Thermal perceptions and skin temperatures during continuous and intermittent ventilation of the torso throughout and after exercise in the heat

Objective: This study tested the hypothesis that intermittent cooling in air-perfused vests (APV) will not only maintain thermal balance but, due to cyclical activations of cutaneous thermoreceptors, also enhance thermal perceptions. Method: Ten physically active males completed four conditions where they exercised (walking: 5 km h−1, 2 % gradient) in a hot environment (~34.0 °C, 50 % RH) for 72 min, followed by a 33-min period of rest. They wore an APV throughout. The four conditions differed in respect to the profile of ambient air that was perfused through the APV: continuous perfusion (CP); intermittent perfusion of 6 min ON/OFF periods (IPonoff); a steady increase and decrease in flow rate in equal increments (IPramp); and an initial step-increase in the flow rate followed by an incremental decrease to zero flow rate (IPtriang). Whole body and torso thermal comfort (TC, TTC), whole body and torso temperature sensation (TS, TTS), whole body and torso skin temperature (T ¯ sk, T¯sktorso), local relative humidity (RH¯torso) and rectal temperature (Tre) were measured. Results:
There were no significant differences in Tre, absolute whole body and local T¯sk, TC, TTC and TS between the cooling profiles. However, TTS was cooler in CP and IPramp than IPonoff and IPtriang. Even though intermittent cooling did not significantly enhance thermal perceptions in CP, a trend existed for TC (P = 0.063) to become less favourable over time. Conclusion: To reduce the power consumption and extend the battery life of an APV, it is recommended that an intermittent cooling profile should be adopted.