Impact of Synbiotics Intake on Body-Composition-Related Indicators and Physical Performance in Judokas Before the Match

Background/Objectives: This study aimed to investigate the effects of synbiotics intake on body-composition-related indicators and physical performance in judokas from 4 weeks to 3 days before the match. The associations between the changes in fecal succinic acid concentration and the rate of change in physical performance were also examined. Methods: A total of 16 male participants from Aichi University Judo Club were included in a repeated-measures design to compare the effects of non-synbiotics and synbiotics. Body-composition-related indicators and physical performance were assessed, and fecal samples were collected 4 weeks and 3 days before the match. Results: From 4 weeks to 3 days before the match, no significant changes in body composition were observed in either the non-synbiotics or synbiotics group. Regarding physical performance, the non-synbiotics group demonstrated a significant reduction in countermovement jump and rebound jump power. In contrast, the synbiotics group maintained physical performance without significant changes. In addition, the change in fecal succinic acid concentration in the synbiotics group was negatively associated with the rate of change in physical performance, particularly rebound jump power (p = 0.052). In the rebound jump power-decreased group, the change in the fecal succinic acid concentration increased, whereas it decreased in the rebound jump power-increased group, and the difference between the two groups was statistically significant (p = 0.024; AUC = 0.84). Conclusions: Before the match, synbiotics intake and a reduction in the fecal succinic acid concentration may be associated with the maintenance of physical performance in judokas, which may have implications for match performance.