Menthol Mouth Rinsing Improves Cycling Performance in Trained Adolescent Males Under Heat Stress

<bold>Purpose: </bold>This study investigated the effect of menthol (MEN) mouth rinsing (MR) on cycling performance during a modified variable cycle test (M-VCT) in adolescent athletes under hot conditions (31.4 +/- 0.9 degrees C, 23.4 +/- 3.7% relative humidity). <bold>Methods: </bold>Trained adolescent male cyclists (n = 11, 16.7 +/- 1.3 years, height 176.6 +/- 8.8 cm, body mass 65.8 +/- 11.6 kg, maximal oxygen uptake 62.97 +/- 7.47 ml<middle dot>kg(-1)<middle dot>min(-1)) voluntarily completed three trials (familiarization and two experimental) of a 30-min M-VCT, which included five 6-min laps consisting of three 6-s accelerations and three 10-s sprints throughout each lap. In a randomized crossover design, MEN (0.01%) or placebo (PLA) (crystal-light), was swilled for 5 s before the start of each lap (total of 6 MR). Power output, distance (in kilometers), core temperature, heart rate, perceptual exertion, thermal stimulation (thermal comfort and thermal sensation), and blood lactate concentration were recorded. <bold>Results: </bold>MEN MR significantly improved M-VCT mean power output by 1.81 +/- 1.57% compared to PLA (MEN, 177.8 +/- 31.4 W; PLA, 174.7 +/- 30.5 W, p < .001, 95% confidence interval [1.73, 4.46], d = 1.53). For maximal intermittent sprints, 6- and 10-s mean power output was significantly higher with MEN than PLA (6 s, p = .041, 95% confidence interval [0.73, 27.19], d = 0.71; 10 s, p = .002, 95% confidence interval [11.08, 35.22], d = 1.29). There was no significant difference in core temperature, heart rate, blood lactate concentration, or any perceptual measure between trials (p > .05) despite significantly higher work with MEN. <bold>Conclusion: </bold>64% of athletes (7/11) improved M-VCT performance with MEN. The results of this investigation suggest that a MEN MR may improve power output during a sport-specific stochastic cycling task in elite adolescent male cyclists.