Physiological changes in women during exercise in cold environments.

Abstract

Both the stress of exercise and the stress of a cold environment have been shown to increase the mobilization and utilization of body fat, thereby reducing body fat stores. Much of the research has been done on either rats or male human subjects. The purpose of this research was to show the physiological changes which occur to young, relatively obese, women who exercised during five consecutive days, for 200 min per day, in each of three environmental, chamber conditions: (1) warm-warm (WW), +15‡C; (2) cold-cold (CC), −20‡C; and (3) cold-warm (CW), −20‡C ambient temperature, with +18‡C air pumped to face masks for warmed air breathing. Oxygen cost of exercise, respiratory quotients, energy intake and utilization, and body composition changes were measured before, during, and after each environmental condition. While the respiratory quotients and the skinfold measurements decreased in the colder conditions, the underwater weighing determined percentage body fat did not show the same decrement as the skinfold measures, indicating a possible translocation of body fat from the subcutaneous depots to the deep body fat depots. Body mass loss was significant (P<0.05) only in the WW condition. Thermogenesis would have been centred in the skeletal muscle and liver during the CW condition; however, with facial and upper airway cooling in the CC condition; brown adipose tissue (BAT) hypertrophy may be postulated at this more intense level of cold stress. Due to a greater stability of depot fat in the female, a longer cold exposure would be required to observe the fully developed BAT thermogenesis which would follow after the consequences of fat translocation which we have documented.