Post-activation potentiation: The neural effects of post-activation depression.

Abstract

Our knowledge of the neurophysiology of post-activation potentiation (PAP) is limited. The purpose of this study was to examine the effect of PAP on twitch torque and H-reflex amplitude after a 10-s maximal voluntary contraction (MVC). PAP measurements were assessed with the plantarflexors in a relaxed state and during a tonic contraction at 10% MVC. The H-reflex/maximum M-wave ratio (H/M) decreased significantly (P<0.05) and returned to baseline levels after 1 min. The decrement in H/M was depressed when the plantarflexors were active at 10% MVC, and the depression was more obvious in the lateral gastrocnemius than in the soleus muscle. The inhibition induced immediately after contraction could be attributed to post-activation depression. We conclude that PAP after a 10-s MVC cannot be attributed to increased motor neuron excitability through the reflex pathway as assessed by the H-reflex technique.