INTERMITTENT MICROCLIMATE COOLING DURING REST INCREASES WORK CAPACITYAND REDUCES HEAT-STRESS

Requirements for special protective equipment while working in hazardo us environments can present a significantly increased thermal burden a nd early onset of physical fatigue. Ambulatory (backpack) or tethered personal cooling can accelerate metabolic heat removal, but is often n ot practical from an ergonomic standpoint. The efficacy of incorporati ng personal cooling during non-ambulatory rest periods was evaluated i n subjects (n = 8) with varying levels of fitness. Treadmill work (app roximate to 475 W, 40% VO2 max) was alternately performed for 30 min f ollowed by 30 min of rest. Subjects walked and rested under three sepa rate experimental conditions: (1) control (C), in which light clothing was worn; (2) CPE, in which a chemical protective ensemble (CPE) was worn, and (3) CPE plus intermittent microclimate cooling (COOL). The W BGT condition for all trials was 31 degrees C. During the COOL trial t he subjects additionally wore a personal cooling vest which allowed fo r the circulation of chilled liquid over the torso during rest. Under C conditions, relatively modest changes in rectal temperature (T-re) w ere observed, which stabilized over time. CPE wear resulted in a proge ssive rise in T-re and early fatigue. The addition of intermittent coo ling during each rest cycle (COOL trial) significantly attenuated heat storage such that an oscillating, but equilibrated T-re was establish ed and work capacity was at least doubled. Moreover, the perceived coo ling effect was appreciable for all subjects. Therefore, intermittent personal cooling provided a useful means of enhancing work productivit y and may have application for certain military and industrial personn el performing heavy work in hot environments. This approach should pro vide a practical alternative for reducing stress/fatigue when work/res t cycles are employed.