Synergistic effects of caffeine, l-theanine, and diaphragmatic breathing on esports performance: A randomized...

Esports athletes require exceptional cognitive and motor performance, particularly rapid reaction times (RTs). Although caffeine is widely recognized for its ergogenic effects, the benefits of combining caffeine with l-theanine or diaphragmatic breathing on esports performance have not been thoroughly examined. In this randomized, single-blind, three-arm crossover trial, 15 professional male esports athletes (mean age = 22.9 ± 3.8 years) each received three interventions in randomized order: (1) caffeine only, (2) caffeine + l-theanine, and (3) caffeine + diaphragmatic breathing, with a 7-day washout period between sessions. Primary outcomes included auditory and visual RTs and Aim Lab performance scores. Statistical analysis was performed using the Friedman and Wilcoxon signed-rank tests with Bonferroni correction. Both caffeine + l-theanine and caffeine + diaphragmatic breathing significantly improved auditory RT compared to caffeine alone (P = .027). AimLab scores also improved significantly in both combined intervention arms (P = .015 and P = .006, respectively). Visual RT did not differ between conditions. These findings suggest that combining caffeine with either l-theanine or diaphragmatic breathing may offer synergistic cognitive benefits for esports athletes, particularly in enhancing auditory RT and precision, supporting in-game performance beyond caffeine supplementation alone. Trial Registration: This study was registered at ClinicalTrials.gov (ID: NCT06621797).