Amann Markus, Sidhu Simranjit K, Weavil Joshua C, Mangum Tyler S, Venturelli Massimo
Department of Medicine, University of Utah, Salt Lake City, UT, USA; Department of Exercise & Sport Science, University of Utah, Salt Lake City, UT, USA.
Department of Medicine, University of Utah, Salt Lake City, UT, USA.
Auton Neurosci. 2015 Mar;188:19-23. doi: 10.1016/j.autneu.2014.10.018. Epub 2014 Oct 23.
Group III and IV muscle afferents originating in exercising limb muscle play a significant role in the development of fatigue during exercise in humans. Feedback from these sensory neurons to the central nervous system (CNS) reflexively increases ventilation and central (cardiac output) and peripheral (limb blood flow) hemodynamic responses during exercise and thereby assures adequate muscle blood flow and O2 delivery. This response depicts a key factor in minimizing the rate of development of peripheral fatigue and in optimizing aerobic exercise capacity. On the other hand, the central projection of group III/IV muscle afferents impairs performance and limits the exercising human via its diminishing effect on the output from spinal motoneurons which decreases voluntary muscle activation (i.e. facilitates central fatigue). Accumulating evidence from recent animal studies suggests the existence of two subtypes of group III/IV muscle afferents. While one subtype only responds to physiological and innocuous levels of endogenous intramuscular metabolites (lactate, ATP, protons) associated with 'normal', predominantly aerobic exercise, the other subtype only responds to higher and concurrently noxious levels of metabolites present in muscle during ischemic contractions or following, for example, hypertonic saline infusions. This review discusses the mechanisms through which group III/IV muscle afferent feedback mediates both central and peripheral fatigue in exercising humans. We also briefly summarize the accumulating evidence from recent animal and human studies documenting the existence of two subtypes of group III/IV muscle afferents and the relevance of this discovery to the interpretation of previous work and the design of future studies.
起源于运动肢体肌肉的Ⅲ类和Ⅳ类肌肉传入神经在人类运动疲劳的发展中起重要作用。这些感觉神经元向中枢神经系统（CNS）的反馈在运动过程中反射性地增加通气以及中枢（心输出量）和外周（肢体血流量）的血流动力学反应，从而确保充足的肌肉血流量和氧气输送。这种反应是将外周疲劳发展速率降至最低以及优化有氧运动能力的关键因素。另一方面，Ⅲ/Ⅳ类肌肉传入神经的中枢投射通过其对脊髓运动神经元输出的减弱作用（即促进中枢疲劳）损害运动表现并限制运动中的人体。最近动物研究积累的证据表明存在Ⅲ/Ⅳ类肌肉传入神经的两种亚型。一种亚型仅对与“正常”、主要是有氧运动相关的内源性肌肉代谢物（乳酸、ATP、质子）的生理和无害水平作出反应，而另一种亚型仅对缺血性收缩期间或例如高渗盐水输注后肌肉中存在的更高且同时有害水平的代谢物作出反应。本综述讨论了Ⅲ/Ⅳ类肌肉传入神经反馈介导运动中人体中枢和外周疲劳的机制。我们还简要总结了最近动物和人体研究积累的证据，这些证据记录了Ⅲ/Ⅳ类肌肉传入神经的两种亚型的存在以及这一发现与以往工作解释和未来研究设计的相关性。
