This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial 4.0 Unported License, permitting all non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ICPESK 2015 : 5 th International Congress of Physical Education, Sports and Kinetotherapy Theoretical Background and Practical Applications of the Physiological Mechanism of Post-Activation Potentiation Dimitrios Patikas a *, Anthi Xenofondos a , Christos Kotzamanidis a * Corresponding author: Dimitrios Patikas, dpatikas@auth.gr a Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece Abstract Post-activation potentiation (PAP) is a mechanism that has gained interest in research during the past years. This is due to the fact that several studies use this physiological mechanism as a tool to improve athletic performance. This review will describe the basic principles of PAP and how exercise can influence the existence and magnitude of PAP. As definition, PAP is the phenomenon of increased force or twitch output that occurs after a high-intensity voluntary or evoked contraction. Although PAP is assumed to occur within the muscle due to the increased phosphorylation of the myosin light chains, several other factors can influence its appearance. The fact that fatigue counteracts the level of PAP, muscular as well as neural properties of the neuromuscular system contribute to the final outcome, despite the fact that PAP is mainly a mechanism that is attributed to changes in muscular level. During the past 5 years, our research group has examined in depth central and peripheral mechanisms that influence performance under the co-existence of PAP and fatigue. Numerous techniques combining the application of electromyography, electrical stimulation and force recording are briefly presented and discussed with emphasis on the practical aspect of interpretation on athletic performance. Using such techniques, some of the recent findings of our research group are presented, giving an insight in the PAP effect immediately after a contraction or after series of contractions and the effectiveness of long-term combined training programs. © 2016 Published by Future Academy www.FutureAcademy.org.uk Keywords: Post-activation potentiation; physiology; isometric; training. 1. Introduction Post-activation potentiation (PAP) is a topic of increased research interest during the past years and more recently has been more intensively investigated among the athletic research community as well. The phenomenon is rather complex and currently there is a significant body of literature that targets to explain its underlying mechanisms and to determine more precisely the range of applications that might have in human performance. Therefore, the purpose of this study is to analyse the basic principles of http://dx.doi.org/10.15405/epsbs.2016.06.6