During the off-season, soccer players in Korea attend the winter training season (WTS) to build running stamina for the next season. For young soccer players, proper recovery time is needed to prevent injury or muscle damage. In this study, urinary metabolites in young players after 1, 5, and 10 days of the WTS were analyzed using nuclear magnetic resonance spectroscopy (NMR) combined with multivariate analysis to suggest appropriate recovery times for improving their soccer skills. After NMR analysis of the urine samples obtained from young players, 79 metabolites were identified, and each group (1, 5, or 10 days after WTS) was separated from the before the WTS group in the target profiling analysis using partial least squares-discriminant analysis (PLS-DA). Of these, 15 metabolites, including 1-methylnicotinamide, 3-indoxylsulfate, galactarate, glutamate, glycerol, histamine, methylmalonate, maltose, N-phenylacetylglycine, trimethylamine, urea, 2-hydroxybutyrate, adenine, alanine, and lactate, were significantly different than those from before the WTS and were mainly involved in the urea, purine nucleotide, and glucose-alanine cycles. In this study, most selected metabolites increased 1 day after the WTS and then returned to normal levels. However, 4 metabolites, adenine, 2-hydroxybutyrate, alanine, and lactate, increased during the 5 days of recovery time following the WTS. Based on excess ammonia, adenine, and lactate levels in the urine, at least 5 days of recovery time can be considered appropriate.

OBJECTIVES The purpose of this study was to compare the risk factors associated with anterior cruciate ligament (ACL) injuries in elite soccer and taekwondo players by examining landing error scoring system (LESS) scores and limb symmetry index (LSI).METHODS A total of 20 male athletes (10 soccer players and 10 taekwondo players) were evaluated. Participants completed a drop-landing task, and their landing mechanics were evaluated using the LESS. Muscle activation was measured with surface electrodes placed on the rectus femoris and biceps femoris. LSI values were calculated as a percentage based on muscle activation data, using the ratio of the nondominant limb to the dominant limb, to assess asymmetry.RESULTS Significant differences were observed between the two groups in knee valgus angle at initial contact (p=0.005), knee joint displacement (p=0.024), and overall impression (p=0.011). Notably, the soccer players demonstrated a significantly higher LESS score (total score, p=0.024) compared to the taekwondo players. However, no significant differences in LSI were found between the two groups.CONCLUSIONS The findings suggest that elite male soccer players may benefit from targeted interventions, such as neuromuscular control training, to enhance joint stability and correct landing mechanics, compared to taekwondo players.