Microenvironment and microcooling for soft body armor

Physical activity in a hot environment has been shown to increase heat storage, which can lead to elevated core body temperature (Tre). This heat storage is more problematic when an individual is wearing soft body armor (SBA), which inhibits convective and evaporative heat loss. Law enforcement personnel typically depend on Level II SBA for protection, which can be worn concealed or external, covers most of the upper body, and weighs ~3 kg. One way to circumvent excess heat storage is to promote air flow under the SBA. The three purposes of this study were to investigate the cooling effects of adding an ambient air induction system (~ 100 L * min-1) and 1.27 cm standoffs in a WBGT = 30 °C environment to: 1) a concealed Level II SBA, 2) an external Level II SBA; and 3) to determine to establish WBGT corrections for concealed Level II SBA at two separate macro- WBGTs (26 °C & 30 °C) for a 60-min workload. Counterbalanced, repeated measures protocols were performed with 9 participants (27 ± 4 yr). Each participant performed cycles of 12-min of walking (1.25 L * min-1) and 3-min of arm curls (14.3 kg, 0.6 L * min-1) with a 5-min rest after the first two cycles for a total of 60-min. During each trial the following variables were recorded every 5-min: Tre; SBA microclimate (iButtons); heart rate; thermal comfort; and perceived exertion. A two-way, repeated measures ANOVA with Bonferroni post hoc analysis was used to evaluate: Tre, microclimate, heart rate, sweat loss, perceived exertion, and comfort. A two-way repeated measures ANOVA was conducted on macro- WBGTs and micro- WBGT differences within both environments (26 °C & 30 °C) and noted a WBGT correction of 6-9 °C appears necessary for individuals wearing concealed Level II SBA in the two tested environments. Ambient air induction, at a rate of ~ 100 L * min-1, improved the microclimate under the SBA, but was unsuccessful in attenuating heat strain (smaller change in Tre, HR) associated with wearing a Level II SBA in either a concealed or external state. (Published By University of Alabama Libraries