Velocity-specific and mode-specific effects of eccentric isokinetic training of the hamstrings

Ms. Ryan and Ms. Magidow completed this research project in partial fulfillment of the requirement for the degree of Masters of Science in the Department of Physical Therapy in the Graduate School, Duke University, 1989 This study examined velocity-specific and mode-specific effects of eccentric isokinetic training of the hamstrings. Female volunteers aged 21 to 40 were assigned to an exercise group (n = 17) or nonexercise group (n = 17). The average force of three concentric and eccentric hamstring contractions was evaluated pre- and post-training at 120 degrees /sec +/- 60 degrees /sec. Subjects trained three times a week for six weeks with 15 maximal eccentric isokinetic contractions at 120 degrees /sec. The ANOVA procedure and T-tests were used to determine the effects of training. A general linear model (GLM) for repeated measures determined the interaction effect between speed and mode. Results showed that the exercise group increased significantly (p < 0.0083) in eccentric force at all tested speeds and increased significantly (p < 0.0083) in concentric force at 120 degrees /sec and 180 degrees /sec. The GLM results showed no interaction effect between speed and mode. The study concluded that eccentric isokinetic training of the hamstrings at 120 degrees /sec is not speed-specific at 120 degrees /sec +/- 60 degrees /sec and is not mode-specific at 120 degrees /sec and 180 degrees /sec. J Orthop Sports Phys Ther 1991;13(1):33-39.     

Effects of Speed and Limb Dominance on Eccentric and Concentric lsokinetic Testing of the Knee

This study investigated the effects of speed and limb dominance on torque values and ratios of the quadriceps and hamstrings during both eccentric and concentric exercise. Both knees of 12 males and 13 females, 21-33 years of age, were tested at 30 degrees /sec and 180 degrees /sec on the KIN-COM. Results indicated that: 1) concentric quadriceps torque values and torque/body weight ratios decreased significantly at the higher speed, 2) no significant changes in eccentric quadriceps or eccentric hamstrings torque occurred at the two speeds, 3) no significant differences were demonstrated in the torque values or torque/body weight ratios between dominant and nondominant knees during both concentric and eccentric exercise at both speeds, 4) hamstrings/quadriceps torque ratios increased significantly at the higher speed during concentric exercise, and 5) for males, the hamstrings/quadriceps ratios were significantly greater in the nondominant limb during both concentric and eccentric exercise at both speeds. These findings are important when establishing appropriate and safe rehabilitation goals during isokinetic eccentric activity.J Orthop Sports Phys Ther 1988;10(2):59-65.     

The Relationships among Isometric, Isotonic, and Isokinetic Concentric and Eccentric Quadriceps and Hamstring Force and Three Components of Athletic Performance

This study was supported in part by a grant from the Foundation for Physical Therapy, Inc. The purpose of this study was to compare the relationships among isometric, isotonic, and isokinetic concentric and eccentric quadriceps and hamstring forces and three components of athletic performance in college-aged, male athletes. Bilateral quadriceps and hamstring muscle torque were obtained (N = 39) using a KinCom(R) for concentric (rate at 60 degrees /sec and 180 degrees /sec), eccentric (rate at 30 degrees /sec and 90 degrees /sec), isotonic, and isometric (knee angles at 30 degrees and 60 degrees ) contractions. Athletic performance was assessed using vertical jump performance, 40-yard dash time, and agility run time. The best predictor of 40-yard dash time was the right peak isokinetic concentric hamstring force at 60 degrees /sec (R = .57; p < 0.05). The best predictor of agility run time was the left mean isokinetic eccentric hamstring force at 90 degrees /sec (R = .58; p < 0.05). There were no significant correlations between any quadriceps or hamstring force and vertical jump. It was concluded that isokinetic eccentric quadriceps and hamstring forces were no better predictors of athletic performance than muscle forces assessed in other ways. However, they may be more predictive of some specific components of performance. J Orthop Sports Phys Ther 1991;14(3):114-120.     

Torque Characteristics of the Quadriceps and Hamstring Muscles during Concentric and Eccentric Loading

Additional fundamental information is needed on the effects of speed and dominant limb on torque values and ratios of the quadriceps and hamstring muscles during both eccentric and concentric contractions. The purpose of this study was to determine the dominant leg's peak isokinetic torque production of male college athletes. One hundred subjects, from 18 to 25 years of age, were tested on a Biodex B-2000 isokinetic dynamometer concentrically at 60, 120,300, and 450 degrees /sec and eccentrically at 60 and 120 degrees /sec. All data were analyzed by means of a repeated measures analysis of variance to determine if significant differences (p < 0.01) existed. Concentric torque production of the quadriceps and hamstring muscles decreased significantly (p < 0.01) as the angular velocity increased. No significant differences (p > 0.01) existed between the quadriceps or hamstring muscles' eccentric torque production at 60 and 120 degrees /sec. Torque production of the quadriceps and hamstring muscles was significantly greater (p < 0.01) during eccentric than concentric loading at 60 and 120 degrees /sec. Concentric hamstring/quadriceps ratios increased significantly (p < 0.01) as the angular velocity increased. Hamstring/quadriceps ratios were significantly greater (p < 0.01) during eccentric than concentric loading at 60 and 120 degrees /sec. These findings are important when establishing testing, rehabilitation, and conditioning techniques for athletes who participate in various high-speed loading conditions during concentric and eccentric muscle contractions. J Orthop Sports Phys Ther 1991;14(4):149-154.     

Comparative study of isokinetic eccentric and concentric quadriceps training

Address reprint requests to Dr. J. R. Basford, Mayo Clinic, 200 First Street S.W., Rochester, MN 55905. The purpose of this study was to compare the effects of eccentric and concentric isokinetic training exercises on eccentric and concentric quadriceps performance in 63 healthy subjects during a six-week training period. The subjects were randomly divided into three groups: eccentric training, concentric training, and no training. Members of the training groups exercised their right quadriceps only. Orientation, training, and testing were performed on a computer-assisted isokinetic dynamometer (KIN-COM) at 100 degrees /sec. All subjects were tested concentrically and eccentrically on both quadriceps; and peak torque, total work, and position angle at peak torque were measured. Analysis of variance and post hoc analyses were performed on the mean changes (pretest and posttest differences) for all groups. The concentric training group demonstrated the most significant increases in concentric torque and work; the eccentric training group demonstrated the most significant increases in eccentric torque and work. No significant changes were seen in the untrained left limbs of any group. These results support the concept of mode specificity in isokinetic exercise training. J Orthop Sports Phys Ther 1991;14(1):31-36.     

Concentric and eccentric isokinetic lower extremity strength in persons with multiple sclerosis

This study was supported by the Levine-Rubenstein MS Research Fund and The Rehabilitation Research and Development Service of the U.S. Department of Veterans Affairs. Clinicians might be reluctant to institute exercise training programs for individuals with multiple sclerosis (MS) because so little information is available regarding their muscle performance capability. The purpose of this project was to compare the quadriceps and hamstrings muscle groups' torque capacity of individuals with MS (N = 9) to matched non-MS controls (N = 9). Muscle torques at several speeds were measured using a KIN-COM II isokinetic dynamometer during both concentric (30, 60, and 90 degrees /sec) and eccentric (45, 60, and 75 degrees /sec) contractions. Peak torque for both muscle groups at all velocities were higher for the non-MS group; however, this difference was only significant for the concentric quadriceps muscle contraction (p < .05). All subjects demonstrated higher torque eccentrically than concentrically for the quadriceps, but these differences were only significant for the experimental subjects. The MS group showed a greater decrease in torque with increasing speed than the non-MS group. Deficits between the MS and control groups related to changes in contraction velocity were greater during concentric than eccentric contractions. These findings suggest that strengthening programs that emphasize concentric exercise at the higher of the three speeds of movement included in this study may be most effective in treating this particular type of strength deficit in MS patients. J Orthop Sports Phys Ther 1992;16(3):114-122.     

The effect of eccentric strength training at various speeds on concentric strength of the quadriceps and hamstring muscles

This study investigated the effect of eccentric training on concentric strength of the quadriceps and hamstring muscles. The dominant legs of 43 college-age males were pretested concentrically using the KIN-COM(R) at speeds of 60 and 180 degrees /sec. Twenty-eight treatment subjects trained eccentrically at one of the testing speeds for a period of eight weeks; the remainder served as the control group. Prior to each training session, the subjects gave a subjective evaluation of muscle soreness. Delayed muscle soreness did not affect the subjects' ability to train eccentrically. A concentric posttest was taken to determine any treatment effects. The quadriceps muscle did not show any significant change after eccentric training. Eccentric training at 60 and 180 degrees /sec significantly increased the concentric strength of the hamstrings. Eccentric training does appear to be effective in developing concentric strength in the hamstrings. The speed of eccentric training was not a factor in concentric conditioning. J Orthop Sports Phys Ther 1991;13(5):226-230.     

Effects of isokinetic soreness-inducing exercise on blood levels of C-reactive protein and creatine kinase

This study examined whether acute inflammation was the mechanism underlying delayed muscle soreness (DMS) by assessing the effect of soreness-inducing exercise on blood levels of C-reactive protein (CRP), an acute inflammation marker. Sixteen female college students (= 20.6 +/- 2.6 years) performed three sets of 35 isokinetic contractions of the knee flexors and extensors at 120 degrees /set on a Biodex isokinetic dynamometer. Group 1 (N = 8) exercised eccentrically and Group 2 (N = 8) concentrically at an intensity of 80% of a concentric 120 degrees /set peak torque. Pre-exercise and 1, 24, 48 and 72 hours postexercise, DMS of the quadriceps femoris (QF) and hamstrings (HA) were assessed and blood samples were collected for creatine kinase (CK), an indicator of muscle damage, and CRP, which was measured by a radial immunodiffusion procedure. The mean CK values 72 hours postexercise were 14,856 and 360 IU/L for groups 1 and 2, respectively. No significant elevations of CRP occurred in either group. ANOVAs using a split plot factorial design found Group 1 to have significantly larger logarithmic CK elevations, ranked QF soreness, and ranked HA soreness than Group 2. In contrast to myocardial infarct patients and marathon runner investigations, this study did not demonstrate abnormal elevations of CRP when increases in CK were induced. With high-repetition submaximal isokinetic exercise, eccentric contractions induce higher levels of muscle damage and DMS than concentric contractions. Further, the hamstrings are more susceptible to DMS than the quadriceps femoris when eccentric isokinetic exercise is performed at the same relative intensity. J Orthop Sports Phys Ther 1992;16(5):208-214.     

Effect of Contraction Type, Angular Velocity, and Arc of Motion on VMO:VL EMG Ratio

This research was supported by a grant from the Walter P. Inman Fund through the Duke University Medical Research Council. Selected quadriceps muscle action may influence the movement path of the patella in the malaligned patellofemoral joint. The purpose of this study was to investigate the effects of arc of motion, angular velocity, and contraction type on the vastus medialis obliques:vastus lateralis (VMO:VL) absolute averaged electromyographic (AAEMG) ratio. Thirty healthy subjects performed maximum concentric and eccentric isokinetic quadriceps muscle contractions on the Kin-Com(R) dynamometer at velocities of 60 and 120 degrees /sec. Electromyography data from the VMO and the VL were acquired, and a VMO:VL AAEMG ratio was calculated for all combinations of the three independent variables. The results indicate that the VMO:VL AAEMG ratio for the 60 degrees -85 degrees arc was significantly greater than the ratio for the 35 degrees -60 degrees arc (p < 0.05), the ratio for the 60 degrees -85 degrees arc was significantly greater than the ratio for the 10 degrees -35 degrees arc (p < 0.05), and the ratio for the 35 degrees -60 degrees arc was significantly greater than the ratio for the 10 degrees -35 degrees arc (p < 0.05). The VMO:VL AAEMG ratio for concentric contraction at 120 degrees /sec was significantly greater than the ratio for concentric contraction at 60 degrees /sec (p < 0.05) and was significantly greater than the ratio for eccentric contraction at 120 degrees /sec (p < 0.05). The results indicate that the VMO:VL AAEMG ratio is affected by isokinetic exercise parameters. The use of isokinetic exercise parameters that produce a greater VMO:VL AAEMG ratio may be effective in altering muscular imbalance between the VMO and VL. J Orthop Sports Phys Ther 1991;14(6):256-262.     

Eccentric and concentric force-velocity relationships of the quadriceps feimoris muscle

Most functional activities utilize all three types of muscle contraction. The purpose of this study was to examine concentric and eccentric force-velocity relationships of the knee extensors of 30 young, healthy females at seven velocities between 30 and 210 degrees /sec using the Kinetic Communicator. The average force produced by the quadriceps during three concentric and three eccentric contractions was calculated at each velocity. The force-velocity relationships were graphed and analyzed using linear regression techniques. Results showed that the mean slope of the combined linear regression lines of concentric data was -0.55, which is significantly different from a zero slope. This indicates that concentric force of the knee extensors decreases as velocity increases. The mean slope of the combined linear regression lines of the eccentric data was -0.04, indicating no significant change in eccentric force with an increase in velocity. It appears, therefore, that in the knee extensors of healthy, young females, concentric force decreases as velocity increases to 210 degrees /sec, while eccentric force remains the same. Both concentric and eccentric work are often emphasized in strength training programs. It is, therefore, important for professionals involved in the rehabilitation or training of patients and athletes to be aware of differences between eccentric and concentric force-velocity relationships. J Orthop Sports Phys Ther 1992;16(2):82-86.     

Reliability of Concentric and Eccentric Measurements of Quadriceps Performance Using the KIN-COM Dynamometer: The Effect of Testing Order for Three Different Speeds

This study assessed the effect of test order for three different speeds (60, 120, and I80 degrees /sec) on the reliability of measures of peak torque, average torque, and the joint angle at which peak torque occurred, using the KIN-COM dynamometer to measure concentric and eccentric contractions of the quadriceps muscle. The effect of test order in assessing the reliability of measures of isokinetic movement at different speeds has not been systematically considered in other studies and is important because of the traditional clinical practice of testing patients at several speeds. Eighteen healthy subjects (14 females, 4 males) between the ages of 22 and 37 were selected for the study. None of the subjects had prior experience using the KIN-COM, and none of the subjects were engaged in strength training. The ICCs for concentric and eccentric peak torque and average torque, collapsed across testing order, ranged from .76 to .95 and were significant at the p < .01 level for all three speeds. When testing order was analyzed, the measurements of subjects who began testing at 180 degrees /sec had much lower reliability than the measurements of subjects who experienced the high speed as either the second or third speed within each session. Measures of joint angle were less reliable than peak torque and average torque measures, with ICCs ranging from -.16 to .64. Thus, these results suggest that normal persons being tested at different speeds on the KIN-COM dynamometer should be tested at slower speeds before higher speeds. In addition, this study showed no evidence of low reliability for measures of eccentric peak torque at the slower speed of 60 degrees /sec, as reported by other researchers in an earlier study. J Orthop Sports Phys Ther 1992;15(4):175-182.     

Isokinetic torque of the knee extensor and flexor in patients with recurrent patellar dislocation]

In order to establish the role of muscle strength in the recurrent dislocation of the patella, an isokinetic study was performed using BIODEX, by which the concentric (CC) and passive eccentric (PEC) torques of the quadriceps and hamstrings were measured. The angle velocity was set at 30 degrees and 90 degrees/sec. The subjects were divided into three groups: (I) non-surgical, (II) surgical and (III) normal control. In each group 20 knees were tested, and the following results were obtained. 1. Peak torque: At either 30 degrees/sec or 90 degrees/sec of velocity, it was significantly smaller in group I. On the other hand, the torque in group II was similar to that of group III. 2. E/C (eccentric torque/concentric torque) ratio: PEC was divided by CC to express a muscular strength balance. At 30 degrees/sec velocity, group I showed a significantly high E/C ratio. Conclusion: The knees with recurrent dislocation of the patella exhibited significantly lower peak torque and irregular curve patterns. The muscle strength, has been restored to a near-normal level in the surgical group, therefore, the muscle weakness in this disorder can be considered to be a secondary factor. The eccentric torque appeared to play a major role in the development of recurrent dislocation of the patella.     

Effects of Motorized vs Non-Motorized Treadmill Training on Hamstring/Quadriceps Strength Ratios

Previous literature suggests that muscular involvement and biomechanical changes elicit different responses between overground and treadmill training. The objective of this study was to examine the effects of training on two different treadmill designs on the conventional (CR; concentric only) and functional (FR; eccentric to concentric) hamstring and quadriceps strength ratios. Fifteen men and sixteen women were randomly divided into three groups: motorized (MT), non-motorized (NMT) or control (C). Subjects completed pre and post-test isokinetic concentric and eccentric quadriceps and hamstring testing of both legs. Subjects completed 4 weeks of training on their respective treadmills with mileage increasing ½ mile each week, beginning with 2 miles. The C group did not participate in any training. The CR revealed a significant two way interaction of group x time with MT increasing (pre: 0.80 ± 0.09 to post: 0.84 ± 0.09), NMT decreasing (pre: 0.76 ± 0.13 to post: 0.74 ± 0.10), and C showing no change (pre: 0.79 ± 0.10 to post: 0.79 ± 0.09. The FR revealed a significant two way interaction of speed x sex with the FR increasing as speeds increased for men (60 degrees.s^-1: 1.04 ± 0.11; 180 degrees.s^-1: 1.66 ± 0.27; 300 degrees.s^-1: 2.36 ± 0.45) and women (60 degrees.s^-1: 1.05 ± 0.16; 180 degrees.s^-1: 1.90 ± 0.26; 300 degrees.s^-1: 2.75 ± 0.47) but women increased greater relative to men. Training mode elicited a specific change in concentric hamstring and quadriceps strength resulting in specific changes to the CR; however, neither training mode had an effect on eccentric hamstrings nor the FR. Special attention should be given to the mode of endurance training when the goal is to alter the hamstring/quadriceps CR.

Key points

• Specificity of treadmill training had different effects on concentric strength.
• Specificity of treadmill training had little or no effect on eccentric strength.
• Conventional and functional strength ratios may give different results based on training mode.
• Four weeks is long enough for strength results to be apparent in untrained people.

Key words: Concentric, eccentric, conventional, functional, running, walking     

Anterior tibial translation during different isokinetic quadriceps torque in anterior cruciate ligament deficient and nonimpaired individuals

STUDY DESIGN: Factorial quasi-experimental design. OBJECTIVES: To quantify the effect of different levels of isokinetic concentric and eccentric knee extensor torques on the anterior tibial translation in subjects with anterior cruciate ligament (ACL) deficiency. Electromyogram (EMG) activity of 4 leg muscles was recorded in order to detect any co-activation of extensors and flexors. BACKGROUND: The rehabilitation after an ACL injury is of importance for the functional outcome of the patient. In order to construct a rehabilitation program after that injury, it is important to understand the in vivo relationships between muscle force and tibial translation. METHODS AND MEASURES: Twelve patients with unilateral ACL injury and 11 uninjured volunteers performed 36 repetitions of a quadriceps contraction at different isokinetic concentric and eccentric torque levels, on a KinCom machine (60 degrees x s(-1)), with simultaneous recordings of tibial translation (CA-4000) and EMG activity from quadriceps and hamstrings muscles. Tibial translations and EMG levels were normalized to the maximum of each subject. RESULTS: The individual anterior tibial translation increased with increased quadriceps torque in a similar manner in both quadriceps contraction modes in all legs tested. During concentric mode, translation was similar in all groups, but during eccentric mode, the mean translation was 38% larger in the ACL injured knees. No quadriceps-hamstrings co-activation occurred in any test or group. CONCLUSIONS: An ACL deficient knee can limit the translation within a normal space during concentric muscle activity but not during eccentric activity. That limitation depends on other mechanisms than hamstrings co-activation.     

Investigation of the Physiological Overflow Effect from Speed-Specific lsokinetic Activity

This article investigates the concept of physiological overflow during speed-specific isokinetic exercise. The idea was tested on 30 volunteers; 14 female, 16 male; mean age 24.5 years, age range 17-29 years; who were subjected to a repeated m o r e s experimental design. Testing involved 5 repetitions of knee extension/flexion at the velocity spectrum speeds of 80, 7 20, 180,240, and 300 degrees /sec preceded by a warm-up at 3 gradient submaximal repetitions and 1 maximal effort at each speed. The experimental treatment consisted of isokinetic exercise of the knee musculature to the level of 50% quadriceps fatigue at the speed of 180 degrees /sec in a format of 3sessions per week over a period of 8 weeks. Analysis of variance testing with repeated measures revealed statistically significant differences in quadriceps and hamstrings function for peak torque, torque acceleration energy, and watts average power at all velocity spectrum speeds over the period of experimentation. It was concluded that a +/-120 degrees /sec physiological overflow of exercise effects to both slower and faster speeds existed during the program of isokinetic activity. J Orthop Sports Phys Ther 1987;9(3):106-110.     

The Effect of Electrical Stimulation and lsokinetic Exercise on Muscular Power of the Quadriceps Femoris

The purpose of this study was to compare the power and strength changes, of the quadriceps femoris muscle group, following 6 weeks of training. Twenty-seven moderately trained, female subjects were placed into three equated groups: electrical stimulation plus isokinetic exercise (ES + IE), isokinetic exercise (IE), and electrical stimulation (ES). A CybexQ I1 isokinetic dynamometer was used for testing the quadriceps ' power and strength output at the velocities of 0, 30, 100, and 180 O/ sec. The ES + IE and ES groups received faradic stimulation (progressive from 10- 20 mA) from a Multitone Multifaradic Unit (model F283, Multitone Electric Co., London, England). In addition, the ES + IE group performed isokinetic contractions concurrently with the faradic stimulation. Thigh circumference (TC) and time to peak tension (TPT) were also calculated during the pre-, mid-, and post-tests. Results indicated that a significant power increment was evident between the pre- and posttests and the pre- and mid-tests for the combined groups (p < 0.05). However, there were no significant power increases between the three separate groups at the four velocities. Significant power differences (P c 0.05) for the combined groups between the pre- and post-tests and the pre- and mid-tests at the isokinetic velocities of 30 and OO/sec were also identified. TPT and TC did not change significantly for any group over the 6-week training period. This study indicated that the combined effects of ES + IE, IE, and ES are potentially effective means of improving power and strength; however, data did not reveal one method of training as being significantly superior to another. J Orthop Sports Phys Ther 1986;8(5):260-268.     

Effect of a Lateral Step-up Exercise Protocol on Quadriceps Isokinetic Peak Torque Values and Thigh Girth

Knee injury rehabilitation often includes the step-up exercise. However, the authors have been unable to locate documentation of the effect of the step-up exercise on lower extremity strength indices. The purpose of this study was to determine the effect of a six-week lateral step-up exercise protocol on quadriceps muscle group strength. Twenty female nonathletes (age = 20 +/- 1.5 yrs, ht = 162.6 +/- 4.9 cm, wt = 64.1 +/- 0.5 kg) were randomly assigned to a control or experimental group. Pretest concentric and eccentric strength measures were obtained at 60 degrees /sec on a Kin-Com isokinetic dynamometer. Thigh girth measurements were obtained 10 and 20 cm superior to the knee joint line. An independent t-test of the difference between pre and post isokinetic strength and girth measurements between the control and experimental groups revealed no significant difference (p > .05). In addition, no significant difference was found for the exercised and nonexercised extremity for the experimental group (p > .05). These findings suggest that this lateral step-up protocol did not provide sufficient overload to increase isokinetic strength of the quadriceps muscle group or increase thigh girth in healthy subjects. In addition, open chain assessment of muscle strength may not adequately assess strength changes incurred via closed chain exercise. Clinicians should use caution in assuming that step-up exercises provide sufficient overload to increase thigh girth or isokinetic quadriceps peak torque values. J Orthop Sports Phys Ther 1992;15(3):151-155.     

The effect of mild symptomatic patellar tendinopathy on the quadriceps contractions and the Fente motion in elite fencers

To investigate how mild symptomatic patellar tendinopathy (PT) affects quadriceps contractions and the Fente motion, this case-control study examined elite fencers who continue to train and play fully with mild tendon pains. Twenty-four elite fencers (10 women) with mild symptomatic PT and 24 controls (10 women) participated in the study. Concentric/eccentric isokinetic strength of the quadriceps was tested, and peak torque and total work were recorded. Kinematic data from the knee during the Fente motion were collected. The first analysis period (P1) was after heel contact to the maximal flexion of the knee, and the second (P2) was right after P1 to heel-off. Normalized peak torque and work of concentric/eccentric contractions were not significantly different. Affected fencers demonstrated significantly reduced angular velocities at P2 (p = 0.042). The male fencers did not demonstrate any differences. The affected female fencers demonstrated significantly weaker concentric peak torque at 60°·s^-1 (p = 0. 009) and 180°·s^-1 (p = 0.047) and less concentric work at 60°·s^-1 (p = 0.020). They also demonstrated significantly reduced average angular velocities at P2 (p = 0.001). Therefore, mild symptomatic PT seems to have an effect on the isokinetic concentric contraction of the quadriceps and the angular velocity of the knee during the backward Fente motion in elite female fencers who are participating fully in training and competition.

Key points

• It is likely that even mild symptomatic patellar tendinopathy could affect the athletic performances in elite fencers.
• Elite female fencers are more likely to be affected substantially by symptomatic patellar tendinopathy in their sporting ability than male fencers.
• Because weak concentric knee extensors may affect the performance in fencing, not only eccentric training for symptomatic patellar tendinopathy but also proper concentric training of the quadriceps may be helpful in a rehabilitation program of elite female fencers who are participating fully in their training and competition.

Key words: Patellar tendinopathy, elite fencers, isokinetic, kinematics     

Prediction of knee extensor and flexor isokinetic strength in young male soccer players

STUDY DESIGN: Single group, cross-sectional study. OBJECTIVES: To measure various anthropometric and demographic variables in young male soccer players and to use these measurements to develop equations with which to predict the isokinetic, concentric, and eccentric moment of force. BACKGROUND: The development of equations that can predict isokinetic muscle strength from commonly measured subject characteristics can assist in the effective design of training and rehabilitation programs for athletic children. METHODS AND MEASURES: One hundred thirteen male soccer players (13.50 +/- 2.21 years of age) performed eccentric and concentric maximum efforts of the knee extensors and flexors at 60, 120, and 180 degrees/second. Stepwise regression tests were used to develop predictive equations using combinations of age, height, body mass, sexual maturation (Tanner) stage, percentage of body fat, and hours spent training per week. RESULTS: The results indicated a significant relationship of concentric and eccentric isokinetic strength for both knee extensors and flexors with 73-93% of the variance explained by using combinations of age, body mass, percentage of body fat, and hours training per week. Body mass and age were the main predictor variables under concentric conditions, whereas chronological age was not included in the models under eccentric conditions. CONCLUSIONS: The relation between isokinetic moment and multiple anthropometric and demographic variables depends on the type of muscle action examined. The results suggest that the equations we developed can be used to predict the isokinetic moment in trained, young soccer players. A cross-validation analysis is required to confirm the accuracy and the suitability of the equations developed in our study.     

Strength relationship of the knee musculature: effects of gravity and sport*

The purposes of this study were to examine the effects of gravity and sport on the hamstrings-quadriceps strength relationships. The peak torques at four speeds of isokinetic exercise (60, 180, 240, 300 degrees /sec) were determined for 20 male college track athletes, including 10 sprinters and 10 distance runners. The runners were tested on a Cybex(R) II isokinetic dynamometer. Peak torque measurements were corrected for the effects of gravity. Results of the present study showed that: 1) the effects of gravity significantly alters the hamstrings to quadriceps ratio at all velocities, and 2) there is no statistically significant difference in the hamstrings quadriceps strength ratios between the two groups of athletes except at 300 O/sec. At that speed, sprinters had a higher ratio than distance runners. J Orthop Sports Phys Ther 1986;7(5);232-235.