Intramachine and intermachine reliability for selected dynamic muscle performance tests.

The Cybex 6000 isokinetic dynamometer is a new isokinetic device for which no published reports of reliability have been presented in the literature. In addition, the manufacturer not only claims that the new Cybex 6000 is reliable but that torque data obtained from the Cybex 6000 are consistent with data obtained from past Cybex systems, such as the Cybex II. The purpose of this study was to investigate the intramachine reliability of the Cybex 6000 to itself and the intermachine reliability of the Cybex 6000 and the Cybex II. Data on peak torque, work, and power were collected using the Cybex 6000, and data on peak torque were obtained using the Cybex II for knee flexion and extension in 20 volunteers (10 males, 10 females). Subjects were tested three times, twice on the Cybex 6000 and once on the Cybex II, approximately 1 week apart across a 3-week period of time at angular velocities of 60, 180, and 300 degrees/sec. Data were analyzed using intraclass correlations. Results indicated that the majority of test-retest correlation coefficients for all parameters for intramachine reliability of the Cybex 6000 were above .90. Comparing peak torque obtained with the Cybex 6000 to that obtained with the Cybex II (intermachine reliability), correlation coefficients ranged from .72 to .89. In conclusion, information obtained on the Cybex 6000 appears to be quite reliable in a test-retest situation using the same equipment and moderately reliable when compared to the Cybex II. Clinical implications for these results are discussed.