Cold and Heat Strain during Cold-Weather Field Training with Nuclear, Biological, and Chemical Protective Clothing

Military Medicine, Feb 2007 by Rissanen, Sirkka, Rintam�ki, Hannu

The PSI was developed to differentiate the heat strain associated with different climatic conditions, hydration levels, types of clothing (including protective clothing), and exercise intensities.28 Like T^sub re^, the PSI was influenced by the metabolic rate. Because the PSI is based on T^sub re^ and heart rate, the PSI indicated moderate strain during heavy exercise, although the decrease in storage of body heat might at the same time be 6 kJ/kg. It is probable that, when the surface of the body is still cool, the PSI indicates primarily physical strain and, if the work continues and heat production increases, then the PSI indicates also heat strain in a cold environment.

NBC protective clothing provides a minimum of 24 hours of protection under battlefield conditions. Soldiers should be able to sustain their performance while wearing the suit for that period. During field training, the full use of NBC protective clothing is actually much shorter and is divided into 60- to 120-minute periods, because of, for example, eating, transportation to certain areas by vehicle, or other training. Marching does not cover the wide range of NBC training. However, marching at fixed exercise levels provides information on the thermal responses during continuous work. It should be noted that the present results are based on experiments with young healthy men. Individual differences in thermoregulation, physical fitness, and gender or different clothing may affect markedly the thermal state of individuals.

In conclusion, the present results obtained during field training confirmed the previous results based on laboratory studies. Slight heat strain is possible at a heavy exercise level in a cold environment if the duration of the work is ~60 minutes. Cooling of the extremities is most critical while wearing NBC protective clothing during cold-weather training. Additional studies are needed to validate a temperature criterion or a calculated index for thermal strain during variable physical activities while wearing protective clothing in cold-weather conditions.

Acknowledgments

This study was financially supported by the Finnish Defence Forces.

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