Thermal responses and physiological strain in men wearing impermeable and semipermeable protective clothing in the cold.

The purpose of the present study was to examine the effects of long term cold exposure on thermal responses and physical performance in men while wearing nuclear, biological and chemical (NBC) protective clothing. Six healthy men performed 60 min work/60 min rest cycles during 8 hours at an ambient temperature of -10 degrees C. Work was performed by stepping on a 20 cm high bench 15 times.min-1. Subjects were tested while wearing two different types of NBC clothing: impermeable rubber suit (IP) or semipermeable charcoal impregnated suit (SP) with cold weather underwear layers, as well as rubber gloves, boots and a full-face mask. During the tests oxygen consumption (VO2), rectal (Tre) and skin temperatures and sweat production were measured. Rectal and skin temperatures and body heat content followed the work/rest cycles in both types of NBC clothing. T(re) averaged 37.1 +/- 0.04 and 37.3 +/- 0.1 degrees C for IP and SP (NS), respectively. On average, mean skin temperature (Tsk) was 28.6 +/- 0.2 and 29.7 +/- 0.2 degrees C for IP and SP (p < 0.01), respectively. Finger skin temperature decreased rapidly to below 10 degrees C in both ensembles during the rest periods. During work the finger rewarming rate was 0.49 +/- 0.06 and 0.70 +/- 0.02 degree C.min-1 for IP and SP (p < 0.01), respectively. Decrease in body heat storage (S) during cold exposure was smaller in SP than in IP and S was restored to the level of -0.6 +/- 0.3 and -3.0 +/- 0.6 kJ.kg-1 in SP and IP (p < 0.01), respectively, during the work. Work load, according to VO2 measurements, was 1.5 +/- 0.1 and 1.3 +/- 0.11.min-1 for IP and SP (p < 0.05), respectively. Furthermore, during rest VO2 was 30% (p < 0.001) higher in IP than in SP. In conclusion, both types of NBC protective clothing could be used for long periods in cold conditions at a moderate work load without marked whole body heat debt or heat load. However, peripheral parts of the body experienced a rapid and severe cooling during the rest periods. The semipermeable suit enabled higher body heat storage and faster rewarming of extremities during work than the impermeable suit.