Mode and speed specificity of eccentric and concentric exercise training

This research was supported by a Duke University Research Council Grant. The purpose of this study was to examine mode and speed specificity of strength training by comparing concentric and eccentric isokinetic exercise of the quadriceps. Forty-eight healthy men (mean age = 23.9 years) were randomly assigned to one of three groups: concentric training (C), eccentric training (E), or control (K). Average force (in Newtons) of 3 concentric and of 3 eccentric quadriceps contractions on the KIN-COM(R) dynamometer at 60, 120, and 180 degrees /sec was evaluated prior to and following a 6 week period during which only the C and E groups trained. Training sessions (3/week) included 4 submaximal and 1 maximal warm-up followed by 10 maximal effort isokinetic contractions of the quadriceps at 120 degrees /sec for each leg. Group C subjects trained concentrically only while Group E subjects trained eccentrically only. A t-test for independent means showed no significant right/left differences. ANOVA and Scheffe's F-tests were then used to assess the differences in training effects among the 3 groups for the left leg only. Results showed that although Group C increased slightly in both concentric and eccentric force at all speeds, the gains were significant only for concentric force at 180 degrees /sec. Group E showed significant gains (p < 0.05) in eccentric force at all speeds but not in concentric force. The K group had no significant change in concentric or eccentric force at any speed. We conclude that the eccentric mode of isokinetic exercise has highly specific strength training effects while the concentric mode has less specific training effects. In addition, speed of exercise does not appear to have specific training effects. J Orthop Sports Phys Ther 1989;11(2):70-75.     

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.     

Muscular power in young women after slow and fast isokinetic training*

The purpose of this study was to determine, via a pilot study, if training at a fast isokinetic velocity (180 degrees /sec) would result in a greater increase in upper-extremity muscular power than training at a slow isokinetic velocity (60 /sec) while exercising through a specific range of motion (1 80"). Twenty normal young women were randomly selected into one high velocity and one slow velocity experimental group. The exercise protocol consisted of four bouts of five maximal reciprocal isokinetic contractions of the shoulder flexor and extensor muscle groups, three times a week for four weeks. Pre- and post-testing with a Cybex I$ isokinetic dynamometer was performed to determine if significant power gains were elicited within the training range of motion. Aiter training, both fast and slow velocity groups showed significant power gains (p < 0.0005). However, the results indicated that neither fast nor slow isokinetic training is more effective for power production within the 1 80 degrees range of motion of shoulder extension in the young women studied. J Orthop Sports Phys Ther 1986;8(1);1-9.     

lsokinetic Torque Levels for Adult Females: Effects of Age and Body Size

The effects of age and body size on isokinetic torque levels for adult females were statistically analyzed. Results indicate that age and to a lesser extent weight and height can account for torque differences in adult women. Additionally, this relationship exists regardless of speed of movement (i. e., 60 degrees /sec and 240 degrees /sec).J Orthop Sports Phys Ther 1984;6(1):21-24.     

Test-retest reliability of the biodex isokinetic dynamometer

The purpose of this study was to determine the test-retest reliability of the Biodex (Biodex, Corp., Shirley, NY) isokinetic concentric mode for a healthy active population for knee extension/flexion utilizing the parameters peak torque and work. Nineteen healthy active male and female subjects ages 20-35 with no history of knee injury were tested bilaterally for concentric knee extension and flexion at 60, 180, 240, and 300 degrees /sec., utilizing standard Biodex protocol. Seven days following the pre-test, a post-test was administered using identical protocol. Data collection of pre- and posttesting was done via a Compaq Desk Pro personal computer and Biodex software programming. The parameters of peak torque and single repetition work were analyzed for knee extension/flexion. Statistical analysis of data showed the intraclass correlation coefficient (ICC) of knee extension peak torque at 60 degrees /sec to be r = 0.95; at 180 degrees /sec, r = 0.96; at 240 degrees /sec, r = 0.95; and at 300 degrees /sec, r = 0.97. Knee extension work ICC values were at 60 degrees /sec, r = 0.96; at 180 degrees /sec, r = 0.97; at 240 degrees /sec, r = 0.96 and r = 0.95 at 300 degrees /sec. All ICCs are significant at the 0.05 level. Therefore, the isokinetic concentric mode of the Biodex dynamometer was reliable for test-retest measures of peak torque, and single repetition work. J Orthop Sports Phys Ther 1990;11(7):298-300.     

Dynamic strength and work variations during three stages of the menstrual cycle

The purpose of this article was to investigate the effects of three different phases of the menstrual cycle on dynamic strength and work performance of the knee flexors and extensors. Twenty-one women (18-36 years of age) were tested for dynamic strength and endurance on a Cybex II isokinetic dynamometer at speeds of 60, 180, and 240 degrees /sec. Each subject was tested within 24 hours from the onset of the menses, at the time of ovulation, and during the luteal phase. Strength was determined by peak torque values of knee flexion and extension at the three speeds. Flexion and extension endurance ratios and a work ratio was determined at a speed of 240 degrees /sec. ANOVA failed to show any significant differences among the strength variables during the three phases of the menstrual cycle. The endurance ratios indicated that peak torque values were less than two-thirds of original strength at the end of 20 repetitions. Flexors fatigued slightly less than extensors. There were no significant differences in work ratios among the three phases. Thus it was concluded that the active woman with a normal cycle should experience no discernible change in strength and work performance as a result of cycle changes.J Orthop Sports Phys Ther 1988;10(4):113-116.     

The effect of a forearm strap on wrist - extensor strength*

Thirty subjects with no pathology of the right elbow were tested using an isokinetic dynamometer to measure wrist extensor strength. Subjects were tested under control and experimental conditions with and without a forearm strap. Tests were conducted at 30 and 120 degrees /sec. Results were plotted on separate graphs using a sequential trials method. No difference in strength was noted at the slower speed. A statistically significant increase in strength with the strap was found at 120 degrees /sec. It was concluded that, in these subjects, the forearm strap made no difference in strength at the slower speed, but significantly increased strength at the faster speed. Facilitation due to sensory stimulation of the skin and pressure on the muscle belly was offered as an explanation. Further research is needed in this area. J Orthop Sports Phys Ther 1984;6(3):184-189.     

Reliability of Testing the Knee Extensors and Flexors in Healthy Adult Women Using a Cybex II Isokinetic Dynamometer

This work was supported by NIH grant P50-AR39221. The purpose of this study was to determine intraobserver and interobserver reliability using a Cybex II isokinetic dynamometer for the measurement of isometric and isokinetic strength (0, 60, 180, 300 degrees /sec) and endurance (240 degrees /sec) in 20 healthy untrained females. Subjects were randomly assigned to one of two testers. Intraobserver reliability coefficients for tester one and tester two ranged from 0.89 to 0.98 and 0.72 to 0.97, respectively. Interobserver reliability coefficients ranged from 0.69 to 0.95 across speeds and movements. Although the testers differed significantly in reliability (p < 0.01), no systematic differences in measured levels of performance were noted between testers one and two for the majority of the measurements. The results indicate that comparable muscular strength and endurance values can be obtained from knee extension/flexion tests at various speeds using a Cybex II isokinetic dynamometer. Comparable values were obtained whether subjects were tested by a single tester on two separate occasions or whether subjects were tested by a different tester on two separate occasions. J Orthop Sports Phys Ther 1991;14(1):37-41.     

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.     

A comparative study of the torque generated by the shoulder internal and external rotator muscles in different positions and at varying speeds

The torque generated by the shoulder internal and external rotator muscles duringconcentric isokinetic contractions has been investigated. Recordings were made in three positions: neutral, 90 degrees of flexion, and 90 degrees of abduction; and at three speeds of contraction (60, 120, and 180 /sec) in each of these positions. Twelve healthy female university students were randomly selected from a 100 female volunteer population. Testing was accomplished using an isokinetic dynamometer. A two-way analysis of variance for position and speed was conducted. The greatest torque values for the internal rotator muscles were achieved in the neutral position, while maximum values for the external rotators were developed in 90 of shoulder flexion. The test speed of 60 degrees /sec was shown to produce the highest torque values for the external rotator muscles. However, no difference in test speeds of contraction was found when analyzing the torque values generated by the internal rotator muscles. Implications for strength training are discussed.J Orthop Sports Phys Ther 1987;9(6):217-222.     

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.     

Sources of error in isokinetic dynamometry: effects of visual feedback on maximum torque

The purpose of this study was to examine the effects of visual feedback on isokinetic maximum torque and reciprocal muscle group ratio of the knee extensors and flexors at a slow (60 degrees /set) and a fast (180 degrees /sec) speed of movement. The real-time gravity-corrected torque output, used as the visual feedback source, elicited a significant increase in the maximum torque output of both muscle groups at the slow speed. There was no improvement at the fast speed of movement. The knee flexor/extensor ratio was not effected by visual feedback or speed of movement. It was concluded that visual feedback of the torque output can improve maximum voluntary contraction in isokinetic dynamometry under certain restrictions on speed and range of movement. J Orthop Sports Phys Ther 1991;13(3):138-142.     

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.     

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 position and speed on ankle plantarflexion in females

This study was undertaken to determine isokinetic plantarflexion strength at various speeds and positions on a Cybex II+ dynamometer. A second purpose of this study was to identify any relationship between calf circumference and strength. Speeds used were 0, 30, and 180 degrees /sec. Positions used were supine with 0 degrees knee extension, supine with 90 degrees knee flexion, and prone with 0 degrees knee extension. Speeds and positions are randomly ordered. Nineteen female subjects were classified as either trained (N = 9) or untrained (N = 10). Plantarflexion strength was greatest in the supine position with 0 degrees knee extension in each of the three speeds tested. The results of a two-way repeated measures analysis of variance test were significant across all speeds occurring only with the trained group at a speed of 0 degrees /sec. Further comparisons of position with other speeds were not significant. Since plantarflexion torques were higher in the supine position with 0 degrees knee extension with a speed of 30 degrees /sec, clinicians might want to use this position and speed to test ankle plantarflexion torque. The relationship between calf circumference and torque was not significant. J Orthop Sports Phys Ther 1990;12(4):153-156.     

The effect of electrical stimulation on quadriceps strength and thigh circumference in menisectomy patients

The purpose of this study was to assess the effects of two training regimens: electrical stimulation and exercise versus exercise alone in increasing quadriceps strength and thigh circumference. Subjects were 21 postmenisectomy patients who were randomly assigned to one of the two groups. The experimental group received quadriceps stimulation 5 days/week for 3 weeks. Both groups maintained a knee rehabilitation program consisting of quadriceps and hamstrings isometric and isotonic strengthening exercises 3 days/week. Results indicated that electrical stimulation combined with a regular program of quadriceps exercise have a significant effect in strengthening the quadriceps at four different contraction speeds (1 20, 180, 240, and 300 degrees /sec). The control group exhibited significant strength gains only at the slower two speeds. Thus, electrical stimulation may be valuable in strengthening at high speeds of contraction. The thigh circumference changes were significant for both groups. J Orthop Sports Phys Ther 1986;8(3):143-146.     

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.     

Effects of Knowledge of Results on Reciprocal, lsokinefk Strength and Fatigue

The purpose of this study was to determine the effects of knowledge of results, i.e., visual feedback from watching the torque curve on the Cybex II recorder, on knee extensor and flexor strength (peak torque in ft-lb), and fatigue (strength decrement) during reciprocal, isokinetic testing at speeds of 15O/sec (slow) and 300 degrees /sec (fast). Knowledge of results induced higher strength and fatigue values in both muscle groups during slow, but not fast, speed tests. The greater amounts of fatigue resulted from elevated initial strength levels at the beginning of the slow speed fatigue tests. The superior quality of the slow speed knowledge of results and longer times to utilize the visual feedback may explain the enhanced strength values. The effect of knowledge of results on strength levels decreased during the course of the slow speed fatigue tests. Results are discussed in terms of information processing and motivation theory. J Orthop Sports Phys Ther 1984;6(3):190-197.     

Isokinetic evaluation of anterior cruciate ligament reconstruction: hamstring versus patellar tendon.

The purpose of the study was to compare the hamstring and quadriceps isokinetic results 6 months postoperatively in patients having patellar tendon or hamstring anterior cruciate ligament (ACL) reconstruction. The study group was comprised of 106 randomly selected patients who had ACL reconstruction with either autogenous patellar tendon (PT), semitendinosus (ST), or semitendinosus and gracilis (ST/G). Hamstring and quadriceps isokinetic strength were assessed at 180 degrees/sec and 300 degrees/sec with the results of the operatively treated leg expressed as a percent compared with the nonoperative leg. The mean results for knee extension at 180 degrees/sec were 68.3%, 74.3%, and 78.1%; and at 300 degrees/sec were 70.7%, 76.7%, and 81.7% for PT, ST, and ST/G, respectively. The mean results for knee flexion at 180 degrees/sec were 86.1%, 80.6%, and 81.7%; and at 300 degrees/sec were 77.6%, 79.1%, and 75.6% for PT, ST, and ST/G, respectively. No statistically significant differences were found in regard to knee extension or flexion strength when evaluating the different tissue sources. The results show that selection of autogenous hamstring or PT used for ACL reconstruction should not be based solely on the assumption of the tissue source altering the recovery of quadriceps and/or hamstring strength. In addition, a majority of the patients had not achieved adequate strength to safely partake in unlimited activities at 6 months postoperatively.     

Peak torque and total work relationship in the thigh muscles after anterior cruciate ligament injury

The purpose of the present study was to 1) assess the relationship between the isometric and isokinetic peak torques (speed of movement 0, 60, 180 degrees /sec) and the total work output of multiple contractions (180 degrees /sec) of the quadriceps and hamstrings in 36 patients having a chronic anterior cruciate ligament (ACL) insufficient knee joint, and 2) determine the possible association of these muscle function parameters with the subjective and functional outcome of the ACL insufficient knees. At every test speed the Pearson product moment (r) and the Spearman rank (r,) correlation coefficients between the peak torque and the total work were highly significant for the quadriceps and hamstrings in the uninjured (r = 0.71-0.93, rs = 0.70-0.90) as well as in the anteriorly unstable (r = 0.82-0.89, rs = 0.79-0.86) knees. All correlation coefficients were higher at the highest speed (180 degrees /sec) of the isokinetic test (r = 0.85-0.93, rs = 0.85-0.90) than at the other speeds (0 and 60 degrees /sec) (r = 0.71 -0.90, rs = 0.70-0.85) obviously since the total work was registered at that speed. Both the peak torque and total work parameters of quadriceps as well as hamstrings correlated significantly with the subjective and functional outcome of the ACL insufficient knees (r = 0.75-0.84, rs = 0.76-0.85): the better the muscular function the better the outcome. In conclusion, in anteriorly unstable knees the total work analysis offers little additional information to that attained by the peak torque measurements. J Orthop Sports Phys Ther 1988;10(3):97-101.