Liu Fang, Jones Alice Y M, Tsang Raymond C C, Yam Timothy T T, Tsang William W N
Department of Physiotherapy, School of Nursing and Health Sciences, Hong Kong Metropolitan University, Hong Kong, China.
Department of Rehabilitation, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University Health Science Centre, Shenzhen, China.
Sci Rep. 2025 Feb 18;15(1):5856. doi: 10.1038/s41598-025-90199-6.
This study reports the concomitant contraction pattern of the diaphragm and sternocleidomastoid (SCM) muscles at various inspiratory pressure loads in patients after stroke. Thirty-six participants (stroke duration: 3.6 ± 2.9 months) performed in random order, sets of 10 breaths at inspiratory loads of 30, 40, 50, 60, 70 and 80%, maximum inspiratory pressure (MIP). Bilateral muscle activity of the SCMs and diaphragm thickness were recorded simultaneously using surface electromyography (sEMG) and ultrasonography, respectively. Diaphragmatic thickness was significantly lower on the hemiplegic side compared to the non-affected side. The magnitude of diaphragmatic contraction, reflected by the calculated thickening fraction (DTf) for both hemidiaphragms, increased with inspiratory load and peaked at 50% MIP, but then decreased with any further increase in inspiratory pressure. SCM recruitment continued to increase bilaterally with increasing inspiratory pressure and was highest at 80% MIP, with recruitment activity significantly higher on the hemiplegic side compared to the non-affected side. Our results suggest that inspiratory load demands above 50%MIP are primarily met by increased SCM activity without any increase in diaphragmatic contraction. Adopting training intensities greater than 50%MIP in clinical inspiratory muscle training (IMT) programs needs to be re-considered.
本研究报告了中风后患者在不同吸气压力负荷下膈肌和胸锁乳突肌（SCM）的伴随收缩模式。36名参与者（中风病程：3.6±2.9个月）以随机顺序在吸气负荷分别为最大吸气压力（MIP）的30%、40%、50%、60%、70%和80%的情况下进行每组10次呼吸。分别使用表面肌电图（sEMG）和超声检查同时记录双侧SCM的肌肉活动和膈肌厚度。与未受影响侧相比，偏瘫侧的膈肌厚度明显更低。通过计算两侧膈肌增厚分数（DTf）反映的膈肌收缩幅度随吸气负荷增加而增加，并在50%MIP时达到峰值，但随后随着吸气压力的进一步增加而下降。随着吸气压力增加，双侧SCM的募集持续增加，并在80%MIP时达到最高，且偏瘫侧的募集活动明显高于未受影响侧。我们的结果表明，高于50%MIP的吸气负荷需求主要通过增加SCM活动来满足，而膈肌收缩没有任何增加。在临床吸气肌训练（IMT）计划中采用大于50%MIP的训练强度需要重新考虑。
