Martin V, Millet G Y, Lattier G, Perrod L
INSERM/ERIT-M 0207 Motricité-Plasticité Faculté des Sciences du Sport, Université de Bourgogne, Dijon, France.
J Sports Med Phys Fitness. 2005 Jun;45(2):143-51.
The purpose of this study was to re-examine central and peripheral origins of neuromuscular fatigue after a highly strenuous eccentric exercise of the knee extensor muscles (KE) using both voluntary/evoked contractions and electromyographic recordings (EMG).
Before, and 30 min after 15 min of intermittent one-logged downhill running, maximal percutaneous electrical stimulations (single twitch, 0.5 s tetanus at 20 Hz and 80 Hz) were applied to the femoral nerve of 10 male subjects. Electrically evoked superimposed twitches were delivered during isometric maximal voluntary contraction (MVC) to determine maximal voluntary activation (%VA). Vastus lateralis (VL), vastus medialis (VM) and biceps femoris (BF) EMG were recorded during MVC and quantified using the root mean square (RMS) value. M-wave characteristics were also determined.
KE MVC and %VA decreased significantly with fatigue (-19.6+/-6.1%; P<0.001 and -7.8+/-6.6%; P<0.01, respectively). Peak tetanus tension at 20 and 80 Hz (P20 and P80, respectively) declined (P<0.001), concurrently with a decrement of the P20 x P80(-1) ratio (-37.3+/-16.6%; P<0.001). Antagonist muscle coactivation, RMS to M-wave peak-to-peak amplitude and MVC x P80(-1) ratios were unchanged after the fatiguing exercise.
The results reveal that part of the large loss in MVC may have a central origin but most of the MVC decrement is due to the presence of low-frequency fatigue while possible contractile failure cannot be excluded.
本研究旨在通过自愿/诱发收缩和肌电图记录（EMG），重新审视膝伸肌（KE）进行高强度离心运动后神经肌肉疲劳的中枢和外周起源。
10名男性受试者在进行15分钟间歇性单腿下坡跑之前和之后30分钟，对股神经施加最大经皮电刺激（单抽搐、20Hz和80Hz的0.5秒强直收缩）。在等长最大自主收缩（MVC）期间给予电诱发叠加抽搐，以确定最大自主激活（%VA）。在MVC期间记录股外侧肌（VL）、股内侧肌（VM）和股二头肌（BF）的EMG，并使用均方根（RMS）值进行量化。还测定了M波特征。
KE的MVC和%VA随疲劳显著降低（分别为-19.6±6.1%；P<0.001和-7.8±6.6%；P<0.01）。20Hz和80Hz时的强直收缩峰值张力（分别为P20和P80）下降（P<0.001），同时P20×P80（-1）比值降低（-37.3±16.6%；P<0.001）。疲劳运动后，拮抗肌共激活、RMS与M波峰峰值幅度以及MVC×P80（-1）比值均未改变。
结果表明，MVC的大幅下降部分可能源于中枢，但MVC下降的大部分原因是低频疲劳的存在，同时不能排除可能的收缩功能衰竭。
