Carbohydrate and menthol mouth-swilling have been used to enhance exercise performance in the heat. However, these strategies differ in mechanism and subjective experience. Participants (n=12)sat for 60 min in an environmental chamber (35°C; 15±2%). Following a 15-minute control period participants undertook three 15-minute testing blocks. A different randomised swill (Carbohydrate; Menthol; Water) was administered per testing block (one swill every three minutes per block). Heart rate, tympanic temperature, thermal comfort, thermal sensation and thirst were recorded for each swill. Small elevations in heart rate were observed after carbohydrate (ES: 0.22 ± 90% CI: -0.09 to 0.52) and water (0.26; -0.04 to 0.54). Tympanic temperature was moderately different between control and all testing blocks. Menthol showed small improvements in thermal comfort relative to carbohydrate (-0.33; -0.63 to 0.03) and water (-0.40; -0.70 to -0.10), and induced moderate
reductions in thermal sensation (-0.71; -1.01 to -0.40 and -0.66; -0.97 to -0.35, respectively). Menthol also reduced thirst by a small to moderate extent. To conclude, carbohydrate and water may elevate heart rate, whereas menthol elicits small improvements in thermal comfort, moderately improves thermal sensation and may mitigate thirst. This suggests a hedonic response of value in hot conditions for a short-moderate duration.