Neuromuscular function and systemic immune response following a simulated soccer match: potential predictors of injury risk and recovery effect of post-match hot and cold water immersion

Abstract: Objective: The injury incidence in youth soccer remains high, and the incidence pattern suggests an increased susceptibility to injury during fatigue. However, the support for the recovery modalities used in professional soccer, such as cold/hot water immersion (CWI/HWI), is either conflicting or lacking. Thus, the present study aimed to evaluate the effect of (1) a simulated soccer match (SSM) on neuromuscular function (peak force [PF], time-to-fatigue [TTF], PF immediately post-TTF [PFpost-TTF], and the hamstrings-to-quadriceps [H:Q] ratio of all measures), and (2) CWI and HWI compared to placebo on the recovery of neuromuscular function and systemic immune response (neutrophil-to-lymphocyte ratio [NLR]). Methods: All outcome measures were assessed before and up to 45 hours post-SSM in 40 professional male youth soccer players randomly assigned to CWI, HWI, or placebo. PF was assessed through maximal isometric voluntary contractions (MVICs), TTF through a sustained isometric voluntary contraction performed at 60% MVIC, and PFpost-TTF by performing a MVIC immediately post-TTF. H:Q ratios were calculated from all isometric measurements. NLR was calculated based on neutrophil and lymphocyte counts obtained through venous blood samples. Results: PF and TTF was significantly reduced immediately post-SSM. A small reduction in PFpost-TTF was observed in the hamstrings, but not the quadriceps, and no change for any H:Q ratio was found. There was no group or group × time interaction on neuromuscular function or immune markers, but within-group analyses displayed a shorter recovery time of TTF and PF following HWI and CWI than following placebo. Conclusion: The SSM induced a significant reduction in PF and TTF, but no difference between recovery modalities was observed in any outcome measure. However, by analysing the pattern of recovery, our results suggest a possible benefit of water immersion on the restoration of PF and TTF, but further research is required to make any definitive conclusions.