CENTRAL AND PERIPHERAL FATIGUE OF HUMAN DIAPHRAGM AND LIMB MUSCLES ASSESSED BY TWITCH INTERPOLATION
CENTRAL AND PERIPHERAL FATIGUE OF HUMAN DIAPHRAGM AND LIMB MUSCLES ASSESSED BY TWITCH INTERPOLATION
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DOI：
10.1113/jphysiol.1992.sp019284
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发表时间：
1992-08-01
影响因子：
5.5
通讯作者：
GANDEVIA, SC
中科院分区：
文献类型：
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作者：
MCKENZIE, DK;BIGLANDRITCHIE, B;GANDEVIA, SC
1.本研究使用了一个敏感的修改抽搐插值技术比较的程度自愿神经驱动的膈肌和手肘屈肌在疲劳。对于隔膜，测试吸气和呼气努力。通过最大自主收缩（MVC，10 s持续时间，50%占空比）或次最大收缩（50%MVC，3 s持续时间，60%占空比）诱发疲劳.在30个MVC系列中，峰值肘关节扭矩下降至57.9 +/-3.0%（平均值+/- S.E.M.）最大吸气压下降78.7 ± 7.3%（P < 0.05）。对于膈肌，自主吸气（和呼气）力峰值的相对下降类似于对单个和双胞胎（10 ms间隔）刺激的抽搐反应的下降。然而.对于手肘屈肌，抽搐力的下降不成比例地大于最大随意力的下降。膈肌收缩力的下降不能归因于神经肌肉接头的失效。在运动开始时，膈肌的抽搐增强（三次短暂的MVC后）明显低于手肘屈肌（20%对61%）。P < 0.01）。在非疲劳状态下，受试者的最大随意努力激活了98-4 +/- 0.4%的受刺激肘屈肌，而膈肌激活了95.0 +/- 1.5%（P < 0.05）。在运动期间，激活肢体肌肉的能力逐渐丧失（“中枢疲劳”：自愿驾驶从98.4 +/- 0.4下降到86.8 +/-2.2%，P < 0.01），而在吸气收缩期间自主激活的下降并不显著（从95.0 +/-15%下降到91.5 +/- 2- 5%）。自愿激活在尝试最大的努力是不完全的两块肌肉时，刺激提供没有警告。膈肌对未警告刺激的自主激活指数（执行驱逐努力，81.0 ± 2.8%）低于肢体肌肉（89.9 ± 1.5%，P < 0.01）.在重复的次最大呼气努力中，我们证实受试者明显不能自主收缩隔膜，但当隔膜在相同的收缩疲劳水平下进行吸气动作时，自主驱动指数大于94%。总之，当测试与吸气的努力，隔膜开发较少的中央疲劳比肢体肌肉在相同的运动期间。然而，在长时间的一系列明显升高腹压的排出性收缩过程中，确实会出现膈肌的实质性中枢疲劳。
1. This study used a sensitive modification of the twitch interpolation technique to compare the extent of voluntary neural drive to the diaphragm and the elbow flexors during fatigue. For the diaphragm both inspiratory and expulsive efforts were tested. and fatigue was induced by expulsive efforts which were either maximal voluntary contractions (MVCs, 10 s duration, 50 % duty-cycle) or submaximal contractions (50 % MVC, 3 s duration, 60 % duty cycle).2. Over the series of thirty MVCs peak elbow torque declined to 57.9 +/- 3.0 % (mean +/- S.E.M.) of the initial value while maximal inspiratory pressure declined to 78.7 +/- 7.3 % (P < 0.05). For the diaphragm the relative decline in voluntary peak inspiratory (and expulsive) force was similar to the decline in twitch responses to single and twin (10 ms interval) stimuli. However. for the elbow flexors the decline in twitch force was disproportionately greater than the decline in maximal voluntary force. The decline in twitch force for the diaphragm could not be attributed to failure at the neuromuscular junction.3. At the start of the exercise, twitch potentiation (following three brief MVCs) was significantly less for the diaphragm than for the elbow flexors (20 % versus 61 %. P < 0.01).4. In the unfatigued state maximal voluntary efforts by subjects activated 98-4 +/- 0.4% of the stimulated elbow flexors compared with 95.0 +/- 1.5% of the diaphragm (P < 0.05). During the exercise period there was a progressive failure in the ability to activate the limb muscle ('Central fatigue': voluntary drive declined from 98.4 +/- 0.4 to 86.8 +/- 2.2 %, P < 0.01) whereas the decline in voluntary aetivation during inspiratory contractions was not significant (from 95.0 +/- 15 to 91.5 +/- 2-5 %).5. Voluntary activation during attempted maximal efforts was less complete for both muscles when stimuli were delivered without warning. The index of voluntary activation for unwarned stimuli was lower for the diaphragm (performing expulsive efforts, 81.0 +/- 2.8 %) than for the limb muscle (89.9 + 1.5 %, P < 0.01).6. During repeated submaximal expulsive efforts we confirmed that subjects develop a marked inability to contract the diaphragm voluntarily, but when the diaphragm performed inspiratory manoeuvres at the same level of contractile fatigue, the index of voluntary drive was greater than 94 %.7. In conclusion, when tested with inspiratory efforts the diaphragm developed less central fatigue than the limb muscle over the same exercise period. However, substantial central fatigue of the diaphragm does develop during prolonged series of expulsive contractions which markedly elevated abdominal pressure.