Comparison of two cool vests on heat-strain reduction while wearing a firefighting ensemble

This study evaluated the effectiveness of a six-pack versus a four-pack cool vest in reducing heat strain in men dressed in firefighting ensemble, 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 (Tre), mean skin temperature (Tsk), heart rate, and energy expenditure during three test trials: control (no cool vest), four-pack vest, and six-pack vest. The cool vests were worn under the firefighting ensemble and over Navy dungarees. 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). Tolerance time for the control trial (93 min) was significantly less than both vest trials (120 min). Throughout heat exposure, energy expenditure varied during rest and exercise, but no differences existed among all trials (P > 0.05). During the first 60 min of heat exposure, physiological responses were similar for the four-pack and six-pack vests. However, 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. Peak Tre and Tsk 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 compared to four-pack [38.6(0.4) degrees C and 38.1(0.5) degrees C] and controls [38.9(0.5) degrees C and 38.4(0.5) degrees C].(ABSTRACT TRUNCATED AT 250 WORDS)