Cardiac vs. Peripheral Vascular Dependency of Cardiovascular Circuit Flow in Exercise

随着年龄的增长，身体活动可以保护我们的生活质量和福祉。了解什么决定运动耐量提供了关键的指导，使身体活跃的生活方式。因此，我的研究调查了心血管系统如何满足人体运动肌肉对氧气的需求，因为限制运动耐力的肌肉疲劳和运动中的不适感对氧气输送的充足性非常敏感。 目前的研究问题：锻炼肌肉有巨大的能力，以增加其对氧气的需求。这对心血管系统在维持动脉血压的同时增加回路血流量（心输出量到肌肉血流量到静脉回流到心输出量）的能力提出了相当大的挑战。虽然已经了解了很多关于1）在运动肌肉中扩张血管以实现更高血流量的机制，2）激活心脏以增加其收缩的速率和强度的神经机制，以及3）对抗运动肌肉血管扩张的神经机制;这些机制的作用和相互作用的方式已经从增加肌肉血流量是对动脉血压的潜在威胁的观点来解释，允许超过心输出量。它反映了循环的结构，其中心脏的反应决定了心血管回路流量随着运动增加的速度和程度。目前的解释忽视了越来越多的证据，即心脏泵送从运动肌肉中接收的任何血流量，因此除非达到其泵送能力的极限，否则该流量不能超过。问题：我认为“心脏限制和驱动”的心血管回路流动的观点可能是有缺陷的，需要重新审查。 本提案的总体目标是：1）挑战目前对运动肌肉血流量交感神经抑制的解释，2）确定运动中心血管回路流量受运动肌肉血流量与心输出量驱动/限制的程度。预期结果：支持目前公认的心血管运动控制的观点提供了一个研究环境，在这个环境中，HQP将制定蓝图，以创建应用创新思维，实验创造力和不断重新思考目前公认的范式的意愿的研究计划。换句话说，培养范式转换研究的能力。第二，证明了驱动心血管回路流动的外周起源，心脏仅响应于将体积转移回动脉循环，从根本上改变了理解运动中心血管控制的范式。这对于指导有针对性的方法来改善运动中的心血管功能具有重要意义，当它由于衰老，不活动或疾病而下降时。

Being physically active protects quality of life and well-being as we age. Understanding what determines exercise tolerance provides key guidance for enabling a physically active lifestyle. Therefore, my research investigates how the cardiovascular system functions to meet exercising muscle demand for oxygen in humans, because fatigue of muscle and feelings of discomfort in exercise that limit exercise tolerance are highly sensitive to the adequacy of oxygen delivery. Current Research Problem: Exercising muscle has a tremendous capacity to increase its demand for oxygen. This poses a considerable challenge to the cardiovascular system's ability to increase the circuit blood flow (cardiac output to muscle blood flow to venous return to cardiac output) while maintaining arterial blood pressure. While much has been learned about 1) mechanisms that dilate blood vessels in exercising muscle to achieve higher blood flow, 2) neural mechanisms that activate the heart to increase the rate and strength of its contractions, and 3) neural mechanisms that oppose exercising muscle blood vessel dilation; the way these mechanisms act and interact has been interpreted from the point of view that increasing muscle blood flow is a potential threat to arterial blood pressure if it is allowed to exceed the cardiac output. It reflects a construct of the circulation where the response of the heart determines how quickly and how much the cardiovascular circuit flow can increase with exercise. This current explanation ignores accumulating evidence that the heart pumps whatever blood flow it receives from exercising muscle and therefore cannot be exceeded by that flow unless the limits of its pumping capacity are reached. The Problem: I propose that the "cardiac-limited and driven" view of cardiovascular circuit flow may be flawed and requires renewed scrutiny.   Overall objectives of this proposal are: 1) to challenge the current explanation for sympathetic restraint of exercising muscle blood flow, 2) to determine the extent to which cardiovascular circuit flow in exercise is driven/limited by exercising muscle blood flow vs. cardiac output. Anticipated Outcomes: Challenging currently accepted views of cardiovascular control in exercise provides a research environment in which HQP's will develop the blueprint for creating research programs that apply innovative thinking, experimental creativity and the willingness to continually rethink currently accepted paradigms. In other words, develop the capacity for paradigm-shifting research. Second, demonstrating a peripheral origin of driving cardiovascular circuit flow with a heart that simply responds to transfer volume back over to the arterial circulation fundamentally changes the paradigm of understanding cardiovascular control in exercise. This has critical implications for guiding targeted approaches to improving cardiovascular function in exercise when it declines due to aging, inactivity or disease.