Effects of fan cooling with an air-perfused rucksack on physiological and perceptual strains in young men while running in uncompensable hot environment.

Background: Cooling devices reduce thermal strain during pre-, between-, and postexercise. However, their efficacy during moderate/intensity runs in hot conditions with airflow equivalent to the running speed remains unclear. This study assessed physiological and perceptual responses to neck and upper back fan-cooling through an air-perfused rucksack under such conditions.

Methods: Ten young men ran at 60% V̇O2peak for 30 min in 35 °C, 50% relative humidity with (FAN) and without (CON) air-perfused rucksacks with a hood in a randomized order. Headwind equal to running speed was provided in both conditions. The fan-cooling trial consisted of upper back and neck fan cooling with airflow at 4-5 m/s via two fans attached on either side of the rucksack. Rectal and skin temperatures, whole-body thermal sensation, thermal comfort, and changes in body mass were measured.

Results: Upper back skin temperature and thermal sensation were significantly lower throughout the exercise in the FAN than in the CON, whereas thermal comfort was significantly higher at 15-40 min in the FAN (all P≤0.05). Heart rate elevation during 30 min of running was attenuated in the FAN compared to that in the CON (P≤0.05). No significant differences in rectal and mean skin temperatures, or total body mass loss were observed between the two trials.

Conclusions: These results indicate that additional fan-cooling on the upper back and neck during running in uncompensable hot conditions with a headwind had limited physiological benefits. However, whole-body-based thermal sensation and comfort are partially improved with the use of an air-perfused rucksack.