Abstract
The reliability of the specially adapted Orthotron KT-II, with stress indicators, has been examined as compared with the Cybex II, which is the established mechanism for isokinetic testing of the knee. Two testing speeds were used with the HUMAC/software system for each machine: 60 deg/sec, and 240 deg/sec. Forty-four healthy men and women, both athletes and nonathletes, with no previous knee injuries, were selected from a university population. Subjects were randomly assigned to one of two groups. Subjects tested once on each machine, with at least a 48-hour recovery period between testing sessions. A two-way analysis of variance was conducted for type of machine and order of machine testing. Sample means for nine measurements of muscular performance, selected from the Humac menu, were compared. What may be significant clinical and statistical differences were found in four of the measurements: (1) work per repetition to body weight ratio; (2) fatigue index; (3) force decay; and (4) total range of motion. Due to problems in achieving proper joint-axis alignment on the Orthotron KT-II, as compared with the Cybex II, position parameters were manipulated mathematically such that both machines had the same zero baseline for reference. Significant amounts of variance were attributed to differences in height, weight, sex, and activity status among subjects in the two groups. The inherent differences between a mechanical hydraulic system such as the Orthotron KT-II, compared with an electrically powered system such as the Cybex II seemed to be most evident in the measurement of fatigue index. Test scores on the Orthotron KT-II tended to show less fatigue than the Cybex II over the same test interval. All other measurements of muscular performance showed insignificant differences between the sample means on the two machines.