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Keywords:

  • dose response;
  • exercise;
  • heat loss;
  • nonthermal factors;
  • skin perfusion;
  • sweat rate

Abstract

The influence of peripheral factors on the control of heat loss responses (i.e., sweating and skin blood flow) in the postexercise period remains unknown in young and older adults. Therefore, in eight young (22 ± 3 years) and eight older (65 ± 3 years) males, we examined dose-dependent responses to the administration of acetylcholine (ACh) and methacholine (MCh) for sweating (ventilated capsule), as well as to ACh and sodium nitroprusside (SNP) for cutaneous vascular conductance (CVC, laser-Doppler flowmetry, % of max). In order to assess if peripheral factors are involved in the modulation of thermoeffector activity postexercise, pharmacological agonists were perfused via intradermal microdialysis on two separate days: (1) at rest (DOSE) and (2) following a 30-min bout of exercise (Ex+DOSE). No differences in sweat rate between the DOSE and Ex+DOSE conditions at either ACh or MCh were observed for the young (ACh: = 0.992 and MCh: = 0.710) or older (ACh: = 0.775 and MCh: = 0.738) adults. Similarly, CVC was not different between the DOSE and Ex+DOSE conditions for the young (ACh: = 0.123 and SNP:= 0.893) or older (ACh: = 0.113 and SNP:= 0.068) adults. Older adults had a lower sweating response for both the DOSE (ACh: = 0.049 and MCh: = 0.006) and Ex+DOSE (ACh: = 0.050 and MCh: = 0.029) conditions compared to their younger counterparts. These findings suggest that peripheral factors do not modulate postexercise sweating and skin blood flow in both young and older adults. Additionally, sweat gland function is impaired in older adults, albeit the impairments were not exacerbated during postexercise recovery.