Skin wettedness does not influence thermoregulatory behavior during moderate-intensity exercise in tropical natives

The influence of skin wettedness on thermal behavior responses during exercise was investigated under different ambient temperature and relative humidity at a fixed vapor pressure of 2.69 kPa (E1: 35.0°C, 48% relative humidity; E2: 31.0°C, 60% relative humidity; E3: 25.0°C, 85% relative humidity) in tropical natives. Eleven physically active, heat-acclimated males completed three trials: 15 min passive exposure before exercise, 45 min cycling at 60% V˙ O₂peak and 15 min of passive exposure after exercise, with voluntary fan use to maintain thermal comfort. The results indicated that mean skin wettedness was significantly lower in E1 vs. E2 and E3 (0.68 ± 0.05 a.u. vs. 0.76 ± 0.06 and 0.88 ± 0.05 a.u., respectively, all P < 0.05) at the end of exercise. Despite these differences, no participants used the fan in any of the trials (P = 1.000). Rectal and mean skin temperatures were significantly higher in E1 and E2 compared to E3 at the end of exercise (all P < 0.05). Regarding sudomotor responses, forearm sweat rate was higher in E1 and E2 compared to E3 throughout the exercise, whereas forehead sweat rate was significantly higher in E1 than E3 at 45 min (P < 0.05). In contrast, no differences were observed in skin blood flow between environments at 45 min (P > 0.05). These findings indicated that behavioral thermal effectors were not recruited despite greater sudomotor responses, suggesting that tropical natives maintained their thermal perception via effective autonomic effector activation rather than relying on thermoregulatory behavior.