Abstract：
OBJECTIVE: To assess the effect of a remote handgrip contraction during wide-pulse high-frequency (WPHF) neuromuscular electrical stimulation (NMES) on the magnitude of extra torque, progressive increase in torque during stimulation, and estimates of the persistent inward current (PIC) contribution to motoneuron firing in the plantar flexors.
METHODS: Ten participants performed triangular shaped contractions to 20% of maximal plantar flexion torque before and after WPHF NMES with and without a handgrip contraction, and control conditions. Extra torque, the relative difference between the initial and final torque during stimulation, and sustained electromyographic (EMG) activity were assessed. High-density EMG was recorded during triangular shaped contractions to calculate ∆F, an estimate of PIC contribution to motoneuron firing, and its variation before vs after the intervention referred to as ∆F change score.
RESULTS: While extra torque was not significantly increased with remote contraction (WPHF + remote) vs WPHF (+ 37 ± 63%, p = 0.112), sustained EMG activity was higher in this condition than WPHF (+ 3.9 ± 4.3% MVC EMG, p = 0.017). Moreover, ∆F was greater (+ 0.35 ± 0.30 Hz) with WPHF + remote than control (+ 0.03 ± 0.1 Hz, p = 0.028). A positive correlation was found between ∆F change score and extra torque in the WPHF + remote (r = 0.862, p = 0.006).
CONCLUSIONS: The findings suggest that the addition of remote muscle contraction to WPHF NMES enhances the central contribution to torque production, which may be related to an increased PIC contribution to motoneuron firing. Gaining a better understanding of these mechanisms should enable NMES intervention optimization in clinical and rehabilitation settings, improving neuromuscular function in clinical populations.
METHODS: Ten participants performed triangular shaped contractions to 20% of maximal plantar flexion torque before and after WPHF NMES with and without a handgrip contraction, and control conditions. Extra torque, the relative difference between the initial and final torque during stimulation, and sustained electromyographic (EMG) activity were assessed. High-density EMG was recorded during triangular shaped contractions to calculate ∆F, an estimate of PIC contribution to motoneuron firing, and its variation before vs after the intervention referred to as ∆F change score.
RESULTS: While extra torque was not significantly increased with remote contraction (WPHF + remote) vs WPHF (+ 37 ± 63%, p = 0.112), sustained EMG activity was higher in this condition than WPHF (+ 3.9 ± 4.3% MVC EMG, p = 0.017). Moreover, ∆F was greater (+ 0.35 ± 0.30 Hz) with WPHF + remote than control (+ 0.03 ± 0.1 Hz, p = 0.028). A positive correlation was found between ∆F change score and extra torque in the WPHF + remote (r = 0.862, p = 0.006).
CONCLUSIONS: The findings suggest that the addition of remote muscle contraction to WPHF NMES enhances the central contribution to torque production, which may be related to an increased PIC contribution to motoneuron firing. Gaining a better understanding of these mechanisms should enable NMES intervention optimization in clinical and rehabilitation settings, improving neuromuscular function in clinical populations.
摘要：
目的：评估宽脉冲高频（WPHF）神经肌肉电刺激（NMES）过程中远程握把收缩对额外扭矩大小的影响，刺激期间扭矩逐渐增加，以及对足底屈肌运动神经元放电的持续内向电流（PIC）贡献的估计。
方法：10名参与者在WPHFNMES前后进行了三角形收缩，达到最大足底弯曲扭矩的20％，有和没有手柄收缩，和控制条件。额外的扭矩，刺激期间初始扭矩和最终扭矩之间的相对差，和持续的肌电图（EMG）活动进行评估。在三角形收缩期间记录高密度肌电图以计算ΔF，PIC对运动神经元射击的贡献估计，及其在干预前与干预后的变化称为ΔF变化评分。
结果：虽然远程收缩（WPHF+远程）与WPHF（+37±63%，p=0.112),在这种情况下，持续的EMG活性高于WPHF（+3.9±4.3%MVCEMG，p=0.017)。此外，带WPHF+遥控器的ΔF(+0.35±0.30Hz)大于控制(+0.03±0.1Hz,p=0.028)。在WPHF+远程中，ΔF变化分数与额外扭矩之间存在正相关（r=0.862，p=0.006）。
结论：研究结果表明，在WPHFNMES中添加远程肌肉收缩可增强对扭矩产生的中央贡献，这可能与PIC对运动神经元放电的贡献增加有关。更好地理解这些机制应该能够在临床和康复环境中优化NMES干预措施。改善临床人群的神经肌肉功能。
方法：10名参与者在WPHFNMES前后进行了三角形收缩，达到最大足底弯曲扭矩的20％，有和没有手柄收缩，和控制条件。额外的扭矩，刺激期间初始扭矩和最终扭矩之间的相对差，和持续的肌电图（EMG）活动进行评估。在三角形收缩期间记录高密度肌电图以计算ΔF，PIC对运动神经元射击的贡献估计，及其在干预前与干预后的变化称为ΔF变化评分。
结果：虽然远程收缩（WPHF+远程）与WPHF（+37±63%，p=0.112),在这种情况下，持续的EMG活性高于WPHF（+3.9±4.3%MVCEMG，p=0.017)。此外，带WPHF+遥控器的ΔF(+0.35±0.30Hz)大于控制(+0.03±0.1Hz,p=0.028)。在WPHF+远程中，ΔF变化分数与额外扭矩之间存在正相关（r=0.862，p=0.006）。
结论：研究结果表明，在WPHFNMES中添加远程肌肉收缩可增强对扭矩产生的中央贡献，这可能与PIC对运动神经元放电的贡献增加有关。更好地理解这些机制应该能够在临床和康复环境中优化NMES干预措施。改善临床人群的神经肌肉功能。
