Inertial effects on the assessment of performance in isokinetic dynamometry.

Moments due to acceleration and deceleration periods influence the joint moment (torque) in isokinetic dynamometry. The purpose of this study was to evaluate the differences in the peak moment and the moment development during the initial acceleration period of isokinetic concentric knee extension before and after correction for inertial effects, and evaluate their relationship. The moment development was expressed by the work produced during the initial 0.125 s of the movement. Five male and five female healthy young adults participated in the study. Seven concentric knee extensions at 1.04, 3.14 and 5.24 rad/s were performed on a Biodex dynamometer. Inertial moments were calculated using acceleration data derived from the Biodex software angular displacement data. After inertial correction, the maximum errors in the original peak moment and the moment development at the inital 0.125 s were 7 and 16%, respectively, and were recorded at 5.24rad/s. At slower velocities (1.04 and 3.14 rad/s) the effects of inertial moments on the peak moment and the work at the initial 0.125 s were negligible. Inertial moments did not influence the relationship between the examined parameters at the three velocities. In conclusion, inertial moments affect the peak moment and moment development during the initial acceleration period at high velocities of isokinetic testing and therefore these effects should be considered in order to obtain valid results in isokinetic dynamometry.