Influence of menthol nasal inhalation on self-paced cycling time-trial performance, perceptual and physiological responses in active adult males and females

Abstract

Menthol has been investigated as a perceptual ergogenic aid because it produces a cooling sensation without directly reducing core or skin temperature. However, nasal inhalation remains underexplored during self-paced endurance exercise, particularly in studies examining sex-based differences. This study examined the effects of repeated menthol nasal inhalation and sex on performance, perceptual, and physiological responses during self-paced cycling in physically active adults. Forty participants (20 males and 20 females) completed a pseudo-randomized, counterbalanced study consisting of a familiarization session and two experimental trials: menthol and control. During each trial, participants completed a 15-minute self-paced cycling time trial at an individualized resistance. Menthol vapour or air was administered nasally for 5 seconds at 0, 5, and 10 minutes. Performance outcomes included total distance and distance normalized to body mass. Perceptual outcomes included ratings of perceived exertion (RPE), thermal sensation (TS), and respiratory comfort (RC), while the physiological outcome was heart rate (HR). RPE, TS, RC, and HR were averaged across the 5-, 10-, and 15-minute time points. Performance and HR were analysed using 2 × 2 mixed-design ANOVAs, whereas RPE, TS, and RC were analysed using Wilcoxon signed-rank tests, with Mann–Whitney U tests used to compare condition-related changes between sexes. Participants covered a greater total distance during menthol than control, F(1, 38) = 7.65, p = .009, ηp² = .168, and achieved a greater normalized distance, F(1, 38) = 7.63, p = .009, ηp² = .167. Significant Condition × Sex interactions indicated larger performance improvements among females. Within the perceptual domain, RPE did not differ significantly between conditions (p = .054), whereas TS (p = .029) and RC (p = .041) were significantly lower during menthol, indicating cooler thermal sensations and less respiratory discomfort. Condition-related changes in TS (p = .039) and RC (p = .024) differed significantly between sexes, with larger responses among females. Within the physiological domain, mean HR was significantly higher during menthol (p = .016), with no significant Condition × Sex interaction. These findings indicate that repeated menthol nasal inhalation influences performance, perceptual, and physiological responses during self-paced cycling, with sex contributing to the magnitude of selected performance and perceptual responses.