MANUAL PERFORMANCE IN COLD CONDITIONS WHILE WEARING NBC CLOTHING

Manual performance while wearing a whole body covering NBC garment was studied at -10 degrees C. Hands were protected by thin cotton gloves, which were covered with rubber gloves. The test subjects were exposed for 40 min in one of the four conditions: standing at - 10 degrees C, standing for 10 min followed by walking (5 km/h) for 30 min on a trea dmill, standing while holding a solid steel bar (see 2.2), or standing at 20 degrees C. Six different manual tasks were performed after each 40-min exposure. All tests were also performed with bare hands at 20 degrees C. Moreover, the effect of contact cooling on skin temperature s and rewarming thereafter was examined by means of gripping a steel b ar (-10 degrees C) during cold exposure. During exposure to -10 degree s C conditions finger skin temperature rapidly decreased to 10.7+/-2.2 degrees C (mean+/-SD). Improvement of body heat balance by exercise i ncreased finger temperatures to 19.6+/-9.0 degrees C. Hand temperature remained at a higher level both during rest and exercise at -10 degre es C (20.1 +/- 1.7 and 20.6 +/- 6.1 degrees C, respectively). Cold exp osure deteriorated manual performance and especially those functions t hat are related to finger dexterity. Finger skin temperature had high correlation with screwing, peg-board and magazine loading tests (r = - 0.90, r = -0.77 and r = -0.72, respectively, p < 0.01)but no relation was found with hand grip strength (r = -0.03). Manual performance was impaired in every test both by gloves and cooling. Contact cooling dec reased skin temperatures on the palm side of the hand and fingers arou nd twice as effectively in normothermic subjects and 3.9-6.5 times mor e effectively in cooled subjects in comparison to cooling by cold air alone. Contact cooling had no significant effect on skin temperatures on the dorsal side of the fingers. The rewarming rate after the releas e of the steel bar was clearly higher in the dominant hand in comparis on to the non-dominant hand. In conclusion, the present results show t hat the thermal insulation of rubber gloves was clearly insufficient, allowing unacceptably low finger temperatures during work in the cold. However, only those tasks requiring finger dexterity were clearly adv ersely affected. Heat production by physical exercise was able to incr ease finger skin temperature and to partly restore manual performance. Handling of cold tools is especially harmful for the palm side temper ature of the non-dominant hand.