Gondin Julien, Guette Marie, Jubeau Marc, Ballay Yves, Martin Alain
Motricity Plasticity Laboratory, Faculty of Sport Sciences, University of Burgundy, Dijon Cedex, FRANCE.
Med Sci Sports Exerc. 2006 Jun;38(6):1147-56. doi: 10.1249/01.mss.0000222843.04510.ca.
We examined the effect of 4 (WK4) and 8 wk (WK8) of neuromuscular electrical stimulation (NMES) training on both endurance time and mechanisms contributing to task failure.
Ten males performed a fatiguing isometric contraction with the knee extensor muscles at 20% of maximal voluntary contraction (MVC) until exhaustion before (B), at WK4, and at WK8 of NMES training. The electromyographic (EMG) activity and muscle activation obtained under MVC were recorded before and after the fatiguing task to assess central fatigue. Torque and EMG responses obtained under electrically evoked contractions were examined before and after the fatiguing task to analyze peripheral fatigue.
Knee extensor MVC torque increased significantly between B and WK4 (+16%), between WK4 and WK8 (+10%), and between B and WK8 (+26%), which meant that the average target torque sustained during the fatiguing contraction increased between the testing sessions. Endurance time decreased significantly over the three sessions (493+/-101 s at B, 408+/-159 s at WK4, and 338+/-126 s at WK8) despite a similar reduction in knee extensor MVC (approximately 25%). Negative correlations were found between endurance time absolute changes and target torque absolute gains. Average EMG activity of the knee extensor muscles was lower after training, but the mean rate of increase was similar over the three sessions. Single-twitch contractile properties were not affected by the task.
We conclude that the endurance time was shorter after 4 and 8 wk of NMES training, and this was associated with higher absolute contraction intensity. Despite endurance time reduction, NMES training did not affect the amount of fatigue at exhaustion nor the central and peripheral contributions to fatigue.
我们研究了4周（WK4）和8周（WK8）的神经肌肉电刺激（NMES）训练对耐力时间以及导致任务失败的机制的影响。
10名男性在最大自主收缩（MVC）的20%下，用膝伸肌进行疲劳性等长收缩，直至在NMES训练前（B）、WK4和WK8时力竭。在疲劳任务前后记录MVC下获得的肌电图（EMG）活动和肌肉激活情况，以评估中枢疲劳。在疲劳任务前后检查电诱发收缩下获得的扭矩和EMG反应，以分析外周疲劳。
膝伸肌MVC扭矩在B和WK4之间显著增加（+16%），在WK4和WK8之间增加（+10%），在B和WK8之间增加（+26%），这意味着在疲劳收缩期间持续的平均目标扭矩在测试阶段之间增加。尽管膝伸肌MVC有类似程度的下降（约25%），但在这三个阶段中耐力时间显著减少（B时为493±101秒，WK4时为408±159秒，WK8时为338±126秒）。耐力时间的绝对变化与目标扭矩的绝对增加之间存在负相关。训练后膝伸肌的平均EMG活动较低，但在这三个阶段中平均增加率相似。单收缩收缩特性不受该任务影响。
我们得出结论，NMES训练4周和8周后耐力时间较短，这与更高的绝对收缩强度有关。尽管耐力时间减少，但NMES训练并未影响力竭时的疲劳量以及中枢和外周对疲劳的影响。
