COMPARISON OF 2 COOL VESTS ON HEAT-STRAIN REDUCTION WHILE WEARING A FIREFIGHTING ENSEMBLE

This study evaluated the effectiveness of a six-pack versus a four-pac k cool vest in reducing; heat strain in men dressed in firefighting en semble, while resting and exercising in a warm/humid environment [34.4 degrees C (day bulb), 28.9 degrees C (wet bulb)]. Male volunteers (n = 12) were monitored for rectal temperature (T-re), mean skin temperat ure (T-sk), heart rate, and energy expenditure during three test trial s: control (no cool vest), four-pack vest, and six-pack vest. The cool vests were worn under the firefighting ensemble and over Navy dungare es. The protocol consisted of two cycles of 30 min seated rest and 30 min walking on a motorized treadmill (1.12 m . s(-1), 0% grade). Toler ance time for the control trial (93 min) was significantly less than b oth vest trials (120 min). Throughout heat exposure, energy expenditur e varied during rest and exercise. but no differences existed among al l trials (P > 0.05). During the first 60 min of heat exposure, physiol ogical responses were similar for the four-pack and six-pack vests. Ho wever, during the second 60 min of heat exposure the six-pack vest had a greater impact on reducing heat strain than the four-pack vest. Pea k T-re and T-sk at the end of heat exposure for 6-pack vest [mean (SD) 38.0(0.3)degrees C and 36.8(0.7)degrees C] were significantly lower c ompared to four-pack [38.6(0.4)degrees C and 38.1(0.5)degrees C] and c ontrols [38.9(0.5)degrees C and 38.4(0.5)degrees C]. Our findings sugg est that the six-pack vest is more effective than the four-pack vest a t reducing heat strain and improves performance of personnel wearing a firefighting ensemble.