Paul P, Holmes W L
Med Sci Sports. 1975 Fall;7(3):176-83.
The amount of fat available as substrate to provide the energy needed for submaximal exercise is almost unlimited; therefore, it stands to reason that the organism will adapt so that it uses fat as the major energy substrate during very prolonged exercise. Nevertheless, the quantitatively smaller body stores of carbohydrate, which contain only one to two percent as many calories as the fat stores, play a very important role during exercise, since depletion of either muscle or liver glycogen will force an individual to terminate strenuous muscular work. In normal dogs during long-lasting exercise, at energy expenditures ranging from the resting state of 0.73 kcal/m2 min to a work load of 4.66 kcal/m2 min, the FFA mobilization, and participation of FFA oxidation in total energy expenditure increases. During prolonged exercise in trained dogs, 50-90% of the energy may derive from plasma FFA, while plasma glucose contributes not more than 10% to the energy expenditure. However, there is an inverse relationship between the amount of glycogen stored inside the muscle, its rate of depletion, and muscular endurance during prolonged strenuous work. Oxidation of FFA spares muscle glycogen and in this way increases work endurance.
作为底物可用于提供次最大运动所需能量的脂肪量几乎是无限的；因此，有理由认为机体将进行适应性变化，以便在长时间运动期间将脂肪用作主要能量底物。然而，碳水化合物在体内的储存量相对较少，所含热量仅为脂肪储存量的1%至2%，但在运动过程中却起着非常重要的作用，因为肌肉或肝糖原的耗尽会迫使个体终止剧烈的肌肉活动。在正常犬类进行持久运动时，能量消耗从静息状态的0.73千卡/平方米·分钟到工作负荷为4.66千卡/平方米·分钟，游离脂肪酸（FFA）的动员以及FFA氧化在总能量消耗中的参与度都会增加。在训练有素的犬类进行长时间运动时，50%至90%的能量可能来自血浆FFA，而血浆葡萄糖对能量消耗的贡献不超过10%。然而，在长时间剧烈运动期间，肌肉内储存的糖原量、其消耗速率与肌肉耐力之间存在反比关系。FFA的氧化节省了肌肉糖原，从而增加了工作耐力。
