Ice vests extend physiological work time while wearing explosive ordnance disposal protective clothing in hot and humid conditions

Background: Explosive ordnance disposal (EOD) technicians may be required to work in hot, humid environments while wearing heavy protective clothing. We investigated the ability of an ice vest to attenuate physiological strain and subsequently extend work tolerance. Methods: Eight male participants (24.3 +/- 4.1 yr, 51.9 +/- 4.6 mL kg(-1) min(-1)) walked (4.5 km h(-1)) in simulated hot and humid conditions (35 degrees C; 50% relative humidity). Participants wore either an EOD suit (CON) or EOD and ice vest (IV). Heart rate, core and skin temperature were recorded continuously. Results: Participants walked longer in IV compared to CON (8.1 +/- 7.4 min, p < .05). Over 90% of trials were terminated based on participants reaching 90% of their maximum heart rate. IV resulted in cooled skin (p < .001) and a physiologically negligible change in core temperature (p < .001). A condition by time interaction was identified for heart rate (p < .001), with a lower rate of rise in the IV condition. Conclusions: The cardiovascular inefficiency that limited performance was attenuated in the IV condition. The ice vest facilitated heat loss from the periphery; thus, the observed reduction in heart rate may reflect the preservation of central blood volume. The results identify the efficiency of a simple, inexpensive ice vest to assist EOD technicians working in the heat.