Potentiation of the triceps brachii during voluntary submaximal contractions.

Introduction: The effects of postactivation potentiation (PAP) on evoked contractions are well understood, but less is known about the effect of PAP on voluntary submaximal contractions. Using a measure of neuromuscular efficiency (NME) [NME = (mV EMG/Nm torque)] we explored the effects of PAP in the triceps brachii at two muscle lengths. Methods: Evoked twitch and NME were compared at short (40 degrees elbow flexion) and long (120 degrees) muscle lengths. At each length, 12 subjects performed a contraction of 25% maximum voluntary contraction (MVC) torque before and after a potentiating MVC. Results: Twitch torque potentiated more at short length (216.9 +/- 169.3%) than at long length (77.3 +/- 32.6%), but PAP moderately improved NME only at short length (12.2 +/- 8.7%). Conclusions: The greater capacity for PAP at the short length is reflected by greater NME. Compared with evoked responses, the relatively small change in NME suggests a different and more modest role of PAP during voluntary submaximal contractions. Muscle Nerve 43: 859-865, 2011