Abstract

THermoregulatory responses were studied in 10 men and 8 women at rest in air and during 1-h immersion in water at 20, 24, and 28 degrees C. For men of high body fat (27.6 ), rectal temperature (Tre) and oxygen consumption (VO2) were maintained at air values at all water temperatures (Tw). For men of average (16.8 ) and low (9.2 ) fat the change in Tre (deltaTre) was inversely related to body fat at all Tw with V02 increasing to 1.07 l/min for a -1.6 degrees C deltaTre for lean men. For women of average (25.2 ) and low (18.5) fat Tre decreased steadily during immersion at all Tw. The greatest changes occurred at 20 degrees C with little differences in deltaTre and VO2 noted between these groups of women. In comparison with males of similar percent fat, Tre dropped to a greater extent in females at 20 and 24 degrees C. Stated somewhat differently, lean women with twice the percentage of fat have similar deltaTre as lean men at all Tw. For deltaTre greater than - 1.0 degrees C men showed significantly greater thermogenesis compared with women. The differences in thermoregulation between men and women during cold stress at rest may be due partly to the sensitivity of the thermogenic response as well as the significant differences in lean body weight and surface area-to-mass ratio between the sexes. Verf.-Referat