Potentiating ballistic limb movements through voluntary production of the stretch-shorten cycle.

The purpose of this study was to examine the effect of learning to produce voluntarily a basic biomechanical mechanism, the stretch-shorten cycle (SSC), on the acceleration of a ballistic arm movement. The task required an elbow flexion at maximal effort performed with the forearm resting upon a horizontal manipulandum. Subjects in three groups received either no augmented feedback, feedback concerning the velocity of the flexion, or a combination of feedback on velocity and feedback related to the rate of stretch of the SSC during 80 training trials. The training trials were preceded by a pretest and followed by a posttest without feedback. Analyses showed that the subjects receiving feedback concerning the SSC exhibited earlier and greater peak angular acceleration than the other groups. These findings provide evidence that acquiring the control of relevant, basic mechanisms like the SSC may be useful in facilitating tasks requiring limb movements of maximal effort.