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Eighty-four hours of sustained operations alter thermoregulation during cold exposure
John W Castellani1, Dean A Stulz, David W Degroot
1US Army Research Institute of Environmental Medicine. Natick, MA 01760-5007, USA. john.castellani@na.amedd.army.mil
Medicine and Science in Sports and Exercise
|January 25, 2003
Summary
Short-term military operations (SUSOPS) impair cold tolerance. Sustained operations led to greater core temperature declines and reduced metabolic heat production during cold exposure.
Area of Science:
- Environmental Physiology
- Human Performance
- Military Medicine
Background:
- Sustained military operations (SUSOPS) impose significant physiological stress.
- Understanding thermoregulatory responses to cold is critical for soldier safety and performance.
Purpose of the Study:
- To examine the effects of short-term (84-hour) SUSOPS on thermoregulatory responses during cold stress.
- To assess changes in core body temperature, metabolic heat production, and shivering thresholds.
Main Methods:
- Ten male soldiers underwent a cold-air test (CAT) after a control week and after 84 hours of SUSOPS (restricted sleep and energy intake).
- CAT involved exposure to a temperature ramp from 25°C to 10°C while seminude.
- Physiological parameters including rectal temperature, skin temperature, and metabolic heat production were monitored.
Main Results:
- SUSOPS resulted in significant decreases in body weight, body fat, and fat-free mass.
- Rectal temperature declined more significantly after SUSOPS compared to control.
- Metabolic heat production was lower, and the shivering threshold was reduced following SUSOPS.
Conclusions:
- Eighty-four-hour SUSOPS impairs thermoregulatory capacity in the cold.
- Greater core temperature declines may be attributed to a delayed shivering response or heat redistribution.
- These findings highlight the physiological challenges of sustained operations and the need for effective countermeasures.