Central and peripheral factors in thermal, neuromuscular, and perceptual adaptation of the hand to repeated cold exposures.

We investigated the role of central and peripheral factors in repeated cold exposure of the hand and their effects on temperature response, neuromuscular function, and subjective thermal sensation. Eleven subjects immersed their left hand repeatedly in 8 degrees C cold water for 30 min, 5 d/week, for 2 weeks. Before and following the 2 weeks of exposure, neuromuscular function, blood markers, thermal sensation, and temperature responses of both acclimated (left) and control (right) hands were tested. Minimum index finger temperature pre-acclimation was 10.9 +/- 3.4 degrees C and 10.0 +/- 2.0 degrees C in the left and right hand, respectively, and did not change significantly post-acclimation (left, 12.8 +/- 4.2 degrees C; right, 10.2 +/- 1.1 degrees C). Neuromuscular function was impaired with cooling, but this was significantly different neither between the hands nor over time. Central factors, measured by catecholamines and changes in temperature and cardiovascular response over time, did not change and there were no differences in responses between the exposed and non-exposed hand over time (peripheral adaptation) nor were there any differences in local factors endothelial-1 and nitric oxide. Subjective thermal comfort was improved and the discrepancy that was found between the change in actual and perceived temperature may increase the risk of cold injury in partially acclimatized individuals, owing to an adjustment in behavioural thermoregulation.