Preceding muscle activity influences motor unit discharge and rate of torque development during ballistic contractions in humans
Preceding muscle activity influences motor unit discharge and rate of torque development during ballistic contractions in humans
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先前的肌肉活动影响人类弹道收缩期间运动单位的放电和扭矩发展的速率
DOI：
10.1113/jphysiol.2004.074567
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
J. Duchateau
中科院分区：
文献类型：
--
作者：
M. Van Cutsem;J. Duchateau
为了研究初始条件对快速随意收缩期间运动单位放电调节的影响，我们比较了踝背屈肌在静止状态或叠加在持续收缩上产生的弹道等长收缩。记录背屈肌的扭矩以及胫骨前肌的表面和肌内肌电图。结果表明，持续收缩（约 25% 最大自主收缩（MVC））的弹道收缩对扭矩产生的最大速率有负面影响。尽管机电延迟缩短了，但弹道收缩期间的肌电图活动不太同步。这些观察结果与单运动单位的平均放电率（89.8 ± 3.8 vs 115 ± 5.8 Hz）和在短暂间隔（= 5 ms）内表现出两次放电的单位百分比（整个样本的 6.2% vs 15.5%）的显着下降有关。在持续收缩期间未招募的高阈值单位表现出相同的激活模式，这表明导致放电率下降的机制并不限于先前激活的单位，而是似乎影响整个运动单位池。当在从持续肌肉活动到弹道收缩的过渡过程中观察到运动前静默期 (SP) 时（占试验的 19%），运动单位活动的这些调整不存在，并且弹道收缩与静息状态下进行的收缩相似。总之，这些结果表明初始条件可以影响运动单位放电速率的能力，从而影响快速自主收缩的性能。
To investigate the effect of initial conditions on the modulation of motor unit discharge during fast voluntary contractions, we compared ballistic isometric contractions of the ankle dorsiflexor muscles that were produced from either a resting state or superimposed on a sustained contraction. The torque of the dorsiflexors and the surface and intramuscular EMGs from the tibialis anterior were recorded. The results showed that the performance of a ballistic contraction from a sustained contraction (∼25% maximal voluntary contraction (MVC)) had a negative effect on the maximal rate of torque development. Although the electromechanical delay was shortened, the EMG activity during the ballistic contraction was less synchronized. These observations were associated with a significant decline in the average discharge rate of single motor units (89.8 ± 3.8 versus 115 ± 5.8 Hz) and in the percentage of units (6.2 versus 15.5% of the whole sample) that exhibited double discharges at brief intervals (= 5 ms). High‐threshold units that were not recruited during the sustained contraction displayed the same activation pattern, which indicates that the mechanisms responsible for the decline in discharge rate were not restricted to previously activated units, but appear to influence the entire motor unit pool. When a premotor silent period (SP) was observed at the transition from the sustained muscular activity to the ballistic contraction (19% of the trials), these adjustments in motor unit activity were not present, and the ballistic contractions were similar to those performed from a resting state. Together, these results indicate that initial conditions can influence the capacity for motor unit discharge rate and hence the performance of a fast voluntary contraction.
影响因子：
2.5
作者：
Hsiao, CF;Trueblood, PR;Chandler, SH
通讯作者：
Chandler, SH
外向电流对大鼠舌下运动神经元尖峰频率适应的贡献。
DOI：
10.1152/jn.1997.78.5.2246
发表时间：
1997
期刊：
Journal of neurophysiology.
影响因子：
--
作者：
Sawczuk,A;Powers,RK;Binder,MD
通讯作者：
Binder,MD