Stevens et al. 2016, Running performance and thermal sensation in the heat are improved with menthol mouth rinse but not ice slurry ingestion

Randomised crossover trial (Scand J Med Sci Sports 26(10):1209–1216). Eleven moderately trained male runners each ran a 5-km treadmill time-trial in the heat (33 °C) under three conditions: a 0.01% menthol mouth rinse, ice-slurry ingestion, and a no-intervention control. The menthol rinse significantly improved 5-km time (25.3 ± 3.5 min; P = 0.01 versus control) and lowered perceived thermal sensation, while ice slurry lowered core temperature but did not improve performance. The result is the headline running-specific evidence that a perceptual cooling cue can help while an internal cooling method that actually reduces core temperature does not, implicating perception over thermophysiology. Small, single-sex, unblinded.