Participants wore a long-sleeved t-shirt (100% cotton, 160 g), a ventilation jacket (100% cotton, 430 g), undershorts (100% polyester, 80 g), work pants (100% cotton, 315 g), socks (100% cotton, 40 g), and shoes in all three trials. The intrinsic clothing insulation value of the jacket was 0.21 clo and that for the total clothing was 0.53 clo, was determined using a thermal manikin (Thermal manikin, Kyoto Electronics Manufacturing Co., Ltd., Tokyo, Japan). The size of the t-shirt was selected for each participant to adhere tightly to their body surface. To increase the wetted surface area, the long-sleeved type of t-shirt was selected. The ventilation jacket (KU91400, Kuchofuku, Tokyo, Japan) was long sleeved and equipped with two fans (8 cm blade diameter, 194 g) on the lower back (Supplementary Figure S1 ). The fans used a battery box (4 AA nickel-metal hydride, 140 g) and took in outside air. The airflow rate of the fan was 15.1 L s−1, which was set at the maximum of the apparatus because heat loss increases with ventilation flow rates (Yang et al., 2022 (link)). The jacket was tightened around the waist with an elastic band, and then, the air was exhausted from the cuff and neck openings. The airflow velocity underneath clothing was 4.5, 2.5, and 7.0 m s−1 at the cuff, in front of the neck, and behind the neck, respectively (measured using an anemometer; 6006, Kanomax Japan Inc., Suita, Japan).
After baseline measurements at 25°C (50% RH, <0.3 m/s air velocity), the t-shirt was soaked with 350 ± 5 mL of tap water (37°C) using an electric vaporizer in the WET trial, and water was never added later. This amount of water was chosen to saturate the t-shirt without leaving dry spots or dripping. To ensure the volume of water, the clothed body weight was measured before and immediately after the soaking (±5 g error) because the participants had trouble wearing a pre-determined and pre-soaked t-shirt. At the same time, the fans of the ventilation jacket were turned on in the DRY and WET trials. In the CON trial, the fans remained off. Immediately after each preparation of the clothing, the room temperature was elevated to 37°C (50% RH, <0.3 m/s air velocity) and stabilized within 10 min. The participants remained seated during the Ta transition, then they performed three 20-min bouts of walking exercise (Ex1, Ex2, and Ex3) separated by 10-min breaks (B1, B2, and B3). The walking was conducted at a predefined speed (all participants, 4.5 km h−1) and inclines (young, 6.6% ± 2.4%; older, 3.4% ± 2.1%) for a target heat production of 200 W m-2 on the treadmill (%VO2peak, young 39% ± 9%, older 54% ± 8%, as averaged across trials). During the breaks, drinking water (37°C) was provided ad libitum.
After baseline measurements at 25°C (50% RH, <0.3 m/s air velocity), the t-shirt was soaked with 350 ± 5 mL of tap water (37°C) using an electric vaporizer in the WET trial, and water was never added later. This amount of water was chosen to saturate the t-shirt without leaving dry spots or dripping. To ensure the volume of water, the clothed body weight was measured before and immediately after the soaking (±5 g error) because the participants had trouble wearing a pre-determined and pre-soaked t-shirt. At the same time, the fans of the ventilation jacket were turned on in the DRY and WET trials. In the CON trial, the fans remained off. Immediately after each preparation of the clothing, the room temperature was elevated to 37°C (50% RH, <0.3 m/s air velocity) and stabilized within 10 min. The participants remained seated during the Ta transition, then they performed three 20-min bouts of walking exercise (Ex1, Ex2, and Ex3) separated by 10-min breaks (B1, B2, and B3). The walking was conducted at a predefined speed (all participants, 4.5 km h−1) and inclines (young, 6.6% ± 2.4%; older, 3.4% ± 2.1%) for a target heat production of 200 W m-2 on the treadmill (%VO2peak, young 39% ± 9%, older 54% ± 8%, as averaged across trials). During the breaks, drinking water (37°C) was provided ad libitum.
Free full text: Click here
