Background <p>This study aimed to evaluate the effects of caffeinated chewing gum on 50-m freestyle swimming performance, as well as on pre- and post-performance measures of maximal isometric shoulder flexion strength and blood lactate concentration in male swimmers.</p> Methods <p>In a randomized, double-blind, crossover, placebo-controlled design, ten male swimmers (mean ± SD; age 27 ± 10 years; body mass 82.7 ± 13.6&#xa0;kg; height 179 ± 6&#xa0;cm; body fat 11.9 ± 7.3%) completed two experimental trials. Participants ingested either caffeinated (300&#xa0;mg) or placebo chewing gum followed by a 10-minute absorption period. Swimmers then performed a 50-m freestyle time trial in a pool. Maximal isometric shoulder flexion strength and blood lactate concentrations were measured before and after the swim.</p> Results <p>Compared to the placebo, caffeinated gum reduced the 50-m swim time from 28.70 ± 1.21 to 28.18 ± 1.31&#xa0;s, resulting in a performance improvement of -1.83% [95% confidence interval: -2.69%, -0.63%] (<i>p</i> = 0.013). However, there were no significant effects of caffeine supplementation on maximal strength (<i>p</i> = 0.261) or blood lactate levels (<i>p</i> = 0.586), nor significant interactions between supplementation and time.</p> Conclusion <p>Ingesting caffeinated chewing gum just 10&#xa0;min prior to exercise led to a significant enhancement (-1.83%) in 50-m freestyle swimming performance time, independent of changes in maximal shoulder flexion strength or blood lactate concentrations. This suggests that rapid caffeine absorption can benefit sprint swimming performance without affecting muscle strength or lactate metabolism in male swimmers.</p> Clinical trial number <p>Brazilian Clinical Trial Registry (<a href="https://ensaiosclinicos.gov.br">https://ensaiosclinicos.gov.br</a>: RBR-3GX2H7F). Registered on October 1, 2025, retrospectively registered.</p>