Lapole Thomas, Tindel Jérémy, Galy Robin, Nordez Antoine
Université de Lyon, Laboratoire de Physiologie de l'Exercice, 42023, Saint-Étienne Cedex 2, France,
Eur J Appl Physiol. 2015 Mar;115(3):497-505. doi: 10.1007/s00421-014-3037-0. Epub 2014 Nov 4.
Since experimental techniques classically used to investigate the mechanical behavior of muscle in vivo assess global mechanical properties of the musculo-articular complex, the aim of the present study was to assess the feasibility and reliability of localized contracting biceps brachii elastic properties' measurements using elastography.
Twelve subjects participated in intra-session, inter-session and inter-observer reliability experiments. They were asked to perform a linear torque ramp of 30 s from 0 to 75 % of maximal voluntary contraction. Joint torque, electromyographic (EMG) activity and shear elastic modulus were synchronously measured in the biceps brachii. Elastic properties were determined by stiffness indexes calculated as the slopes of the linear regressions established between shear modulus and joint torque or EMG levels. Compliance indexes were also obtained by plotting logarithmic values of shear modulus versus torque or EMG.
Determination coefficients were high for the four relationships (0.87-0.94). In addition, reliability was significantly higher for the compliance index taking into account logarithmic values of EMG activity (mean coefficient of variation of 5.3 ± 4.1%; P = 0.003). Although not statistically different from other methods (P = 0.111), the mean intra-class correlation coefficient was excellent (0.98 ± 0.01) and the standard error in measurement very low (0.04 ± 0.01 for a mean index of -0.73 ± 0.28).
Biceps brachii elastic properties can be reliably investigated during contraction via elastography using the proposed fitting method. Use of this technique could provide new insights into the understanding of localized muscle elastic properties adaptations.
由于传统上用于研究体内肌肉力学行为的实验技术评估的是肌肉关节复合体的整体力学特性，本研究的目的是评估使用弹性成像技术测量肱二头肌局部收缩弹性特性的可行性和可靠性。
12名受试者参与了组内、组间和观察者间的可靠性实验。他们被要求从0到最大自主收缩的75%进行30秒的线性扭矩斜坡运动。在肱二头肌中同步测量关节扭矩、肌电图（EMG）活动和剪切弹性模量。弹性特性通过刚度指数来确定，刚度指数计算为剪切模量与关节扭矩或EMG水平之间建立的线性回归的斜率。还通过绘制剪切模量与扭矩或EMG的对数值来获得顺应性指数。
四种关系的决定系数都很高（0.87 - 0.94）。此外，考虑到EMG活动对数值的顺应性指数的可靠性显著更高（平均变异系数为5.3 ± 4.1%；P = 0.003）。虽然与其他方法没有统计学差异（P = 0.111），但平均组内相关系数极佳（0.98 ± 0.01），测量标准误差非常低（对于平均指数 -0.73 ± 0.28，为0.04 ± 0.01）。
使用所提出的拟合方法，通过弹性成像技术可以在收缩过程中可靠地研究肱二头肌的弹性特性。使用该技术可为理解局部肌肉弹性特性的适应性提供新的见解。
