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10 Muscle Metabolism and Shivering During Cold Stress
Pages 181-188

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From page 181...
... These expeditions demonstrated that it is possible to perform hard physical work for months on end in cold environments, provided adequate planning enables appropriate preparation of food rations and protective clothing arid equipment. These expeditions and others suggest there are probably no particular nutritional considerations specific to long-term operations in the cold other than the requirement for sufficient energy consumption to balance energy expenditure.
From page 182...
... In resting subjects exposed to either cold air or cold water, carbohydrates and fat contribute approximately equally to heat production (Martineau and Jacobs, 1989a, b; Vallerand and Jacobs, 19893. From a strategic point of view, this finding seems unfortunate because the body's availability of carbohydrates is quite limited compared to the abundant fat and protein stores.
From page 183...
... Initial studies suggested that part of this increase in metabolic rate is fueled by muscle glycogen, as all of the subjects demonstrated a decrease in leg glycogen concentration after the water immersion (MartineauandJacobs,1988~.Thesecondobjectiveoftheseexperimentswas to evaluate the effects of manipulating the Reimmersion glycogen levels on heat production during cold-water immersion. The manipulations did result in the subjects entering the water during one trial with muscle glycogen levels that were only about 50 percent of normal and during another trial when they were about 150 percent of normal (Martineau and Jacobs, 1989a)
From page 184...
... This effect was demonstrated by the dramatic reduction in plasma free fatty acids and glycerol levels prior to and during the water Immersion. Again contrasting with the effects of manipulating the carbohydrate stores, metabolic heat production was virtually unaffected; the proportion of total heat production that
From page 185...
... This author's opinion is that the primary requirement is to balance the increased energy expenditure associated with shivering and exercising in the cold, with a commensurate increase in energy consumption. Can performance be enhanced in a cold environment by providing increased amounts of specific nutrients?
From page 186...
... 66:72-78. 1989b Free fatty acid availability and temperature regulation in cold water.
From page 187...
... Pandolf 1989 Therrnoregulation during cold water immersion is unimpaired by low muscle glycogen levels.


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