Fluid replacement and heat stress

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Summary

Advances in our understanding of the value of carbohydrate-electrolyte solutions have come from information derived from two major fields of study -- exercise physiology and sports nutrition--and f...

Advances in our understanding of the value of carbohydrate-electrolyte solutions have come from information derived from two major fields of study -- exercise physiology and sports nutrition--and from research on diarrheal diseases. Research in the first area has been concerned with physical performance, primarily of athletes. Research results have demonstrated that even small fluid deficits have adverse effects on performance through elevated heart rates, reduced sweat rates, and elevated body temperature. Glucose-electrolyte solutions have been found useful in rehydration and in preventing dehydration. Carbohydrate is needed to facilitate sodium and water absorption. Other ions may or may not be needed, depending on sweat losses or losses from the gastrointestinal tract. Advances in exercise physiology also have demonstrated the value of carbohydrate solutions in providing energy for muscular activity in endurance events that last at least 60 minutes and involve vigorous exercise. Military personnel are often called upon to perform heavy physical activity during training or combat conditions in very hot environments--either dry climates, as in Middle-Eastern deserts, or under humid tropical conditions. The resultant high sweat rates can lead to dehydration. In some cases, the subjects may be acclimated to heat, but in others (for example, in basic training, or in emergency troop deployment to the tropics) they may not, and may thus be vulnerable to extensive electrolyte losses. This problem could be accentuated when personnel have been given garrison or field rations with reduced sodium to meet prudent dietary goals established for the general population in 1989 by the Diet and Health Committee of the Food and Nutrition Board, National Academy of Sciences.

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