Torque variations during repeated passive isokinetic knee movements in persons with multiple sclerosis.

The purposes of this study were to investigate the effect of movement repetitions on resistive torque during passive isokinetic dynamometry of the knee and to determine the role of electromyographic activity in the stretched muscles on the torque measurements. Ten persons with multiple sclerosis and hypertonia of the knee muscles were compared with 10 healthy age- and gender-matched control subjects. During series of 10 flexion and extension movements of the knee at 60, 180 and 300 degrees/s, torque and electromyographic activity in the stretched muscles were registered. The persons with hypertonia presented a significantly larger torque reduction (p < 0.05) than the control subjects in all test conditions except for repeated knee flexion at 300 degrees/s. Electromyographic activity in the stretched muscles was not identified as the only explanatory mechanism for the reduction in hypertonia during the movement repetitions, suggesting that other factors were also involved.