Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, Royal Veterinary College, Hatfield, UK.
Human Anatomy Resource Centre, University of Liverpool, Liverpool, UK.
J Anat. 2023 Feb;242(2):289-311. doi: 10.1111/joa.13767. Epub 2022 Oct 7.
In vertebrates, active movement is driven by muscle forces acting on bones, either directly or through tendinous insertions. There has been much debate over how muscle size and force are reflected by the muscular attachment areas (AAs). Here we investigate the relationship between the physiological cross-sectional area (PCSA), a proxy for the force production of the muscle, and the AA of hindlimb muscles in Nile crocodiles and five bird species. The limbs were held in a fixed position whilst blunt dissection was carried out to isolate the individual muscles. AAs were digitised using a point digitiser, before the muscle was removed from the bone. Muscles were then further dissected and fibre architecture was measured, and PCSA calculated. The raw measures, as well as the ratio of PCSA to AA, were studied and compared for intra-observer error as well as intra- and interspecies differences. We found large variations in the ratio between AAs and PCSA both within and across species, but muscle fascicle lengths are conserved within individual species, whether this was Nile crocodiles or tinamou. Whilst a discriminant analysis was able to separate crocodylian and avian muscle data, the ratios for AA to cross-sectional area for all species and most muscles can be represented by a single equation. The remaining muscles have specific equations to represent their scaling, but equations often have a relatively high success at predicting the ratio of muscle AA to PCSA. We then digitised the muscle AAs of Coelophysis bauri, a dinosaur, to estimate the PCSAs and therefore maximal isometric muscle forces. The results are somewhat consistent with other methods for estimating force production, and suggest that, at least for some archosaurian muscles, that it is possible to use muscle AA to estimate muscle sizes. This method is complementary to other methods such as digital volumetric modelling.
在脊椎动物中，肌肉力量通过直接或通过腱附着点作用于骨骼来驱动主动运动。关于肌肉大小和力量如何反映在肌肉附着区域 (AA) 上，一直存在很多争议。在这里，我们研究了生理横截面积 (PCSA)，即肌肉产生力的代表，与尼罗鳄和五种鸟类后肢肌肉的 AA 之间的关系。在将四肢固定在一个位置的同时，进行钝性解剖以分离单个肌肉。使用点数字化仪对 AA 进行数字化，然后将肌肉从骨骼上取下。然后进一步对肌肉进行解剖，测量纤维结构，并计算 PCSA。研究并比较了原始测量值以及 PCSA 与 AA 的比值，以评估观察者内误差以及种内和种间差异。我们发现，无论是在种内还是种间，AA 与 PCSA 之间的比值都存在很大差异，但在个体物种内，肌肉束长度是保守的，无论是尼罗鳄还是恐鸟。虽然判别分析能够将鳄类和鸟类的肌肉数据分开，但对于所有物种和大多数肌肉，AA 与横截面积的比值可以用一个单一的方程来表示。其余的肌肉有特定的方程来表示它们的缩放，但方程通常在预测肌肉 AA 与 PCSA 的比值方面具有相对较高的成功率。然后，我们对 Coelophysis bauri 的肌肉 AA 进行了数字化，以估计 PCSA，从而估计最大等长肌肉力。结果与其他估计力产生的方法有些一致，并且表明，至少对于一些恐龙肌肉，使用肌肉 AA 来估计肌肉大小是可行的。这种方法与数字体积建模等其他方法互补。
