The effect of lung volume on the co-ordinated recruitment of scalene and sternomastoid muscles in humans
The effect of lung volume on the co-ordinated recruitment of scalene and sternomastoid muscles in humans
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DOI：
10.1113/jphysiol.2007.137240
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发表时间：
2007-10-01
影响因子：
5.5
通讯作者：
Butler, Jane E.
中科院分区：
文献类型：
--
作者：
Hudson, Anna L.;Gandevia, Simon C.;Butler, Jane E.
人类斜角肌是一种强制性的吸气肌，它比胸锁乳突肌（一种副肌）具有更大的机械优势。本研究确定了自主吸气任务中斜角肌和胸锁乳突肌的活动，以及当肺和吸气肌的反馈不同时，这种活动是否随肺容量的变化而变化。如果传入反馈在决定斜角肌和胸锁乳突肌的招募中起主要作用，那么在每个肺体积上，活动将会改变。当受试者（n = 7）进行吸气等容量斜坡至最大吸气压力（MIP）和从功能剩余容量（FRC）到总肺活量（TLC）的动态吸气时，记录斜角肌和胸锁乳突肌肌内肌电图和食管压力。在三种肺容积：FRC、FRC +潮气量和TLC下重复静态吸气斜坡。为了确定吸气激活的轮廓，即肌肉的初始和持续的恢复，在整个任务过程中测量肌电图的均方根。肌电图随着压力的增加而增加，在80% MIP时达到平稳期。相反，胸锁乳突肌活动开始较晚，但随后随着压力从20%增加到100%。在所有三个肺容量中都出现了类似的激活谱（n.s.）。胸锁乳突肌肌电图与斜角肌肌电图的比值也相同，与初始肺体积无关（n.s）。在动态激励下，斜角肌和胸锁乳突肌的激活与静态任务相似，但斜角肌肌电图比静态任务高15-40% （P < 0.05）。在两项任务中，胸锁乳突肌的激活是相同的。这些结果表明，在自愿任务中，斜角肌和胸锁乳突肌按照其机械优势的顺序被招募，并且与肺体积变化相关的反馈改变未能改变它们的激活。因此，在人类中，负责这两种吸气肌不同激活的机制有一个预先设定的元素。
The human scalenes are obligatory inspiratory muscles that have a greater mechanical advantage than sternomastoid, an accessory muscle. This study determined scalene and sternomastoid recruitment during voluntary inspiratory tasks, and whether this activity varied with lung volume, when feedback from the lungs and inspiratory muscles would differ. If afferent feedback has a major role in determining the recruitment of the scalenes and sternomastoid, then at each lung volume, activity would be altered. Intramuscular EMG from scalene and sternomastoid muscles, and oesophageal pressure were recorded while subjects (n = 7) performed inspiratory isovolumetric ramps to maximal inspiratory pressure (MIP) and dynamic inspirations from functional residual capacity (FRC) to total lung capacity (TLC). The static inspiratory ramps were repeated at three lung volumes: FRC, FRC + tidal volume, and TLC. To determine the profile of inspiratory activation, i.e. the initial and ongoing recruitment of the muscles, the root mean square of the EMG was measured throughout the tasks. Scalene was recruited early, and EMG increased with pressure, reaching a plateau at 80% MIP. In contrast, sternomastoid activity began later, but then increased with pressure from 20 to 100% MIP. Similar profiles of activation occurred at all three lung volumes (n.s.). The ratio of sternomastoid to scalene EMG was also the same irrespective of the initial lung volume (n.s.). In dynamic inspirations, scalene and sternomastoid activation had similar stereotypical profiles to the static tasks, but scalene EMG was 15-40% greater (P < 0.05). Sternomastoid activation was the same in both tasks (n.s.). These results suggest that in voluntary tasks, scalene and sternomastoid are recruited in the order of their mechanical advantages, and that alterations in feedback related to changes in lung volume failed to alter their activation. Thus, in humans, the mechanism responsible for the differential activation of these two inspiratory muscles has an element that is preset.