Evidence for a fatigue-induced reflex inhibition of motoneuron firing rates.
Evidence for a fatigue-induced reflex inhibition of motoneuron firing rates.
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疲劳引起的运动神经元放电率反射抑制的证据。
DOI：
10.1152/jn.1987.58.1.125
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发表时间：
1987
影响因子：
2.5
通讯作者：
Bigland-Ritchie,B
中科院分区：
文献类型：
--
作者：
Woods,JJ;Furbush,F;Bigland-Ritchie,B
1. 在之前对拇内收肌和肱二头肌的研究中，我们认为运动神经元放电率在疲劳期间受到肌肉反射的抑制，因为： 在持续最大自主收缩（MVC）期间放电率下降；如果通过局部阻断其血液供应而将肌肉的疲劳状态保持 3 分钟，则 MVC 放电率的恢复将受到阻碍；一旦周围肌肉的血液供应恢复，在此期间就会完全恢复。这些发现在本次股四头肌收缩研究中得到了证实。 2. 这些结果并不一定意味着抑制反射。疲劳后缺血 3 分钟后的 MVC 期间，从肌肉纤维记录到的较低放电率可能是由于受试者努力程度降低（中枢神经系统的肌肉激活减少）或在这些条件下外周脉冲传递受损所致。目前在股四头肌和拇内收肌上进行的实验旨在检验这种替代解释。 3. 对于两块肌肉，MVC 收缩持续 40 秒，血压袖带充气至 200 mmHg。随后进行 3 分钟缺血休息，并在释放袖带之前进行第二次 20 秒 MVC。肌肉血液供应恢复三分钟后，进行第三次 20 秒 MVC。在每次 MVC 之前和之后对肌肉进行单次电击，记录放松肌肉 (Tr) 的抽搐，以及叠加在随意收缩 (Ts) 上的任何抽搐。根据比率 [1 - Ts/Tr] 评估肌肉可以通过自愿努力激活的程度。对于拇内收肌，还测量了诱发的 M 波幅度的变化。 4.仅在股四头肌实验期间记录尖峰频率。在最初的 40 秒 MVC 期间，这些下降了 30%。缺血休息 3 分钟后，第二个 MVC 未见恢复，但袖带释放后 3 分钟内完全恢复。 5. 在所有三种 MVC 中，经常出现无法保持完全肌肉激活的情况。然而，对于许多积极性良好的受试者来说，与血液供应恢复后 3 分钟进行的 MVC 相比，在缺血休息 3 分钟后进行的 MVC 中，抽搐阻断显示出拇内收肌或股四头肌的自愿激活程度没有降低。（摘要截断为 400 字）
1. In previous studies on the adductor pollicis and biceps brachii muscles we suggested that motoneuron firing rates are inhibited by a reflex from the muscle during fatigue, since: the firing rates decline during a sustained maximal voluntary contraction (MVC); recovery of MVC firing rates is prevented if the fatigued state of the muscle is preserved for 3 min by local occlusion of its blood supply; and full recovery occurs during this time once the blood supply to the peripheral muscle is restored. These findings were confirmed in the present study for quadriceps contractions. 2. These results do not necessarily imply an inhibitory reflex. The lower firing rates recorded from the muscle fibers during an MVC following 3 min of postfatigue ischemia may have been caused by either reduced subject effort (decreased muscle activation by the CNS) or impaired peripheral impulse transmission under these conditions. The present experiments, carried out on the quadriceps and adductor pollicis muscles, were designed to test this alternative explanation. 3. For both muscles, MVC contractions were sustained for 40 s with a blood pressure cuff inflated to 200 mmHg. This was followed by 3 min ischemic rest and a second 20-s MVC before cuff release. Three minutes after the blood supply to the muscle was restored a third 20-s MVC was made. Single shocks were delivered to the muscle throughout to record twitches from the relaxed muscle (Tr) before and after each MVC, and any twitches super-imposed on the voluntary contractions (Ts). The degree to which the muscle could be activated by voluntary effort was assessed from the ratio [1 - Ts/Tr]. For adductor pollicis, changes in the amplitude of the evoked M-waves were also measured. 4. Spike frequencies were only recorded during quadriceps experiments. These declined by 30% during the initial 40-s MVC. No recovery was seen in the second MVC following 3 min ischemic rest, but full recovery occurred within 3 min of cuff release. 5. Failure to retain full muscle activation was frequently seen in all three MVCs. However, for many well-motivated subjects twitch occlusion showed no reduction in the degree to which either the adductor pollicis or quadriceps muscles could be activated voluntarily during the MVC executed after 3 min of ischemic rest compared with that performed 3 min after the blood supply had been restored.(ABSTRACT TRUNCATED AT 400 WORDS)