Paton M E, Brown J M
Department of Biomedical Science, University of Wollongong, Australia.
Electromyogr Clin Neurophysiol. 1995 Aug-Sep;35(5):301-9.
"Functional differentiation" within skeletal muscle refers to the ability of the Central Nervous System (CNS) to control, with a degree of independence, individual subunits of a muscle during a particular muscle contraction. Essentially, the concept of functional differentiation within skeletal muscle suggests an ability of the CNS to selectively activate those segments of a muscle which have the most appropriate line of action for the task as a means of ensuring the muscles efficient utilisation. The present study was undertaken to determine whether functional differentiation was present within the radiate muscle, Latissimus Dorsi, during a series of isometric muscle contractions. Six surface electrode pairs were placed along the origin of the muscle and electromyographic (EMG) potentials were recorded during isometric contractions in various planes and levels of contraction intensity. The EMG waveforms were integrated (IEMG) and then normalised. The normalised EMG waveforms (nIEMG) were then statistically compared to determine if muscle fibres within the detection area of each electrode pair had varied their contribution to the total activity of the muscle, from one isometric contraction to another. Alterations in the contribution of each site were taken to be indicative of functional differentiation. The results of this study indicated that functional differentiation did occur within Latissimus Dorsi. In essence, the most caudal fibres were utilised preferentially when subjects performed adduction from an abducted position of the shoulder joint. Conversely, activity was distributed over the entire muscle when subjects attempted adduction from the anatomical position. A similar situation was observed when subjects performed horizontal extension from either a flexed or abducted position.(ABSTRACT TRUNCATED AT 250 WORDS)
骨骼肌内的“功能分化”是指中枢神经系统（CNS）在特定肌肉收缩过程中，能够在一定程度上独立控制肌肉的各个亚单位。从本质上讲，骨骼肌内功能分化的概念表明，中枢神经系统有能力选择性地激活肌肉中那些对特定任务具有最合适作用方向的部分，以此确保肌肉的高效利用。本研究旨在确定在一系列等长肌肉收缩过程中，背阔肌的辐射状肌肉内是否存在功能分化。沿着肌肉起点放置了六对表面电极，并在不同平面和收缩强度水平的等长收缩过程中记录肌电图（EMG）电位。对EMG波形进行积分（IEMG），然后进行归一化处理。接着对归一化后的EMG波形（nIEMG）进行统计学比较，以确定每个电极对检测区域内的肌纤维在从一次等长收缩到另一次等长收缩过程中，对肌肉总活动的贡献是否发生了变化。每个部位贡献的改变被视为功能分化的指标。本研究结果表明，背阔肌内确实发生了功能分化。实际上，当受试者从肩关节外展位置进行内收时，最尾端的纤维被优先利用。相反，当受试者从解剖位置尝试内收时，活动分布在整个肌肉上。当受试者从屈曲或外展位置进行水平伸展时，也观察到了类似情况。（摘要截断于250字）
