Electric fan-based cooling strategies to mitigate heat strain during prolonged heat exposure in young males

Prolonged exposure to hot-humid environments can elevate core temperature and induce severe cardiovascular strain, potentially triggering an inflammatory response. Electric fan use and cold water consumption are common cooling strategies to reduce core temperature, but it remains unclear whether combining these two can effectively alleviate heat strain during daylong exposure. This study aimed to evaluate the efficacy of combining fan use with cold drink or ice slurry intake in mitigating physiological responses and thermal perceptions during 8 h of heat exposure (36.5 °C, 57 % RH). Fourteen male participants were exposed to four conditions: (i) limited fluid intake (2.5 mL/kg/hour, Con), (ii) fan use with limited fluid intake (2.5 mL/kg/hour, Fan), (iii) fan use with full fluid intake (6 mL/kg/hour, Fan + Fluid), and (iv) fan use with full ice slurry intake (6 mL/kg/hour, Fan + Ice slurry). Body temperature, heart rate, blood pressure, sweat loss, blood immune cell counts, and thermal perceptions were measured. Fan significantly reduced core temperature, cardiovascular strain and immune cell counts after exposure compared to Con (all P < 0.05), but led to a higher dehydration rate (P < 0.001). Fan + Fluid exhibited significantly greater cooling effects across all measured parameters than Fan (all P < 0.01). Except for a lower skin temperature in Fan + Fluid (P < 0.01), no significant differences were found in the improvement of other parameters between Fan + Fluid and Fan + Ice slurry (all P > 0.05). This study demonstrates the effectiveness of fan use combined with full fluid intake in mitigating physiological strain during heatwaves, providing practical implications for public health policy.