Reliability of isokinetic Measures

Isokinetic resistance is frequently used to strength profile healthy athletes and to evaluate the status of injured athletes involved in rehabilitation programs. The purpose of this investigation was to determine the reliability of peak torque, torque acceleration energy, endurance ratio, average power, and total work measures obtained with a Cybex isokinetic dynamometer. Fifteen college students underwent a test retest procedure for right and left knee flexion and extension, shoulder flexion and extension, and shoulder internal and external rotation. Highest reliability coefficients were found for peak torque, torque acceleration energy, average power, and total work measures. Lower coefficients were observed for the endurance ratio measure. Higher reliability was generally observed for the knee extension/ flexion test procedure than for the shoulder tests. Article: Since the use of isokinetic exercise by Hislop and Perrine (5), Moffroid et al. (10), and Thistle et al. (15), the procedure has received increasing interest in sports medicine research and clinical practice. Its usefulness in research has included examination of the relationship of muscle strength to fiber type and metabolic enzyme activity (16), the effects of training and performance on muscular strength and endurance (7), the influence of limb speed on torque production (12), and the relationship of peak torque to age, sex, performance, and body weight (9, 13). In the clinical setting, isokinetic exercise is used to evaluate the effectiveness of physical rehabilitation and to provide progressive resistance exercise therapy (3, 4). Most clinicians assume that isokinetic dynamometers provide reliable measures of strength, power, and endurance. While some research has proven the reliability of torque measures (1, 6, 10, 11), little attention has been devoted to the reliability of power and endurance measures. The development of a computer' interface with the Cybex apparatus has enabled the precise and rapid isokinetic measurement of peak torque, angle of occurrence of peak torque, average power, total work, torque acceleration energy, and endurance ratio (14). Barbee and Landis (2) assessed the reliability of some of these computer obtained measurements and reported coefficients of r = .91 to .97 for peak torque, r = .86 to .95 for power, r = .85 to .97 for total work, and r = .13 to .27 for torque acceleration energy. The purpose of this investigation was to examine the reliability of peak torque, torque acceleration energy, endurance ratio, average power, and total work measures obtained with a Cybex isokinetic dynamometer interfaced with a Cybex Data Reduction Computer. METHODOLOGY Fifteen male college students participated as subjects in the study (mean age = 20.53 yrs, weight = 73.56 kg, height = 177.30 cm). Each subject received information regarding the testing protocol and was informed of the comparitively low risk of isokinetic testing. The subjects were given a detailed description of the study, and then asked to sign a form giving their voluntary consent to participate. Each subject was medically screened for previous injury to the knee or shoulder, and only individuals who were free of clinically significant injuries were allowed to