EXERCISE SUBSTRATE UTILIZATION--THE CROSSOVER CONCEPT

我们的总体目标是确定和了解 控制来自内源性碳水化合物（CHO）的能量平衡 和脂质利用率的影响。 的 我们的方法的理论基础是“交叉”的概念，我们 在我们的经文中充分发展。 简单地说，我们认为，在休息和 轻度到中度强度的运动，脂质提供最大的 运动能量的比例。 然而，随着运动量的增加， 从中度到重度再到最大， 从脂类转变为碳水化合物。 关于“Crossover 点”被确定为碳水化合物衍生的能量输出。 作为能源，燃料比脂质占优势， 在功率引起碳水化合物利用的成比例增加 和脂质利用率的降低。 我们进一步认为，虽然事先 运动（耐力训练）增强利用脂质的能力 在轻度至中度强度运动期间，交叉至碳水化合物 依赖性不可避免地发生在从中等强度到中等强度的过渡过程中， 到剧烈运动，交叉到碳水化合物依赖不可避免地发生 在从中等强度到高强度运动的过渡中，即使在 训练状态。 为达致我们的整体目标，我们建议探讨五项具体措施， 目标。 这些是：（1）描述运动强度对 来自葡萄糖和游离脂肪酸（FFA）的能量平衡 利用率，（2）描述了耐力训练对此的影响 平衡，（3）探讨交感神经系统（SNS）的作用， 特别是肾上腺素，在运动中控制这种平衡， (4)评估乳酸作为代谢中间体的作用，以及（5） 评估妇女在其性别方面可能与男子不同的可能性， 运动和运动训练的代谢反应。 为了实现这些目标，我们建议研究静止的男性和女性， 在给予绝对和相对强度的练习中， 经过长期的训练。 在男性方面，我们也计划利用短- 长期耐力训练，以及β-肾上腺素能阻滞， 试图将交感神经与其他训练诱发的适应性分离开来 对运动时基质供应平衡的影响。 技术 间接量热法，预充-连续稳定同位素输注，肌肉 活组织检查和腿部动静脉差[（a-v）]的测量，以及 将使用血流以及糖调节激素的反应 以实现上述具体目标。

Our overall objective is to identify and understand the factors which control the balance of energy derived from endogenous carbohydrate (CHO) and lipid utilization during sustained, submaximal exercise. The theoretical basis of our approach is the "crossover" concept which we develop fully in our text. Simply put, we believe that during rest and mild to moderate intensity exercise, lipids provide the greatest proportion of energy for exercise. However, as the exercise increases from moderate to hard to maximal, the balance of substrate utilization switches, or 'crosses over' from lipid to carbohydrate. The "Crossover Point" is identified as the power output at which carbohydrate-derived fuels predominate over lipids as energy sources with further increases in power eliciting proportional increments in carbohydrate utilization and decrements in lipid utilization. We further believe that while prior exercise (endurance training) enhances the ability to utilize lipids during mild to moderate intensity exercise, crossover to carbohydrate dependence inevitably occurs in the transition from moderate intensity to hard exercise, crossover to carbohydrate dependence inevitably occurs in the transition from moderate intensity to hard exercise, even in the trained state. In pursuit of our overall objective, we propose to explore five specific aims. These are to: (1) describe the effects of exercise intensity on the balance of energy derived from glucose and free fatty acid (FFA) utilization, (2) described the effects of endurance training on this balance, (3) explore the role of the sympathetic nervous system (SNS), specifically epinephrine, in controlling this balance during exercise, (4) evaluate the role of lactate as a metabolic intermediate, and (5) evaluate the possibility that women may differ from men in their metabolic response to exercise and exercise training. To address these aims, we propose to study men and women at rest and during exercises of give absolute and relative intensities, both before and after long-term training. On men, we plan to also to utilize short- term endurance training, as well as beta-adrenergic blockade in an attempt to dissect sympathetic from other training-induced adaptations on the balance of substrate supply during exercise. Techniques of indirect calorimetry, primed-continuous stable isotope infusion, muscle biopsies and measurements of leg arterial-venous difference [(a-v)] and blood flow as well as response of glucoregulatory hormones will be used to address the above indicated specific aims.