Neuromuscular fatigue, exercise intensity, and elite Australian football

http://www.ncbi.nlm.nih.gov/pubmed/22395264

J Strength Cond Res. 2012 Mar 5. [Epub ahead of print]
Impact of Neuromuscular Fatigue on Match Exercise Intensity and Performance in Elite Australian Football.
Mooney M, Cormack S, Oʼbrien B, Morgan W, McGuigan M.
Source
1 School of Human Movement & Sports Sciences, University of Ballarat, Australia; 2 High Performance Unit, Essendon Football Club, Australia; 3 School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Australia; 4 Sport Performance Research Institute, Aukland University of Technology, New Zealand.

Abstract
This study aimed to quantify the influence of neuromuscular fatigue (NMF) via flight time to contraction time ratio (FT:CT) obtained from a countermovement jump on the relationships between yo-yo intermittent recovery (level 2) test (yo-yo IR2), match exercise intensity (HIR m·min and Load™·min) and Australian football (AF) performance.Thirty seven data sets were collected from 17 different players across 22 elite AF matches. Each data set comprised an athlete's yo-yo IR2 score prior to the start of the season, match exercise intensity via Global Positioning System and on-field performance rated by coaches' votes and number of ball disposals. Each data set was categorised as normal (>92% baseline FT:CT, n = 20) or fatigued (<92% baseline FT:CT, n = 17) from a single countermovement jump performed 96 hours after the previous match. Moderation-mediation analysis was completed with yo-yo IR2 (independent variable), match exercise intensity (mediator) and AF performance (dependent variable) with NMF status as the conditional variable. Isolated interactions between variables were analysed by Pearson's correlation and effect size statistics.Yo-yo IR2 score showed an indirect influence on number of ball disposals via HIR m·min regardless of NMF status (normal FT:CT indirect effect = 0.019 p <0.1, reduced FT:CT indirect effect = 0.022 p <0.1). However, yo-yo IR2 score only influenced coaches' votes via Load™·min in the non-fatigued state (normal: FT:CT indirect effect = 0.007 p <0.1, reduced: FT:CT indirect effect = -0.001 p > 0.1). In isolation, NMF status also reduces relationships between yo-yo IR2 and load™·min, yo-yo IR2 and coaches votes, Load™·min and coaches' votes (Δr > 0.1).Routinely testing yo-yo IR2 capacity, NMF via FT:CT and monitoring Load™·min in conjunction with HIR m·min as exercise intensity measures in elite AF is recommended.