A Standardized Small Sided Game Can Be Used to Monitor Neuromuscular Fatigue in Professional A-League Football Players

Introduction: Training and competition load can cause neuromuscular fatigue (NMF) and modified movement strategy such as an increase in the contribution of the medio-lateral (PlayerLoad™ML(%)) and decrease in the % vertical (PlayerLoad™V(%)) vectors, to total PlayerLoad™ (accelerometer derived measurement in vertical, medio-lateral and anterior-posterior planes) in matches. NMF assessment involves expensive equipment, however given the modification of match movement strategy with NMF, this may be present in a standardised drill. The aim of this study was to determine the utility of a small sided game (SSG) for the measurement of NMF. Materials and Methods: Data was collected throughout a competitive football season. External load was quantified using global positioning (GPS) and accelerometry, and internal load by session rating of perceived exertion (sRPE). A 5 vs 5 SSG and countermovement jump (CMJ), for determination of flight time:contraction time (FT:CT), were performed the day prior to each match. Weekly volume from GPS, PlayerLoad™ and sRPE were calculated across the season. Weekly SSG activity profile and FT:CT was compared between “high” and “low” load weeks determined relative to season average. SSG activity profile was assessed between weeks where FT:CT was above or below pre-season baseline. Impact on match activity profile was examined between weeks where FT:CT and SSG activity profile were higher or lower than baseline. The difference (high vs low load and pre-season baseline) was calculated using the Effect Size (ES) ± 90% CI and practically important if there was a >75% likelihood of exceeding an ES of 0.2. Results: All weekly load metrics increased SSG PlayerLoad™∙m∙min-1 when above season average, however the impact on FT:CT was trivial. Reduced weekly FT:CT compared to baseline resulted in lower SSG PlayerLoad™∙min-1 and PlayerLoad™Slow∙min-1. FT:CT below baseline increased match PlayerLoad™ML(%) and decreased PlayerLoad™V(%) during subsequent match play. Similarly, a reduction in SSG PlayerLoad™∙m∙min-1 was followed by increased match PlayerLoad™ML(%). Conclusion: Changes in select match activity profile variables following a reduction in SSG PlayerLoad™.m.min-1, mirror those seen when FT:CT is reduced. Increased PlayerLoad™ML(%) during matches likely represents fatigue driven modification to movement strategy. Small-sided games may be a useful tool to detect NMF.