Levine B D
Institute for Exercise and Environmental Medicine, Presbyterian Hospital, University of Texas Southwestern Medical Center, Dallas 75235.
Med Sci Sports Exerc. 1993 Jun;25(6):727-32.
Orthostatic intolerance may result from either an abnormally large postural decrease in central blood volume, cardiac filling pressures, and stroke volume, or inadequate neurohumoral responses to orthostasis. Endurance athletes have been reported as having a high incidence of orthostatic intolerance, which has been attributed primarily to abnormalities in baroreflex regulation of heart rate and peripheral resistance. In this review, we present evidence that athletes also have structural changes in the cardiovascular system that although beneficial during exercise, lead to an excessively large decrease in stroke volume during orthostasis and contribute to orthostatic intolerance. A unifying hypothesis based on cardiac mechanics that may explain the divergence of findings in conditions such as bed rest or spaceflight, and short- and long-term endurance training is presented.
一是体位改变时中心血容量、心脏充盈压和每搏输出量异常大幅下降；二是对直立状态的神经体液反应不足。据报道，耐力运动员直立不耐受的发生率较高，这主要归因于压力反射对心率和外周阻力调节的异常。在本综述中，我们提供证据表明，运动员的心血管系统也存在结构变化，这些变化虽然在运动期间有益，但在直立状态下会导致每搏输出量过度大幅下降，并导致直立不耐受。本文提出了一个基于心脏力学的统一假说，该假说可能解释在诸如卧床休息或太空飞行以及短期和长期耐力训练等情况下研究结果的差异。
