The Influence of Activewear Worn Under Standard Work Coveralls on Whole-Body Heat Loss

Abstract

This study evaluated the influence of activewear undergarments worn under the standard mining coveralls on whole-body heat exchange and change in body heat content during work in the heat. Each participant performed 60 min of cycling at a constant rate of heat production of 400 W followed by 60 min of recovery in a whole-body calorimeter regulated at 40°C and 15% relative humidity donning one of the four clothing ensembles: (1) cotton underwear and shorts only (Control, CON); (2) Activewear only (ACT); (3) Coveralls+Cotton undergarments (COV+COT); or (4) Coveralls+Activewear undergarments (COV+ACT). In the latter two conditions a hard hat with earmuffs, gloves, and socks with closed toe shoes were worn. We observed that both COV+ COT and COV+ACT resulted in a similar mean (±SE) change in body heat content, which was significantly greater compared with the CON and ACT during exercise, suggesting that the rate of thermal strain was elevated to a similar degree in both coverall conditions (CON: 245 ± 32 kJ; ACT: 260 ± 29 kJ; COV+COT: 428 ± 36 kJ; COV+ACT: 466 ± 15 kJ; p < 0.001). During recovery, the negative change in body heat content was greater for both COV+COT and COV+ACT compared with the CON and ACT but similar between COV+COT and COV+ACT due to the greater amount of heat stored during exercise (CON: −83 ± 16 kJ; ACT: −104 ± 33 kJ; COV+COT: −198 ± 30 kJ; COV+ACT: −145 ± 12 kJ; p = 0.048). Core temperatures and heart rate were also significantly elevated for the COV+COT and COV+ACT compared with the CON and ACT conditions during and following exercise (p < 0.05). These results suggest that while activewear undergarments are not detrimental, they provide no thermoregulatory benefit when replacing the cotton undergarment worn under the standard coverall during work in the heat.