Significance of the ‘Silent Period’ of Muscles

Abstract

THE most attractive theory of the silent period of muscle action potentials is that of Matthews^1,2 (following a speculation of Fulton and Pi-Suñer³). In his pioneer work on single nerve endings in muscle, he showed that during a twitch, at a time corresponding to the silent period, there was a pause in sensory discharge from the muscle spindles—the endings believed responsible for exciting postural muscular contractions through the stretch reflex. This cessation of excitatory impulses clearly explained the silent period in the motor discharge. Matthews pointed out that the arrangement of muscle spindles in parallel with the main contractile fibres (which is responsible for the pause during a twitch) formed a self-regulating device, or servo-mechanism, for controlling tonic contraction of the muscle. Increased load or the onset of muscular fatigue would cause elongation of the spindles, thereby reflexly calling up a greater contraction of the muscle tending to restore the system to its original length. The classical type of stretch reflex experiment discloses the static characteristics of the servo; the silent period is its transient response.