Urinary Metabolic Profiles Before and After the Winter Training Season in Female Soccer Players

Background/Objectives: Female soccer players differ from males in body composition, muscular strength, and hormonal fluctuations, which may influence performance, fatigue, recovery, and injury risk. This study aimed to characterize the time course of urinary metabolic perturbation and its persistence during a 20-day winter training season (WTS) using urinary metabolomics. Methods: Urinary metabolites in female soccer players were analyzed before (Bef) and 1 (After_1D) and 7 days after completion (After_7D) of the 20-day WTS using nuclear magnetic resonance (NMR) spectroscopy combined with multivariate analysis. Results: A total of 84 metabolites were identified in urine samples, and distinct group separation was observed by partial least squares discriminant analysis (PLS-DA) in targeted profiling. Among these, 13 metabolites, including adenine, alanine, citrate, creatine, creatine phosphate (PCr), formate, glutamine, glycine, malonate, mannitol, taurine, trimethylamine N-oxide (TMAO), and urea, showed significant changes in the three groups (Bef, After_1D and After_7D). Conclusions: Of the identified metabolites, six metabolites-alanine, PCr, formate, glutamine, glycine, and malonate-were significantly increased at 1 day post-WTS (After_1D) compared with pre-WTS (Bef) levels. These metabolites were lower at 7 days post-WTS (After_7D) than at 1 day post-WTS (After_1D). However, the metabolic profile had not fully returned to pre-WTS levels by day 7, suggesting that recovery following WTS may require longer than at least 7 days after a 20-day WTS.