Repeated exposures to severe cold activate adaptive mechanisms characterized by a diminished sympathetic response and an enhanced vagal activation during cold exposure.
Observational
Does repeated exposure to severe cold alter the autonomic nervous system response to cold tests in humans?
Repeated exposure to severe cold induces physiological adaptation through decreased sympathetic and increased vagal responses.
The responses to cold hand test (blood pressure increase and tachycardia) and to a cold face test (blood pressure increase and bradycardia) were used to study the role of the autonomic nevrous system in cold adaptation in humans. The Eskimos (men, women, children) were shown to have a very weak sympathetic response to cold but the vagal response (bradycardia) was identical to that of white people. A group of mailmen from Quebec city living outdoors approximately 30 h/wk throughout the year was also studied. A significant decline in the cold pressor response and an enhanced bradycardia (cold face test) were observed at the end of the winter. Similarly the fall in skin temperature of the cheek was not as pronounced when the measurements were made in May compared to those made in October. A group of soldiers was also studied before and after an Arctic expedition. It was found that the bradycardia of the cold face test was also more pronounced after sojourning in the cold. These results indicate that repeated exposures to severe cold in men activate some adaptive mechanisms characterized by a diminution of the sympathetic response and a concomitant enhancement of the vagal activation normally observed when the extremities and the face are exposed to cold.
LeBlanc et al. (Fri,) conducted a observational in Cold adaptation. Repeated exposure to severe cold vs. Less exposed state (white people, before winter, before Arctic expedition) was evaluated on Autonomic nervous system response (blood pressure and heart rate) to cold hand and cold face tests. Repeated exposures to severe cold activate adaptive mechanisms characterized by a diminished sympathetic response and an enhanced vagal activation during cold exposure.