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the same in all climates when calculated on the basis of body weight plus clothing and equipment weight manually transported. A kcal intake of 47 to 49 kcal per kg per day was found for moderate work in the three climates. During relatively heavy work, kcal intake increased from 60 to 62 kcal per kg per day (Welch et al., 1958). They concluded that the differences in energy expenditure among environments are largely accounted for by differences in body weight plus weight of clothing and equipment carried during the performance of duties in the respective environments.

A recent field study showed that troops operating in a warm environment and performing moderate work loads consumed an average of between 44.3 and 47.2 kcal per kg per day (Rose and Carlson, 1986), values that agree with those found by Welch et al. (1958).

ENERGY EXPENDITURE: SUBMAXIMAL EXERCISE

An issue that has been investigated over the years with mixed results is the impact of heat on metabolic rate, both during rest and during exercise. A variety of hypothesized causes for different responses of the metabolic rate to exercise in the heat have been proposed and are listed in Table 6-4. The case for a relatively elevated metabolic rate was put forth by Consolazio et al. (1961, 1963, 1970) (Tables 6-5 and 6-6). The primary explanation of the relatively higher energy expenditure in hot compared to cooler environments was the energy expenditure associated with the production and secretion of sweat. Consolazio et al. expanded on the observations of Dill et al. (1931) and Welch et al. (1958). Results from the latter study appear in Table 6-7. Although the differences across climates and locations in the

TABLE 6-4 Differences Among Studies: Hypothesized Causes of Different Responses in Metabolic Rate to Exercise in the Heat

Physical condition of subjects

Extent of heat acclimatization

Skill

Duration of exercise

Exercise intensity

Environmental heat stress

Type

Intensity

Hydration state

Febrile state

Clothing worn

Equipment carried



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