Distribution of the forces produced by motor unit activity in the human flexor digitorum profundus
Distribution of the forces produced by motor unit activity in the human flexor digitorum profundus
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DOI：
10.1113/jphysiol.2002.023861
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发表时间：
2002-08-15
影响因子：
5.5
通讯作者：
Gandevia, SC
中科院分区：
文献类型：
--
作者：
Kilbreath, SL;Gorman, RB;Gandevia, SC
在人类中，指深屈肌(FDP)是一种多腱肌肉，它产生的力量可以弯曲手指的四个远端指间关节。我们确定了在自然抓握时，与FDP中单个运动单位的活动相关的力是限制在单个手指上，还是分配到多个手指上。记录单个低阈值运动单位(n=69)在涉及所有手指的弱随意握力时横跨肌肉的部位的放电，并使用棘波触发的每个指垫下的力的平均值来评估其分布模式。尖峰触发的平均值显示，在“测试”手指(单元主要作用的手指)和“非测试”手指下，力发生了时间锁定的变化。然而，对于食指、中指和无名指单元，在非测试手指下的力变化通常很小(测试手指下的力变化是50%)。小指单位的力量分布与其他三个手指的力量分布有很大不同。除了非测试手指的力量增加外，偶尔还会有相邻手指的松动(22/267个组合)，通常影响食指。测试手指下的力的增加与作用在中指、无名指和小指上的单元的背景力显著相关。在功能抓取过程中，FDP中单个单位的活动允许相对选择性地控制食指、中指和无名指尖端的力量，但这仅限于小指单位。
In humans, the flexor digitorum profundus (FDP), which is a multi-tendoned muscle, produces forces that flex the four distal interphalangeal joints of the fingers. We determined whether the force associated with activity in a single motor unit in the FDP was confined to a single finger or distributed to more than one finger during a natural grasp. The discharge of single low-threshold motor units (n = 69) was recorded at sites across the muscle during weak voluntary grasping involving all fingers and spike-triggered averaging of the forces under each of the finger pads was used to assess the distribution pattern. Spike-triggered averaging revealed that time-locked changes in force occurred under the 'test' finger (that finger on which the unit principally acted) as well as under the 'non-test' fingers. However, for the index-, middle- and ring-finger units, the changes in force under non-test fingers were typically small (50% of those under the test finger). The distribution of forces by little-finger units differed significantly from that for each of the other three fingers. Apart from increases in force under non-test fingers, there was occasional unloading of adjacent fingers (22/267 combinations), usually affecting the index finger. The increases in force under the test finger correlated significantly with the background force for units acting on the middle, ring and little fingers. During a functional grasp, the activity of single units in the FDP allows for a relatively selective control of forces at the tips of the index, middle and ring fingers, but this is limited for little-finger units.