Influence of physical contact on neuromuscular fatigue and markers of muscle damage following small-sided games

Objectives: Physical contact is frequent in rugby league competition and is thought to be a major contributor to the fatigue and creatine kinase (CK) response, although direct evidence is lacking. The aim of this study was to investigate the influence that physical contact had on the fatigue and CK response to small-sided games. Design: Cross-over, counter-balanced study. Methods: Twenty-three junior elite rugby league players were divided into two groups. Group one played a contact game on day 1 before playing a non-contact game 72 h later; group two played the games in reverse order. The rules were identical for each game, with the only difference being a 10 s contact bout every 50 s during the contact game. Upper and lower body neuromuscular fatigue and blood concentrations of CK were assessed immediately before, immediately after, and 12 and 24 h after the games. During each game, players wore global positioning system units to provide information on movements. Results: CK increased after both games, peaking immediately following the non-contact game; CK was still rising 24 h following the contact game. The difference between the two conditions was practically meaningful at this point (likelihood = likely, 82%; ES = 0.86). There were moderate to large reductions in upper body power following the contact game (ES = -0.74 to -1.86), and no reductions following the non-contact game. Conclusions: This study indicates that large increases in blood CK and upper body fatigue result from physical contact. Training sessions involving physical contact should be performed well in advance of scheduled games. (C) 2013 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.