EFFECTS OF FITNESS, FATNESS, AND AGE ON MENS RESPONSES TO WHOLE-BODY COOLING IN AIR

Simple and multiple regression analyses were used to assess the influence of 12 white men's fitness (aerobic capacity 44-58 ml O2 . min-1 . kg fat-free mass-1), fatness (mean skin-fold thickness 5-20 mm, body fat content 15-36%), and age (26-52 yr) on their thermal, metabolic, cardiovascular, and subjective responses to 2 h of whole body cooling, nude, in air at 10-degrees-C. Fitter men had slower heart rates, and fatter men had higher blood pressures. Fitness had no effect (P > 0.39) on any measured response to cold. Fatness was associated (P < 0.01) with reduced heat loss, heat production, and mean skin temperature; unchanged heat debt; and increased tissue insulation. Age had the opposite effects. When the confounding effects of fatness were held constant by multiple regression, older men responded to cold as though they were 1 mm of skinfold thickness leaner for each 3-4 yr of age. We conclude that aging, even between the relatively youthful ages of 26 and 52 yr, is accompanied by a progressive weakening of the vasoconstrictor response to cold.