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Hypohydration and thermoregulation in cold air
C O'Brien1, A J Young, M N Sawka
1United States Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 6, 1998
Summary
Mild hypohydration did not affect body heat balance in moderate cold. However, hypertonicity associated with hypohydration may impair vasoconstriction responses during cold exposure.
Area of Science:
- Environmental Physiology
- Thermoregulation
- Human Performance
Background:
- Hypohydration, or dehydration, can impact physiological responses to environmental stressors.
- Understanding the effects of hypohydration on thermoregulation is crucial for maintaining performance and safety in cold conditions.
Purpose of the Study:
- To investigate the effects of hypohydration on thermoregulation during cold exposure.
- To differentiate the independent effects of hypertonicity and hypovolemia associated with hypohydration.
Main Methods:
- Nine male volunteers underwent controlled cold exposure (7°C) under three conditions: euhydration, hypertonic hypohydration, and isotonic hypohydration.
- Hypohydration was induced via sweating or furosemide administration.
- Physiological parameters including body weight, plasma osmolality, plasma volume, heat debt, skin temperature, and temperature gradients were monitored.
Main Results:
- Body weight loss was similar across hypohydration conditions, but plasma osmolality and volume reduction differed significantly.
- Mean skin temperature plateaued during hypohydration conditions, unlike in euhydration.
- A trend towards a reduced forearm-finger temperature gradient suggested weaker vasoconstriction during hypohydration.
Conclusions:
- Mild hypohydration does not significantly alter body heat balance during short-term moderate cold exposure.
- Hypohydration-associated hypertonicity may subtly impair the vasoconstrictor response to cold, potentially impacting tolerance during more severe cold exposure.