Project: Research project

Project Details


Although morbidity and mortality data consistently demonstrate the 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. If
decreased thermoregulatory function is linked solely with lowered fitness,
physical conditioning of older individuals could potentially result in
improved heat tolerance.

Previous investigations in this area have suffered from the inability to
match groups of older and younger subjects with respect to aerobic
capacity. We have alleviated that problem by recruiting a subject
population of highly fit postmenopausal women over the age of 55 which we
propose to compare with (1) younger women of similar aerobic fitness, (2)
postmenopausal women with lower fitness levels, and (3) very fit younger

This investigation proposes 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 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 number and density, and sweat
production per gland;

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. In summary, we propose to examine the extent to which differences
in aerobic capacity conceivably contribute to age related decrements in
thermal tolerance.
Effective start/end date12/31/8912/31/89