The effects of manipulating human blood flow with exercise

运动时在肢体周围使用止血带，即所谓的血流限制(BFR)训练，在康复和运动环境中越来越受欢迎，因为无需举起重物就可以改善力量和肌肉质量。新的证据进一步表明，小强度有氧运动中的BFR也可能提高耐力。除了在应用环境中具有重要的实用价值外，BFR还提供了一个独特的模型来研究心血管系统和下游器官(如骨骼肌)对应激源的反应。通过仔细强调负责心血管调节、动态平衡和训练适应的系统的个别组件，我们可以深入了解BFR刺激变化和理解生理控制的增强功效的机制。越来越多的数据表明，BFR运动可以意外地大幅提高健康水平，即使是在训练有素的运动员中也是如此，这些运动员通常对变化持抵制态度；然而现有证据表明，这些变化似乎并没有在肌肉层面上被夸大。由于有氧能力(最大摄氧量；或吸收和利用氧气的能力)既受供氧血的影响，也受工作组织从血液中提取的氧气量的影响，因此需要进行研究来填补这一空白，研究BFR对血液输送的潜在影响。组织的有氧血液供应可能受到心脏功能、血管功能、血容量、血压、血液成分或这些因素的某种组合的影响，从而改变心血管性能。在这项研究中，我们将专门试图了解：1)从循环中移除(捕获)血容量的含义以及对容量调节反应和携氧能力的短期影响2)血液捕获对心脏增加心输出量的能力的影响，以及交感神经活动控制血压的敏感性；3)随着时间的推移，反复应激这些系统对静息血压和心血管控制的影响。最后，我们将研究血浆容量、携氧能力和肌肉耐力的变化与有氧能力变化的因果关系。我们将考虑这些变化的时间反应，以及与施加的应激源的大小之间的因果关系。对BFR诱导适应能力的潜在机制的理解将允许优化这些旨在引起适应性变化的方法。因此，这项工作对临床治疗以及改善身体表现(国防、紧急服务、运动员)、血液服务以及从漫长的太空旅行归来的宇航员具有潜在的应用意义。

The use of a tourniquet around a limb during exercise, known as blood flow restriction (BFR) training, has become increasingly popular in both rehabilitative and athletics settings as improvements in strength and muscle mass can occur without the need to lift heavy weights. Emerging evidence further suggests BFR during light intensity aerobic exercise may also improve endurance capacity. In addition to having important utility in the applied setting, BFR offers a unique model to study the response to stressors of the cardiovascular system and downstream organs like skeletal muscle. By carefully emphasizing individual components of the systems that are responsible for cardiovascular regulation, homeostasis, and training adaptation, we can gain insight into the mechanisms that underly the enhanced efficacy of BFR to stimulate change and understand physiological control. Accumulating data suggests that BFR exercise can elicit unexpectedly large increases in fitness, even amongst well trained athletes who are typically resistant to change; yet existing evidence suggests these changes do not appear to be exaggerated at the level of the muscle. As aerobic capacity (VO2max; or the ability to take up and use oxygen) is influenced by both the amount of oxygenated blood supplied and the amount of oxygen extracted from the blood at the working tissue, research is needed to fill the void examining the potential effects of BFR on blood delivery. Oxygenated blood supply to the tissue could be influenced by changes in cardiac function, vascular function, blood volume, blood pressure, blood composition, or some combination of these factors to alter cardiovascular performance. In this research we will specifically seek to understand: 1) the implications of removing (trapping) blood volume from circulation and the short-term effects on volume regulating responses and O2 carrying capacity 2) the effects of blood trapping on the ability of the heart to increase cardiac output, along with the sensitivity of sympathetic nerve activity to control blood pressure and 3) the influence on resting blood pressure and cardiovascular control over time with repeated stressing of these systems. Finally, we will examine the causal role of alterations in plasma volume, O2 carrying capacity, and muscular endurance with alterations in aerobic capacity. We will consider the temporal response of these changes and cause-and-effect relationships with the magnitude of the applied stressor. An understanding of the mechanisms underlying the ability of BFR to elicit adaptations will allow for the optimization of these methods targeted toward causing adaptive changes. As such, this work has implications for use in clinical treatment as well as potential applications to physical performance (national defense, emergency services, athletes), blood services, and astronauts returning from prolonged space travel.