The application of menthol in sport, exercise and occupational settings: To apply, ingest or discard?

The cold-receptor agonist menthol has been utilised to improve performance by imparting feelings of coolness and freshness to alleviate thermal discomfort. These effects are mediated by peripheral cold-sensitive neurons and trigeminal nerves of the face and oral cavity via activation of TRPM8 channels by either applying, ingesting or swilling menthol solutions. The forcing function exerted by topically applied menthol is probably influenced by a combination of factors, including the percentage of body surface area (BSA) exposed, body region, and dose, but the weighting of each requires clarification, as do factors influencing oral administration. Topically, a greater menthol-mediated forcing function has been shown to alter thermoregulation resulting in heat gain, but the precise mechanisms require clarification. It is unknown whether there is a similar effect when menthol is administered orally, but higher concentrations are reportedly preferred. Consequently, menthol has the potential to improve thermal perception but evoke heat gain responses placing biophysical and behavioural thermoregulation in conflict. Nevertheless, there is a growing body of literature that supports the efficacy of menthol application to improve endurance performance and, more recently, muscular performance. Oral menthol application has been shown to improve time to exhaustion and time trial performance with emerging evidence in power based activities. Independently of the heat storage response, topically applied menthol has also been shown to improve endurance performance and enhance recovery from exercise-induced muscle damage, possibly due to increased motor unit activation. Both methods of application have consistently been shown to ameliorate subjective measures of thermal strain during exercise. Accordingly, the aim of this symposium is to present key literature on the perceptual, thermoregulatory and performance effects of menthol and actively debate the merits of: the medium of application, advised protocols for menthol use during these modalities, the timing of application and the resultant thermoregulatory effects