Thermoregulatory responses to intermittent exercise are influenced by knit structure of underwear

Summary The purpose of this study was to evaluate the role of knit structure in underwear on thermoregulatory responses. Underwear manufactured from 100% polypropylene fibres in five different knit structures (1-by-1 rib, fleece, fishnet, interlock, double-layer rib) was evaluated. All five underwear prototypes were tested as part of a prototype clothing system. Measured on a thermal manikin these clothing systems had total thermal resistances of 0.243, 0.268, 0.256, 0.248 and 0.250 m² · K · W^–1, respectively (including a value for the thermal resistance of the ambient environment of 0.104 m² · K · W^–1). Human testing was done on eight male subjects and took place at ambient temperature (T _a)=5°C, dew point temperature (T _dp)=–3.5° C and air velocity (V _a)=0.32 m · s^–1. The test comprised a repeated bout of 40-min cycle exercise (315 W · m^–2; 52%, SD 4.9% maximal oxygen uptake) followed by 20 min of rest (62 W · m^–2). The oxygen uptake, heart rate, oesophageal temperature, skin temperature,T _a,T _dp at the skin and in the ambient air, onset of sweating, evaporation rate, non-evaporated sweat accumulated in the clothing and total evaporative loss of mass were measured. Skin wettedness was calculated. The differences in knit structure of the underwear in the clothing systems resulted in significant differences in mean skin temperature, local and average skin wettedness, non-evaporated and evaporated sweat during the course of the intermittent exercise test. No differences were observed over this period in the core temperature measurements.The views, opinions and/or findings in this report are those of the authors and should not be construed as an official Department of the Army position, policy, or decision, unless so designated by other official documentation