Control of Thermoregulatory Sweating during Exercise in the Heat

Abstract

The purposes of this study are to: (a) determine if erythrocyte infusion alters the control of thermoregulatory sweating; and (b) demonstrate how increases and decreases of both plasma tonicity and blood volume influence the thermoregulatory control parameters of threshold temperature and sweating sensitivity. Six non-heat acclimated and five heat acclimated males attempted Heat Stress Tests (HST's) both before and shortly after (48-96h) autologous erythrocyte infusion. The non-heat acclimated subjects were euhydrated for both HST's; whereas, the heat acclimated subjects were studied in a euhydrated and a hypohydrated (-5% body weight) condition both pre- and post-infusion (500 ml of solution containing approx. 60% hct of autologous erythrocytes). The HST's consisted of treadmill exercise (335 W.m) in a hot (35 C, 45% relative humidity) environment, and esophageal temperature and local sweating rate were continuously measured during 25 minutes of exercise. These experiments resulted in a matrix of conditions where both plasma tonicity and blood volume were increased or decreased relative to control conditions (euhydration, pre-infusion). The findings concerning thermoregulatory sweating during exercise in the heat are summarized: 1) acute polycythemia will decrease the threshold temperature and increase the sweating sensitivity; 2) both threshold temperature and sweating sensitivity are increased or decreased from control levels dependent upon the combined influence of plasma tonicity and blood volume; and 3) threshold temperature changes are primarily influenced by plasma tonicity, and sweating sensitivity changes are primarily influenced by blood volume.

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Document Details

Document Type
Technical Report
Publication Date
Oct 01, 1988
Accession Number
ADA206001

Entities

People

  • Andrew J Young
  • C. R. Valeri
  • Kent B. Pandlof
  • Michael N. Sawka
  • Richard C. Dennis
  • Richard R. Gonzalez

Organizations

  • United States Army Research Institute of Environmental Medicine

Tags

DTIC Thesaurus Topics

  • Acclimatization
  • Availability
  • Blood
  • Blood Volume
  • Body Temperature
  • Body Weight
  • Cellular Structures
  • Central Nervous System
  • Control Systems
  • Environment
  • Humidity
  • Hydration
  • Nervous System
  • Osmotic Pressure
  • Statistical Analysis
  • Stress Tests
  • Treadmills

Readers

  • Cardiovascular Physiology
  • Exercise and Sports Science.