Timing and torque involvement in the organisation of a rapid forearm flexion

The study was designed to determine whether the magnitude of force and the timing of force are response parameters involved in the organisation of a rapid forearm flexion to a target. The magnitude of torque and the timing of torque were manipulated independently through manipulations of the total moment of inertia and movement time, and the effect of these manipulations on premotor and motor reaction times was observed. Planned comparison analyses revealed that premotor and motor reaction times increased when a movement, which required the same magnitude of torque as in a fast movement, was performed slower. However, premotor and motor reaction times were not affected when movements were performed at the same speed, but differed with respect to the magnitude of torque required. These results indicate that a different timing requirement in the forthcoming movement is associated with a corresponding change in the amount of central processing time required. Therefore, the timing of torque appears to be a parameter of the movement that is organised in advance of movement execution. However, a change in the specification for the magnitude of torque does not affect the amount of time needed to organise the movement.