Cool Vests Worn Under Firefighting Ensemble Increase Tolerance to Heat.

Firefighting in the Navy firefighting ensemble FFE prevents heat dissipation while exposure to high temperatures leads to progressive heat gain. Previous studies in air up to 35 deg C show that cool vests worn under FFE reduce heat strain. However, the effectiveness of cool vests on heat strain during exposure to hothumid air is unknown. The purpose of this study was to compare a small 4- pack vest cVs and a large 4-pack vest cVl in minimizing heat strain in men dressed in the Navy FFE, while resting and exercising in hothumid air 480C1180F, 50 rh - Eight males attempted to complete as many cycles as possible of 30 min rest and 30 min walking during three trials no vest, CVs, and cVl. Measurements included rectal and four skin temperatures, and heart rate. Tolerance time for CVs 58.2i15.8 min and CVL 60.1 or - 10.4 min were longer p.05 than NV 49.9 or - 6.2 min. During the first exercise period, rate of heat storage was greater p.05 for NV 111.7 or - 29.3 W.m2 compared to CVs 96.2 or - 17.9 W.m2 and CVL 96.7 or - 20.5 W.m2. Our findings indicate that cool vests worn under the firefighting ensemble attenuate rate of heat storage and prolong heat exposure tolerance time in a hothumid environment.