Premotion silent period in rapid voluntary movement.

The silent period in the agonist prior to rapid voluntary movement (premotion silent period) was observed in the lower limb muscles. The subject was asked to respond to the flashing light by performing a vertical jump as quickly as possible. The most consistent results were obtained in the extensors, particularly the quadriceps. The frequency of the silence of six subjects was 53% in the rectus femoris, 61% in the vastus medialis, and 72% in the vastus lateralis. A neural switching mechanism, directing excitation from preparation phase of jumping into rapid contraction phase, seemed to be attributable to the occurrence of the premotion silent period.