Reliability of testing the knee extensors and flexors in healthy adult women using a Cybex II isokinetic dynamometer

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°/sec) and endurance (240°/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.