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.

Keywords:

• activewear
• body heat content
• calorimetry
• clothing
• mining

ACKNOWLEDGMENTS

This work was supported by the Deep Mining Research Consortium, which comprises Agnico-Eagle Mines Ltd., Barrick Gold Corporation, Vale, Rio Tinto PLC, Xstrata-Copper, and Xstrata Nickel. Funding support was provided by the Canadian Mining Industry Research Organization and Leaders Opportunity Fund from the Canada Foundation for Innovation (funds held by Dr. Glen Kenny). Dr. Glen Kenny was supported by a University of Ottawa Research Chair Award. The authors would like to thank Ms. Cheryl Allen of Vale and Mr. Daniel Gagnon of the University of Ottawa for their assistance in the preparation of this manuscript.