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Heat intolerance, heat exhaustion monitored: a case report
L E Armstrong1, R W Hubbard, P C Szlyk
1U.S. Army Research Institute of Environmental Medicine, Heat Research and Exercise Physiology Divisions, Natick, Massachusetts 01760-5007.
Aviation, Space, and Environmental Medicine
|March 1, 1988
Summary
An unexpected heat exhaustion case during heat acclimation revealed a potential host factor influencing physiological responses. This study details unique clinical and blood analyses during heat intolerance, offering new insights into thermoregulation.
Area of Science:
- Environmental Physiology
- Human Thermoregulation
- Exercise Physiology
Background:
- Heat acclimation (HA) is a standard protocol to improve heat tolerance.
- Individual variability in HA response necessitates understanding underlying physiological mechanisms.
- This study investigated an unusual case of heat exhaustion during a controlled HA protocol.
Observation:
- A 32-year-old male (Mr. A.) developed heat intolerance and exhaustion on days 5-8 of an 8-day HA investigation, unlike 13 other participants.
- Physiological markers including body weight loss, increased heart rate (HR), skin temperature (Tsk), and rectal temperature (Tre) preceded the heat exhaustion episode.
- Symptoms suggested salt depletion, though the calculated deficit was minimal, indicating a complex etiology.
Findings:
- Post-exhaustion blood analysis revealed normal ALT and AST levels, elevated CPK, and significantly increased beta-endorphin and cortisol levels compared to controls.
- The timing of Mr. A.'s symptoms suggested an unknown host factor emerged during the latter half of the HA protocol.
- This case provides unique, comprehensive physiological and biochemical data before, during, and after heat intolerance and exhaustion.
Implications:
- Highlights the potential for unknown host factors to mediate heat tolerance.
- Suggests a need for closer monitoring of specific physiological and hormonal markers during HA protocols.
- Contributes valuable data for refining understanding of heat exhaustion pathophysiology and individual susceptibility.