# BODY FLUID REGULATION IN AGING ADULTS WITH EXERCISE

> **NIH NIH R01** · JOHN B. PIERCE LABORATORY, INC. · 1992 · $305,226

## Abstract

Older people are reported to be chronically dehydrated, although the
cause of the inability to maintain euhydration is not well understood.
Dehydration results in circulatory and thermoregulatory impairments,
particularly during physical activity or heat exposure, and places the
individual at an increased risk of cardiovascular and heat-related
injury.  The overall hypotheses of this project are:

A. The relative dehydration in older people is in part the consequence of
physical inactivity and is due to deadaptation of the systems involved in
maintenance of extracellular fluid volume.
B.A physical activity program will result in improvements in body fluid
regulation, and thus restore circulatory and thermoregulatory potential.

The first aim of the project is to determine the reason(s) for the
chronic dehydration in older people and to determine how these are
reversed by increased physical activity.  We will dehydrate and rehydrate
older people to determine the site of deficit in the regulatory circuit.
We will repeat the studies during the course of an endurance training
program.

The second aim is to test the hypotheses that a) a low blood volume
restricts the ability of older people to thermoregulate during physical
activity or heat exposure and b) increased physical activity induces
blood volume expansion, thus improving the ability to thermoregulate
during a standard exercise/heat protocol.  It is not known whether older
people retain the ability to expand blood volume.

The third aim is to characterize cardiopulmonary (CP) baroreflex
sensitivity in older people before and during a training program.  CP
baroreflex sensitivity affects arterial blood pressure regulation;
therefore, changes in CP baroreflex sensitivity may be involved in the
progressive impairment with age.  CP baroreflex sensitivity also affects
body fluid balance; a high sensitivity, associated with unfit
individuals, will result in a lower blood volume.  We will test the
hypothesis that older people have a high CP baroreflex sensitivity, as do
unfit younger people, and that CP baroreflex sensitivity will decrease
with increasing fitness.

By determining the mechanisms associated with the chronic dehydration in
inactive older people and the extent to which these can be changed with
activity; and by determining whether the capability for blood volume
expansion, and its associated benefits, is retained with advancing age;
and by determining whether CP baroreflexes are altered with age or with
activity, we hope to provide insight into the mechanisms associated with
reductions in function with aging and how improvements in function are
induced by increased activity.

## Key facts

- **NIH application ID:** 3121810
- **Project number:** 1R01AG009872-01A1
- **Recipient organization:** JOHN B. PIERCE LABORATORY, INC.
- **SAM.gov UEI:** KRKPFMRJ5H19
- **Principal Investigator:** ETHAN R NADEL
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1992
- **Award amount:** $305,226
- **Award type:** 1
- **Project period:** 1992-06-15 → 1997-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3121810

## Citation

> US National Institutes of Health, RePORTER application 3121810, BODY FLUID REGULATION IN AGING ADULTS WITH EXERCISE (1R01AG009872-01A1). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3121810. Licensed CC0.

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