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TABLE 6-10 Possible Reasons for an Increase in Metabolic Rate in Hot Environments

Lack of acclimatization

Inefficient physical activity, psychomotor stress

Q10 effect, elevated body temperature

Greater sweat gland activity


Increased pulmonary ventilation

Increased anaerobic metabolism

Increased RQ

Increased O2 debt

Increased lactate

Increased muscle glycogen utilization

Increased blood glucose utilization

Lessened skeletal muscle blood flow

NOTE: Q10 = adjustment in metabolic rate in relation to temperature change; RQ = respiratory quotient.

TABLE 6-11 Possible Factors That Would Tend to Reduce Metabolic Rate in Hot Environments

Complete acclimatization

Lower basal metabolic rate

Reduced physical activity, particularly intense activity

Lighter-weight clothing

Decreased appetite and associated dietary-induced



A finding that has been repeatedly documented is that unacclimatized personnel suffer the consequences when suddenly exposed to stressful environments, whether the environmental stress is heat, cold, or altitude. The psychological and physical stresses associated with combat only complicate the adverse situation. At issue is inadequate acclimatization, which with sudden exposure to heat, not only perpetrates physiological strain but lessens initiative and appetite, which negatively affects nutritional status including water balance. The acclimatization process with exposure to hot environments proceeds rapidly, being virtually complete in the working soldier within 10 days (Adolph, 1947; Buskirk and Bass, 1957; Dill, 1938). During this time, body weight is invariably lost due to undernutrition, but the weight may be subsequently regained in toto or in part. Johnson (1946), in his review, concluded that following acclimatization, dietary require-

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