Grosprêtre Sidney, Gueugneau Nicolas, Martin Alain, Lepers Romuald
Université de Bourgogne-Franche Comté, Dijon, FRANCE.
Med Sci Sports Exerc. 2017 Aug;49(8):1530-1540. doi: 10.1249/MSS.0000000000001270.
This study analyzed the impact of several protocols of neuromuscular electrical stimulation (NMES), matched with a similar total torque-time integral, on muscle activation pathways and neuromuscular fatigue.
Ten young healthy participants (age, 24.6 ± 4.2 yr) performed three randomized NMES sessions on the triceps surae muscles with 20-, 60-, or 100-Hz stimulation frequencies (pulse duration, 1 ms), with pulse amplitude (IES) set at 20% of isometric maximal voluntary contraction (MVC). Muscle activity during NMES was assessed by means of the twitch, the soleus H-reflex and M wave responses evoked by single muscle stimulation at IES. Neuromuscular fatigue was assessed as the changes in evoked and MVC torques and the underlying mechanisms by analyzing variations in superimposed maximal M-waves (Msup), normalized H-reflexes (Hsup/Msup) and V-waves (V/Msup) of the triceps surae muscles.
Electromyographic responses at IES suggested that the relative contribution of the indirect muscle activation increases as the stimulation frequency was high and the pulse amplitude was low (P = 0.03). The decrease in MVC torque after NMES was significantly (P = 0.003) greater after 100-Hz protocol (20 Hz, -9.6% ± 3.3%; 60 Hz, -10.7% ± 3.2%; 100 Hz, -16.3% ± 2.7%). Hsup/Msup decreased significantly (P < 0.01) by 31% ± 4% after the 100-Hz protocol only and V/Msup decreased significantly (P <0.05) after both 60- and 100-Hz protocols.
The combination of high-stimulation frequencies and low-pulse amplitude induced the greatest neuromuscular fatigue. Low frequencies (20 Hz) induced alterations mainly at the muscle level, whereas higher frequencies (60 to 100 Hz) rather induced modulations at both spinal and supraspinal levels.
本研究分析了几种神经肌肉电刺激（NMES）方案对肌肉激活途径和神经肌肉疲劳的影响，这些方案的总扭矩-时间积分相似。
10名年轻健康参与者（年龄24.6±4.2岁）在腓肠肌上进行了三次随机NMES训练，刺激频率分别为20Hz、60Hz或100Hz（脉冲持续时间1ms），脉冲幅度（IES）设定为等长最大自主收缩（MVC）的20%。通过在IES下对单块肌肉刺激诱发的抽搐、比目鱼肌H反射和M波反应来评估NMES期间的肌肉活动。通过分析腓肠肌叠加最大M波（Msup）、归一化H反射（Hsup/Msup）和V波（V/Msup）的变化，将神经肌肉疲劳评估为诱发扭矩和MVC扭矩的变化以及潜在机制。
IES时的肌电图反应表明，随着刺激频率升高和脉冲幅度降低，间接肌肉激活的相对贡献增加（P = 0.03）。NMES后MVC扭矩的降低在100Hz方案后显著更大（P = 0.003）（20Hz，-9.6%±3.3%；60Hz，-10.7%±3.2%；100Hz，-16.3%±2.7%）。仅在100Hz方案后Hsup/Msup显著降低（P < 0.01）31%±4%，在60Hz和100Hz方案后V/Msup均显著降低（P < 0.05）。
高刺激频率和低脉冲幅度的组合诱发了最大的神经肌肉疲劳。低频（20Hz）主要在肌肉水平引起改变，而高频（60至100Hz）则更多地在脊髓和脊髓上水平引起调节。
