Post-activation Potentiation Versus Post-activation Performance Enhancement in Humans: Historical Perspective, Underlying Mechanisms, and Current Issues.

Anthony J Blazevich,Nicolas Babault

doi:10.3389/fphys.2019.01359

Abstract

Post-activation potentiation (PAP) is a well-described phenomenon with a short half-life (~28 s) that enhances muscle force production at submaximal levels of calcium saturation (i.e., submaximal levels of muscle activation). It has been largely explained by an increased myosin light chain phosphorylation occurring in type II muscle fibers, and its effects have been quantified in humans by measuring muscle twitch force responses to a bout of muscular activity. However, enhancements in (sometimes maximal) voluntary force production detected several minutes after high-intensity muscle contractions are also observed, which are also most prominent in muscles with a high proportion of type II fibers. This effect has been considered to reflect PAP. Nonetheless, the time course of myosin light chain phosphorylation (underpinning “classic” PAP) rarely matches that of voluntary force enhancement and, unlike PAP, changes in muscle temperature, muscle/cellular water content, and muscle activation may at least partly underpin voluntary force enhancement; this enhancement has thus recently been called post-activation performance enhancement (PAPE) to distinguish it from “classical” PAP. In fact, since PAPE is often undetectable at time points where PAP is maximal (or substantial), some researchers have questioned whether PAP contributes to PAPE under most conditions in vivo in humans. Equally, minimal evidence has been presented that PAP is of significant practical importance in cases where multiple physiological processes have already been upregulated by a preceding, comprehensive, active muscle warm-up. Given that confusion exists with respect to the mechanisms leading to acute enhancement of both electrically evoked (twitch force; PAP) and voluntary (PAPE) muscle function in humans after acute muscle activity, the first purpose of the present narrative review is to recount the history of PAP/PAPE research to locate definitions and determine whether they are the same phenomena. To further investigate the possibility of these phenomena being distinct as well as to better understand their potential functional benefits, possible mechanisms underpinning their effects will be examined in detail. Finally, research design issues will be addressed which might contribute to confusion relating to PAP/PAPE effects, before the contexts in which these phenomena may (or may not) benefit voluntary muscle function are considered.

Highlights

Both acute and chronic increases in physical function are goals of practitioners in both athletic and clinical arenas
It was confirmed that post-activation potentiation (PAP) is a distinct physiological phenomenon with short window of action that can be largely attributed to myosin light chain phosphorylation within type II fibers and which is observable as an increase in muscle twitch response in skeletal muscle
PAP and PAPE are often considered to be indistinguishable phenomena, which makes sense from the perspective that many similarities exist, e.g., (1) contractile force is enhanced, (2) some delay exists before potentiation is observed that speculatively results from “fatigue,” and (3) the response is much greater in type II fibers

Summary

INTRODUCTION

Both acute and chronic increases in physical function are goals of practitioners in both athletic and clinical arenas. In order to explore the effects of acute bouts of physical activity on muscle function during both electrically evoked (used to test “classical” PAP effects) and voluntary tests, the aims of the current review were to: (1) provide an historical perspective of the evolution of PAP research, (2) critically evaluate the existing literature with respect to the mechanisms that might enhance functional performance or the muscle’s contractile response following a conditioning contraction (i.e., PAP/PAPE), (3) consider the potential functional implications of PAP/PAPE in both athletic and clinical populations, and (4) briefly discuss research study design limitations that need to be considered in future studies

A BRIEF HISTORY OF POST-ACTIVATION POTENTIATION

Summary

CONCLUSIONS