[Nutrient utilization during cold exposure and adaptation].

Abstract

BACKGROUND: Repeated exposure to cold leads to a decline in the intensity of physiological defence reactions. In the complex of adaptational responses metabolic, thermogenic and insulation reactions predominate. The objective of the present investigation was to provide evidence of the predominating type of response of sportsmen exposed repeatedly to cold in an aqueous environment and to elucidate metabolic processes which serve to meet the energy demands of a certain type of adaptation to cold. METHODS AND RESULTS: The examination was made in a group of volunteers (men, mean age 21.0 +/- 1.8 years, height 1.80 +/- 0.04 m, body weight 77.0 +/- 3.1 kg, body fat 13.2 +/- 1.7%, anaerobic capacity expressed as maximum oxygen consumption 4.5 +/- 0.43 l.min-1). The cold acclimation programme involved immersion of the body into water 14 +/- 1 degree C 3 times a week for 1 month. During cold exposure the median body temperature before the acclimation programme dropped by 3.9 degrees C, after the acclimation programme by 4.1 degrees C. The total metabolic turnover after the programme declined by a 0.23 multiple of the metabolism at rest, at the end of the programme merely by a multiple of 0.07. During immersion the oxygen consumption doubled regardless of the stage of adaptation and an insignificant rise of non-esterified fatty acids occurred before the onset of the programme as well as after its termination. After the first exposure to cold a significant drop of the blood sugar was observed, while after the acclimation programme it increased insignificantly. The serum level of the thyroid stimulating hormone and triiodothyronine were affected only insignificantly by exposure to cold, the thyroxine level only at the borderline of significance before the onset of the acclimation programme. CONCLUSIONS: From values of the blood sugar level, respiratory quotient RQ, the non-esterified fatty acid level and body temperature at the periphery we may conclude that there is a restriction of the carbohydrate component as regards meeting energy demands of cold exposure before adaptation and a mixed type of meeting energy demands after termination of the cold acclimation programme.