Abstract

Peppermint oil (menthapiperita), a commonly used herbal remedy for gastrointestinal distress because of its effect of reduced smooth muscle tonicity, has been shown to improve results on pulmonary function tests, possibly due to bronchodilatory mechanisms. Given the potential benefits of peppermint on pulmonary function, our pilot study aimed to investigate the acute effects of peppermint oil ingestion on exercise performance, in particular the ventilatory threshold. Characterized as the inflection point at which pulmonary ventilation increases out of proportion to metabolic rate, the ventilatory threshold is positively associated with endurance performance. We hypothesized that a single ingestion of 1mL peppermint oil diluted in 250mL water would raise the ventilatory threshold as a percentage of maximal oxygen consumption (VO_2max) during a cycling graded exercise test 10 minutes following ingestion. Six healthy male participants performed two graded maximal exercise tests on a cycle ergometer under randomized, single blind trials of peppermint oil and placebo. For each exercise test, agreement amongst three analytical methods was used to validate the inflection point at which the ventilatory threshold occurred. We found that ingestion of peppermint oil resulted in the ventilatory threshold occurring at a significantly higher percentage of VO_2max compared to placebo (70.2±2.2% of VO2maxvs66.2±2.0% of VO_2max, p<.05). In contrast, VO_2max values were not different between the two conditions. Our findings suggest that peppermint oil ingestion may acutely have a positive impact on the ventilatory threshold by raising the percentage of VO_2max at which the ventilatory threshold occurs. Further research is needed to elucidate the mechanism through which peppermint oil elicits this response.

Keywords: Peppermint oil;Ventilatory threshold;Endurance exercise

Abbreviations: VO_2max: Maximal oxygen consumption; VO₂: Oxygen consumption; VCO₂: CarbonDProduction; W: Watts; PER: Respiratory Exchange Ratio; V_E: Ventilation