Abstract
Background and Purpose: Fixture congestion, game-intensities and limited recovery negatively influence physical/physiological responses during a competitive soccer season. Therefore, the aim of the investigation was to examine weekly alterations in neuromuscular performance markers, creatine kinase and hydration in elite soccer players throughout a season. Study Design: Longitudinal Observational Study. Methods: Sixteen male professional soccer players competing in the English Football League Championship were assessed over the course of a season. All players provided a urine sample, a blood sample to assess creatine-kinase concentration and performed a countermovement jump test at the start of the season, in-season, pre-and post-match over 38 weeks. Results: Jump height was the most common marker of performance to be significantly reduced in-season compared to baseline (-5.4 to -11.3%, P<0.05) with 45.2% of the time-points affected. Measures of FT:CT (-7.5 to -12.4%) and AP (-9.4 to -11.5%), also showed significant deteriorations throughout the season compared to baseline (P<0.05) at several time-points. Max force (MF) significantly increased in-season (+5.1 to 7.0%) in 20% of the observed time-points compared to baseline. CK concentration significantly increased during 19% of the time-points (P<0.05; 62 to 159%). Urine osmolality demonstrated significant differences in season compared to baseline, but none to levels of dehydration. Conclusion: Monitoring elite soccer players over the course of a competitive season shows alterations in neuromuscular performance and hydration status. These data suggest that assessing counter-movement jump performance may be a useful marker for monitoring responses to training/competition, while creatine-kinase and hydration status may be limited.