Effects Of Cooling On Performance Time And Recovery In Individuals Wearing A Prototype Firefighter Ensemble

Abstract

While providing protection in hazardous environments, a firefighter ensemble (FE) contributes to the development of uncompensable heat stress due to high clothing insulation and the reduction in evaporative heat loss. Prolonged exposure to heat stress increases the risk of overexertion and heat illness in firefighters and reduces the performance time (PT) and rate of recovery even at low work intensity. PURPOSE: The purpose of this study was to investigate the effects of body cooling (BC) by utilizing water (conductive) cooled garments on PT and recovery in individuals exercising while wearing a prototype FE (PFE). METHODS: Six male subjects completed three randomly assigned exercise sessions in an environmental chamber (35 °C, 50% relative humidity) while wearing a PFE under control (CON; no cooling) or two cooling conditions: a top (head, neck, forearms) cooling garment (TCG) or a whole body cooling garment (CG); at water inlet temperature (Tin) of 18 °C. The treadmill walking protocol consisted of 3 stages of 15 min exercise at 75% VO2max, and 3 stages of 10 min rest following each exercise stage. Each stage of exercise was stopped if the subjects reached 90% of HRmax or requested to stop. Core and skin temperatures, and heart rate (HR) were measured pre, during, and post session, and PT was recorded. RESULTS: The results showed that PT for CG was 13.5 and 12.8 min longer than CON and TCG (p≤ 0.05), respectively, while thermal strain on HR (DHRt=HRendrecovery -HR0) in CON was 14.7 and 26.8 (beats/min) greater than TCG and CG (p≤ 0.01), respectively. The rate of increase (total change divided by PT) in mean body temperature (Tb) was also significantly less in CG than either CON or TCG (p≤ 0.05). CONCLUSIONS: The results of this study suggest that the application of a BC garment prolongs performance duration and improves the recovery time of individuals working in this PFE. These results also suggest that conductive BC was effective in promoting heat dissipation from the body while wearing the PFE and mitigated a level of uncompensable heat stress. In addition, the study also showed that the BC on a greater body surface area (CG) better suppressed elevation in Tb and elicited a longer PT than cooling on a limited area (TCG). However, the optimal level of cooling needed to support firefighting activities is not conclusive in this study.