Torque curves produced at the knee during isometric and isokinetic exercise.

Torque curves recorded during knee extension and flexion at various speeds of isokinetic effort and at selected positions of isometric effort were studied to determine the amount of torque generated at selected speeds of motion, the point in the arc of motion where maximal torque output occurred, the relationship between isometric and isokinetic torques, the relative value of knee flexion and extension torques at various speeds, and the constancy of results in isokinetic testing. The isokinetic torques produced were less than isometric values and decreased as the rate of motion increased. Production of peak torque output occurred later in the arc of motion as the speed of contraction increased in extension. No significant change in the relative ability of the flexors and extensors was seen as a rate of motion increased. Isokinetic test-retest differences were similar at the rates of motion tested.