Ineffectiveness Of Torso Cooling Vests In Reducing Uncompensable Heat Stress

Abstract

Introduction Personal cooling systems have been widely used by both civilian and military personal to reduce the effects of heat stress. Clothing designed to protect military, industrial, rescue personnel and racecar drivers in hazardous environments generally have high thermal insulation and low permeability. The lack of permeability greatly reduces the potential for evaporative and conductive heat loss thereby producing a condition known as uncompensable heat stress. Purpose The purpose of this investigation was to evaluate the physiological responses of individuals exposed to uncompensable heat stress when using a commercially available personal microclimate cooling system. Methods Ten recreationally active male subjects participated in this investigation (24.5 ± 4.3 yrs. and 76.2 ± 9.9 kg). In a randomized fashion, the subjects completed three uncompensable heat stress exposures while walking on a treadmill for up to 60 min at 4.1 km/h in a 43°C and 60% RH environment. The three heat stress treatment conditions were no cooling, cooling vest soaked in ice water, and cooling vest soaked in ice water with an ice water filled insert. Subjects wore a four layer fire-retardant race car driving suit and a closed-faced protective driving helmet during all heat stress exposures. Metabolic and heart rate data were continuously recorded during each heat stress exposure via a portable metabolic analyzer. Core temperature and RPE data were monitored at five min intervals during each exposure. Pre and post body weight was recorder prior to and following each heat stress exposure. Results Core temperature, heart rate, VO2, VE, and RPE all significantly increased (p<0.05) from rest to the cessation of each exercise heat stress exposure with no significant differences between no cooling and the cooling treatment conditions. Time to exhaustion was not significantly different between treatment conditions. Body weight significantly decreased (p<0.05) following each exposure with no significant differences detected between treatment conditions. Conclusion Cooling vests either soaked in ice water or soaked in ice water with an ice water filled insert are not effective in attenuating the rise in core temperature to critical levels during exercise while in an uncompensable heat stress environment.