Age and hypohydration independently influence the peripheral vascular response to heat stress

W. L. Kenney, C. G. Tankersley, D. L. Newswanger, D. E. Hyde, S. M. Puhl, N. L. Turner

Research output: Contribution to journalArticle

Abstract

Seven young (Y, 22-28 yr) and seven middle-aged (MA, 49-60 yr) normotensive men of similar body size, fatness, and maximal oxygen uptake (V̇O2(max)) were exposed to a heat challenge in an environmental chamber (48°C, 15% relative humidity). Tests were performed in two hydration states: hydrated (H, 25 ml water/kg body wt 1 h before the test, 2.5 h before exercise) and hypohydrated (Hypo, after 18-20 h of water deprivation). Each test began with a 90-min rest period during which the transiently increased plasma volume and decreased osmolality after drinking in the H condition returned to base line. This period was followed by 30 min of cycle exercise at a mean intensity of 43% V̇O2(max) and a 60-min resting recovery period with water ad libitum. Although prior drinking caused no sustained changes in plasma osmolality, Hypo increased plasma osmolality by 7-10 mosmol/kg in both groups. There were no significant age differences in water intake, urine output or osmolality, overall change in body weight, or sweating rate. In the H state, the percent change in plasma volume was less (P < 0.01) during exercise for the Y group (-5.9 ± 0.7%) than for the MA group (-9.4 ± 0.6%). Esophageal temperature (T(es)) was higher in the Hypo condition for both groups with no age-related differences. Throughout the 3-h period, mean skin temperature was higher in the Y group and significantly so (P < 0.05) in the Hypo condition. During exercise, forearm blood flow (FBF) was significantly (i.e., 50-60%) lower and mean arterial pressure was significantly (15-20 mmHg) higher in the MA group in both hydration states, yielding an elevated forearm vascular resistance compared with the Y group. Furthermore, there was no interaction between age and hydration state in these peripheral vascular responses. Estimated core-to-skin heat conductance was ~ 50% lower in the Hypo condition but was not significantly different between age groups because the higher FBF of the Y group offset their lower core-to-skin temperature gradient (thus accounting for the similar ΔT(es) in both age groups). It was concluded that age-related alterations in the peripheral circulation limit vasodilation and maintain higher arterial pressures during exercise in a warm environment. These differences are not a function of age-related differences in cardiorespiratory fitness or hydration state but appear to be a primary consequence of the aging process.

Original languageEnglish (US)
Pages (from-to)1902-1908
Number of pages7
JournalJournal of applied physiology
Volume68
Issue number5
DOIs
StatePublished - 1990

Keywords

  • aging
  • blood pressure
  • body temperature
  • peripheral vascular resistance
  • skin blood flow
  • temperature regulation

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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    Kenney, W. L., Tankersley, C. G., Newswanger, D. L., Hyde, D. E., Puhl, S. M., & Turner, N. L. (1990). Age and hypohydration independently influence the peripheral vascular response to heat stress. Journal of applied physiology, 68(5), 1902-1908. https://doi.org/10.1152/jappl.1990.68.5.1902