Prince of Wales Medical Research Institute and University of New South Wales, Sydney, New South Wales, Australia.
J Neurophysiol. 2010 Mar;103(3):1622-9. doi: 10.1152/jn.00887.2009. Epub 2010 Jan 20.
The parasternal intercostal muscles are obligatory inspiratory muscles. To test the hypothesis that they are also involved in trunk rotation and to assess the effect of any postural role on inspiratory drive to the muscles, intramuscular electromyographic (EMG) recordings were made from the parasternal intercostals on the right side in six healthy subjects during resting breathing in a neutral posture ("neutral breaths"), during an isometric axial rotation effort of the trunk to the right ("ipsilateral rotation") or left ("contralateral rotation"), and during resting breathing with the trunk rotated. The parasternal intercostals were commonly active during ipsilateral rotation but were consistently silent during contralateral rotation. In addition, with ipsilateral rotation, peak parasternal inspiratory activity was 201 +/- 19% (mean +/- SE) of the peak inspiratory activity in neutral breaths (P < 0.001), and activity commenced earlier relative to the onset of inspiratory flow. These changes resulted from an increase in the discharge frequency of motor units (14.3 +/- 0.3 vs. 11.0 +/- 0.3 Hz; P < 0.001) and the recruitment of new motor units. The majority of units that discharged during ipsilateral rotation were also active in inspiration. However, with contralateral rotation, parasternal inspiratory activity was delayed relative to the onset of inspiratory flow, and peak activity was reduced to 72 +/- 4% of that in neutral breaths (P < 0.001). This decrease resulted from a decrease in the inspiratory discharge frequency of units (10.5 +/- 0.2 vs. 12.0 +/- 0.2 Hz; P < 0.001) and the derecruitment of units. These observations confirm that in addition to an inspiratory function, the parasternal intercostal muscles have a postural function. Furthermore the postural and inspiratory drives depolarize the same motoneurons, and the postural contraction of the muscles alters their output during inspiration in a direction-dependent manner.
胸肋间肌是必需的吸气肌。为了验证它们也参与了躯干旋转的假设，并评估任何姿势作用对肌肉吸气驱动的影响，在 6 名健康受试者中立位休息呼吸时（“中立呼吸”）、向右侧（“同侧旋转”）或左侧（“对侧旋转”）进行等长轴向躯干旋转时以及在躯干旋转时进行休息呼吸时，对右侧胸肋间肌进行了肌内肌电图（EMG）记录。同侧旋转时，胸肋间肌通常活跃，但对侧旋转时始终保持安静。此外，同侧旋转时，胸肋吸气肌的峰值活动是中立呼吸时吸气峰值活动的 201 +/- 19%（平均值 +/- SE）（P < 0.001），并且活动相对于吸气流量的开始更早开始。这些变化是由于运动单位放电频率的增加（14.3 +/- 0.3 与 11.0 +/- 0.3 Hz；P < 0.001）和新运动单位的募集。在同侧旋转时放电的大多数单位也在吸气时活跃。然而，在对侧旋转时，胸肋吸气肌的活动相对于吸气流量的开始延迟，并且峰值活动减少到中立呼吸时的 72 +/- 4%（P < 0.001）。这种减少是由于单位吸气放电频率的降低（10.5 +/- 0.2 与 12.0 +/- 0.2 Hz；P < 0.001）和单位去募集。这些观察结果证实，除了吸气功能外，胸肋间肌还具有姿势功能。此外，姿势和吸气驱动使相同的运动神经元去极化，并且肌肉的姿势收缩以依赖方向的方式改变它们在吸气期间的输出。
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