Efficacy of Body Ventilation System for Reducing Strain in Warm and Hot Climates

This study determined whether a torso-vest forced ambient air body ventilation system BVS reduced physiological strain during exercise-heat stress. Seven heat-acclimated volunteers attempted nine, 2-h treadmill walks at 200 Wsq m in three environments, -40 C, 20 rh HD, 35 C, 75 rh HW, and 30 C, 50 rh, WW wearing the Army Combat Uniform, interceptor body armor IBA and Kevlar helmet. Three trials in each environment were BVS turned on BVS On, BVS turned off BVSOff, and no BVS IBA. In HD, BVSOn significantly lowered core temperature Tak, mean torso skin temperature Ttorso, thermal sensation TS, heat storage S, and physiological strain index PSI, versus BVSoff and IBA P 0.05. For HW n 6, analyses were possible only through 60 min. Exercise tolerance time min during HW was significantly longer for BVSOn 116 - 10 min versus BVSoff 95 - 22 min and IBA 96 - 18 min P 0.05. During HW, BVSOn lowered HR at 60 min versus IBA Tsk from 30 to 60 min. versus BVSOff and IBA, and PSI from 45 to 60 min versus BVSOff and at 60 min versus IBA P 0.05. BVSOn changes in Tre and HR were lower in HD and HW. During WW, BVSOn significantly lowered HR, T sk and Ttorso versus BVSOff and IBA P 0.05 during late exercise. Sweating rates were significantly lower for BVSOn versus BVSOff and IBA in both HD and WW P 0.05, but not HW. These results indicate that BVSOn reduces physiological strain in all three environments by a similar amount however, in hot-dry conditions the BVSOff increases physiological strain.