Age predicts cardiovascular, but not thermoregulatory, responses to humid heat stress

George Havenith, Yoshimitsu Inoue, Viktor Luttikholt, W. Larry Kenney

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56 Scopus citations

Abstract

Cross-section comparisons of the effect of age on physiological responses to heat stress have yielded conflicting results, in part because of the inability to separate chronological age from factors which change in concert with the biological aging process. The present study was designed to examine the relative influence of age on cardiovascular and thermoregulatory responses to low intensity cycle exercise (60 W for 1 h) in a warm humid environment (35°C, 80% relative humidity). Specifically, the relative importance of age compared to other individual characteristics [maximal oxygen uptake ((Formula presented.)max), physical activity level, anthropometry, and adiposity] was determined by multiple regression analysis in a heterogeneous sample of 56 subjects in which age (20–73 years) and(Formula presented.)max (1.864–44 l · min−1) were not interrelated. Dependent variables (with ranges) included final values of thermoregulatory responses [rectal temperature (Tre, 37.8–39.2°C), calculated heat storage (S, 3.4–8.1 J · g−1), sweat loss (238–847 g · m−2)] and cardiovascular responses [heart rate (HR, 94–176 beats min−1), forearm blood flow (FBF, 5.3–31.3 ml · 100 ml−1 · min−1), mean arterial blood pressure (MAP, 68–122 mmHg), and forearm vascular conductance (FVC = FBF · MAP−1, 0.06–0.44 ml · 100 ml−1 · min−1 · mmHg−1). Age had no significant influence on Tre, S, or sweat loss, all of which were closely related to(Formula presented.)max. On the other hand, HR, MAP, FBF, and FVC were related to both age and(Formula presented.)max. Anthropometric variables and adiposity had secondary, but statistically significant, effects on MAP, FBF, FVC, and sweat loss. With respect to exercise in a warm humid environment, it was concluded that the effect of age on body temperature and sweating was negligible compared to effects related to(Formula presented.)max, but that chronological age had an independent effect on cardiovascular effector responses.

Original languageEnglish (US)
Pages (from-to)88-96
Number of pages9
JournalEuropean Journal of Applied Physiology and Occupational Physiology
Volume70
Issue number1
DOIs
StatePublished - Jan 1995

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All Science Journal Classification (ASJC) codes

  • Physiology
  • Public Health, Environmental and Occupational Health

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