Torque-producing capacity is affected by moment arm in the human knee extensors.

The quadriceps femoris MV and knee extensor MA correlated significantly with the knee extensor isometric torque (r = 0.785 and 0.790, respectively, both Ps < 0.001). Furthermore, the knee extensor MA correlated significantly with the knee extensor torque-producing capacity (r = 0.635, P < 0.001). These findings suggest that longer MA is an important factor for achieving higher torque-producing capacity in the human knee extensors.