Abstract
We examined whether blowing hot air above body temperature under work clothing may suppress core temperature. Nine Japanese men engaged in two 30-min bicycle ergometer sessions at a workload of 40% VO2max at 40 °C and 50% relative humidity. The experiment was conducted without wearing any cooling apparatus (CON), wearing a cooling vest that circulated 10.0 °C water (VEST), and wearing a fan-attached jacket that transferred ambient air underneath the jacket at a rate of 30 L/s (FAN). The VEST and FAN conditions suppressed the increases of rectal temperature (CON, VEST, FAN; 38.01 ± 0.19 °C, 37.72 ± 0.12 °C (p = 0.0076), 37.54 ± 0.19 °C (p = 0.0023), respectively), esophageal temperature (38.22 ± 0.30 °C, 37.55 ± 0.18 °C (p = 0.0039), 37.54 ± 0.21 °C (p = 0.0039), respectively), and heart rate (157.3 ± 9.8 bpm, 136.9 ± 8.9 bpm, (p = 0.0042), 137.5 ± 6.5 bpm (p = 0.0023), respectively). Two conditions also reduced the estimated amount of sweating and improved various subjective evaluations. Even in the 40 °C and 50% relative humidity environment, we may recommend wearing a fan-attached jacket because the heat dissipation through evaporation exceeded the heat convection from the hot ambient air.
Highlights
The Tre, Tes, and Tsk-head during two sessions of 30 min exercise at 40% of VO2max intensity (Fig. 1) performed in the 40 °C-Ta and 50%-relative humidity (RH) environment increased slowly and the peak values were markedly suppressed under vest that circulated 10.0 °C water (VEST) or FAN conditions compared to cooling apparatus (CON) condition
Under the VEST condition, T re increased upon entry into the 40 °C-Ta and 50%-RH room and was higher than that under the CON condition until nearly the end of the first exercise session
The amount of heat dissipation by evaporation exceeded the amount of heat convection from the hot ambient air, which was above body temperature
Summary
In FAN condition, a fan-attached long-sleeve jacket made from 100% woven polyester was worn, where the jacket had had two fans (10 cm in diameter, attached at the left and right sides of the back of the waist), which were set at airflow rate of 30 L/s, the strongest of four-level air volume switch equipped in this garment, and were each powered by four AA batteries (KU90720, Kuchofuku, Tokyo, Japan). The body weight of each participant was measured without clothing, and the participant entered a room maintained at 28 °C-Ta and 50%-RH while wearing underwear, a short-sleeve shirt made of 100% polyester, and long, summertime work trousers. Under the VEST condition, the participants wore the cool circulating-water garment between the short-sleeve shirt and the long-sleeve jacket and were asked to remove the long-sleeve jacket during the rest period. The statistical analysis was performed using JMP Pro v.15
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