ECCENTRIC AND CONCENTRIC ISOKINETIC KNEE FLEXION AND EXTENSION - A RELIABILITY STUDY USING THE CYBEX-6000 DYNAMOMETER

Objective-To determine the reliability of the Cybex 6000 isokinetic dy namometer in measuring the knee muscle performance concentrically and eccentrically. Methods-18 male and 12 female subjects with no previous knee injuries, who had not previously undergone any isokinetic testin g, were studied. The flexor and extensor muscles groups of both knees were tested at 60 degrees s(-1) and 120 degrees s(-1) with the continu ous concentric-eccentric cycle testing protocol. Variables studied inc luded peak torque, total work, and average power. The interclass corre lation coefficient (ICC 2,1) was used to determine the reliability wit h P < 0.05. Results-Peak torque showed significantly greater ICC than the total work and average power, with test-retest reliability ranging from 0.82 to 0.91 for peak torque, from 0.76 to 0.89 for total work, and 0.71 to 0.88 for average power. Average variability for the three variables studied ranged from 9% to 14%. The ICCs for the three variab les studied were significantly greater at 120 degrees s(-1). The knee extensor muscle group showed greater test-retest reliability, and the results of isokinetic testing in the concentric contraction mode were more reproducible. Conclusions-The Cybex 6000 isokinetic dynamometer s hows high reliability in measuring isokinetic concentric and eccentric variables. Some fluctuation should be allowed when evaluating variati ons of muscle performance between tests.