Menthol as an Ergogenic Aid for the Tokyo 2021 Olympic Games: An Expert-Led Consensus Statement Using the Modified Delphi Method

Abstract

Introduction Menthol topical application and mouth rinsing are ergogenic in hot environments, improving performance and perception, with differing effects on body temperature regulation. Consequently, athletes and federations are beginning to explore the possible benefits to elite sport performance for the Tokyo 2021 Olympics, which will take place in hot (~ 31 °C), humid (70% RH) conditions. There is no clear consensus on safe and effective menthol use for athletes, practitioners, or researchers. The present study addressed this shortfall by producing expert-led consensus recommendations. Method Fourteen contributors were recruited following ethical approval. A three-step modified Delphi method was used for voting on 96 statements generated following literature consultation; 192 statements total (96/96 topical application/mouth rinsing). Round 1 contributors voted to “agree” or “disagree” with statements; 80% agreement was required to accept statements. In round 2, contributors voted to “support” or “change” their round 1 unaccepted statements, with knowledge of the extant voting from round 1. Round 3 contributors met to discuss voting against key remaining statements. Results Forty-seven statements reached consensus in round 1 (30/17 topical application/rinsing); 14 proved redundant. Six statements reached consensus in round 2 (2/4 topical application/rinsing); 116 statements proved redundant. Nine further statements were agreed in round 3 (6/3 topical application/rinsing) with caveats. Discussion Consensus was reached on 62 statements in total (38/24 topical application/rinsing), enabling the development of guidance on safe menthol administration, with a view to enhancing performance and perception in the heat without impairing body temperature regulation.

Perceptual and Physiological Responses to Carbohydrate and Menthol Mouth-Swilling Solutions: A Repeated Measures Cross-Over Preliminary Trial

“…Quasi-single blinding was employed, whereby solutions were matched to be colourless, but were not matched for taste. Solutions were known to the experimenter who accompanied participants in the heat chamber, to ensure appropriate medical attention could be given, in the unlikely case of an adverse reaction [53].…”

Short-term effects of menthol on walking dyspnoea in patients with COPD: a randomised, single blinded, cross-over study

“…Chewing menthol gum prior to exercise is a safe, easy-to-implement, low-cost, nonpharmacologic intervention that provides a clinically important reduction in dyspnea in one third of patients and decreases the perception of discomfort during exercise in two-thirds of patients. Continuous release or repeated administration of menthol may have a greater effect on dyspnea reduction throughout exercise [4]. Continuous data are presented as means (SD) and as means and 95% confidence intervals for the difference between the two conditions.…”

“…Exertional respiratory discomfort is the most common symptom in patients with Chronic Obstructive Pulmonary Disease (COPD) [1]. Menthol has recently been proposed as an ergogenic aid to decrease the perception of dyspnea during exercise [2][3][4]. Menthol activates the Transient Receptor Potential Melastatin 8 (TRMP8) channels in the sensory nerve fibers of the tongue, promoting a feeling of freshness and a cognitive illusion of airflow into the airways [2,5,6].…”

“…For example, breathing fresh air (7°C) modestly decreased dyspnoea and increased peak exercise performance in patients with COPD [ 12 ]. Menthol can provide a cooling sensation by stimulating the membrane bound ion channel, TRPM8, inducing a perceived reduction in temperature within the range of 8–28°C [ 4 ]. This cooling sensation could increase the cognitive inspiratory flow and may alter the emotional and affective perception of dyspnoea [ 2 ].…”

Dilution Method of Menthol Solutions Affects Subsequent Perceptual Thermal Responses during Passive Heat Exposure in Non-Heat Acclimated Participants

“…Research has been completed in the areas of time to exhaustion [12][13][14], time trial performance [15][16][17] and repeated sprint activity [18,19]. A recent consensus statement [20] highlighted several areas where the research in menthol and performance is lacking, but also highlighted important safety considerations, concluding that if menthol is to be applied orally (e.g., as a mouth rinse or ingested), that solutions are prepared according to scientific literature and in a well-ventilated area [20]. Another related review pointed to the likely existence of individual sensory thresholds for menthol users and that this may be further altered by timing of administration [21], which has shown some variation in sport and exercise literature, but is yet to be examined methodically, that is, as an independent variable in orally applied menthol [22].…”