A-32 Free Communication/Poster – Military Physiology: MAY 30, 2007 7:30 AM - 12:30 PM ROOM: Hall E
Spacer-vest technologies have recently been developed to reduce the potential heat strain imposed by body armor, but their efficacy has not yet been studied.
PURPOSE: This study examined the effects of body armor (BA) and spacer-vest (SV) technologies on thermoregulatory responses during exercise-heat stress.
METHODS: Fourteen male Soldiers were studied during 3 randomized trials of intermittent treadmill walking (3.5 mph, 2-3% grade) over 4 h in a hot, dry environment (35°C, 30% rh, 1 m/s wind speed). Clothing configurations for the 3 trials were 1) battledress uniform (BDU), 2) BDU + BA, and 3) BDU + BA + SV Thermal strain measurements included core (Tc), mean skin (Tsk) and local chest (Tchest) temperatures, heart rate, and sweat losses. Exercise intensity was equated (∼530W) by increasing the percent grade for BDU trials to compensate for the added load (7.3 kg) of wearing BA or BA + SV. This allowed isolated examination of the clothing property contribution to thermal strain. Data were analyzed using one (trial) or two-way (trial x time) repeated measures ANOVA and Tukey's HSD post-hoc test.
RESULTS: BDU Tsk (34.9°C) and Tchest (35.5°C), were lower (P<0.05) than BA by 1.0°C and 1.5°C and SV by 0.5°C and 1.1°C, respectively (main effect of trial over 4 h). Heart rate was also lower (P<0.05) in BDU by 7–19 bpm compared with both BA and SV Tc was similar among trials until 2h of exercise, after which BA and SV were 0.25-0.31°C higher than BDU (P<0.05). Sweat losses were also significantly less in BDU (P<0.05) compared to BA and SV, but the magnitude of the difference was small (∼100 ml/h). No differences were observed between BA and SV except for Tsk and Tchest, which were lower in SV by 0.4°C (P<0.05).
CONCLUSION: These results indicate that the clothing properties of BA increase thermal strain independent of added weight. The only effect of the SV technology was to lower Tchest and subsequently Tsk with no change in whole-body sweat losses. Therefore, SV may provide small local improvements in evaporative efficiency. This improvement was not large enough, however, to alter other gross measures of thermal strain.