Topical application of isolated menthol and combined menthol-capsaicin creams: exercise tolerance, thermal perception, pain, attentional focus and thermoregulation in the heat

We determined the effects of topically applied i) isolated menthol cream, ii) menthol and capsaicin co-application or iii) placebo cream on exercise tolerance, thermal perception, pain, attentional focus and thermoregulation during exercise in the heat. Ten participants cycled at 70% maximal power output until exhaustion in 35°C and 20% relative humidity after application of i) 5% isolated menthol, ii) 5% menthol and 0.025% capsaicin co-application or iii) placebo cream. Thermo-physiological responses were measured during exercise, with attentional focus and pain determined post-exercise on a 0-to-10 scale. Across the three conditions, time to exhaustion was 13.4±4.8 min, mean±SD infrared tympanic and skin temperature was 37.2±0.6°C and 35.1±1.2°C, respectively, and heart rate was 152±47 beats/min, with no changes between conditions (p>0.05). Perceived exertion was lower in the isolated menthol vs. all other conditions (p<0.05, ηp2=0.44). Thermal sensation was higher in menthol-capsaicin co-application vs. isolated menthol (p<0.05, d=1.1), while sweat rate was higher for capsaicin and menthol co-application compared to menthol (p<0.05, d=0.85). The median and interquartile range scores for pain were lower (p<0.05) in the menthol condition (8, 7-8) compared to both menthol and capsaicin (10, 9-10) and placebo (9, 9-10), which was coupled with a greater distraction (p<0.05) in the menthol condition (9, 7-10) compared to placebo (6, 5-7). Despite no performance effects for any topical cream application condition, these data reiterate the advantageous perceptual and analgesic role of menthol application and demonstrate no advantage of co-application with capsaicin.