84 Hours of Exertional Fatigue, Negative Energy Balance, and Sleep Deprivation Impairs Shivering During Cold Air Exposure in Men

Abstract

Long-term (61 d) military operations that induce exertional fatigue, caloric deficiency, and sleep deprivation impair thermoregulatory responses to cold. However, there is no information regarding thermoregulation following short-term (3.5 d) sustained military operations (SUSOPS). This study examined thermoregulatory control during cold exposure following this multi-factorial stress. Thermoregulation of six men (22.8 +/- 1.4 yrs) was assessed during a standardized cold air test (SCT) both before (CONTROL) and following an 84 h SUSOPS (sleep = 2 h/d, energy intake = ~ 1800 kcal/d, energy expenditure = ~ 5000 kcal/d). SCT consisted of a ramp from 25 deg C to 10 deg C during the initial 30 min, with the ambient temperature then remaining at 10 deg C for an additional 150 min. SUSOPS decreased (P < 0.05) body weight, % body fat, and fat free mass by 3.9 kg, 1.6%, and 1.8 kg, respectively. Metabolic heat production was lower (P < 0.05) during CAT following SUSOPS. Examination of the mean body temperature-metabolic heat production relationship indicated that the threshold for shivering was lower (P < 0.05) following SUSOPS (34.61 deg C) than CONTROL (35.73 deg C). There were no differences between trials in either peripheral heat flow (W/sq m) or mean weighted skin temperature (deg C). Partitional calorimetry revealed that body heat content tended to decrease (P = 0.09) more during the CAT following SUSOPS (- 1298 kJ) vs. CONTROL (- 1164 kJ). These results indicate that 84 h of SUSOPS impairs the shivering response to cold exposure but does not increase the risk of hypothermia after 3 h of cold air exposure, but may potentially increase risk during longer exposures.

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Document Details

Document Type
Technical Report
Publication Date
Apr 01, 2002
Accession Number
ADP012447

Entities

People

  • Bradley C. Nindl
  • Bruce S. Cadarette
  • Dean A. Stulz
  • John W Castellani
  • Laurie A. Blanchard
  • Scott J. Montain

Organizations

  • United States Army Research Institute of Environmental Medicine

Tags

Communities of Interest

  • Energy and Power Technologies
  • Human Systems

DTIC Thesaurus Topics

  • Army Rangers
  • Body Composition
  • Body Temperature
  • Body Weight
  • Carbon Dioxide
  • Deprivation
  • Energy
  • Enthalpy
  • Experimental Design
  • Heat Energy
  • Heat Loss
  • Military Operations
  • Norepinephrine
  • Performance Tests
  • Sleep Deprivation
  • Statistical Analysis
  • Thermogenesis

Readers

  • Exercise and Sports Science.