Nutritional Needs in Hot Environments Applications for Military Personnel in Field Operations (1993) / Chapter Skim
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6. Energetics and Climate with Emphasis on Heat: A Historical Perspective
6. Energetics and Climate with Emphasis on Heat: A Historical Perspective
Pages 97-116
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From page 97... ...
Aero Medical Laboratory, Wright Air Development Center, United States Air Force, Wright Patterson Air Force Base, Ohio ~ Elsworth R Buskirk, Noll Laboratory for Human Performance Research, College of Health and Human Development, The Pennsylvania State University, University Park, PA 16802 97
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Army's Quartermaster Food and Container Institute for the Armed Forces (Johnson and Kark, 19461. Their summarized nutrient intake data from several studies appear in Table 6-1.
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100 > ._ Ct Cal so ED an Ct 4_ Ct so o V a: Cal Cal ._ o so o o Ct Cal _ .^ ~ .° o c., lo: U
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Caloric intake decreased as ambient temperature decreased, but the regression slope was considerably less than that of Johnson and Kark, when either moderate or relatively heavy work was performed. In fact, the regression slope was also considerably less than that emphasized in 1950 by the Committee of Caloric Requirements of the Food and Agricultural Organization (FAG)
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102 ._ o 3 Cal o o o so Ct .
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During relatively heavy work, kcal intake increased from 60 to 62 kcal per kg per day (Welch et al., 19581. 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.
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From page 104... ...
were nonsignificant, there appeared to be a trend for a higher energy expenditure during walking in a hot desert environment when expressed either as kcal per hour or kcal per kg per hour, where kg represents total weight transported. However, more recent studies have failed to find significant differences (Klausen et al., 1967; Rowell et al., 1969; Sen Gupta et al., 1977; Shvartz et al., 1977; Young et al., 1985~.
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8 Days of Heat Acclimation Mean Oxygen Uptake (m! per m2 per minute)
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From page 106... ...
Brief intense exercise in a hot environment may elevate energy expenditure by evoking anaerobic processes, but the increment in daily energy expenditure is likely to be negligible. Thus, the earlier investigators posed the problem, but in terms of meeting the daily kcal needs of troops working in a hot environment, the submaximal exercise they perform has no greater impact than if they performed the same tasks in a more comfortable environment.
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From page 107... ...
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, 19384. During this time, body weight is invariably lost due to undernutrition, but the weight may be subsequently regained in toto or in part.
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From page 108... ...
Despite interindividual differences in physical fitness, the postacclimation oxygen uptakes were invariably slightly less in all of the environments studied including a 39.4°C (103°F) environment (see Table 6-8~.
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Heat acclimatization/acclimation is a valuable physiological adaptation, but the process plays only a minor role in modifying energy turnover and ~ . caloric requirements.
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Protein and fat deficiencies produce symptoms within weeks and months, respectively. Based on this early information, attention was paid to water, kcal, and carbohydrate deficiencies in a variety of early studies involving hard work by soldiers in either temperate or warm/hot environments (Grande et al., 1957; Taylor and Keys, 1958~.
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(1950~. A further discussion of negative nitrogen balance based on the experience of those working at the University of Minnesota was prepared by Taylor and Keys (1958~.
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Although the focus was on adequate carbohydrate supply during the 1940s and 1950s, largely to avoid the debilitating effects of ketosis, there was also concern about adequate protein and preservation of body tissue including skeletal muscle mass. Mitchell and Edman (1949, 1951)
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Friedemann 1956 Caloric Intake and Energy Expenditure in a Sub-Arctic Environment. Report No.
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Friedemann 1956 Caloric intake and energy expenditure of eleven men in a desert environment. Report No.
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Mechtinger, and S Shibolet 1977 Heat acclimation, physical fitness, and responses to exercise in temperate and hot environments.
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Buskirk, and P.F. Iampietro 1957b Caloric intake and energy expenditure of eight men in a temperate environment.
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