The effect of mouth rinsing with high concentrations of caffeine solutions on lower body muscular endurance among Hong Kong college athletes

Introduction: The use of caffeine mouth rinse (CMR) solutions to enhance athletic and workout performance while mitigating the possible adverse effects of caffeine is increasingly gaining attention. Although one previous study investigated the effect of different dosages of CMR on upper-body muscular performance (Karayigit et al., 2021), the possible benefits of a very high concentration of CMR on lower-body strength were not explored. Purpose: This study aimed to investigate whether high-concentration CMR impacted lower-body muscular endurance in male college athletes who had engaged in resistance training. Methodology: In a randomized, single-blind, and cross-over design, thirteen college athletes with prior experience in resistance training completed three conditions. The conditions involved a 5-second mouth rinse with 25 mL solutions containing 4% CAF solution (VHCMR), 3% CAF solution (HCMR), or sweetened water as a placebo (PLA) prior to a test measuring leg press muscular endurance. The blinding method was to add sucralose, which contains no glucose. In each condition, muscular endurance (repetitions), heart rate, muscle soreness, and ratings of perceived exertion (RPE) were measured. These metrics were recorded for all conditions. The data collected were analyzed using IBM SPSS. Repeated measures ANOVA was used to examine the main effects for (1) condition, (2) time or trial, and (3) condition x time or trial interaction. Results: VHCMR significantly increased muscular endurance compared to PLA (p=0.006), but there was no difference between VHCMR and HCMR (p=0.109). In addition, no significant difference in muscular strength was detected between HCMR and PLA (p=0.062). Moreover, there was no significant difference in heart rate, RPE, and muscle soreness among the three conditions. Conclusion: The VHCMR, but not the HCMR adopted in the present study, seems to improve lower-body muscular endurance.