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Efficacy of intermittent, regional microclimate cooling
Samuel N Cheuvront1, Margaret A Kolka, Bruce S Cadarette
1United States Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760-5007, USA. samuel.cheuvront@na.amedd.army.mil
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 8, 2003
Summary
Intermittent, regional microclimate cooling (MCC) is more effective than constant MCC for reducing heat strain during exercise. This approach improves heat loss and reduces cooling power requirements.
Area of Science:
- Exercise Physiology
- Thermoregulation
- Protective Clothing Technology
Background:
- The body's response to cold can limit the effectiveness of microclimate cooling (MCC) in reducing heat strain.
- Constant MCC may not be the most efficient method for heat loss during exercise.
Purpose of the Study:
- To test if intermittent, regional MCC (IRC) reduces the cold response and enhances heat loss compared to constant MCC (CC) during exercise.
- To compare the effectiveness of four different IRC strategies.
Main Methods:
- Five heat-acclimated men performed treadmill walking in a warm environment wearing protective clothing with a cooling undergarment.
- Six trials were conducted: no cooling (NC), CC (72% body surface area - BSA), and four IRC regimens (36% BSA with 2:2 or 4:4 min on-off; 18% BSA with 1:3 or 2:6 min on-off).
Main Results:
- Both CC and IRC significantly reduced rectal temperature and heart rate compared to NC.
- The four IRC regimens were 164-215% more efficient than CC, achieving similar reductions in heat strain.
- IRC demonstrated greater heat flux over a smaller BSA.
Conclusions:
- Intermittent, regional MCC is a more efficient cooling strategy than constant MCC.
- IRC enhances MCC capacity and can reduce energy demands for cooling during exercise heat stress.