Project: Research project

Project Details


Although morbidity and mortality data consistently demonstrate
that older individuals are at greater risk in hot environments, few
investigators have studied the relationship between age and
thermoregulatory response. It is unclear to what extent
decreased heat tolerance in the elderly is a function of decreased
aerobic capacity, as opposed to age-related changes in neural
function, functional capacity of the sweat gland, etc.
Statistically, more older women than men are victims of heat-
related illness. Yet it is equally unclear whether this simply
reflects the relatively larger number of women in this population,
or whether a sex-difference exists in thermoregulatory function
of older adults. Previous investigations in this area have suffered from the
inability to match groups of older and younger subjects with
respect to aerobic capacity (Drinkwater et al., 1982). We have
alleviated that problem by recruiting a subject population of
highly fit men and women over the age of 55 which we propose to
compare with (1) younger men and women of similar aerobic
fitness, (2) men and women with lower fitness levels, and (3) very
fit younger men and women. This investigation proposed to systematically compare
physiological effector (body temperature, cardiovascular, and
sudomotor) responses to hyperthermia among these groups.
Subjects will be tested at rest and during moderate exercise in 3
environments (neutral, hot-dry, and warm-humid) before and after
heat acclimation. The specific aims of this research include the
following comparisons among the aforementioned groups. 1. onset characteristics (temporal and temperature thresholds) of
effector responses (sweating and cutaneous vasodilation);
2. body temperature, heart rate, blood pressure, and sweating
responses to moderate exercise in the 3 environments;
3. differences in heat-activated sweat gland (HASG) number and
density, sweat production per gland, and HASG dose-response
characteristics relative to a neurotransmitter analog
4. percentage changes in blood volume, red cell volume, and
plasma volume due to exercise in these environments, and
5. alterations in magnitude and control of cutaneous blood flow
and cardiac output.
Effective start/end date12/31/898/31/15