Lei Yuming, Suresh Nina L, Rymer William Z, Hu Xiaogang
The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami, 1095 NW 14th Terrace #48, Miami, Florida 33136, USA.
Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois, USA.
Muscle Nerve. 2018 Jan;57(1):E85-E93. doi: 10.1002/mus.25963. Epub 2017 Sep 14.
Muscle force generation involves recruitment and firing rate modulation of motor units (MUs). The control of MUs in producing multidirectional forces remains unclear.
We studied MU recruitment and firing properties, recorded from the first dorsal interosseous muscle, for 3 different directions of contraction: abduction; abduction/flexion combination; and flexion.
MUs were recruited systematically at higher threshold force during flexion. Larger MUs were recruited and firing rates of MUs were lower during abduction. There was an orderly recruitment of MUs according to MU size regardless of contraction direction, obeying the "size principle." Firing rates of earlier-recruited MUs were consistently higher than later-recruited MUs, affirming the "onion-skin" property.
Our findings suggest that the size principle and onion-skin organization together provide a general description of MU recruitment patterns and firing properties. The directional alternations of MU control properties likely reflect changes in neural drive to the muscle. Muscle Nerve 57: E85-E93, 2018.
肌肉力量的产生涉及运动单位（MU）的募集和放电频率调制。运动单位在产生多方向力量时的控制机制仍不清楚。
我们研究了从第一背侧骨间肌记录的运动单位募集和放电特性，针对3种不同收缩方向：外展；外展/屈曲组合；以及屈曲。
在屈曲过程中，运动单位在较高阈值力时被系统性地募集。在外展过程中，较大的运动单位被募集且运动单位的放电频率较低。无论收缩方向如何，运动单位均根据其大小有序募集，遵循“大小原则”。早期募集的运动单位的放电频率始终高于后期募集的运动单位，证实了“洋葱皮”特性。
我们的研究结果表明，大小原则和洋葱皮组织共同提供了运动单位募集模式和放电特性的一般描述。运动单位控制特性的方向变化可能反映了对肌肉神经驱动的变化。《肌肉与神经》57: E85-E93, 2018。
