Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.
Eur J Appl Physiol. 2021 May;121(5):1241-1254. doi: 10.1007/s00421-021-04598-4. Epub 2021 Feb 4.
We explore the motor unit recruitment and control of perfusion of microvascular units in skeletal muscle to determine whether they coordinate to match blood flow to metabolic demand.
The PubMed database was searched for historical, current and relevant literature.
A microvascular, or capillary unit consists of 2-20 individual capillaries. Individual capillaries within a capillary unit cannot increase perfusion independently of other capillaries within the unit. Capillary units perfuse a short segment of approx. 12 muscle fibres located beside each other. Motor units consist of muscle fibres that can be dispersed widely within the muscle volume. During a contraction, where not all motor units are recruited, muscle fibre contraction will result in increased perfusion of associated capillaries as well as all capillaries within that capillary unit. Perfusion of the entire capillary unit will result in an increased blood flow delivery to muscle fibres associated with active motor unit plus approximately 11 other inactive muscle fibres within the same region. This will result in an overperfusion of the muscle resulting in blood flow in excess of the muscle fibre needs.
Given the architecture of the capillary units and the dispersed nature of muscle fibres within a motor unit, during submaximal contractions, where not all motor units are recruited, there will be a greater perfusion to the muscle than that predicted by the number of active muscle fibres. Such overperfusion brings into question if blood flow and metabolic demand are as tightly matched as previously assumed.
我们探索骨骼肌微血管单位的运动单位募集和灌注控制，以确定它们是否协调以匹配血流与代谢需求。
在 PubMed 数据库中搜索了历史、当前和相关文献。
一个微血管或毛细血管单位由 2-20 个单独的毛细血管组成。一个毛细血管单位内的单个毛细血管不能独立于该单位内的其他毛细血管增加灌注。毛细血管单位灌注大约 12 个相邻的肌纤维短段。运动单位由可以在肌肉体积内广泛分散的肌纤维组成。在收缩过程中，并非所有运动单位都被募集，肌纤维收缩将导致相关毛细血管以及该毛细血管单位内的所有毛细血管灌注增加。整个毛细血管单位的灌注将导致与活跃运动单位相关的肌纤维的血液流量增加，以及同一区域内大约 11 个其他非活跃肌纤维的血液流量增加。这将导致肌肉过度灌注，导致血流超过肌纤维的需求。
鉴于毛细血管单位的结构和运动单位内肌纤维的分散性质，在亚最大收缩时，并非所有运动单位都被募集，与活跃肌纤维数量相比，肌肉的灌注会更多。这种过度灌注使得血流与代谢需求是否像以前假设的那样紧密匹配受到质疑。
