Electromyographic Kinesiology Laboratory, Faculty of Applied Health Sciences, Brock University, St Catharine's, ON, Canada.
Acta Physiol (Oxf). 2011 Apr;201(4):483-92. doi: 10.1111/j.1748-1716.2010.02233.x.
The purpose of this study was to examine the influence of post-activation potentiation (PAP), the transient increase in low-frequency isometric force observed after muscle activity, on motor unit discharge rates measured during submaximal contractions.
A quadrifilar needle electrode was inserted into the tibialis anterior muscle to determine discharge rate of individual motor units while monopolar electrodes were used to monitor the root-mean-square (RMS) and mean power frequency (MPF) of the surface EMG signal. Control (unpotentiated) and experimental (potentiated) measures were obtained during a 5 s voluntary contraction at 50% of maximal. In between these measures, subjects performed a 10 s maximal voluntary contraction (MVC) to induce PAP.
All subjects data are reported as means ± SEM (n = 10). Compared to baseline values measured prior to the MVC, isometric twitch force measured immediately after the MVC was increased by 260 ± 16% (day 3). Motor unit discharge rate in the potentiated tibialis anterior muscle decreased by approx. 10%, from 20.3 ± 0.8 (before) to 18.3 ± 0.99 pps (P = 0.01) (after). Moreover, the MPF was decreased by approx. 9% (from 58.1 ± 2.84 to 53.6 ± 2.85 Hz; P = 0.01) in the potentiated tibialis anterior. On the other hand, consistent with the absence of fatigue during the MVC, the RMS signal was not altered in the potentiated tibialis anterior (0.29 ± 0.03 vs. 0.33 ± 0.04 mV; P = 0.07).
Motor unit discharge rates determined during a brief, submaximal contraction were decreased in the potentiated human tibialis anterior muscle.
本研究旨在探讨肌肉活动后短暂出现的低频等长力增强（PAP）对亚最大收缩期间测量的运动单位放电率的影响。
将四股针电极插入胫骨前肌以确定单个运动单位的放电率，同时使用单极电极监测表面肌电图信号的均方根（RMS）和平均功率频率（MPF）。在 50%最大自愿收缩的 5 秒期间获得对照（未增强）和实验（增强）测量值。在这些测量值之间，受测者进行 10 秒最大自愿收缩（MVC）以诱导 PAP。
所有受测者的数据均以平均值±SEM（n = 10）报告。与 MVC 前测量的基线值相比，MVC 后立即测量的等长抽搐力增加了 260±16%（第 3 天）。增强的胫骨前肌中的运动单位放电率下降了约 10%，从 20.3±0.8（之前）降至 18.3±0.99pps（P=0.01）（之后）。此外，增强的胫骨前肌中的 MPF 下降了约 9%（从 58.1±2.84 降至 53.6±2.85 Hz；P=0.01）。另一方面，与 MVC 期间没有疲劳一致，增强的胫骨前肌中的 RMS 信号没有改变（0.29±0.03 与 0.33±0.04 mV；P=0.07）。
在短暂的亚最大收缩期间确定的运动单位放电率在增强的人类胫骨前肌中降低。
