Dyspnea Reduction With L‐Menthol Inhalation Improves High‐Intensity Endurance Running Performance in Healthy Trained Adults

Dyspnea occurs during high‐intensity running in healthy trained individuals and may limit endurance performance. Given that L‐menthol inhalation can alleviate dyspnea in other contexts, we investigated whether L‐menthol inhalation reduces dyspnea and improves endurance performance during high‐intensity running in healthy trained individuals. Nine females (mean ± standard deviation; O 2peak = 55.8 ± 6.8 mL/kg/min) and nine males (O 2peak = 60.3 ± 4.6 mL/kg/min) endurance runners with normal spirometry completed a randomized crossover counterbalanced trial with L‐menthol inhalation or a strawberry scent (placebo). Performance was measured with a treadmill time‐to‐exhaustion (TTE) test at 85% of the peak velocity achieved during a preliminary cardiopulmonary exercise test. Cardiorespiratory, metabolic, and perceptual responses were measured throughout. Compared with the placebo, L‐menthol inhalation reduced dyspnea across the TTE test (∼1 AU; p = 0.004) and extended the TTE test duration (406 ± 94 vs. 445 ± 106 s; p = 0.009). Pulmonary ventilation ( p = 0.377), tidal volume ( p = 0.298), O 2 consumption ( p = 0.277), CO 2 production ( p = 0.786), pulse O 2 saturation ( p = 0.766), and heart rate ( p = 0.974) did not differ between conditions. Breathing frequency was lower with L‐menthol inhalation than with placebo ( p = 0.045). L‐menthol inhalation attenuated dyspnea and enhanced high‐intensity running endurance performance without substantial changes in cardiorespiratory and metabolic responses to exercise. These results suggest that dyspnea constitutes an important constraint on endurance performance during high‐intensity running in healthy trained individuals, and identify acute L‐menthol inhalation as an effective ergogenic strategy for this exercise modality and population.