Age predicts cardiovascular, but not thermoregulatory, response to humid heat stress
article
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 humid environment (35°C, 80% relative humidity). Specifically, the relative importance of age compared to other individual charact-eristics [maximal oxygen utake (V_O2 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 V_O2 max (1.86-4.44 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 V_O2 max. On the other hand, HR, MAP, FBF, and FVCand FVC were related to both age and V_O2 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 V_O2 max, but that chronolog-ical age had an independent effect on cardiovascular effector responses.
Topics
AgingExerciseSkin blood flowSweatingTemperature regulationadultagedaginganthropometryarticlebicycle ergometrycardiovascular responseclinical articlefemaleforearm blood flowheart rateheat stresshumanhuman experimenthumiditymalemean arterial pressuremultiple regressionnormal humanobesityoxygen consumptionpriority journalrectum temperaturesweatingthermoregulationAdultAgedAgingBlood PressureBody Temperature RegulationComparative StudyElectrocardiographyHeart RateHeatHemodynamicsHumanHumidityMiddle AgeOxygen ConsumptionStressSweatingVascular ResistanceVital Capacityheat toleranceagesweatingheart rateblood pressureeffects of humidity
TNO Identifier
8256
Source
European Journal of Applied Physiology and Occupational Physiology, 70(1), pp. 88-96.
Pages
88-96
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