The Effect of Knee Joint Angle on Torque Control

The purpose of the author's investigation was to examine the effect of knee joint angle on torque control of the quadriceps muscle group. In all, 12 healthy adults produced maximal voluntary contractions and submaximal torque (15, 30, and 45% MVC [maximal voluntary contraction]) at leg flexion angles of 15°, 30°, 60°, and 90° below the horizontal plane. As expected, MVC values changed with respect to joint angle with maximum torque output being greatest at 60° and least at 15°. During the submaximal tasks, participants appropriately scaled their torque output to the required targets. Absolute variability (i.e., standard deviation) of torque output was greatest at 60° and 90° knee flexion. However, relative variability as indexed by coefficient of variation (CV) decreased as joint angle increased, with the greatest CV occurring at 15°. These results are congruent with the hypothesis that joint angle influences the control of torque.