The changes in perceptual parameters caused by absorbing a cold/menthol beverage reflect the psychological impact. The mechanism leading to these results seems to involve brain integration of signals from physiological and psychological sources.

In this situation, menthol appears to have the greatest beneficial effect on 9 performance when applied internally. In contrast, the majority of investigations into 10 the external application of menthol demonstrated no performance benefit.

Dallam’s study suggest that the body adapts to nasal breathing by developing an increased tolerance to changes in blood CO₂, lessening air hunger. They also show that it is possible to maintain VO₂ max and peak performance following a period of training using only nasal breathing, and that nasally restricted breathing during training may be beneficial for endurance athletes who want to boost their performance and maintain good respiratory health⁷. This is coherent with findings of previous research, which demonstrated that air hunger could be lessened by using exercises to increase end tidal carbon dioxide and push feelings of air hunger beyond normal ‘comfortable’ level

Menthol applied topically to the tracheal mucosa prior to and during citric acid application or administered continuously as vapors or as an aerosol to the lower airways was without effect on cough. These actions of upper airway menthol treatment were mimicked by cold air delivered to the upper airways but not by (+)-menthol, the inactive isomer of menthol, or by the TRPM8/TRPA1 agonist icilin administered directly to the trachea. Subsequent molecular analyses confirmed the expression of TRPM8 in a subset of nasal trigeminal afferent neurons that do not coincidently express TRPA1 or TRPV1. We conclude that menthol suppresses cough evoked in the lower airways primarily through a reflex initiated from the nose.

• TRPM8 receptors in nasal passages have different effects than those located in the mouth