The present study was designed to examine the relative influence of calendar age, anthropometric measures, such as percentage body fatness (%fat) and surface area-to-weight ratio (Ad/Wt), maximal oxygen uptake (VO
2max), pedometer readings (PR) and microclimate temperatures in daily life on thermoregulatory responses of older men to heat and cold stress. During 60-min heat exposures [by placing the lower legs and feet in a 42°C water bath under a warm condition (35°C, 45% rh) ] in summer, final rectal temperature (T
re), whole body sweating rate (M
sw), M
sw/ΔT
re, and final mean bloodpressure (MBP) were closely related to PR. Final skin blood flow and cutaneous vascular conductance on the thigh were mainly affected by VO
2mx. Final mean skin temperature (T
sk) and the thigh sweating rate (T
msw) were mainly influenced by age and Ad/Wt, respectively. PR had a secondary influence on T
Sk and T
msw, age a secondary influence on M
sw, M
sw/ΔT
re and MBP, and thirdly %fat had an influence on M
sw/ΔT
re. A similar tendency was observed in summer, although the parameters of heat responses related to PR were decreased. During 60-min cold exposures (12°C, 45% rh) in winter, VO
2max had significant influence on final T
sk, metabolic heat production (M), dry heat loss (DHL), respiratory heat loss (RHL), and skin thermal conductance, and PR affected on heart rate. The %fat was a secondary factor for T
sk and DHL, Ad/Wt a secondary factor for M and RHL, and also VO
2max a secondary factor for final heart rate, respectively. Similar relations were also found for the summer responses to cold stress (17°C, 45% rh) . The PR had significant negative correlations with microclimate temperatures on the chest (spring), upper arm (spring and summer) and back (winter) in daily life. It was concluded that thermoregulatory responses of older men to heat and cold were mainly influenced by pedometer readings reflecting exercise habits and aerobic fitness, together with secondary effects of calendar age and anthropometric factors.
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