Abstract
Coaches and athletes in elite sports are constantly seeking to use innovative and advanced training strategies to efficiently improve strength/power performance in already highly-trained individuals. In this regard, high-intensity conditioning contractions have become a popular means to induce acute improvements primarily in muscle contractile properties, which are supposed to translate to subsequent power performances. This performance-enhancing physiological mechanism has previously been called postactivation potentiation (PAP). However, in contrast to the traditional mechanistic understanding of PAP that is based on electrically-evoked twitch properties, an increasing number of studies used the term PAP while referring to acute performance enhancements, even if physiological measures of PAP were not directly assessed. In this current opinion article, we compare the two main approaches (i.e., mechanistic vs. performance) used in the literature to describe PAP effects. We additionally discuss potential misconceptions in the general use of the term PAP. Studies showed that mechanistic and performance-related PAP approaches have different characteristics in terms of the applied research field (basic vs. applied), effective conditioning contractions (e.g., stimulated vs. voluntary), verification (lab-based vs. field tests), effects (twitch peak force vs. maximal voluntary strength), occurrence (consistent vs. inconsistent), and time course (largest effect immediately after vs. ~ 7 min after the conditioning contraction). Moreover, cross-sectional studies revealed inconsistent and trivial-to-large-sized associations between selected measures of mechanistic (e.g., twitch peak force) vs. performance-related PAP approaches (e.g., jump height). In an attempt to avoid misconceptions related to the two different PAP approaches, we propose to use two different terms. Postactivation potentiation should only be used to indicate the increase in muscular force/torque production during an electrically-evoked twitch. In contrast, postactivation performance enhancement (PAPE) should be used to refer to the enhancement of measures of maximal strength, power, and speed following conditioning contractions. The implementation of this terminology would help to better differentiate between mechanistic and performance-related PAP approaches. This is important from a physiological point of view, but also when it comes to aggregating findings from PAP studies, e.g., in the form of meta-analyses, and translating these findings to the field of strength and conditioning.
Highlights
In elite sport, small performance differences can decide whether an athlete makes it to the podium or not
We propose alternative terminology to unambiguously differentiate between increases in muscular force/torque production during an electrically-evoked twitch and enhancements of measures of maximal strength, power, and speed following conditioning contractions
The important question that has to be faced and answered is how can researchers and practitioners in the field of strength and conditioning prevent the misconceptions between PAP effects and performance enhancements in the future? In an effort to solve this problem and in accordance with a recent narrative review [12], we suggest to consistently use the terms “postactivation potentiation” (PAP, when referring to the mechanistic approach) vs. “postactivation performance enhancement” (PAPE, when referring to the performance approach)
Summary
A mechanistic (e.g., twitch peak force) and a performance-related understanding (e.g., jump height) of PAP have been established in the literature with different characteristics, e.g., in terms of effective conditioning contractions, testing procedures, or time courses of effects. In light of the available evidence from studies with animals and human beings, Sale [15] defined PAP as an increase in isometric twitch peak force or low-frequency tetanic force/torque after (1) a series of evoked twitches, (2) an evoked tetanic contraction, or (3) a MVC (i.e., conditioning contraction) According to this definition, the evaluation of PAP effects focuses on muscle contractile properties and requires an electrically-evoked response to ensure that the enhancements occur for the same level of electrical stimulation ([9, 12]; Table 1). Before peaking at ~ 7 min following the conditioning contractions, performance is initially decreased most likely due to the negative net effect of fatigue and twitch force/torque potentiation and/or movement pattern interference between conditioning contractions and subsequent exercise [12, 15, 18] These studies consistently showed that, in contrast to the originally suggested definition by Sale [15], the mechanistic factors were marginalized and PAP effects were merely discussed on a performance level
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