Length-force characteristics of in vivo human muscle reflected by supersonic shear imaging
Length-force characteristics of in vivo human muscle reflected by supersonic shear imaging
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DOI：
10.1152/japplphysiol.01058.2013
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发表时间：
2014-07-01
影响因子：
3.3
通讯作者：
Ishii, Naokata
中科院分区：
文献类型：
--
作者：
Sasaki, Kazushige;Toyama, Sho;Ishii, Naokata
近来，基于超声的弹性成像技术已被用于测量活动的人体肌肉沿收缩轴的沿着刚度（剪切模量）。使用这种技术，我们探讨了1）肌肉剪切模量是否像肌肉力量一样是长度依赖性的;以及2）肌肉剪切模量的长度依赖性在电诱发收缩和自主收缩之间是否一致。从9名健康受试者，踝关节扭矩和胫骨前肌的剪切模量进行了测量，在强直收缩和最大随意收缩期间，在五个不同的踝关节角度。从超声图像计算的强直胫骨前肌的肌束长度，pennation角和肌腱力臂长度被用来揭示肌肉力和剪切模量的长度依赖性变化。在关节角度的范围内检查，力和剪切模量的强直肌肉增加，增加肌束长度。回归分析表明，力与剪切模量之间存在显著的线性关系（R-2 = 0.52，n = 45，P < 0.001）。虽然剪切模量的长度依赖性是一致的，无论收缩模式，长度-剪切模量关系的斜率是陡峭的最大自主收缩比在强直收缩。这些结果提供了新的证据，长度-力的关系，肌肉的最基本的特征之一，可以推断出在胫骨前肌的剪切模量在体内成像。此外，长度-力关系的估计可能适用于涉及多个肌肉的神经和机械相互作用的自主收缩。
Recently, an ultrasound-based elastography technique has been used to measure stiffness (shear modulus) of an active human muscle along the axis of contraction. Using this technique, we explored 1) whether muscle shear modulus, like muscle force, is length dependent; and 2) whether the length dependence of muscle shear modulus is consistent between electrically elicited and voluntary contractions. From nine healthy participants, ankle joint torque and shear modulus of the tibialis anterior muscle were measured at five different ankle joint angles during tetanic contractions and during maximal voluntary contractions. Fascicle length, pennation angle, and tendon moment arm length of the tetanized tibialis anterior calculated from ultrasound images were used to reveal the length-dependent changes in muscle force and shear modulus. Over the range of joint angles examined, both force and shear modulus of the tetanized muscle increased with increasing fascicle length. Regression analysis of normalized data revealed a significant linear relationship between force and shear modulus (R-2 = 0.52, n = 45, P < 0.001). Although the length dependence of shear modulus was consistent, irrespective of contraction mode, the slope of length-shear modulus relationship was steeper during maximal voluntary contractions than during tetanic contractions. These results provide novel evidence that length-force relationship, one of the most fundamental characteristics of muscle, can be inferred from in vivo imaging of shear modulus in the tibialis anterior muscle. Furthermore, the estimation of length-force relationship may be applicable to voluntary contractions in which neural and mechanical interactions of multiple muscles are involved.