RESPONSE TO REST AND EXERCISE IN THE COLD - EFFECTS OF AGE AND AEROBIC FITNESS

The aim of this study was to determine whether age-related differences in the response to cold exposure are due to aging per se or are caused by a reduced maximal oxygen uptake (Vo(2max) often observed with aging. Three groups of men, 8 young adults (YA), 8 well-trained seniors (TS), and 11 untrained seniors (US), were tested on a cycle ergometer in thermoneutral (22 degrees C) and cold (5 degrees C) conditions during rest and then during exercise (similar to 50 W). In the thermoneutral conditions, 10 min of rest were followed by 10 min of exercise. After 60 min of rest, subjects entered the cold where 30 min of rest were followed by 30 min exercise. The subjects of the three groups had similar body surface area and subcutaneous fat thickness. It was found that rectal temperature (T-re) decreased during rest in the cold and continued to decrease at a higher rate during exercise in TS and US but not in YA. The mean skin temperature was similar in all the groups, except for the thigh temperature, which was lower in YA than in TS and US. Oxygen uptake (Vo(2)) increased during cold, significantly more so at rest than during exercise. YA displayed the highest Vo(2) during the first 10 min of rest in the cold, whereas TS displayed the highest Vo(2) during exercise in the cold. Neither aging nor Vo(2max) appeared to affect thermal comfort or cold sensation. The results show that during rest and low-intensity exercise in the cold, older men have a faster drop in core temperature than younger men, without protection by enhanced Vo(2max). In conclusion, older age per se, and not reduced Vo(2max), is responsible for the age-related difference in responses to rest and exercise in the cold.