Voluntary increase in finger temperature in man in a cooling environment.

To test whether man can increase voluntarily skin temperature in a cool environment, 14 subjects (age 15--51) were studied. They came once or twice a week for five to eight sessions of 1 h. The room temperature of various sessions varied from 21.2 to 15.6 degrees C. Temperatures of six fingers were recorded using thermocouples. During trials to increase temperature, subjects were shown a dial indicating temperature of an index finger and were instructed to try to warm their hands. The trials were begun when skin temperatures were stable or were falling, indicating that vasoconstriction was occurring. They were preceded and followed by a rest period. The differences between changes in temperature during the trials and the rest periods were significant for the group of 14 subjects (p less than 0.01). In 10 subjects with individually significant results, differences between the trial and rest periods averaged 5.0 degrees C for 'the best' and 3.9 degrees C for 'the worst' finger. The maximum temperatures during the trials averaged 30.9 +/- 1.0 degrees C (mean +/- SE) in 'the best' finger. During later sessions, subjects were able to increase temperatures without seeing the dial. The results indicate that humans are able to increase voluntarily cutaneous finger blood flow in a cool environment.