EXERCISE SUBSTRATE UTILIZATION--THE CROSSOVER CONCEPT

我们的总体目标是识别和了解 控制内源性碳水化合物(CHO)的能量平衡 以及在持续的次极量运动中的脂肪利用。这个 我们方法的理论基础是“交叉”概念，我们 在我们的文本中充分发展。简单地说，我们相信在休息和 小到中等强度的运动，提供最大的血脂 运动所需的能量比例。然而，随着锻炼的增加， 从中到硬再到最大，基质利用率的平衡 从脂肪到碳水化合物的转换，或“转换”。“跨界车” 点“被识别为碳水化合物衍生的功率输出 燃料作为能源的地位超过了脂肪，并将进一步增加 在碳水化合物的利用中产生成比例的增量 并减少了对脂肪的利用。我们进一步认为，虽然之前 运动(耐力训练)增强利用脂质的能力 在小到中等强度的运动中，转换为碳水化合物 依赖不可避免地发生在从中等强度过渡的过程中 对于艰苦的运动，不可避免地会发生对碳水化合物依赖的交叉 在从中等强度运动向剧烈运动过渡的过程中，即使在 训练有素的国家。 为了实现我们的总体目标，我们建议探索五个具体的 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，(2)描述了耐力训练对此的影响 平衡，(3)探索交感神经系统(SNS)的作用， 具体地说，肾上腺素在运动过程中控制这种平衡， (4)评价乳酸作为代谢中间体的作用，以及(5) 评估女性与男性在以下方面存在差异的可能性 运动和运动训练的代谢反应。 为了达到这些目标，我们建议研究男性和女性的休息和 在练习给出绝对和相对强度时，都是在 经过长期的训练。在男性方面，我们也计划利用短发- 长期耐力训练，以及β-肾上腺素能阻断 试图从其他训练诱导的适应中分离交感神经 关于运动中底物供应的平衡。技术问题 间接量热法，预充-持续稳定同位素输注，肌肉 腿动静脉差值的活检和测量[(A-V)]和 将使用血流和糖调节激素的反应 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.