Brown Stephen H M, Gerling Michael E
Department of Human Health and Nutritional Sciences, University of Guelph, Canada.
Proc Inst Mech Eng H. 2012 May;226(5):384-8. doi: 10.1177/0954411912441325.
Muscle physiological cross-sectional area predicts the maximum capability of a muscle to generate isometric force. Biomechanical models often use estimates of individual muscle physiological cross-sectional area to partition internal forces among different muscles and predict joint forces and stability. In the spine literature, these physiological cross-sectional area values are generally obtained from imaging or cadaveric studies that have not accounted for a potential lengthened or shortened (and thus thinned or thickened, respectively) state of the muscles in question. Sarcomere length measurements can be used to normalize muscle lengths and correct for these length discrepancies. This article was designed to demonstrate potential effects of not accounting for instantaneous sarcomere length when calculating the physiological cross-sectional area of muscles of the spine region. Because some muscles of the spine region appear to be shortened and others lengthened in the neutral spine posture, both over- and under-estimations of physiological cross-sectional area are possible. Specifically, it is shown that the muscle physiological cross-sectional area could be over-estimated or under-estimated by as much as + 36% (multifidus) and -21% (rectus abdominis), respectively. This differential error effect poses difficulties in accurately estimating individual muscle forces and subsequent spine forces and stability that result from biomechanical models incorporating physiological cross-sectional area data obtained in the absence of sarcomere length measurements. Future work is needed to measure the dynamic range of sarcomere lengths of all spinal muscles to ensure correct inputs to biomechanical models.
肌肉生理横截面积可预测肌肉产生等长力的最大能力。生物力学模型通常使用个体肌肉生理横截面积的估计值来在不同肌肉之间分配内力，并预测关节力和稳定性。在脊柱相关文献中，这些生理横截面积值通常是从成像或尸体研究中获得的，而这些研究并未考虑到所讨论肌肉可能处于拉长或缩短（因而分别变薄或变厚）的状态。肌节长度测量可用于使肌肉长度标准化，并校正这些长度差异。本文旨在证明在计算脊柱区域肌肉的生理横截面积时未考虑瞬时肌节长度的潜在影响。由于脊柱区域的一些肌肉在脊柱中立姿势下似乎缩短，而另一些则拉长，因此生理横截面积可能被高估或低估。具体而言，研究表明，肌肉生理横截面积可能分别被高估多达 +36%（多裂肌）和低估多达 -21%（腹直肌）。这种差异误差效应给准确估计个体肌肉力以及随后由纳入未进行肌节长度测量时获得的生理横截面积数据的生物力学模型所产生的脊柱力和稳定性带来了困难。未来需要开展工作来测量所有脊柱肌肉的肌节长度动态范围，以确保为生物力学模型提供正确的输入数据。
