Recruitment of motor units in the medial gastrocnemius muscle during human quiet standing: is recruitment intermittent? What triggers recruitment?
Recruitment of motor units in the medial gastrocnemius muscle during human quiet standing: is recruitment intermittent? What triggers recruitment?
复制标题
人体安静站立时腓肠肌内侧运动单位的募集：募集是间歇性的吗？
DOI：
10.1152/jn.00659.2011
复制
发表时间：
2012
影响因子：
2.5
通讯作者：
S. Birnbach
中科院分区：
文献类型：
--
作者：
H. Kunz;S. Birnbach
运动单位的招募和放电率是肌力的决定因素。在一个运动神经元池中，单个运动单元的招募和速率编码可能是独立控制的，这取决于具体情况。在这项研究中，我们测试了在人类安静站立时，内侧腓肠肌（MG）的力量是否主要由招募或速率编码控制。如果站立期间的MG控制主要是由于招募，那么我们进一步询问触发机制是什么。它是内部决定的，还是与人体运动学有关？同时，7名健康受试者静静地站着，用三对丝电极记录MG肌肌内肌电图。在不同的摇摆速度和位置下，比较了主动运动单元的数量及其平均放电率。当身体快速向前摇摆时，运动单元放电更频繁（Pearson R = 0.63; P < 0.0001）。观察到运动单元电位的高可能性主要是由于增加了额外的单元。在身体向前移动期间，检测到的单位中位数从3个增加到11个（P < 0.0001），而放电速率从8±1.1（平均±SD）变化到10±0.9脉冲/s （P = 0.001）。引人注目的是，运动单元在站立过程中并没有连续放电。他们以每秒钟两次招募的模式，以个体、向前摇摆和间歇性的方式被招募。这一模态比率与先前有关站立控制与内在的、更高层次的规划过程的间接证据是一致的。
The recruitment and the rate of discharge of motor units are determinants of muscle force. Within a motoneuron pool, recruitment and rate coding of individual motor units might be controlled independently, depending on the circumstances. In this study, we tested whether, during human quiet standing, the force of the medial gastrocnemius (MG) muscle is predominantly controlled by recruitment or rate coding. If MG control during standing was mainly due to recruitment, then we further asked what the trigger mechanism is. Is it determined internally, or is it related to body kinematics? While seven healthy subjects stood quietly, intramuscular electromyograms were recorded from the MG muscle with three pairs of wire electrodes. The number of active motor units and their mean discharge rate were compared for different sway velocities and positions. Motor unit discharges occurred more frequently when the body swayed faster and forward (Pearson R = 0.63; P < 0.0001). This higher likelihood of observing motor unit potentials was explained chiefly by the recruitment of additional units. During forward body shifts, the median number of units detected increased from 3 to 11 (P < 0.0001), whereas the discharge rate changed from 8 ± 1.1 (mean ± SD) to 10 ± 0.9 pulses/s (P = 0.001). Strikingly, motor units did not discharge continuously throughout standing. They were recruited within individual, forward sways and intermittently, with a modal rate of two recruitments per second. This modal rate is consistent with previous circumstantial evidence relating the control of standing to an intrinsic, higher level planning process.