Askew E W
Clin Sports Med. 1984 Jul;3(3):605-21.
Fat and carbohydrate are the two major energy sources used during exercise. Either source can predominate, depending upon the duration and intensity of exercise, degree of prior physical conditioning, and the composition of the diet consumed in the days prior to a bout of exercise. Fatty acid oxidation can contribute 50 to 60 per cent of the energy expenditure during a bout of low intensity exercise of long duration. Strenuous submaximal exercise requiring 65 to 80 per cent of VO2 max will utilize less fat (10 to 45 per cent of the energy expended). Exercise training is accompanied by metabolic adaptations that occur in skeletal muscle and adipose tissue and that facilitate a greater delivery and oxidation of fatty acids during exercise. The trained state is characterized by an increased flux of fatty acids through smaller pools of adipose tissue energy. This is reflected by smaller, more metabolically active adipose cells in smaller adipose tissue depots. Peak blood concentrations of free fatty acids and ketone bodies are lower during and following exercise in trained individuals, probably due to increased capacity of the skeletal musculature to oxidize these energy sources. Trained individuals oxidize more fat and less carbohydrate than untrained subjects when performing submaximal work of the same absolute intensity. This increased capacity to utilize energy from fat conserves crucial muscle and liver glycogen stores and can contribute to increased endurance. Further benefits of the enhanced lipid metabolism accompanying chronic aerobic exercise training are decreased cardiac risk factors. Exercise training results in lower blood cholesterol and triglycerides and increased high density lipoprotein cholesterol. High-fat diets are not recommended because of their association with atherosclerotic heart disease. Recent evidence suggests that low-fat high-carbohydrate diets may increase blood triglycerides and reduce high density lipoproteins. This suggests that the chronic ingestion of diets that are extreme in their composition of either fat or carbohydrate should be approached with caution in health-conscious athletes, as well as in sedentary individuals.
脂肪和碳水化合物是运动过程中使用的两种主要能量来源。哪种来源占主导取决于运动的持续时间和强度、先前的身体适应程度以及运动前几天所摄入饮食的成分。在长时间的低强度运动中，脂肪酸氧化可提供50%至60%的能量消耗。需要65%至80%最大摄氧量的剧烈次最大运动将消耗较少的脂肪（所消耗能量的10%至45%）。运动训练伴随着骨骼肌和脂肪组织发生的代谢适应，这些适应有助于在运动期间更多地输送和氧化脂肪酸。训练状态的特征是脂肪酸通过较小的脂肪组织能量池的通量增加。这表现为较小的脂肪组织库中较小且代谢活性更高的脂肪细胞。在训练有素的个体中，运动期间及运动后游离脂肪酸和酮体的峰值血浓度较低，这可能是由于骨骼肌氧化这些能量来源的能力增强。在进行相同绝对强度的次最大运动时，训练有素的个体比未训练的受试者氧化更多的脂肪和更少的碳水化合物。这种增加的利用脂肪能量的能力可保存关键的肌肉和肝脏糖原储备，并有助于提高耐力。长期有氧运动训练所带来的脂质代谢增强的进一步益处是降低心脏危险因素。运动训练可降低血液中的胆固醇和甘油三酯，并增加高密度脂蛋白胆固醇。不建议食用高脂肪饮食，因为它们与动脉粥样硬化性心脏病有关。最近的证据表明，低脂高碳水化合物饮食可能会增加血液中的甘油三酯并降低高密度脂蛋白。这表明，无论是对注重健康的运动员还是久坐不动的个体，在长期摄入脂肪或碳水化合物成分极端的饮食时都应谨慎。
