- Email: [email protected]
Muscle Balance between Hamstrings and Quadriceps during Isokinetic Exercise
Muscle Balance between Hamstrings and Quadriceps during Isokinetic Exercise
The maximum flexor and extensor peak torques about the knee joint of 17 male and 17 female subjects were determined using a CYBEX isokinetic dynamometer. These values were used to evaluate the influence of changing joint angular-velocity on the ratio of peak hamstrings WtQUQ to peak quadriceps torque. Additionally, an a$$e$sment of the influence of gravity on the recorded peak torques, and thus the ratio, <$$$ made Values for the flexion-extension f$ffO corrected for gravity were found not sigt$ft£antly different at the measured joint angular-velocities whereas the values of the ratio ftdi corrected for gravity were found signifi&mtfy different at increasing joint angularvelocities It is necessary that the physiotherapist recognize the importance of the influence &f gravity when recording forces developed in the vertical plane.
Physiotherapists' utilization of resistive exercise techniques has developed beyond isometric and isotonic contractions with the advent of the concept of isokinetic exercise. Isokinetic exercise was introduced by Hislop and Perrine (1967) as a means of holding velocity of body movements constant irrespective of the magnitude of the force generated by the participating muscles. That is, isokinetic exercise is accommodating resistive exercise (Thistle, Hislop, Moffroid and Lowman 1967). One application of this new technique has been in the examination of the relationship between peak isokinetic torque values for flexion and extension of the knee joint at different joint angular-velocities. The flexionextension ratio has been expressed as a percentage by dividing the peak hamstrings torque by the peak quadriceps torque recorded at the different joint angular-velocities. Scudder (1980) reported that this ratio remained constant at 62 per cent over velocities of 18 degrees/second
DAVID J. SANDERSON David Sanderson, B.Sc (Kines.) M.Sc (Kines.), is currently completing his Ph.D. in Biomechanics at The Pennsylvania State University. The present study was completed while he was a lecturer in Biomechanics at Cumberland College of Health Sciences, Sydney. TIM P. MUSGROVE DEBBIE A. WARD Tim Musgrove, B.App. Sc. (Physio) and Debbie Ward, B.App.Sc.(Physio) undertook this project as third year physiotherapy students at Cumberland College of Health Sciences, Sydney.
through 90 degrees/second. However, Gilliam, Sady, Freeson and Villanacci (1979), Murray, Gardner, Mollinger and Sepic (1980), Richards (1981) and Wyatt and Edwards (1981) reported changes in this ratio from 47 per cent to 83 per cent as the velocity increased from 30 degrees/second to 300 degrees/second, respectively. Goslin and Charted (1979) and Moffroid, Hofkosh, Lowman and Thistle (1969) found that at both 22.5 and 30 degrees/second the ratio was 50 per cent. The importance of expressing the ratio or balance as a function of joint angular-velocity is evident when the conflicting evidence of Coplin (1971) and Cross (1981) is considered. Coplin (1971) stated that the ratio was 60 per cent whereas Cross (1981) stated that the ratio was 70 per cent. Neither author made reference to the joint angular-velocity at which the recordings were made which, in light of more recent work (Richards 1981), reduces the value of their findings. Understanding the concept of muscle balance is important to the phy-
siotherapist when application of the term 'muscle imbalance* is to be used diagnostically. Imbalance has been considered between agonist and antagonist of the same limb (Klafs and Arnheim 1977), between agonists of opposite limbs (Burkett 1970), within a muscle group (Gordon 1977) and when normal balance is exceeded (Wyatt and Edwards 1981). Evidence of a difference in torque output between quadricep and hamstring muscle groups has been suggested as a possible predictor of cause of injury of the muscles and/or affiliated joints. Klafs and Arnheim (1977) report the need to equate the strengths of the hamstrings and quadriceps to prevent injury. Burkett (1970) determined that imbalance between these groups was a causative factor in hamstring strains. Cross (1981) stated emphatically that the hamstring group have to be at least 70 per cent as strong as the quadricep group in order to avoid trauma while Coplin (1971) placed this value at 60 per cent. Goslin and Charteris (1979) defined a normal
The Australian Journal of Physiotherapy. Vol. 30, No. 4, August, 1984
107
Muscle Balance between Hamstrings and Quadriceps
ratio between hamstrings and quadriceps and found values considered abnormally lower or higher than this value indicative of a pathological state. As a term, muscle imbalance has been used by Bowman (1951), Gordon (1977) and Wise (1981) as a predictor of cause of injury or pathology without determining a value for this imbalance. It is evident that there still remains some confusion regarding the exact nature of muscle imbalance and, indeed, what are the ideal values for pairs of muscles working antagonistically. Consideration of other factors, such as joint angular-velocity, only serve to complicate the concept. With the development of the isokinetic device there is now an opportunity to investigate aspects of muscle imbalance much more objectively than has been done in the past. There are, however, some aspects of this device which seem to have been overlooked in the first instances of reported use of the CYBEX. The main factor which influences recordings in the vertical plane is gravity. Muscle contractions in this plane will either bp assisted or retarded by gravity depending upon the direction of the movement. Inclusion of a gravitation correction factor is necessary before valid conclusions about the functional state of the muscles can be made. The aim of the present study was to examine the influence of two joint angular-velocities on the ratio of peak hamstrings torque to peak quadriceps torque and to see how these ratios may be affected by the inclusion of a gravitational correction factor.
Method Seventeen male and seventeen females between 18 and 25 years of age volunteered for participation in this project. All attended a local college and none had any musculo-skeletal complaints. A CYBEX II isokinetic dynamometer was used to determine the maximum extensor and flexor 108
torque at two joint angular-velocities, 60 degrees/second and 180 degrees/second. Calibration of the CYBEX for torque and angular displacement was performed according to the manufacturer's instructions prior to each recording session. Upon arrival the subjects were weighed using a balance scale (Wedderburn) in kilograms to the nearest one hundreth of a kilogram and name, age, date and sex were recorded. The subjects completed a warm-up protocol consisting of five minutes passive quadriceps stretch and five minutes passive hamstring stretch to the right lower limb. On completion of the warm-up subjects were individually informed that during experimentation a maximum effort was required and should they experience any pain they must cease activity. During testing verbal encouragement was provided in the form of a demand to push out and to pull back hard to motivate the subjects to maximize their efforts. Prior to the experiment the subjects were given no information about the aims of the experiment. The subjects were seated with hips flexed to 90 degrees (measured by a goniometer). The centre of rotation of the lever arm of the CYBEX was adjusted to be coincident with the centre of rotation of the subjects' right knee. A velcro strap was placed securely over the lower one third of the subjects* right thigh and the lever arm pad was securely strapped around the right ankle with the bottom edge of the pad immediately above the level of the malleoli. To familiarize the subjects with the isokinetic device they were permitted a practice period on the machine at a variety of joint angular-velocities. Since the extension and flexion movements were to take place in the vertical plane it was necessary to account for the influence of gravity on the recorded torques. The gravitational moment of the lower limb about the knee joint is the product of the
The Australian Journal of Physiotherapy. Vol. 30, No 4, August, 1984
weight of the segment and the perpendicular distance between the axis of limb rotation and the position of the segment centre of gravity (lethe cosine of the knee joint angle). Since the weight of the segment will not change during the experiment, knowledge of the joint angle is sufficient to correct for gravity as long as one torque can be associated with the resting weight of the segment at a known angle. The latter value was obtained when the subject was relaxed with the knee fully extended. The output of the CYBEX then represented the maximum gravitational moment of the lower limb segment. The cosine of the angle is 1 and thus this term formed the basis of the correction for all other angles where the cosine will be less than 1. That is, multiplying this maximum moment by the cosine of the angle represents the gravitational moment at the desired angle which was then either added to or subtracted from the recorded torque depending upon the direction of movement. Testing began with the subjects' right knee flexed to 90 degrees. Subjects were then requested to perform four maximum contractions in flexion and extension at 60 degrees/second. These were followed after a two minute rest by four contractions at 180 degrees/second. The means and standard deviations of the peak torques for flexion and extension as a fraction of body weight at the two joint angular-velocities were determined, both corrected for and uncorrected for gravity. A t-test for correlated groups was performed for each pair of groups (Nordholm 1976).
Results The corrected flexor and extensor peak torques as a fraction of body weight for the whole group as well as a breakdown for sex are presented in Table 1. The difference in the flexionextension ratio at the two joint angular-velocities was not significantly different in all cases.
Muscle Balance between Hamstrings and Quadriceps
Table 1: Mean peak torque as a fraction of body weight (N.m.kg-1) and flexionextension ratios with standard deviations for mafe, female and all subjects corrected for gravity. Flexion
Extension
F-E Ratio
Males 60 deg/sec 180 deg/sec
1.43 ± 0.34 0.96 ± 0.28
3.10 ± 0.47 1.98 ± 0.43
0.46 ± 0.09 0.48 ±0.14
Females 60 deg/sec 180 deg/sec
0.92 ± 0.23 0.62 ± 0.2
2.36 ± 0.29 1.46 ± 0.29
0.39 ± 0.08 0.42 ± 0.09
Combined 60 deg/sec 180 deg/sec
1.17 ±0.38 0.79 ±0.29
2.71 ± 0.53 1.72 ± 0.45
0.43 ± 0.09 0.45 ± 0.12
Table 2: Mean peak torque as a fraction of body weight (N.m.kg-1) and flexion extension ratio with standard deviations for male, female and all subjects not corrected for gravity. Flexion
Extension
F-E Ratio
Males 60 deg/sec 180 deg/sec
1.67±0.33 1.17±0.29
2.86±0.48 1.71±0.31
0.60±0.09 0.69±0.15
Females 60 deg/sec 180 deg/sec
1.15±0.19 0.72±0.21
2.15±0.28 1.19±0.26
0.54±0.08 0.61±0.12
Combined 60 deg/sec 180 deg/sec
1.41±0.38 0.95±0.34
2.50±0.53 1.45±0.39
0.57+0.09 0.65±0.14
Table 2 summarizes similarly for the uncorrected for gravity torques as a fraction of body weight. The difference in the flexion-extension ratio at the two joint angular-velocities was significantly different (t = -4,64,0<.05).
Discussion In the assessment of joint torque under gravitational influence it is necessary to account for that influence.
This has been demonstrated by Winter, Wells and Orr (1981) to be an error in the use of isokinetic dynamometers when considering movements in the vertical plane. In the present study considerable differences between the corrected and uncorrected torques were found, reinforcing the observations of Winter et a/(1981). If only for this reason, it is necessary to account for the influence of gravity when recording torques in the vertical plane.
The present study showed that the flexion-extension ratio, when corrected for the influence of gravity, did not change significantly with increasing joint angular-velocity. At both 60 and 180 degrees/second the ratios were lower than those reported by Gilliam et a/(1981), Murray et al (1980) and Wyatt and Edwards (1981). In these studies it was suggested that as the velocity increased the flexion-extension ratio also increased. Wyatt and Edwards (1981) suggested that as the angular-velocity approached 300 degrees/second the flexion-extension ratio approached unity. Scudder (1980) reported that the flexion-extension ratio did not change significantly with increasing joint angular-velocity, although the value was found to be 62 per cent. While in agreement with Scudder's (1980) general finding the value for the flexion-extension ratio in the present study was about 44 per cent (averaged for both velocities). The neglect of earlier studies to account for the influence of gravity on the recorded torques could be the source of the discrepancies found between the flexion-extension ratios with increasing joint angular-velocities. The present study demonstrated that the uncorrected flexion-extension ratios were greater than those corrected for gravity and show significant differences with changes in the angularvelocity but are consistent with values presented in previous studies. The only study reporting a gravitational correction (Richards 1981) also reported a significant change in the ratio with increasing joint angular-velocity. The differences between those results and the results from the present study may be a function of subjects or experimental procedure. As joint angular velocity increases so does the linear velocity of shortening of the muscle. The force-velocity relationship of striated muscle shows a decrement in the force generated as the velocity of shortening increases (Hill 1938). Since in our context the gravitational moment is independent
The Australian Journal of Physiotherapy. Voi 30, No. 4, August, 1984
109
Muscle Balance between Hamstrings and Quadriceps
of velocity it plays an increasingly dominant role as the velocity of shortening increases. This arises because peak flexor torques usually occur when the cosine of the knee joint angle is relatively large whereas peak extensor torques usually occur when the cosine of the same angle is relatively small. Therefore, the correction factor for peak flexor torque is greater than the correction factor for peak extensor torque. For example, if the peak flexor torque occurred at 10 degrees the correction factor would be 0.98 (cosine 10=0.98) while a peak extensor torque occurring at 75 degrees would have a correction factor of only 0.26. On this basis, then, one might expect the uncorrected flexion/extension ratio to increase with increases in joint angular velocity as has been shown in this and several other studies. If, on the other hand, corrected flexion/extension ratios changed as a function of velocity, it is likely that those changes would be related to intrinsic mechanical properties of flexor and extensor musculature. One difficulty encountered in developing the flexion-extension ratio in the present study was the need to identify a joint angle. An artifact of the CYBEX II is the time delay between the recorded force and the recorded angle (Winter et a! 1981). This source of error could not be accounted for in the present study and it is not immediately clear what influence this would have on the results. The important point to realize is the difficulties of simply using a piece of equipment as it is presented.
110
The flexion-extension ratio reported herein implies that the torque output of the hamstrings is approximately 44 per cent of that of the quadriceps across 120 degrees/second of joint angular-velocity. During isokinetic exercise this may be termed normal balance between these two muscle groups. Normal balance, therefore, does not imply an equality in torque output but rather a predictable difference in the peak torque output between the two groups. The difference in the ability to produce torque between the quadriceps and hamstrings does not imply muscle imbalance. Muscle imbalance exists when the flexion-extension ratio lies above or below the ratio given. The critical ratio of muscle balance that might be indicative of injury or predictive of injury or pathology needs to be determined through further investigative research. With the increasing use of isokinetic devices in assessment procedures, physiotherapists are achieving more objective measures regarding muscle function. The present study has shown the need to account for inadequancies in the use of such devices when they are to be used as a diagnostic tool. References Bowman J (1957), Muscle imbalance and its treatment in athletic injuries, Physiotherapy, 37, 69-70 Burkett LN (1978), Causative factors in hamstring strain, Medicine and Science in Sports, 8, 39-42. Cophn TH (1971), Isokinetic exercise: clinical usage, National Athletics Trainers Association, 6, 110-114. Cited in Steele V (1980), Rehabilitation in the injured athlete, Physiotherapy, 66, 251-255.
The Australian Journal of Physiotherapy. Vol. 30, No. 4, August, 1984
Cross JR (1981), The treatment of homeopathic remedies in sports medicine, Physiotherapy in Sport, 4, 8-9. Giiiiam TB, Sady SP, Freeson PS and Viiianacci J (1979), Isokinetic torque levels for high school football players, Archives of Physical Medicine and Rehabilitation, 60, 110-114. Gordon HM (1977), Chondromaiacia patellae, The Australian Journal of Physiotherapy, 23, 103-106. Goslin BR and Charteris J (1979), Isokinetic dynamometry; normative data clinical use in lower extremity (knee) cases, Scandinavian Journal of Rehabilitation Medicine, 11, 105109. Hill AV (1938), The heat of shortening and the dynamic constants of muscle, Proceedings of the Royai Society, B126, 136-195. Hisiop HJ and Perrine JJ (1967), The isokinetic concept of exercise, Physical Therapy, 47, 114117. Klafs C and Arnheim DD (1977), Modern principles of athletic training, (4th ed.), CV Mosby Co, Saint Louis. Moffroid J. Whippie R, Hofkosh J, Lowman E and Thistle H (1969), A study of isokmetic Exercise, Physical Therapy, 49, 735-746. Murray PM, Gardner GM, Molhnger LA and Sepic SP (1980), Strength of isometric and isokinetic contractions, Physical Therapy, 60, 412-419. Nordholm LA (1976), Elementary Statistics for the Health Sciences, Cumberland College of Health Sciences, Sydney. Richards CL (1981), Dynamic strength characteristics during isokinetic knee movements in healthy women, Physiotherapy Canada, 33, 141-149. Scudder GN (1980), Torque curves produced at the knee during isometric and isokinetic exercise, Archives of Physical Medicine and Rehabilitation, 61, 68-73. Thistle HG, Hisiop HJ, Moffroid M, and Lowman EW (1967), Isokinetic contraction: a new concept of resistive exercise, Archives of Physical Medicine and Rehabilitation, 48, 279-282. Winter DA, Wells RP and Orr GW (1981), Errors in the use of isokmetic dynamometers, European Journal of Applied Physiology, 46, 397-408. Wise DD (1977), Physiotherapeutic treatment of athletic injuries to the muscle-tendon complex of the leg, Canadian Medical Association Journal, 117, 635-639. Wyatt MP and Edwards AM (1981), Comparison of quadriceps and hamstring torque values during isokinetic exercise, Journal of Orthopaedic and Sports Physiotherapy, 3, 48-56.
The maximum flexor and extensor peak torques about the knee joint of 17 male and 17 female subjects were determined using a CYBEX isokinetic dynamometer. These values were used to evaluate the influence of changing joint angular-velocity on the ratio of peak hamstrings WtQUQ to peak quadriceps torque. Additionally, an a$$e$sment of the influence of gravity on the recorded peak torques, and thus the ratio, <$$$ made Values for the flexion-extension f$ffO corrected for gravity were found not sigt$ft£antly different at the measured joint angular-velocities whereas the values of the ratio ftdi corrected for gravity were found signifi&mtfy different at increasing joint angularvelocities It is necessary that the physiotherapist recognize the importance of the influence &f gravity when recording forces developed in the vertical plane.
Physiotherapists' utilization of resistive exercise techniques has developed beyond isometric and isotonic contractions with the advent of the concept of isokinetic exercise. Isokinetic exercise was introduced by Hislop and Perrine (1967) as a means of holding velocity of body movements constant irrespective of the magnitude of the force generated by the participating muscles. That is, isokinetic exercise is accommodating resistive exercise (Thistle, Hislop, Moffroid and Lowman 1967). One application of this new technique has been in the examination of the relationship between peak isokinetic torque values for flexion and extension of the knee joint at different joint angular-velocities. The flexionextension ratio has been expressed as a percentage by dividing the peak hamstrings torque by the peak quadriceps torque recorded at the different joint angular-velocities. Scudder (1980) reported that this ratio remained constant at 62 per cent over velocities of 18 degrees/second
DAVID J. SANDERSON David Sanderson, B.Sc (Kines.) M.Sc (Kines.), is currently completing his Ph.D. in Biomechanics at The Pennsylvania State University. The present study was completed while he was a lecturer in Biomechanics at Cumberland College of Health Sciences, Sydney. TIM P. MUSGROVE DEBBIE A. WARD Tim Musgrove, B.App. Sc. (Physio) and Debbie Ward, B.App.Sc.(Physio) undertook this project as third year physiotherapy students at Cumberland College of Health Sciences, Sydney.
through 90 degrees/second. However, Gilliam, Sady, Freeson and Villanacci (1979), Murray, Gardner, Mollinger and Sepic (1980), Richards (1981) and Wyatt and Edwards (1981) reported changes in this ratio from 47 per cent to 83 per cent as the velocity increased from 30 degrees/second to 300 degrees/second, respectively. Goslin and Charted (1979) and Moffroid, Hofkosh, Lowman and Thistle (1969) found that at both 22.5 and 30 degrees/second the ratio was 50 per cent. The importance of expressing the ratio or balance as a function of joint angular-velocity is evident when the conflicting evidence of Coplin (1971) and Cross (1981) is considered. Coplin (1971) stated that the ratio was 60 per cent whereas Cross (1981) stated that the ratio was 70 per cent. Neither author made reference to the joint angular-velocity at which the recordings were made which, in light of more recent work (Richards 1981), reduces the value of their findings. Understanding the concept of muscle balance is important to the phy-
siotherapist when application of the term 'muscle imbalance* is to be used diagnostically. Imbalance has been considered between agonist and antagonist of the same limb (Klafs and Arnheim 1977), between agonists of opposite limbs (Burkett 1970), within a muscle group (Gordon 1977) and when normal balance is exceeded (Wyatt and Edwards 1981). Evidence of a difference in torque output between quadricep and hamstring muscle groups has been suggested as a possible predictor of cause of injury of the muscles and/or affiliated joints. Klafs and Arnheim (1977) report the need to equate the strengths of the hamstrings and quadriceps to prevent injury. Burkett (1970) determined that imbalance between these groups was a causative factor in hamstring strains. Cross (1981) stated emphatically that the hamstring group have to be at least 70 per cent as strong as the quadricep group in order to avoid trauma while Coplin (1971) placed this value at 60 per cent. Goslin and Charteris (1979) defined a normal
The Australian Journal of Physiotherapy. Vol. 30, No. 4, August, 1984
107
Muscle Balance between Hamstrings and Quadriceps
ratio between hamstrings and quadriceps and found values considered abnormally lower or higher than this value indicative of a pathological state. As a term, muscle imbalance has been used by Bowman (1951), Gordon (1977) and Wise (1981) as a predictor of cause of injury or pathology without determining a value for this imbalance. It is evident that there still remains some confusion regarding the exact nature of muscle imbalance and, indeed, what are the ideal values for pairs of muscles working antagonistically. Consideration of other factors, such as joint angular-velocity, only serve to complicate the concept. With the development of the isokinetic device there is now an opportunity to investigate aspects of muscle imbalance much more objectively than has been done in the past. There are, however, some aspects of this device which seem to have been overlooked in the first instances of reported use of the CYBEX. The main factor which influences recordings in the vertical plane is gravity. Muscle contractions in this plane will either bp assisted or retarded by gravity depending upon the direction of the movement. Inclusion of a gravitation correction factor is necessary before valid conclusions about the functional state of the muscles can be made. The aim of the present study was to examine the influence of two joint angular-velocities on the ratio of peak hamstrings torque to peak quadriceps torque and to see how these ratios may be affected by the inclusion of a gravitational correction factor.
Method Seventeen male and seventeen females between 18 and 25 years of age volunteered for participation in this project. All attended a local college and none had any musculo-skeletal complaints. A CYBEX II isokinetic dynamometer was used to determine the maximum extensor and flexor 108
torque at two joint angular-velocities, 60 degrees/second and 180 degrees/second. Calibration of the CYBEX for torque and angular displacement was performed according to the manufacturer's instructions prior to each recording session. Upon arrival the subjects were weighed using a balance scale (Wedderburn) in kilograms to the nearest one hundreth of a kilogram and name, age, date and sex were recorded. The subjects completed a warm-up protocol consisting of five minutes passive quadriceps stretch and five minutes passive hamstring stretch to the right lower limb. On completion of the warm-up subjects were individually informed that during experimentation a maximum effort was required and should they experience any pain they must cease activity. During testing verbal encouragement was provided in the form of a demand to push out and to pull back hard to motivate the subjects to maximize their efforts. Prior to the experiment the subjects were given no information about the aims of the experiment. The subjects were seated with hips flexed to 90 degrees (measured by a goniometer). The centre of rotation of the lever arm of the CYBEX was adjusted to be coincident with the centre of rotation of the subjects' right knee. A velcro strap was placed securely over the lower one third of the subjects* right thigh and the lever arm pad was securely strapped around the right ankle with the bottom edge of the pad immediately above the level of the malleoli. To familiarize the subjects with the isokinetic device they were permitted a practice period on the machine at a variety of joint angular-velocities. Since the extension and flexion movements were to take place in the vertical plane it was necessary to account for the influence of gravity on the recorded torques. The gravitational moment of the lower limb about the knee joint is the product of the
The Australian Journal of Physiotherapy. Vol. 30, No 4, August, 1984
weight of the segment and the perpendicular distance between the axis of limb rotation and the position of the segment centre of gravity (lethe cosine of the knee joint angle). Since the weight of the segment will not change during the experiment, knowledge of the joint angle is sufficient to correct for gravity as long as one torque can be associated with the resting weight of the segment at a known angle. The latter value was obtained when the subject was relaxed with the knee fully extended. The output of the CYBEX then represented the maximum gravitational moment of the lower limb segment. The cosine of the angle is 1 and thus this term formed the basis of the correction for all other angles where the cosine will be less than 1. That is, multiplying this maximum moment by the cosine of the angle represents the gravitational moment at the desired angle which was then either added to or subtracted from the recorded torque depending upon the direction of movement. Testing began with the subjects' right knee flexed to 90 degrees. Subjects were then requested to perform four maximum contractions in flexion and extension at 60 degrees/second. These were followed after a two minute rest by four contractions at 180 degrees/second. The means and standard deviations of the peak torques for flexion and extension as a fraction of body weight at the two joint angular-velocities were determined, both corrected for and uncorrected for gravity. A t-test for correlated groups was performed for each pair of groups (Nordholm 1976).
Results The corrected flexor and extensor peak torques as a fraction of body weight for the whole group as well as a breakdown for sex are presented in Table 1. The difference in the flexionextension ratio at the two joint angular-velocities was not significantly different in all cases.
Muscle Balance between Hamstrings and Quadriceps
Table 1: Mean peak torque as a fraction of body weight (N.m.kg-1) and flexionextension ratios with standard deviations for mafe, female and all subjects corrected for gravity. Flexion
Extension
F-E Ratio
Males 60 deg/sec 180 deg/sec
1.43 ± 0.34 0.96 ± 0.28
3.10 ± 0.47 1.98 ± 0.43
0.46 ± 0.09 0.48 ±0.14
Females 60 deg/sec 180 deg/sec
0.92 ± 0.23 0.62 ± 0.2
2.36 ± 0.29 1.46 ± 0.29
0.39 ± 0.08 0.42 ± 0.09
Combined 60 deg/sec 180 deg/sec
1.17 ±0.38 0.79 ±0.29
2.71 ± 0.53 1.72 ± 0.45
0.43 ± 0.09 0.45 ± 0.12
Table 2: Mean peak torque as a fraction of body weight (N.m.kg-1) and flexion extension ratio with standard deviations for male, female and all subjects not corrected for gravity. Flexion
Extension
F-E Ratio
Males 60 deg/sec 180 deg/sec
1.67±0.33 1.17±0.29
2.86±0.48 1.71±0.31
0.60±0.09 0.69±0.15
Females 60 deg/sec 180 deg/sec
1.15±0.19 0.72±0.21
2.15±0.28 1.19±0.26
0.54±0.08 0.61±0.12
Combined 60 deg/sec 180 deg/sec
1.41±0.38 0.95±0.34
2.50±0.53 1.45±0.39
0.57+0.09 0.65±0.14
Table 2 summarizes similarly for the uncorrected for gravity torques as a fraction of body weight. The difference in the flexion-extension ratio at the two joint angular-velocities was significantly different (t = -4,64,0<.05).
Discussion In the assessment of joint torque under gravitational influence it is necessary to account for that influence.
This has been demonstrated by Winter, Wells and Orr (1981) to be an error in the use of isokinetic dynamometers when considering movements in the vertical plane. In the present study considerable differences between the corrected and uncorrected torques were found, reinforcing the observations of Winter et a/(1981). If only for this reason, it is necessary to account for the influence of gravity when recording torques in the vertical plane.
The present study showed that the flexion-extension ratio, when corrected for the influence of gravity, did not change significantly with increasing joint angular-velocity. At both 60 and 180 degrees/second the ratios were lower than those reported by Gilliam et a/(1981), Murray et al (1980) and Wyatt and Edwards (1981). In these studies it was suggested that as the velocity increased the flexion-extension ratio also increased. Wyatt and Edwards (1981) suggested that as the angular-velocity approached 300 degrees/second the flexion-extension ratio approached unity. Scudder (1980) reported that the flexion-extension ratio did not change significantly with increasing joint angular-velocity, although the value was found to be 62 per cent. While in agreement with Scudder's (1980) general finding the value for the flexion-extension ratio in the present study was about 44 per cent (averaged for both velocities). The neglect of earlier studies to account for the influence of gravity on the recorded torques could be the source of the discrepancies found between the flexion-extension ratios with increasing joint angular-velocities. The present study demonstrated that the uncorrected flexion-extension ratios were greater than those corrected for gravity and show significant differences with changes in the angularvelocity but are consistent with values presented in previous studies. The only study reporting a gravitational correction (Richards 1981) also reported a significant change in the ratio with increasing joint angular-velocity. The differences between those results and the results from the present study may be a function of subjects or experimental procedure. As joint angular velocity increases so does the linear velocity of shortening of the muscle. The force-velocity relationship of striated muscle shows a decrement in the force generated as the velocity of shortening increases (Hill 1938). Since in our context the gravitational moment is independent
The Australian Journal of Physiotherapy. Voi 30, No. 4, August, 1984
109
Muscle Balance between Hamstrings and Quadriceps
of velocity it plays an increasingly dominant role as the velocity of shortening increases. This arises because peak flexor torques usually occur when the cosine of the knee joint angle is relatively large whereas peak extensor torques usually occur when the cosine of the same angle is relatively small. Therefore, the correction factor for peak flexor torque is greater than the correction factor for peak extensor torque. For example, if the peak flexor torque occurred at 10 degrees the correction factor would be 0.98 (cosine 10=0.98) while a peak extensor torque occurring at 75 degrees would have a correction factor of only 0.26. On this basis, then, one might expect the uncorrected flexion/extension ratio to increase with increases in joint angular velocity as has been shown in this and several other studies. If, on the other hand, corrected flexion/extension ratios changed as a function of velocity, it is likely that those changes would be related to intrinsic mechanical properties of flexor and extensor musculature. One difficulty encountered in developing the flexion-extension ratio in the present study was the need to identify a joint angle. An artifact of the CYBEX II is the time delay between the recorded force and the recorded angle (Winter et a! 1981). This source of error could not be accounted for in the present study and it is not immediately clear what influence this would have on the results. The important point to realize is the difficulties of simply using a piece of equipment as it is presented.
110
The flexion-extension ratio reported herein implies that the torque output of the hamstrings is approximately 44 per cent of that of the quadriceps across 120 degrees/second of joint angular-velocity. During isokinetic exercise this may be termed normal balance between these two muscle groups. Normal balance, therefore, does not imply an equality in torque output but rather a predictable difference in the peak torque output between the two groups. The difference in the ability to produce torque between the quadriceps and hamstrings does not imply muscle imbalance. Muscle imbalance exists when the flexion-extension ratio lies above or below the ratio given. The critical ratio of muscle balance that might be indicative of injury or predictive of injury or pathology needs to be determined through further investigative research. With the increasing use of isokinetic devices in assessment procedures, physiotherapists are achieving more objective measures regarding muscle function. The present study has shown the need to account for inadequancies in the use of such devices when they are to be used as a diagnostic tool. References Bowman J (1957), Muscle imbalance and its treatment in athletic injuries, Physiotherapy, 37, 69-70 Burkett LN (1978), Causative factors in hamstring strain, Medicine and Science in Sports, 8, 39-42. Cophn TH (1971), Isokinetic exercise: clinical usage, National Athletics Trainers Association, 6, 110-114. Cited in Steele V (1980), Rehabilitation in the injured athlete, Physiotherapy, 66, 251-255.
The Australian Journal of Physiotherapy. Vol. 30, No. 4, August, 1984
Cross JR (1981), The treatment of homeopathic remedies in sports medicine, Physiotherapy in Sport, 4, 8-9. Giiiiam TB, Sady SP, Freeson PS and Viiianacci J (1979), Isokinetic torque levels for high school football players, Archives of Physical Medicine and Rehabilitation, 60, 110-114. Gordon HM (1977), Chondromaiacia patellae, The Australian Journal of Physiotherapy, 23, 103-106. Goslin BR and Charteris J (1979), Isokinetic dynamometry; normative data clinical use in lower extremity (knee) cases, Scandinavian Journal of Rehabilitation Medicine, 11, 105109. Hill AV (1938), The heat of shortening and the dynamic constants of muscle, Proceedings of the Royai Society, B126, 136-195. Hisiop HJ and Perrine JJ (1967), The isokinetic concept of exercise, Physical Therapy, 47, 114117. Klafs C and Arnheim DD (1977), Modern principles of athletic training, (4th ed.), CV Mosby Co, Saint Louis. Moffroid J. Whippie R, Hofkosh J, Lowman E and Thistle H (1969), A study of isokmetic Exercise, Physical Therapy, 49, 735-746. Murray PM, Gardner GM, Molhnger LA and Sepic SP (1980), Strength of isometric and isokinetic contractions, Physical Therapy, 60, 412-419. Nordholm LA (1976), Elementary Statistics for the Health Sciences, Cumberland College of Health Sciences, Sydney. Richards CL (1981), Dynamic strength characteristics during isokinetic knee movements in healthy women, Physiotherapy Canada, 33, 141-149. Scudder GN (1980), Torque curves produced at the knee during isometric and isokinetic exercise, Archives of Physical Medicine and Rehabilitation, 61, 68-73. Thistle HG, Hisiop HJ, Moffroid M, and Lowman EW (1967), Isokinetic contraction: a new concept of resistive exercise, Archives of Physical Medicine and Rehabilitation, 48, 279-282. Winter DA, Wells RP and Orr GW (1981), Errors in the use of isokmetic dynamometers, European Journal of Applied Physiology, 46, 397-408. Wise DD (1977), Physiotherapeutic treatment of athletic injuries to the muscle-tendon complex of the leg, Canadian Medical Association Journal, 117, 635-639. Wyatt MP and Edwards AM (1981), Comparison of quadriceps and hamstring torque values during isokinetic exercise, Journal of Orthopaedic and Sports Physiotherapy, 3, 48-56.