UMR 1253, iBrain, Université de Tours, Inserm, Tours, France.
Laboratoire d'imagerie biomédicale multimodale à Paris-Saclay, Université Paris-Saclay, CEA, CNRS UMR 9011, INSERM UMR 1281, France.
Phys Med Biol. 2021 Jul 13;66(14). doi: 10.1088/1361-6560/ac0f9b.
Using shear wave elastography, we measure the changes in the wave speed with the stress produced by a striated muscle during isometric voluntary contraction. To isolate the behaviour of an individual muscle from complementary or antagonistic actions of adjacent muscles, we select themuscle, whose sole function is to extend the little finger. To link the wave speed to the stiffness, we develop an acousto-elastic theory for shear waves in homogeneous, transversely isotropic, incompressible solids subject to an uniaxial stress. We then provide measurements of the apparent shear elastic modulus along, and transversely to, the fibre axis for six healthy human volunteers of different age and sex. The results display a great variety across the six subjects. We find that the slope of the apparent shear elastic modulus along the fibre direction changes inversely to the maximum voluntary contraction (MVC) produced by the volunteer. We propose an interpretation of our results by introducing the S (slow) or F (fast) nature of the fibres, which harden the muscle differently and accordingly, produce different MVCs. A natural follow-up on this study is to apply the method to patients with musculoskeletal disorders or neurodegenerative diseases.
使用剪切波弹性成像技术，我们测量了在等长自主收缩期间，横纹肌产生的应力下波速的变化。为了将单个肌肉的行为与相邻肌肉的补充或拮抗作用隔离开来，我们选择了唯一功能是伸展小指的肌肉。为了将波速与刚度联系起来，我们针对单轴应力下各向同性、横观各向同性、不可压缩固体中的剪切波开发了一种声弹性理论。然后，我们为六位不同年龄和性别的健康人类志愿者测量了在纤维轴的和横向的表观剪切弹性模量。结果显示，六个测试对象之间存在很大的差异。我们发现，沿着纤维方向的表观剪切弹性模量的斜率与志愿者产生的最大自主收缩（MVC）呈反比变化。我们通过引入纤维的 S（慢）或 F（快）特性来解释我们的结果，这些特性以不同的方式使肌肉变硬，从而产生不同的 MVC。这项研究的一个自然后续是将该方法应用于患有肌肉骨骼疾病或神经退行性疾病的患者。
