METHODOLOGY A t o t a l of si x t y males aged 18-35, having no previous hist o r y of lower extremity muscle or joi n t injury, volunteered as subjects. After being informed of the r i s k s associated with each test procedure and t h e i r consent given, subjects were evenly separated into three groups dependant upon t h e i r physio-l o g i c a l test r e s u l t s . TESTING PROCEDURES A l l p h ysiological measures were performed at the Buchanan Exercise Science Laboratory located at the Aquatic Centre, UBC while torque measurements were performed on the Kin-Com i s o -k i n e t i c dynamometer (Kin-Com, Med-Ex Diagonstics of Canada, Inc., 51 Leeder Ave., Coquitlam, B.C., V3K 3V5) located at the school of Rehabi l i t a t i o n Medicine, Pathokinesiology Laboratory at the Acute Care Hospital, UBC. The i n i t i a l v i s i t included the recording of each i n d i v i d -ual's height, weight, and anthropometric measurements as described by Martin et a l . (1990). Once t h i s was complete sub-jects were allowed to perform a s e l f designed warm-up u n t i l they were ready to proceed. The v e r t i c a l jump test consisted of each subject perform-ing three standing v e r t i c a l jumps as described by Baumgartner & Jackson (1987). The VO2 max test required each subject to r u n a t an i n i t i a l v e l o c i t y o f 8.05 km/hr w i t h 0.805 km/hr i n c r e a s e s i n v e l o c i t y e v e r y minute t h e r e a f t e r as d e s c r i b e d by Parkhouse e t a l . (1985). I f a s u b j e c t r e a c h e d t h e s i x t e e n minute mark and was a b l e t o c o n t i n u e t h e n t h e n e x t w o r k l o a d i n c r e m e n t c o n s i s t e d o f an i n c r e a s e i n t h e grade o f t h e t r e a d -m i l l o f two p e r c e n t and would i n c r e a s e by two p e r c e n t e v e r y minute t h e r e a f t e r u n t i l e x h a u s t i o n . M e t a b o l i c gas a n a l y s i s was d a t a a n a l y z e d u s i n g t h e H e w l e t t P a c k a r d model 3052-A d a t a a c q u i s i t i o n system. F o r a l l s u b j e c t s t h e v e r t i c a l jump t e s t c p r e c e d e d VO2 max assessment. A second v i s i t was r e q u i r e d by t h o s e i n d i v i d u a l s who met t h e g r o u p i n g c r i t e r i a and c o n s i s t e d o f an i s o k i n e t i c e v a l u -a t i o n o f t h e dominant l i m b ' s knee f l e x o r s and e x t e n s o r s . I s o k i n e t i c e v a l u a t i o n i n c l u d e d t h e measurement o f average t o r q u e o f t h e dominant l i m b knee f l e x o r s and e x t e n s o r s d u r i n g f i v e maximum c o n t i n u o u s c o n c e n t r i c and e c c e n t r i c c o n t r a c t i o n s from 85-15° at a n g u l a r v e l o c i t i e s o f 90, 135, and 180 deg/ sec"-'-. A f t e r p e r f o r m i n g a s e l f d e s i g n e d warm-up t h e dominant l i m b o f each s u b j e c t was d e t e r m i n e d by a s k i n g w h i c h l e g t h e y would p r e f e r t o k i c k a s o c c e r b a l l w i t h . S u b j e c t s were i n i t i a l l y p l a c e d i n a s u p i n e p o s i t i o n f o r t h e e x a m i n a t i o n o f t h e knee e x t e n s o r s and t h e n i n a prone p o s i t i o n f o r t h e knee f l e x o r s such t h a t a h i p a n g l e o f 10° was m a i n t a i n e d d u r i n g d a t a c o l l e c t i o n f o r b o t h p o s i t i o n s . The n e x t s t e p was t o l o c a t e t h e l a t e r a l f e m o r a l e p i c o n d y l e which was used t o v i s u a l l y a l i g n t h e a x i s o f t h e Kin-Com's t r a n s d u c e r arm t o t h e a n a t o m i c a l a x i s o f the knee as described by Kramer & MacDermid (1989). The length of each subject's f i b u l a on the dominant leg was then measured. The leg pad on the force transducer, attached at the d i s t a l end, was positioned such that i t corresponded to 75% of the f i b u l a r length and then a s t a b i l i z a t i o n strap, to l i m i t excessive movement during t r i a l s , was positioned across the p e l v i s . The t e s t ROM was then entered into the Kin-Com's computer as was the angular v e l o c i t y . Next, a f a m i l i a r i z a t i o n period was allowed which consisted of f i v e t r a i l s : three submaximal followed by two maximal continuous concentric and eccentric contractions. This was performed p r i o r to each t r i a l for each v e l o c i t y and muscle group. Prior to f a m i l i a r i z a t i o n however, each i n d i v i d u a l ' s maximal voluntary isometric contraction (MVIC) was measured using the Kin-Com's isometric feature. The pre-load force used before the transducer arm moved during data c o l l e c t i o n corresponded to the 75% MVIC value for each subject as described by Jenson et a l . (1991) . I f subjects were c o n f i -dent with t h e i r performance during the p r a c t i c e attempts they were allowed a two minute rest. Those subjects who d i d not f e e l competent were allowed further p r a c t i c e t r i a l s u n t i l con-fident and were then given a two minute break. Gravity was corrected for p r i o r to the commencement of the t r i a l s . This correction involved the manipulation of the transducer arm into a horizontal p o s i t i o n which was checked using a l e v e l . This angle was entered into the Kin-Com's com-puter and used for reference. Then the transducer arm was positioned so that the subject's limb was 10° from f u l l knee extension and i t was at t h i s point that the force applied by the leg to the transducer arm due to gravity was measured and recorded. This was performed p r i o r to the evaluation of each muscle group. The order i n which the t r i a l s occurred was randomized with the knee extensors always being the f i r s t group tested for t h e i r three speeds and then the knee flexors. This was done to minimize any af f e c t that learning may have on subsequent t r i a l s . In an attempt to l i m i t the e f f e c t of p o s i t i v e and negative acceleration during the i s o k i n e t i c t r i a l s only those torques produced from 75-30° of knee fl e x i o n were used i n the data analysis as shown by Jensen et a l . (1991). Each subject was instructed when to begin and when to stop the exercise and was t o l d to give a maximal e f f o r t throughout the en t i r e test ROM. Verbal encouragement was not given by the tester during data c o l l e c t i o n and subjects were not permitted to view the display monitor or to grasp handles to further support themselves. Upon the completion of each t r i a l a further two minute rest i n t e r v a l was allowed before the next t r i a l began. DESIGN AND CHARACTERISTICS OF THE DATA One-way randomized groups analyses of variance were per-formed when examining the differences between each of the three groups of subjects for physical c h a r a c t e r i s t i c s : one analysis for each of height, weight, and age), p h y s i o l o g i c a l character-i s t i c s : one analysis for each of VO2 max and v e r t i c a l jump (VJ), and anthropometric c h a r a c t e r i s t i c s : one analysis for each of s k e l e t a l muscle mass (SMM) and percent body weight accounted for by s k e l e t a l muscle. Secondly, two analyses of variance (ANOVA's) one for each of concentric and eccentric contractions: 3 ( a t h l e t i c group) X 3 (angular v e l o c i t i e s ) X 2 (muscle groups) f a c t o r i a l exper-iments with repeated measures on the l a s t two factors, were performed. These three groups were examined at three d i f f e r e n t angular v e l o c i t i e s : 90, 135, and 180 deg/sec"-"- for both the knee extensors and flexors. The three subject groups, three angular v e l o c i t i e s , and two muscle groups were the three independent variables respectively. The dependent variables for these analyses were the torque measured during the two d i f f e r e n t types of contractions which were examined as measured from 75-30° of knee f l e x i o n . Measured torque was corrected for s k e l e t a l muscle mass by di v i d i n g the absolute torque by the percent body weight that was composed of s k e l e t a l muscle mass which was present i n each subject (Nm/kg corrected). A t h i r d f a c t o r i a l analysis was performed to examine i f differences existed between eccentric and concentric KF-E r a t i o s . A 3 (a t h l e t i c group) X 3 (angular v e l o c i t i e s ) X 2 (ratio contraction types) analysis of variance with repeated measures on the l a s t two factors was performed; once again the three lev e l s of the f i r s t independent variable were power athletes, endurance athletes, and sedentary subjects. The second independent variable included the three t e s t i n g v e l o c i t i e s which the contractions occurred at: 90, 135, and 180 deg/sec"-'- and the t h i r d independent variable was concentric KF-E and eccentric KF-E r a t i o s . The dependent variable for t h i s analysis was the average torque (Nm/kg corrected) r a t i o calculated by di v i d i n g the knee flexor torque by the knee extensor torque as measured from 75-30° of knee f l e x i o n . Lastly, Pearson Product Moment Correlation C o e f f i c i e n t s were calculated to examine the relationships between torque and v e r t i c a l jumping a b i l i t y , VO2 max, and s k e l e t a l muscle mass as measured according to Martin et a l . (1990). S t a t i s t i c a l s i g n i f i c a n c e was accepted at the p< 0.05 l e v e l with s t a t i s t i c a l calculations performed using the BMDP IV, 2V, and BMDP 8D s t a t i s t i c a l packages (BMDP-Biomedical Computer S t a t i s t i c a l Software 1981) and Scheffé's post hoc pairwise analyses were performed for a l l s i g n i f i c a n t F r a t i o s . Chapter 4 RESULTS AND DISCUSSION RESULTS A t o t a l Of 72 individuals were p h y s i o l o g i c a l l y evaluated for maximal oxygen consumption (VO2 max) and v e r t i c a l jumping a b i l i t y . Of these, 60 pa r t i c i p a t e d as subjects i n t h i s study: 20 per group. Of the three groups examined, the power athlete group (PA) had the most varied composition with ten subjects t r a i n - i n g for track sprint events (50 - 200m), f i v e for jumping events (long, t r i p l e , and/or high), two were v a r s i t y basketball players, and three p a r t i c i p a t e d i n v a r s i t y hockey. The mod-erately active group (MA) was comprised of v a r s i t y golfers (N= 12) and people who were p a r t i c i p a t i n g i n personal f i t n e s s a c t i v i t i e s (N= 8). F i n a l l y , the aerob i c a l l y trained runner group (ATR) consisted of eighteen individuals who were t r a i n i n g for competition distances of greater than 800m (range 800m -marathon) and two subjects who were t r a i n i n g for t r i a t h l o n s . Physical C h a r a c t e r i s t i c s The means and standard deviations for each of the three groups of subjects physical c h a r a c t e r i s t i c s can be located i n Table 4.1. In t h i s study there were no s i g n i f i c a n t d i f f e r -ences (p> 0.05) i n height between the three groups even though, on average, PA were t a l l e r than either the ATR or MA groups as seen i n Figure 4.1. Although the PA and MA groups were s i g n i f -i c a n t l y heavier (p< 0.001) than the ATR group, the ATR group was s i g n i f i c a n t l y older (p< 0.001) than eith e r of the other two groups of subjects. For both height and weight there were no s i g n i f i c a n t differences between the MA and PA groups (p> 0.05). TABLE 4.1 Physical Characteristics PA x" sd ATR X sd MA X sd Height(cm) 182.5 4.90 178.6 7.19 179.8 7.56 Weight(kg) 81.6 6.77 70.5 4.48 80.3 8.05 Age{years) 22.2 2.75 27.8 4.07 22.7 3.33 FIGURE 4.1 Group Physical Characteristics HEIGHT (cm) WEIGHT (kg) AGE (years) 182.5 178.9 179.8 81.6 70.5 80.3 22.2 27.8 22.7 Physiological C h a r a c t e r i s t i c s The three groups were c l a s s i f i e d using two d i f f e r e n t p h y s i o l o g i c a l evaluations: the v e r t i c a l jump and the VO2 max t e s t s . As seen i n Table 4.2 the ATR group had a s i g n i f i c a n t l y greater mean VO2 max score r e l a t i v e to body weight (p< 0.001) than either the PA or MA groups who did not d i f f e r (p> 0.05). However, when v e r t i c a l jumping a b i l i t y was examined the ATR and MA groups did not s i g n i f i c a n t l y d i f f e r (p> 0.05) while the PA group s i g n i f i c a n t l y out jumped (p <0.001) eithe r of the other two groups of subjects. Graphical representation for t h i s analysis can be located in Figure 4.2. TABLE 4.2 Physiological Characteristics PA ATR MA "x s d X Sd X s d V.Jump(cm) 70.7 4.26 48.9 9.44 51.6 5.04 V02max(ml/kg/min) 51.1 2.50 64.4 3.58 49.1 4.15 FIGURE 4.2 Group Physiological Characteristics Anthropometric Charact e r i s t i c s The PA group was s i g n i f i c a n t l y greater than either the MA (p< 0.01) or ATR (p< 0.001) groups as seen i n Table 4.3 and Figure 4.3, while the MA group was s i g n i f i c a n t l y greater than the ATR group (p< 0.05) when sk e l e t a l muscle mass was calcu-lated. When body weight was corrected for sk e l e t a l muscle, derived by di v i d i n g s k e l e t a l muscle mass by body weight, the PA group were s i g n i f i c a n t l y greater than either the MA (p< 0.002) or ATR (p< 0.02) groups. These l a s t two groups were not s i g -n i f i c a n t l y d i f f e r e n t from each other. Graphical represent-ation can be located in Figure 4.3. TABLE 4.3 Anthropometric Characteristics PA X sd ATR X Sd MA X Sd Skeletal Muscle Mass(kg) 52.4 5.76 42.6 5.43 47.2 6.67 % Body Weight Accounted for by Skeletal Muscle 64.2 4.96 60.3 5.61 58.6 4.43 FIGURE 4.3 Anthropometric Characteristics 70.0 SMM . Skeletal Muscle Mass BW - Body Weight Past studies have examined torque produced by the knee flexors and extensors, measured i s o k i n e t i c a l l y , as an absolute term: newton meters (Nm) (Bennett & Stauber 1986, Ghena et a l . 1991, Hageman et a l . 1988, Harding et a l . 1988, Kramer & MacDermid 1989, Pieter et a l . 1989, Stafford & Granna 1984, Thorstensson et a l . 1976, Tredinnick & Duncan 1988, Worrell et a l . 1989, Worrell et a l . 1990), i n foot pounds (ft/lb) (Bohannon et a l . 1986, Klopfer & Greij 1988, Wyatt & Edwards 1981), and as a r e l a t i v e term: Nm/kg of body weight (Highgenboten et a l . 1988, Sanderson et a l . 1984, Worrell et a l . 1991). In the present study torque was measured as a r e l a t i v e term also accounting for body weight: Nm/kg corrected. Body weight was corrected for the weight which was accounted for by adipose, bone, and other nonmuscular t i s s u e . This was done by div i d i n g the absolute torque by the percent body weight accounted for by ske l e t a l muscle as described i n the previous analysis of anthropometric c h a r a c t e r i s t i c s . Therefore, i n the following sections, concentric and eccentric torque has been corrected for sk e l e t a l muscle mass (Nm/kg corrected). Corrected Concentric Torque The means and standard deviations for the concentric knee extensor and flexor torque values produced at the three veloc-i t i e s are presented i n Table 4.4 and graphically displayed i n Figure 4.4. The a t h l e t i c group X angular v e l o c i t y X muscle group (3x3x2) repeated measures ANOVA for corrected concentric torque revealed s i g n i f i c a n t differences (F= 1 0 . 6 9 , p< 0 . 0 0 1 ) between the three subject groups i n t h e i r a b i l i t y to produce torque concentrically when averaged over the two muscle groups and three angular v e l o c i t i e s (3rp^= 2 . 2 8 , 3r^TR" 1-97, l ( j ^ = 2 . 0 4 ) . A Scheffé's post hoc analysis indicated that the PA group could produce s i g n i f i c a n t l y greater concentric torque than could the ATR (p< 0 . 0 1 ) and MA groups (p< 0 . 0 5 ) , while there were no s i g -n i f i c a n t differences (p> 0 . 0 5 ) between the MA and ATR groups. A s i g n i f i c a n t muscle main eff e c t (F= 1 4 8 9 . 0 8 , p< 0 . 0 0 1 ) indicates that the corrected concentric torque produced was s i g n i f i c a n t l y greater for the KE than that for the KF when averaged over the three groups of subjects and three angular v e l o c i t i e s ( % E = 2 . 7 2 , 1 . 4 7 ) . The t h i r d and f i n a l main eff e c t for t h i s analysis, angular v e l o c i t y , was also s i g n i f i c a n t (F= 2 9 8 . 1 8 , p< 0 . 0 0 1 ) . When averaged over the three subject groups, and two groups of muscle, the concentric torque that could be produced at the three d i f f e r e n t test v e l o c i t i e s were s i g n i f i c a n t l y d i f f e r e n t from each other 2 . 2 4 , Xi35= 2 . 1 1 , X;i^ gQ= 1 . 9 4 ) . Further post hoc analyses were performed which indicated that the con-ce n t r i c torque produced for X^Q was s i g n i f i c a n t l y greater than ^ 1 8 0 0 . 0 1 ) and X]^35 (p< 0 . 0 5 ) , while ^1^5 was s i g n i f i c a n t l y greater than X-LQQ (p< 0 . 0 1 ) . Although the a t h l e t i c group X angular v e l o c i t y and the a t h l e t i c group X muscle group X angular v e l o c i t y interactions were not s i g n i f i c a n t (p> 0 . 0 5 ) the other two interactions i n th i s analysis were. The s i g n i f i c a n t muscle group X angular v e l o c i t y interaction, as displayed i n Figure 4.5, (F= 42.26, p< 0.001) indicates that when averaged over the three groups of subjects, concentric torque produced by the KE decreased more rapidly from 90° through 180 deg/sec"-'- than did that which was measured for the KF over the same v e l o c i t i e s i^j^ESO^ 2.91, %E135= 2.73, Xj^g280" 2.51 / Xj^pgg^ 1-56, ^KFISS"^ 1.48, XKP280" 1.36). Post hoc analysis revealed that the following compar-isons were s i g n i f i c a n t l y d i f f e r e n t at p < O.Ol: XJ^E90 '^KE135' %E90 > %E180' %E135 > %E180' %F90 > %F180' while at p< 0.05 y^j<i-pi25 s i g n i f i c a n t l y greater than "Xj^pisO-The s i g n i f i c a n t muscle group X a t h l e t i c group i n t e r a c t i o n (F= 4.2 6, p< 0.02) reveals that concentric torque produced by the KE and KF was s i g n i f i c a n t l y d i f f e r e n t between the three groups of subjects when averaged over the three angular v e l o c i -t i e s (X^E-PA"^ 2.85, XJ^E-ATR"^ 2.58, % E - M A ^ 2.72 / Xj^p_pj^= 1.70, ^KF-ATR~ 1*35, ^ K F - M A " 1-35). Further Scheffé's analysis indicated that at p< 0.01 the following relationships were s i g -n i f i c a n t l y d i f f e r e n t : ^ K E - P A ^ ^KE-ATR' ^KF-PA s i g n i f -i c a n t l y greater than either Xj^p_j^ and % F - A T R - This i n t e r -action i s graphically presented i n Figure 4.6. TABLE 4.4 Corrected Concentric Torque Athletic Group Ang.Velocity Mean SD & Muscle Group (deg/sec-1) PA KE 90 3.04 0.26 135 2.88 0.24 180 2.62 0.26 KF 90 1.81 0.22 135 1.73 0.18 180 1.56 0.19 ATR KE 90 2.76 0.41 135 2.59 0.42 180 2.40 0.43 KF 90 1.44 0.26 135 1.35 0.21 180 1.25 0.22 MA KE 90 2.93 0.15 135 2.73 0.18 180 2.51 0.31 KF 90 1.41 0.21 135 1.36 0.21 180 1.28 0.21 * significant Athletic Group main effect (F=10.69, p< 0.001 ) * significant Musde Group main effect (F=1489.08, p< 0.001) * significant Angular Velocity main effect (F=298.18, p< 0.001) FIGURE 4.4 Corrected Concentric Torque Concentric Torque (Nm/kg corr. BW) KE90 135 180 KF90 135 180 PA 3.04 2.88 2.62 1.81 1.73 1.56 ATR 2.76 2.59 2.40 1.44 1.35 1.25 MA 2.93 2.73 2.51 1.41 1.36 1.28 Muscle Group and Velocity(deg/sec-1) m PA ME ATR m i MA Corrected for %BW due to Skeletal Muscle Concentric Torque (Nm/kg corr. BW) 3.00 2.80 2.60 2.40 2.20 2.00 1.80 1.60 1.40 1.20 1.00 90 135 180 KE KF 2.91 1.56 2.73 1.48 2.51 1.36 Velocity (deg/sec-1) KE KF Averaged over the three groups Concentric Torque (Nm/kg corr.) 3.00 2.80 2.60 2.40 2.20 2.00 1.80 1.60 1.40 1.20 1.00 KE KF PA ATR MA 2.85 2.58 2.72 1.70 1.35 1.35 Muscle Group PA +~ ATR MA ] Averaged over angular velocity Corrected Eccentric Torque Means and standard deviations for the 3 (a t h l e t i c group) X 2 (muscle group) X 3 (angular velocity) repeated measures ANOVA for corrected eccentric torque are presented i n Table 4.5 and graphically represented i n Figure 4.7. This analysis revealed that s i g n i f i c a n t differences between the three groups of sub-jects (XpA= 2.61, X^TR" 2.22, X^= 2.29) i n t h e i r a b i l i t y to produce eccentric torque exist when averaged over the two muscle groups and three angular v e l o c i t i e s (F= 12.72, p< 0.001). When Scheffé's post hoc analyses were performed i t was found that the PA group could produce greater eccentric torque than could either the ATR or MA groups at the p< 0.01 l e v e l of sig n i f i c a n c e . However, there were no s i g n i f i c a n t differences (p> 0.05) between the MA and ATR groups. A s i g n i f i c a n t muscle main eff e c t (F= 2395.85, p< 0.001) indicates that the a b i l i t y for the KE to produce eccentric torque i s s i g n i f i c a n t l y greater than that which i s produced by the KF when averaged over the three angular v e l o c i t i e s and subject groups (Xj^g= 3.01, Xj^ p= 1.74). The t h i r d main ef f e c t , angular v e l o c i t y , was not s i g n i f i -cant at p< 0.05 (F= 1.50, p> 0.20). This indicates that there were no s i g n i f i c a n t differences i n the corrected eccentric torque that could be produced for the three angular v e l o c i t i e s when averaged over the three groups of subjects and two groups of muscle 0^90= 2.38, Xi35= 2.37, XIQQ= 2.38). Only the muscle group X a t h l e t i c status i n t e r a c t i o n was s i g n i f i c a n t (F= 17.01, p< 0.001) in d i c a t i n g that the d i f f e r -ences between the a b i l i t y of the KE and KF to produce eccentric torque i s influenced by the demands of one's a c t i v i t y when averaged over the three angular v e l o c i t i e s ( % E - P A ^ 3 . 1 4 , X ^ E -ATR= 2 . 8 8 , X^E-MA" 3 . 0 0 / X^p-PA^ 2 . 0 8 , ^KF-ATR" 1 . 5 6 , X ^ F M A ^ 1 . 5 8 ) as seen i n Figure 4 . 8 . S i g n i f i c a n t post hoc comparisons for t h i s i n t e r a c t i o n we re found to exist between XJ^E—PA ^KE— MA' %F-PA > %F-ATR %F-MA P < ^'^^ %E-PA > "^KE-ATR P"^  0 . 0 5 . The other interactions for t h i s analysis: the muscle group X angular v e l o c i t y , a t h l e t i c group X angular v e l o c i t y interaction, and the three way int e r a c t i o n for a t h l e t i c group X muscle group X angular v e l o c i t y for t h i s analysis were not s i g -n i f i c a n t (p> 0 . 0 5 ) . TABLE 4.5 Corrected Eccentric Torque Athletic Group Ang.Velocity Mean SD & Muscle Group (deg/sec-1) PA KE 90 3.13 0.25 135 3.14 0.24 180 3.14 0.27 KF 90 2.10 0.21 135 2.06 0.21 180 2.09 0.22 ATR KE 90 2.88 0.44 135 2.88 0.44 180 2.88 0.45 KF 90 1.57 0.35 135 1.54 0.32 180 1.57 0.32 MA KE 90 3.00 0.16 135 2.99 0.16 180 3.00 0.15 KF 90 1.58 0.21 135 1.58 0.19 180 1.59 0.20 * significant Atfiletic Group main effect (F=12.72, p< 0.001) * significant Muscle Group main effect (F=2395.85, p< 0.001) * nonsignificant Angular Velocity main effect (F=1.50, p> 0.20) FIGURE 4.7 Corrected Eccentric Torque Ecœntric Torque (Nm/kg of corr. BW) Muscle Group and Velocity (deg/sec-1) PA ATR MA 1 Corrected for %BW due to Skeletal Muscle Eccentric Torque (Nm/kg corr.) 3.20 3.00 2.80 2.60 2.40 2.20 2.00 1.80 1.60 1.40 KE KF PA 3.14 2.08 ATR 2.88 1.56 MA 3.00 1.58 Muscle Group PA ATR MA Averaged over angular velocity Knee F-E Ratios The means and standard deviations for the 3 ( a t h l e t i c groups) X 3 (angular velocity) X 2 (contraction type) repeated measures ANOVA for calculated concentric and eccentric KF-E ra t i o s can be located i n Table 4.6 and i s graphically repre-sented i n Figure 4 . 9 . This analysis found a s i g n i f i c a n t d i f -ference (F= 3 2 . 8 5 , p< 0 . 0 0 1 ) to exist between the three groups of subjects for t h e i r combined concentric and eccentric calcu-lated r a t i o s when averaged over the three l e v e l s of angular v e l o c i t y and two le v e l s of contraction types ('Xpj^ = 6 3 . 1 , Xj^ r[,j^ = 5 2 . 8 , XMA^ 5 1 . 2 ) . Post hoc analyses revealed that the PA group had combined concentric and eccentric KF-E r a t i o s that were greater than either the ATR or MA groups at the p< 0 . 0 1 l e v e l of s i g n i f i c a n c e while there were no s i g n i f i c a n t differences (p> 0 . 0 5 ) between those r a t i o s calculated for the MA and ATR groups. When averaged over the three groups of subjects and three angular v e l o c i t i e s there were s i g n i f i c a n t differences between concentric r a t i o s and those measured e c c e n t r i c a l l y (F= 4 2 . 7 4 , p< 0 . 0 0 1 ) . For a l l groups the concentric r a t i o s were lower than eccentric r a t i o s (XQQN" 5 3 . 7 , X£QQ= 5 7 . 7 ) . There were s i g n i f i c a n t differences between the three angular v e l o c i t i e s (F= 4 . 5 2 , p< 0 . 0 2 ) when averaged over the three groups of subjects and two contraction types (XgQ= 5 5 . 3 , ^ 1 3 5 " 5 5 , 5 , ^iQQ= 5 6 . 3 ) . Further Scheffé's analysis indicated that r a t i o s produced at 1 8 0 deg/sec"-'- were s i g n i f i c a n t l y greater (p< 0 . 0 5 ) than those produced for either 90 or 1 3 5 deg/sec"-^ while those produced for 90 and 1 3 5 deg/sec"-'- were not s i g n i f i c a n t l y d i f f e r e n t (p> 0 . 0 5 ) . S i g n i f i c a n t interactions included a contraction type X a t h l e t i c group (F= 4 . 1 8 , p< 0 . 0 3 ) and a contraction type X angular v e l o c i t y (F= 4 . 6 9 , p< 0 . 0 2 ) while the a t h l e t i c group X angular v e l o c i t y and the a t h l e t i c group X contraction type X angular v e l o c i t y interactions were not s i g n i f i c a n t . When averaged over the three angular v e l o c i t i e s the differences between concentric and eccentric r a t i o s were d i f f e r e n t among the three groups of subjects. While the ATR and MA groups produced si m i l a r r a t i o s both concentrically and e c c e n t r i c a l l y , the P A group r a t i o ' s were s i g n i f i c a n t l y greater e c c e n t r i c a l l y as compared to t h e i r concentric ra t i o s (XQQN-PA^ 5 9 . 9 , "XQQJ^. ATR= 5 1 . 5 , XQQjj_f^= 4 9 . 7 / XgQQ_p;^=66.7, ^ECC-ATK^ 5 4 . 1 , X^QQ_ 5 2 . 7 ) as displayed i n Figure 4 . 1 0 . Post hoc analysis revealed that XgQQ_pj^ was s i g n i f i c a n t l y greater than Xg^Q.^ipj^ and XgQ(-<_j^ at p< 0 . 0 1 , while ^con-FA s i g n i f i c a n t l y greater than XcoN-ATR ^CON-MA p< 0 . 0 1 . The s i g n i f i c a n t contraction type X angular v e l o c i t y i n t e r a c t i o n indicates that when averaged over the three sub-ject groups the difference i n the rati o s that were produced concentrically and e c c e n t r i c a l l y were s i g n i f i c a n t l y d i f f e r e n t between the three angular v e l o c i t i e s . As seen in Figure 4 . 1 1 , as the speed of contraction increased concentric r a t i o s increased while eccentric r a t i o s remained unchanged (X^oN90'^ 5 2 . 7 , XQON135'" 5 3 . 6 , XQQJJ^^sO"" ^^'"^ ^  ^ E C C 9 0 " 5 7 . 9 , Xg(-.c;|^ 35= 5 7 . 3 , XgQQ^BO" 5 7 . 9 ) . Pairwise comparison revealed that XÇ-QJ^^Q was s i g n i f i c a n t l y greater than XQQJJ^^QQ while X(~.QJ^J^35 was s i g -n i f i c a n t l y greater than X^QJ^-^QQ at the p< 0 . 0 1 l e v e l . TABLE 4.6 KF-E Ratios Athletic Group & Ang.Velocity Mean SD Contraction Type (deg/sec-1) PA CON 90 59.6 5.25 135 60.2 4.51 180 59.8 5.22 ECC 90 66.7 3.71 135 65.7 4.23 180 66.6 4.28 ATR CON 90 50.8 7.21 135 51.1 6.19 180 52.6 9.45 ECC 90 54.4 7.10 135 53.4 6.53 180 54.4 6.73 MA CON 90 47.8 6.14 135 49.5 5.82 180 51.7 6.07 ECC 90 52.6 5.38 135 52.8 5.24 180 52.7 5.85 * significant Athletic Group main effect (F=32.85, P< 0.001 ) * Significant Contraction Type main effect (F=:42.74, p< 0.001) * significant Angular Velocity main effect (F=4.52, p< 0.02) FIGURE 4.9 KF-E Ratios Ratio %(KF/KEx 100%) 68.0 -C90 135 180 E90 135 180 PA 59.6 60.2 59.8 66.7 65.7 66.6 ATR 50.8 51.1 52.6 54.4 53.4 54.4 MA 47.8 49.5 51.7 52.6 52.8 52.7 Contraction and Velocity (deg/sec-1) BB PA • • ATR EU MA FIGURE 4.10 Contraction Type x Athletic Group Interaction Ratio %(KF/KEx 100%) 68.0 66.0 64.0 62.0 60.0 58.0 56.0 54.0 52.0 50.0 48.0 46.0 ECCENTRIC CONCENTRIC PA ATR MA 66.7 54.1 52.7 59.9 51.5 49.7 Contraction Type PA — ^ ATR MA 1 Averaged over velocity FIGURE 4.11 Contraction Type x Angular Velocity Interaction 60.0 Ratio %(KF/KEx 100%) 59.0 58.0 57.0 56.0 55.0 54.0 53.0 52.0 1 1 1 90 135 180 ECCENTRIC 57.9 57.3 57.9 CONCENTRIC 52.7 53.6 54.7 Velocity (deg/sec-1) ECCENTRIC - t - CONCENTRIC Averaged over the three groups Correlations The c o r r e l a t i o n matrix can be seen i n Table 4.7, As hypothesized, the correlations between VO2 max and the a b i l i t y to produce torque; both concentric and eccentric, for the knee flexors and extensors averaged over the three groups of sub-jects, are negatively correlated and nonsignificant: r= -0.24 for CKE, -0.28 for CKF, -0.27 for EKE, and -0.24 for EKF; j - c r i t i c a l at o< 0.01, df= 57 = 0.33 for a l l c o r r e l a t i o n s . Also nonsignificant were the correlations between SMM (kg) and torque as produced concentrically and e c c e n t r i c a l l y by the KE and KF when averaged over the three groups: r= 0.02 for CKE, 0.29 for CKF, 0.02 for EKE, and 0.31 for EKF; j - c r i t i c a l at (AO.Ol, df= 57 = 0.33 for a l l c o r r e l a t i o n s . The s i g n i f i c a n t , moderately p o s i t i v e correlations between the a b i l i t y to produce torque and v e r t i c a l jumping a b i l i t y of r= 0.44 for CKE, 0.68 for CKF, 0.48 for EKE, and 0.74 for EKF suggests that the greater one's a b i l i t y to v e r t i c a l l y jump using the protocol as described previously the greater torque a person w i l l be able to generate using the methods as employed for t h i s study ( j ^ c r i t i c a l at<?(0.01, df= 57 = 0.33). TABLE 4.7 Correlation Matrix VER.JUMP V 0 2 MAK SMM CKE CKF EKE EKF VER.JUIVIP 1.00 V 0 2 MAX -0.35 1.00 SMM 0.49 -0.41 1.00 CKE 0.44 -0.24 0.02 1.00 CKF 0.68 -0.28 0.29 0.57 1.00 EKE 0.48 -0.27 0.02 0.86 0.56 1.00 EKF 0.74 -0.24 0.31 0.69 0.88 0.71 1.00 DISCUSSION This study was unique i n that torque was corrected not only for gravity before KF-E r a t i o s were calculated, but was corrected for the percent of an individual's body weight which could be accounted for by s k e l e t a l muscle mass. As such, the r e s u l t s obtained are d i f f e r e n t than what e a r l i e r research has reported. While previous studies have used a multitude of test protocols, only recently has work been performed which has analyzed the KE and KF a b i l i t y to produce i s o k i n e t i c eccentric torque. As well, for t h i s study, average torque was measured instead of the more often used measures of peak or angle s p e c i f i c torques. Kramer & MacDermid (1989) stated that peak torque can occur at d i f f e r e n t j o i n t angles and i s thus affected by angular v e l o c i t y and muscle action. Average torque, however, allows a more appropriate assessment i f the a b i l i t y of a muscle to produce force i s of i n t e r e s t . This study was performed with a two-fold purpose. The f i r s t was to examine both concentric and eccentric torques as produced by the flexors and extensors of the knee i n a manner which best simulated those muscle length-tension relationships found during running. The second purpose of t h i s study was to examine the differences i n a b i l i t y to produce torque between power athletes, aerobically trained runners, and moderately active persons i n an attempt to determine i f there are d i f f e r -ences between them. Group Differences Mentioned previously, subjects for t h i s study were grouped a f t e r v e r t i c a l jumping a b i l i t y and maximal oxygen consumption were measured. As anticipated, the PA group s i g n i f i c a n t l y outperformed the MA and ATR groups by 44.6% and 37.0% respec-t i v e l y when v e r t i c a l jumping a b i l i t y was assessed while these l a s t two groups d i d not s i g n i f i c a n t l y d i f f e r . These results correspond to what previous studies have reported for PA and ATR v e r t i c a l jumping differences (Melichna et a l . 198 9, Vandewalle et a l . 1987). When maximal aerobic capacity was measured the ATR group s i g n i f i c a n t l y outperformed the PA and MA groups. These l a s t two did not s i g n i f i c a n t l y d i f f e r . For t h i s study, the mean score for the ATR group was 64.4 ml/kg/min while Melichna et a l . found VO2 max for t h e i r endurance subjects to be 68 and Crie l a a r d & Pirnay (1981) reported 77.6 ml/kg/min for t h e i r subjects. VO2 max recorded for our PA group was also lower than what was reported by Crielaard & Pirnay and Melichna et a l . for t h e i r sprint/power athletes. They recorded values of 60 and 59 ml/kg/min respectively while the PA for t h i s study had a mean of 51.1 ml/kg/min and the MA subjects had a mean of 49.1. Anthropometric measurement of sk e l e t a l muscle mass revealed higher adipose tissue-free mass for the subjects of t h i s study than what was reported by Martin et a l . (1990). Martin et a l . (1990) reported cadaveric dissected muscle masses which ranged from 27.4% to 4 9.1% of the body mass i n older persons (> 50 years) and i n studies which corrected for adipose tissue these results ranged from 36.6% to 59.4%. They hypothe-sized that athletes who p a r t i c i p a t e d i n a c t i v i t i e s which requi-red strength would have res u l t s , as calculated by t h e i r pre-d i c t i o n equation, which were greater than what they reported. For t h i s study, PA were calculated to have a mean skel e t a l muscle mass of 52.4 kg while the means for the ATR and MA groups were 42.6 kg and 47.2 kg. When ske l e t a l muscle mass was divided by t o t a l body weight, r e s u l t i n g i n the percentage of body weight that could be accounted for by s k e l e t a l muscle mass these re s u l t s increased to 64.2, 60.3, and 58.6% for each of the PA, ATR, and MA groups. Martin et a l . (1990) reported that despite the l i m i t a t i o n s of having a cadaver sample, t h e i r proposed equation appears to provide the best estimate of s k e l e t a l muscle mass to date i n that i t i s the only cadaver-validated equation and i t gives values which are consistent with a l l known dissec t i o n data. The PA group of subjects were able to produce s i g n i f i c a n t -l y greater torque, both concentrically and e c c e n t r i c a l l y , than either the ATR or MA groups at a l l v e l o c i t i e s and for both muscle groups while there were no s i g n i f i c a n t differences between the ATR and MA groups for either contraction or between the two groups of muscle. This i s i n accordance with previous studies which have examined the differences i n torque produc-t i o n between s i m i l a r groups of subjects. The PA group per-formed s i g n i f i c a n t l y higher v e r t i c a l jumps than eith e r of the other two groups which, according to the 1989 study that was performed by Melichna and associates, indicates that t h e i r leg muscles have a predominantly higher percentage of Type II muscle f i b r e than the other groups. It has been reported ( C o s t i l l et a l . 1976, Melichna et a l . 1989, Thorstensson et a l . 1976b, Thorstensson et a l . 1977) that high lev e l s of Type II muscle fi b r e s are found i n e l i t e c a l i b r e athletes who compete i n s p r i n t i n g and jumping events and that these muscles are capable of producing high lev e l s of force at a l l angular v e l o c i t i e s . Gregor et a l . (1979) found that for t h e i r female subjects the sprinters were able to produce greater i s o k i n e t i c concen-t r i c torque than could the endurance group when the knee exten-sors were examined. Thorstensson et a l . (1976b) reported that i t i s reasonable to suggest that a high percentage of Type II muscle f i b r e i s one prerequisite for performing fast contrac-tions with appreciable tension outputs. Henneman et a l . (1965) and Olson & Swett (1966) provided a basis for Thorstensson and colleagues (197 6b) statement reporting that motor units con-t a i n i n g predominantly Type II muscle f i b r e have larger axons, higher conduction v e l o c i t i e s , and r e l a t i v e l y higher thresholds. Thorstensson et a l . (1977) reported that for t h e i r study, subjects with the lowest percentage of Type II f i b r e produced the lowest torque when angular v e l o c i t y was highest. There-fore, the amount of force which can be produced during fast contractions i s influenced by the amount of Type II f i b r e s i n muscle (Thorstensson et a l . 1976a, Thorstensson et a l . 1976b). It should thus be expected that individuals who are anaerobic-a l l y trained and of a high l e v e l of s k i l l to have greater percentages of Type II muscle fi b r e s i n t h e i r leg muscles allowing them to be able to produce greater torque than i n d i -viduals with a lesser percentage of Type II muscle f i b r e i n t h e i r leg muscles. As previously discussed i n the l i t e r a t u r e review, (see section Muscle f i b r e composition) the extent to which an i n d i v i d u a l i s endowed with Type I or II muscle fibres i s g e n e t i c a l l y determined. With t r a i n i n g , only the r e l a t i v e size of muscle fi b r e s w i l l be enhanced while minimal change to the composition of muscle f i b r e w i l l occur. Individuals who t r a i n aerobically w i l l have hypertrophied Type I muscle fibres while those t r a i n i n g anaerobically w i l l have Type II muscle fi b r e s which are enlarged although for either athlete the per-cent composition of f i b r e type which g e n e t i c a l l y occurs i n t h e i r muscles w i l l not change s i g n i f i c a n t l y . Concentric and Eccentric Contractions This study further supports previous research (Bennett & Stauber 1986, Ghena et a l . 1991, Highgenboten et a l . 1988, Kramer & MacDermid 1989, Maclntyre & Wessel 1988, Poulin et a l . 1992, Tredinnick & Duncan 1988, Westing et a l . 1988, Worrell et a l . 1991) finding that eccentric torque was s i g n i f i c a n t l y greater than concentric torque for each of the three groups of subjects at a l l v e l o c i t i e s , and for both groups of muscles. It has been reported elsewhere (Asmussen 1952, Kaneko & Komi 1984, Komi 1973a, Rodgers & Berger 1974) that eccentric muscle actions are more e f f i c i e n t than concentric muscle actions, using less oxygen than do concentric contractions of comparable muscle unit a c t i v i t y . Stauber (1989) also stated that greater p h y s i o l o g i c a l cost occurs during concentric contractions than for work performed e c c e n t r i c a l l y , t h i s difference becoming greater as v e l o c i t y of contraction increases. It was Stauber i n his review of eccentric muscle actions who reported that there are two mechanisms, which during eccentric work, reduce energy expenditure these being: 1) altered recruitment of motor units (increased EMG) and 2) decreased energy u t i l i z a t i o n of active muscles which develop tension while being stretched. Asmussen (1952) stated that during eccentric contractions fewer motor units are employed to produce a contraction than what i s required for concentric contractions. Thus, when a muscle i s f u l l y activated i t i s able to produce more torque e c c e n t r i c a l l y than concentrically providing s i m i l a r muscle length-tension relationships e x i s t . Rodgers & Berger (1974) and Walmsley et a l . (1986) both c i t e d several references which also stated that greater levels of tension occurred eccentric-a l l y than what occurs for either isometric or concentric con-traction s at the same joi n t angle. Asmussen (1952) and Komi (1973a) have further stated that the difference i n the a b i l i t y to produce force between concentric and eccentric contractions i s v e l o c i t y dependent. If v e l o c i t y of contraction increases maximal eccentric force w i l l also increase while maximal con-ce n t r i c force decreases. Therefore, the faster muscle con-t r a c t i o n occurs the greater the difference between eccentric and concentric work while corresponding muscle unit a c t i v i t y (EMG) remains f a i r l y constant (Komi 1973b). It was found for t h i s study, when averaged over the three groups of subjects, the average i s o k i n e t i c concentric torque that was produced s i g n i f i c a n t l y decreased for both the KE and KF as angular v e l o c i t y increased. H i l l ' s i n i t i a l force-v e l o c i t y (F-V) research on i s o l a t e d animal muscle found that during concentric work the force which could be applied to move an object decreased as speed of contraction increased. This would continue to occur u n t i l a v e l o c i t y was reached where even an unloaded muscle could not shorten. For eccentric work the opposite was true; with an increase i n the speed of contraction the force which could be applied also increased to a certa i n point where i t would then l e v e l o f f . Many studies examining F-V relationships have attempted to compare t h e i r r e s u l t s to those reported by H i l l . Research examining concentric F-V relationships found that as contrac-t i o n v e l o c i t y increased the force that was produced decreased as found by H i l l (Asmussen et a l . 1965, Fillyaw et a l . 1986, Gi l l i a m et a l . 1979, Holmes & Alderink 1984, Komi 1973, Oberg et a l . 1986, Sanderson et a l . 1984, Smith et a l . 1981, Stafford & Granna 1984, Thorstensson et a l . 1977, Wyatt & Edwards 1981). It has been hypothesized that such a decline could be due to a decrease i n the amount of time for motor f i b r e recruitment (Rodgers & Berger 1974), muscle f i b r e composition (Poulin et a l . 1992, Thorstensson et a l . 1977), or muscle a c t i v i t y l e v e l (Thorstensson et a l . 1977). Ghena et a l . (1991) also reported that others believe gender may play a role i n the reduction of concentric force with increasing angular v e l o c i t y . Studies which have also analyzed eccentric F-V r e l a t i o n -ships have reported mixed r e s u l t s . That i s not a l l have found eccentric torque to increase as the v e l o c i t y of contraction increases. Walmsley et a l . (1986) found that eccentric wrist extensor torque s i g n i f i c a n t l y increased while Tredinnick & Duncan (1988) found that for males knee extensor eccentric torque increased very s l i g h t l y from 60 to 180 deg/sec"-^. Worrell et a l . (1991) found increasing knee extensor and flexor eccentric torque with increasing angular v e l o c i t i e s i n univer-s i t y athletes from 60 to 180 deg/sec"^. Westing et a l . (1988) reported that when voluntary maximal eccentric contractions of the knee extensors were measured i s o k i n e t i c a l l y at 30 through 270 deg/sec"-*- torque did not s i g n i f i c a n t l y increase with increasing angular v e l o c i t y while Westing et a l . (1990) again reported that knee extensor eccentric torque did not appreci-ably increase at test v e l o c i t i e s of 60, 180, and 360 deg/sec"-'-. Eccentric torque produced by the three groups of subjects i n t h i s study did not d i f f e r s i g n i f i c a n t l y , remaining f a i r l y constant for both the KE and KF as v e l o c i t y of contraction increased. Eloranta & Komi (1980) found eccentric torque to be greater than concentric torque i n the knee extensors of college males, however, no s i g n i f i c a n t differences i n eccentric torque between v e l o c i t i e s were found. Kramer & MacDermid (1989) reported that for t h e i r female subjects concentric knee exten-sor torque s i g n i f i c a n t l y declined as angular v e l o c i t y increased while eccentric torque showed only a 3-5% variance which d i d not s i g n i f i c a n t l y d i f f e r at v e l o c i t i e s between 45 and 180 deg/sec"-*-; increasing very s l i g h t l y , plateauing, or decreasing. They further stated that t h i s was i n agreement with several previous studies which examined both the knee and elbow. Jorgensen (1976), and Hanten & Ramberg (1988) both reported that eccentric torque increased and then decreased for t h e i r subjects. C o n f l i c t i n g F-V results were also reported by Ghena et a l . (1991) and Poulin et a l . (1992). Poulin et a l . found eccentric torque to decrease i n t h e i r younger male subjects from 90 to 180 deg/sec"-'-, but increased for t h e i r older male subjects. They reported several other studies which have also found concentric peak torque to decrease while eccentric peak torque increased s l i g h t l y or plateaued. Ghena and colleagues (1991) found no s i g n i f i c a n t differences to exi s t i n t h e i r male sub-ject's a b i l i t y to produce eccentric torque for both the knee extensors and flexors at angular v e l o c i t i e s of 60 and 120 deg/sec"-'-. Westing et a l . (1988) performed a study which examined eccentric and concentric F-V c h a r a c t e r i s t i c s of male knee extensors. They had subjects perform maximal voluntary, elec-t r i c a l l y stimulated, and a combination of both types of con-traction s during isometric, concentric, and eccentric actions. They also reported that eccentric torque did not increase with corresponding increases i n angular v e l o c i t y . It was reported that a combination of e l e c t r i c a l stimulation and maximal v o l -untary contraction produced the greatest amount of force while force recorded during e l e c t r i c stimulation alone best resembled the F-V model. The lowest force recorded occurred when maximal voluntary contractions were measured without accompanying stim-u l a t i o n . They suggested that the f a i l u r e for eccentric torque to s i g n i f i c a n t l y increase with increases i n angular v e l o c i t y could be due to a neural mechanism becoming active during max-imal contractions of i n s i t u muscle which r e s t r i c t s the muscle's a b i l i t y to produce maximal tension. They reported that such a t e n s i o n - r e s t r i c t i n g mechanism has been suggested to maintain a "safe" maximal l e v e l of tension during isometric and low v e l o c i t y contractions. In a 1990 study by Westing et a l . , they hypothesized that e l e c t r i c a l stimulation of a muscle would be si m i l a r to the pro-posed F-V studies performed on i s o l a t e d animal muscle. This would explain why the e l e c t r i c a l stimulation contraction they measured i n t h e i r subjects resembled the o r i g i n a l F-V curve i n t h e i r 1988 study. By performing such a contraction many neural interactions at the spinal l e v e l are bypassed. Once again r e s u l t s s i m i l a r to t h e i r e a r l i e r study were obtained. They concluded that i t i s indeed possible that neural i n h i b i t i o n could be p a r t i a l l y responsible for causing the f l a t t e n i n g of the eccentric torque curve during maximal voluntary contrac-t i o n , that i s eccentric torque not increasing with increasing v e l o c i t y . Stauber (1989) also mentioned that eccentric force recorded for i n s i t u t e s t i n g i s lower than an i s o l a t e d muscle stimulated e l e c t r i c a l l y thus a neural mechanism must be present which helps to protect muscle from injury. Other factors which have been mentioned as possibly being related to eccentric torque not increasing with corresponding increases i n angular v e l o c i t y include subject po s i t i o n i n g during data c o l l e c t i o n . Previous work has almost exclusively examined torque measurements with subjects i n either a s i t t i n g or semi-reclined p o s i t i o n for t e s t i n g of both the knee exten-sors and flexors (Bohannon et a l . 1986, Currier 1977, Worrell et a l . 1989). For t h i s study subjects were examined with a hip angle of 10° i n a prone (KF) or supine (KE) p o s i t i o n and were not allowed to grasp any hand r a i l s for further support. Another hypothesis as to why there has been a c o n f l i c t with the eccentric F-V rel a t i o n s h i p i s a lack of subject famil-i a r i t y with eccentric contractions which are produced under test conditions. Several studies, including the present one, have reported that they c o l l e c t e d data with the only form of f a m i l i a r i z a t i o n consisting of pre-test repetitions which were performed immediately p r i o r to data c o l l e c t i o n . Subjects for t h i s study commented that performing t h i s computer-controlled contraction was the most d i f f i c u l t portion of the study. Several needed extra practice t r i a l s before they were comfor-table with t h i s section of the t e s t . I f a practice session was performed less than a week p r i o r to data c o l l e c t i o n then sub-ject f a m i l i a r i t y with producing controlled eccentric contrac-tions on an i s o k i n e t i c dynamometer might r e s u l t i n better s i m i l a r i t y to the force-velocity curve. Walmsley et a l . (1986) have suggested that a f a i l u r e for eccentric torque to increase with increasing angular v e l o c i t y i s perhaps due to d i f f e r e n t test v e l o c i t i e s and/or d i f f e r e n t muscle groups tested. However, Hinson (1976), as reported by Kramer & MacDermid (198 9) suggested that during i s o k i n e t i c i n s i t u t e s t i n g the j o i n t ' s angular v e l o c i t y i s constant but the li n e a r v e l o c i t y of the muscle action i s not. Therefore, only general comparisons should be made between human i s o k i n e t i c t e s t i n g and the F-V relat i o n s h i p because c l i n i c a l responses to changes i n angular v e l o c i t y are more important than comparison to the c l a s s i c model. F i n a l l y , Chapman (1985) reported that although the F-V rela t i o n s h i p as proposed by H i l l has not been v e r i f i e d as being un i v e r s a l l y applicable for a l l muscle groups within the human body, there i s evidence which suggests that some form of the F-V relationship, the resu l t of a combination of separate i n t r i n -s i c F-V relationships within the muscle group, does e x i s t . He further stated that the F-V relat i o n s h i p can never be t r u l y viewed as fundamental since many of the conditions under which i t i s tested apparently modify the relat i o n s h i p which include force length relationships, l e v e l of muscle act i v a t i o n , p r i o r state of muscle contraction, and the role that d i f f e r e n t f i b r e types have i n muscular contraction. Knee Extensor and Flexor Torque As hypothesized, the knee extensors of a l l three subject groups produced s i g n i f i c a n t l y greater concentric and eccentric torque than the knee flexors at each test v e l o c i t y examined. These r e s u l t s a r e s u p p o r t e d by t h e p a s t f i n d i n g s o f Ghena e t a l . (1991), H a r d i n g e t a l . (1988), Highgenboten and c o l l e a g u e s (1988), K l o p f e r & G r e i j (1988), P i e t e r e t a l . (1989), Sanderson e t a l . (1984), and Smith e t a l . (1981). P i e t e r e t a l . (1989) s t a t e d t h a t one s h o u l d expect KE t o r q u e t o be g r e a t e r t h a n KF t o r q u e c o n s i d e r i n g i t has a l a r g e r muscle mass. One s t u d y , however, has r e p o r t e d t h a t t o r q u e p r o d u c e d by t h e KF exceeded t h a t o f t h e KE. K l o p f e r & G r e i j , whose s t u d y was p e r f o r m e d c o n c e n t r i c a l l y u s i n g a n g u l a r v e l o c i t i e s o f 300 deg/sec"-'- and g r e a t e r on t h e B i o d e x B-2000 i s o k i n e t i c dyna-mometer, r e p o r t e d t h a t f o r t h e i r u n t r a i n e d female s u b j e c t s , KF t o r q u e was g r e a t e r t h a n t h a t f o r t h e KE a t each t e s t v e l o c i t y . They found t h a t KF t o r q u e a c t u a l l y i n c r e a s e d w i t h i n c r e a s i n g a n g u l a r v e l o c i t i e s . S e v e r a l s u g g e s t i o n s were o f f e r e d as t o why t h i s o c c u r r e d i n c l u d i n g t h a t d u r i n g t h e e x t e n s i o n phase o f e x e r c i s e t h e r e i s an i n c r e a s e i n KF a c t i v i t y w h i c h o c c u r s as t h e r e s u l t o f an attempt t o slow t h e l o w e r l e g d u r i n g t h e e x t e n s i o n phase o f e x e r c i s e (See l i t e r a t u r e r e v i e w : Analysis of Running Motion). K l o p f e r & G r e i j h y p o t h e s i z e d t h a t i f t h e knee f l e x o r s were composed p r e d o m i n a n t l y o f Type I I muscle f i b r e t h e n an i n c r e a s e i n t h e amount o f t o r q u e which c o u l d be p r o d u c e d w i t h i n c r e a s e i n v e l o c i t y may be e x p e c t e d . C o n v e r s e l y , i f knee e x t e n s o r s were p r e d o m i n a n t l y c o m p r i s e d o f Type I f i b r e s t h e n a d e c r e a s e i n t o r q u e p r o d u c t i o n w i t h an i n c r e a s e i n v e l o c i t y may be e x p e c t e d which i s s u p p o r t e d by t h e work o f T h o r s t e n s s o n e t a l . (1977) . This i s a very unique finding i n that i t i s the only study to report torque produced by the KF to exceed that capable by the KE. One other possible factor which might explain t h i s result i s the fact that t h e i r untrained female subjects per-formed concentric contractions at v e l o c i t i e s of contraction which are not commonly examined. As well, remembering the statement by Ghena et a l . (1990), i t i s believed that there i s a gender difference i n the rate at which concentric torque decreases as the v e l o c i t y of contraction increases. The r e s u l t s which were measured for the KE of a l l three groups were higher than anticipated considering the supine test p o s i t i o n which was used. As mentioned previously, several studies have examined the differences i n the a b i l i t y to produce torque from seated, semi-reclined, and/or supine positions. Worrell et a l . (1989) reported that torque produced by the knee extensors i n a seated p o s i t i o n (80° of hip flexion) was s i g n i f -i c a n t l y greater than what was recorded from a supine t e s t p o s i t i o n (10° hip f l e x i o n ) . Worrell et a l . (1989) further stated that the optimal length-tension r e l a t i o n s h i p of the rectus femoris muscle occurs between 50 and 80° of hip f l e x i o n . Any p o s i t i o n less than 50° or greater than 90° does not provide an optimal r e l a t i o n s h i p and w i l l thus re s u l t i n a decrease i n the amount of torque which i s produced. Currier (1977) reported s i g n i f i c a n t differences between a seated and semi-reclined position, however, Bohannon et a l . (1986) did not. Bohannon and colleagues found that no s i g n i f -leant differences existed i n the torque produced from positions of 30 and 80° of hip flex i o n for the KE. They reported that possible differences between t h e i r study and that performed by Currier were due to d i f f e r e n t subject s t a b i l i z a t i o n techniques. Their subjects were not permitted to grasp handles while Currier's subjects were allowed t h i s method of s t a b i l i z a t i o n . For the present study, subjects were examined for KE torque i n a supine position of 10° hip fle x i o n , not the optimal length-tension r e l a t i o n s h i p as suggested by Worrell et a l . (1989), and were not permitted to grasp the handles. However, instead of using an arb i t r a r y pre-load force of 25 or 50N as some studies have done (Bennett & Stauber 1986, Hageman et a l . 1988, Tredinnick & Duncan 1988, Worrell et a l . 1990, Worrell et a l . 1991), 75% of a subject's MVIC was used to determine the pre-load force l e v e l . Jensen et a l . (1991) reported that a 75% MVIC pre-load helped to reduce any affe c t that p o s i t i v e or negative acceleration may have had i n influencing torque. Further reference to Jensen and colleagues work can be located i n the "Faults with previous research" section of the l i t e r -ature review. The author believes that the higher than a n t i c i -pated r e s u l t s for the knee extensors may be accounted for due to the use of t h i s high l e v e l of pre-load as well as the d i f -ferent methods of s t a b i l i z a t i o n . Several authors have reported that as the v e l o c i t y of con-t r a c t i o n increases the amount of torque that can be produced concentrically decreases at a much faster rate for the KE than for the KF (Ghena et a l . 1991, Hageman et a l . 1988, Holmes & Alderink 1984, Klopfer & Greij 1988, Oberg et a l . 1986, Stafford & Granna 1984) . The results of t h i s study support e a r l i e r research also finding that during concentric contractions KE torque decreases at a greater rate than does KF with increasing angular v e l o c i -ty, however KF torque did not exceed KE torque. When the rate of decline between angular v e l o c i t i e s was examined i t was found that MA and PA groups demonstrated si m i l a r l e v e l s of decline with increasing angular v e l o c i t y when concentric torque was measured for the KE while the ATR group had the least amount of decline. When analyzing the differences between 90 to 135 deg/sec"-^ the MA group of subjects demonstrated the greatest decline i n KE concentric torque: 0.20 Nm/kg corr., while the ATR and PA groups rate of decline was measured to be 0.17 and 0.16 Nm/kg corr. respectively. When differences i n KE torque were analyzed between the test v e l o c i t i e s of 135 and 180 deg/sec"-^ the PA group demonstrated the greatest rate of decline (0.26 Nm/kg corr.) while the MA and ATR groups declined only 0.22 and 0.19 Nm/kg corr. respectively. As for the rate of decline when KF torque was evaluated between the angular v e l o c i t i e s of 90 and 135 deg/sec"-*- the ATR group showed only a s l i g h t l y greater rate (0.09 Nm/kg corr.) than did the PA group (0.08 Nm/kg corr.) while the MA group only decreased 0.05 Nm/kg corr.. Decline i n the measured con-c e n t r i c KF torque between 135 and 180 deg/sec"-*- was greatest for the PA at 0.17 Nm/kg corr. while the ATR and MA groups dem-onstrated a decline of 0.1 and 0.08 Nm/kg corr. respectively. Garrett (1983) reported that the KF are known to have r e l a t i v e l y high le v e l s of Type II muscle f i b r e and are involved i n intense contractions. Polgar et a l . (1973), who examined the composition of percent muscle f i b r e i n several d i f f e r e n t muscles, also stated that the KF have a high percentage of Type II f i b r e and further suggested that these muscles are more involved with exercise of high i n t e n s i t y and force production. Thus i f the KF have higher le v e l s of Type II muscle f i b r e than the KE they are more capable of producing greater torque at high v e l o c i t i e s of contraction as compared to the KE. Thorstensson et a l . (1976b) reported that motor units which recorded higher tension outputs and shorter contraction times were shown to contain a greater percentage of Type II f i b r e as compared to Type I muscle f i b r e i n t h e i r subjects. With t h i s knowledge that during concentric contractions torque produced by the KE decreases at a greater rate than for the KF further explanation of the res u l t s reported by Klopfer & Greij (1988) can occur. It i s conceivable that for t h e i r p a r t i c u l a r group of untrained females, beginning at the angular v e l o c i t y of 300 deg/sec"-'- there i s a change i n which group of muscles can produce the greatest torque; from KE to KF, thus explaining why recorded concentric KF torque was greater than that produced by the KE. KF-E Ratios S i g n i f i c a n t l y greater concentric and eccentric KF-E ra t i o s were found to exist between the PA group and both the MA and ATR groups of subjects while the ra t i o s produced by these l a s t two groups were not s i g n i f i c a n t l y d i f f e r e n t from each other. The author suggests that higher KF-E ra t i o s may be required by PA athletes to compete successfully as well as to prevent injury. Unfortunately much of the previous research which examined KF-E r a t i o s has f a i l e d to correct for gravity. This error r e s u l t s i n an i n f l a t e d r a t i o as reported by Fillyaw et a l . (1986) and Sanderson et a l . (1984) when both the knee flexors and extensors are examined i n a supine p o s i t i o n . Thus, uncor-rected studies can not be used to develop standards which aid the athlete, coach, and/or physiotherapists i n determining i f an i n d i v i d u a l i s capable of withstanding those forces s p e c i f i c to t h e i r a c t i v i t y or i f they are at r i s k for future possible injury. The present study performed was unique i n that the KF-E r a t i o s , l i k e measured concentric and eccentric torque, were not calculated using s o l e l y the torque values measured or torque corrected for in d i v i d u a l body weight, but was corrected for the percent of an indiv i d u a l ' s body weight which could be accounted for by s k e l e t a l muscle mass. For each of the three groups of subjects i n t h i s study the concentric KF-E ra t i o s were s i g n i f i c a n t l y lower than those calculated for eccentric contractions. This was e s p e c i a l l y seen i n t h e PA group where t h e d i f f e r e n c e between c o n c e n t r i c and e c c e n t r i c KF-E r a t i o s was on average 6% w h i l e d i f f e r e n c e s f o r each o f t h e o t h e r two groups was between 1 and 5%. I t i s s u g g e s t e d by t h e a u t h o r t h a t because power a t h l e t e s a r e r e q u i -r e d t o p e r f o r m a t h i g h v e l o c i t i e s o f movement and a r e a t t i m e s r e q u i r e d t o p e r f o r m so t h a t h i g h e x t r i n s i c l o a d s a r e p l a c e d upon them l a r g e e c c e n t r i c KF-E r a t i o s a r e r e q u i r e d t o adequate-l y p e r f o r m and do so w i t h o u t i n j u r y . Such f i n d i n g s have been r e p o r t e d e l s e w h e r e (Ghena e t a l . 1991, Highgenboten e t a l . 1988). Highgenboten e t a l . (1988) r e p o r t e d c o n c e n t r i c r a t i o s o f 54% f o r t h e i r u n t r a i n e d young males (15-24 y e a r s ) , 51% f o r t h e i r o l d e r male s u b j e c t s (25-34 y e a r s ) and e c c e n t r i c r a t i o s o f 60% f o r b o t h groups when examined a t 50 deg/sec"-*-. Ghena e t a l . (1991) found e c c e n t r i c r a t i o s o f 64.6% and 65.0% a t 60 and 120 deg/sec"-*- r e s p e c t i v e l y w h i l e c o n c e n t r i c r a t i o s were 55.3, 57.7 a t 60 and 120 deg/sec"•*• i n c r e a s i n g t o 60.9 and 80.4% a t t e s t v e l o c i t i e s o f 300, and 450 deg/sec"-*- f o r t h e i r s u b j e c t s who were male u n i v e r s i t y a t h l e t e s c ompeting i n a v a r i e t y o f s p o r t s . U n f o r t u n a t e l y t h e y were not a b l e t o measure e c c e n t r i c r a t i o s a t a n g u l a r v e l o c i t i e s g r e a t e r t h a n 120 deg/sec"-*- due t o equipment r e s t r i c t i o n s . One f i n d i n g w h i c h has been common t o n e a r l y e v e r y s t u d y e x a m i n i n g KF-E r a t i o s i s f o r c o n c e n t r i c r a t i o s t o i n c r e a s e as t h e v e l o c i t y a t wh i c h t h e y are c a l c u l a t e d f o r i n c r e a s e s (Ghena e t a l . 1991, K l o p f e r & G r e i j 1988, Sanderson e t a l . 1984). T h i s r i s i n g c o n c e n t r i c t o r q u e r a t i o can be e x p l a i n e d by p a s t f i n d i n g s w h i c h r e p o r t e d t h a t KE t o r q u e d e c l i n e s a t a more r a p i d rate than KF torque during concentric contractions. Thus, there i s less of a difference between the two muscle groups as v e l o c i t y increases and the calculated r a t i o w i l l be greater than at a lesser angular v e l o c i t y . It would be of great inter e s t to t h i s f i e l d of research i f a study was performed which examined the hamstring MSI athlete population to see i f they demonstrated a higher difference and i f so how t h i s might be associated with hamstring MSI. The r e s u l t s of the concentric KF-E r a t i o s , for t h i s study, support the previous research which found KF-E r a t i o s to r i s e as angular v e l o c i t y increased for both the MA and ATR groups, however, the PA group's concentric r a t i o s remained r e l a t i v e l y unchanged. This would suggest that, for the PA group, the amount of decline i n concentric torque production for both the KE and KF was approximately s i m i l a r . This i s l o g i c a l because e l i t e sprint athletes have been shown to have higher lev e l s of Type II muscle f i b r e i n a l l leg muscles as reported by Thorstensson et a l . (1977). It i s therefore possible that for t h i s group of subjects, the KE and KF had s i m i l a r percentages of Type II f i b r e s . Only two studies to date have reported gravity corrected eccentric r a t i o s (Ghena et a l . 1991, Highgenboten et a l . 1988) and unfortunately only one at d i f -f e r i n g v e l o c i t i e s . Ghena et a l . (1991) found a very small increase in the eccentric r a t i o produced for t h e i r subjects using v e l o c i t i e s of 60 and 120 deg/sec"-*-. The eccentric KF-E r a t i o s remained steady across angular v e l o c i t i e s for each of the three groups i n t h i s study because eccentric torque for each group's KE and KF d i d not d i f f e r as v e l o c i t y increased, c o n f l i c t i n g with the forc e - v e l o c i t y r e l a -t i o n s h i p . A r i s e i n the eccentric KF-E r a t i o as angular v e l o c i t y increased would require torque produced by the knee flexors to increase at a greater rate than for the knee exten-sors. Stanton & Purdam (1989) f e l t that sprinters which sus-tained hamstring MSI had lower knee flexor eccentric torque e s p e c i a l l y at higher angular v e l o c i t i e s . Thus t h i s may be an area where persons prone to hamstring MSI are d e f i c i e n t or display a degree of asymmetry. Both the concentric and eccentric r a t i o s found for t h i s study are quite s i m i l a r to those reported by Ghena et a l . (1991) when the power and endurance groups are averaged to-gether as was the case for t h e i r study. The MA KF-E r a t i o s calculated for t h i s study were s l i g h t l y higher than those reported by Sanderson et a l . (1984) for t h e i r sedentary sub-j e c t s : concentric KF-E ra t i o s for males to be 44 and 48% at test v e l o c i t i e s of 60 and 180 deg/sec"-*- respectively while t h e i r female subjects had rati o s of 39 and 42% respectively at the same v e l o c i t i e s . The moderately active r e s u l t s were, however, much lower than what Klopfer & Greij (1988) reported for both t h e i r male and female subjects. Klopfer & Greij calculated untrained males KF-E ra t i o s at angular v e l o c i t i e s of 300, 330, 360, 400, and 450 deg/sec"^. They found that these concentric r a t i o s were 72.9, 84.1, 82.8, 85.5, and 97.1% respectively. For t h e i r untrained females r a t i o s of 110, 108, 112, 114, and 108% were found to exist at the same v e l o c i t i e s . KF-E r a t i o s a t b o t h v e l o c i t i e s were found t o be s i m i l a r t o what was r e c o r d e d f o r our endurance group, t h u s b e i n g much l o w e r t h a n what was found t o e x i s t f o r our power s u b j e c t s . Highgenboten e t a l . (1988), whose e c c e n t r i c r e s u l t s were r e p o r -t e d e a r l i e r , found e c c e n t r i c KF-E r a t i o s w h i c h were ap p r o x i m a t -e l y 7% h i g h e r when examined a t 60 deg/sec"-*- as compared t o our MA group whose r a t i o s ranged from 52.6 t o 52.8 a t v e l o c i t i e s o f 90-180 deg/sec"^. P r e v i o u s l i t e r a t u r e has s u g g e s t e d t h a t t h e KF-E r a t i o s measured can be a f f e c t e d by age (Ghena e t a l . 1991, Weltman e t a l . 1988), s k i l l l e v e l and r e s p e c t i v e t r a i n i n g w h i c h accomp-a n i e s a h i g h l e v e l o f s k i l l (Oberg e t a l . 1986), p o s i t i o n p l a y e d ( G i l l i a m e t a l . 1979), v e l o c i t y o f c o n t r a c t i o n (Holmes & A l d e r i n k 1984, W o r r e l l e t a l . 1989), gender (Komi & B u s k i r k 1972, Rodgers & B e r g e r 1974), and h i p p o s i t i o n ( W o r r e l l e t a l . 1989). G i l l i a m e t a l . (1979) p r o p o s e d t h a t each i n d i v i d u a l has a s e p a r a t e and d i s t i n c t KF-E r a t i o w h i c h i s " i d e a l " f o r them dependent upon p h y s i c a l c h a r a c t e r i s t i c s , s p o r t o f p a r t i c i p a t i o n and p o s i t i o n . S i g n i f i c a n c e o f KF-E Asymmetry S e v e r a l s t u d i e s have a t t e m p t e d t o a s s o c i a t e h a m s t r i n g muscle s t r a i n i n j u r y and KF-E asymmetry/imbalance. H e i s e r e t a l . (1984) found t h a t i n c o l l e g e f o o t b a l l p l a y e r s a d r a m a t i c r e d u c t i o n i n h a m s t r i n g i n j u r i e s o c c u r r e d f o l l o w i n g a s p e c i a l l y d e s i g n e d p r o p h y l a c t i c r e h a b i l i t a t i o n program w h i c h i n c r e a s e d every player's KF-E r a t i o to at least 60%. Burkett (1970), i n p r e d i c t i n g hamstring MSI i n professional f o o t b a l l players and track athletes, found that an asymmetry of greater than 10% between the right and l e f t knee flexors resulted i n a greater occurrence of hamstring MSI and further stated that a reduction i n knee extensor and flexor strength differences would be useful i n the prevention of hamstring s t r a i n s . In a larger, retrospective study Knapik et a l . (1991) reported that lower extremity injury was more prevalent i n t h e i r female c o l l e g i a t e athletes i f 1) a difference of 15% or greater existed between the right and l e f t knee flexors when examined at 180 deg/sec"^ and 2) i f a KF-E r a t i o of less than 75% was present when calculated at 180 deg/sec"-*-. A l l of these studies and others have reported d i f f e r e n t KF-E r a t i o s which should be maintained for injury prevention (See l i t e r a t u r e review: KF-E Assessment). Because few studies agree on normative r a t i o s which should e x i s t i n attempts to prevent injury perhaps KF-E r a t i o s are indeed sport and/or po s i t i o n s p e c i f i c as suggested by G i l l i a m et a l . (1979) and Holmes & Alderink (1984). More research needs to be performed which examines not only the association between KF-E muscle asymmetry and hamstring muscle s t r a i n injury i n larger samples l i k e the Knapik et a l . study but also the e f f e c t of between leg asymmetry. This work, however, needs to be performed with consideration to simulating length-tension relationships spe-c i f i c to that sport i n which the measured KF-E r a t i o s are to be associated with. As well, research should be performed to investigate i f KF-E r a t i o s can be changed with t r a i n i n g over a period of time. To date no study has examined the e f f e c t s of t r a i n i n g on KF-E r a t i o s . Goal of Rehabi l i t a t i o n Considering that few v a l i d studies have been performed which investigate uninjured athletes encompassing a variety of ages, weights, sports/positions, and gender an accurate r e l a -tionship between KF-E r a t i o s and r e h a b i l i t a t i o n can not occur. As well, current i s o k i n e t i c dynamometers are not capable of achieving the angular v e l o c i t i e s which are present during a t h l e t i c competition. Thus no one i s d e f i n i t e as to how individuals respond to such v e l o c i t i e s under test conditions. Further investigation of eccentric knee extensor and flexor torque and t h e i r r a t i o s must be undertaken which exam-ines d i f f e r e n t groups of athletes considering the lack of research which examines eccentric muscle actions. Eccentric and concentric research, i f the res u l t s are to be compared to the forces present during competition such as the running motion, need to be performed i n a manner which c l o s e l y approx-imates the knee extensor and flexor length-tension r e l a t i o n -ships that are present during running. Many previous studies have not considered examining KE and KF i n positions which simulate length-tension relationships s i m i l a r to those which occur during running even though they r e l a t e t h e i r r e s u l t s to athletes who compete i n a c t i v i t i e s which these relationships occur. This must be performed i f the res u l t s are to be used as a database to aid coaches, trainers, and/or physiotherapists i n determining i f an athlete i s prepared to withstand the forces experienced during t h e i r p a r t i c u l a r sport. This investigation has revealed several questions which must be answered concerning the r e h a b i l i t a t i o n of a hamstring muscle s t r a i n injured athlete which include: la) Should we aim for less of a decline i n torque as angular v e l o c i t y increases? b) Is a decline i n torque with increasing angular v e l o c i t y related to the incidence of hamstring MSI? 2) Should we aim for an increase i n the KF-E r a t i o to l e v e l s beyond those established for s i m i l a r individuals? 3a) What role does the eccentric KF/E r a t i o play? b) Should a high eccentric r a t i o be achieved and maintained? U n t i l such investigation has been performed the practice of using KF-E r a t i o s and i n d i v i d u a l muscle torque scores to assess the progress and readiness of an athlete during r e h a b i l -i t a t i o n i s speculative. Knee F-E r a t i o s , however, cannot be considered as being the only factor which dictates whether or not an i n d i v i d u a l w i l l sustain a hamstring MSI. The effect(s) of muscular fatigue, f l e x i b i l i t y , and asynchronous neural stimulation of i n d i v i d u a l muscles within a muscle group, i n combination, or associated with a KF-E asymmetry must also be considered as having some rel a t i o n s h i p with the incidence of hamstring MSI. Therefore, research must also be performed which examines these possible factors. Although much has been discovered about the way i n which muscle functions during a t h l e t i c a c t i v i t y there s t i l l remains many unanswered questions as to how events such as muscle s t r a i n i n j u r i e s of the hamstring muscle complex occur. It i s only through comprehensive research that these questions w i l l be answered. Chapter 5 SUMMARY AND CONCLUSIONS Summary The main purpose of t h i s study was to examine the r e l a t -ionship between concentric and eccentric torque as produced by the knee flexors and extensors over three d i f f e r e n t v e l o c i t i e s of contraction i n three d i f f e r e n t groups of subjects: power athletes, a e r o b i c a l l y trained athletes, and moderately active i n d i v i d u a l s . Sixty subjects were separated evenly among the three groups following p h y s i o l o g i c a l assessment consisting of the v e r t i c a l jump and VO2 max t e s t s . Anthropometric measurements were taken to estimate the sk e l e t a l muscle mass for each subject and i s o k i n e t i c concentric and eccentric torque was measured at 90, 135, and 180 deg/sec"-*- for each of the knee extensors and fl e x o r s . For both muscle groups, t e s t i n g was performed with 10° of hip flexion, the knee extensors examined i n a supine test p o s i t i o n while the knee flexors were assessed for torque production i n a prone p o s i t i o n . Isokinetic t e s t i n g results showed that the PA produced s i g n i f i c a n t l y greater average concentric and eccentric torque for both groups of muscle at each angular v e l o c i t y than the ATR or MA groups (p< 0.05). As well, calculated KF-E concentric and eccentric r a t i o s were s i g n i f i c a n t l y greater for the PA group than the MA or ATR groups (p< 0.01) at each angular v e l o c i t y . It was also found that for each of the three groups of subjects i s o k i n e t i c torque produced concentrically and eccen-t r i c a l l y by the KE was s i g n i f i c a n t l y greater (p< 0.001) than that produced by the KF. Eccentric KF-E r a t i o s were s i g n i f -i c a n t l y greater (p< 0.001) for each group at a l l v e l o c i t i e s of contraction than as compared to measured concentric r a t i o s . As angular v e l o c i t y increased, concentric r a t i o s demonstrated a corresponding s i g n i f i c a n t increase (p< 0.02) while eccentric r a t i o s did not s i g n i f i c a n t l y d i f f e r with changes i n angular v e l o c i t y . Pearson Product correlations showed that for t h i s study v e r t i c a l jumping a b i l i t y was s i g n i f i c a n t l y correlated with the a b i l i t y of the knee extensors and flexors to generate concen-t r i c and eccentric torque while v e r t i c a l jumping a b i l i t y was ê not s i g n i f i c a n t l y correlated with either VO2 max or SMM. Conclusions 1. S i g n i f i c a n t differences existed between the power group and the moderately active and a e r o b i c a l l y trained runner groups i n a b i l i t y to produce concentric and eccentric i s o k i n e t i c average torque for both the knee extensors and flexors at a l l angular v e l o c i t i e s . There were no s i g n i f -icant differences between the aero b i c a l l y trained runner and moderately active groups i n concentric or eccentric torque production. 2. For both the knee extensors and flexors concentric average i s o k i n e t i c torque s i g n i f i c a n t l y decreased as the ve l o c i t y of contraction increased i n a l l three groups of subjects. Eccentric average i s o k i n e t i c torque, however, did not s i g n i f i c a n t l y increase nor decrease for any of the three groups of subjects. 3. The power group's KF-E r a t i o s were s i g n i f i c a n t l y greater both concentrically and e c c e n t r i c a l l y at each angular v e l o c i t y than either the aerobically trained runner or moderately active groups of subjects. These l a s t two groups not being s i g n i f i c a n t l y d i f f e r e n t from one another. 4. Average i s o k i n e t i c concentric and eccentric torque for the knee extensors and flexors i s s i g n i f i c a n t l y correlated with v e r t i c a l jumping a b i l i t y while estimated s k e l e t a l muscle mass and VO2 max i s not s i g n i f i c a n t l y correlated. RECOMMENDATIONS 1. Further research should be performed which measures i s o -k i n e t i c concentric and eccentric knee extensor and flexor torque and t h e i r r a t i o s i n a t e s t i n g p o s i t i o n which best simulates the length tension r e l a t i o n s h i p found during running. 2. Inclusion of a pre-test practice session which would allow subjects to become fa m i l i a r with producing mechanically assisted eccentric contractions. 3. Instead of c a l c u l a t i n g torque corrected for body weight, s k e l e t a l muscle mass, or lean body mass examine thigh muscle girths/mass and relate t h i s measure to the amount of i s o k i n e t i c torque which can be produced. 4. A prospective study which evaluates a large sample of individuals, who are approximately the same age, s k i l l l e v e l , and are exposed to s i m i l a r t r a i n i n g methods, for t h e i r KF-E concentric and eccentric r a t i o s should be per-formed. These individuals would then be monitored to for a set period of time (ie. two years) to see which i n d i v i d -uals develop hamstring MSI so that KF-E r a t i o s can be established i n an attempt to prevent future injury. REFERENCES Anderson MA, Gieck JH, Perrin D, et a l . 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