Abstract: An apparatus and method for controlling the torque of an exercise machine acting on a user is disclosed. The invention determines the torque which the user is able to exert at different positions and velocities, and develops a strength model of the user. Based on the strength model of the user, the invention determines a desired velocity profile for the user's exercise. The velocity profile may be chosen to maximize the amount of power output by the user or to provide whatever other type of exercise specified. The invention then controls the torque acting on the user so that the exercise is accomplished according to the desired velocity profile.