Data about a muscle’s fibre pennation angle and physiological cross-sectional area are used in musculoskeletal modelling to estimate muscle forces, which are used to calculate joint contact forces. For the leg, muscle architecture data are derived from studies that measured pennation angle at the muscle surface, but not deep within it. Musculoskeletal models developed to estimate joint contact loads have usually been based on the mean values of pennation angle and physiological cross-sectional area. Therefore, the first aim of this study was to investigate differences between superficial and deep pennation angles within each muscle acting over the ankle and predict how differences may influence muscle forces calculated in musculoskeletal modelling. The second aim was to investigate how inter-subject variability in physiological cross-sectional area and pennation angle affects calculated ankle contact forces. Eight cadaveric legs were dissected to excise the muscles acting over the ankle. The mean surface and deep pennation angles, fibre length and physiological cross-sectional area were measured. Cluster analysis was applied to group the muscles according to their architectural characteristics. A previously validated OpenSim model was used to estimate ankle muscle forces and contact loads using architecture data from all eight limbs. The mean surface pennation angle for soleus was significantly greater (54%) than the mean deep pennation angle. Cluster analysis revealed three groups of muscles with similar architecture and function: deep plantarflexors and peroneals, superficial plantarflexors and dorsiflexors. Peak ankle contact force was predicted to occur before toe-off, with magnitude greater than five times bodyweight. Inter-specimen variability in contact force was smallest at peak force. These findings will help improve the development of experimental and computational musculoskeletal models by providing data to estimate force based on both surface and deep pennation angles. Inter-subject variability in muscle architecture affected ankle muscle and contact loads only slightly. The link between muscle architecture and function contributes to the understanding of the relationship between muscle structure and function.

中文翻译：

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肌羽角和横截面积对踝关节接触力的影响

在肌肉骨骼建模中使用有关肌肉纤维羽化角和生理横截面积的数据来估计肌肉力，这些力用于计算关节接触力。对于腿部，肌肉结构数据来自在肌肉表面测量羽状角的研究，但不在其深处。用于估计关节接触载荷的肌肉骨骼模型通常基于羽状角和生理横截面积的平均值。因此，本研究的第一个目的是调查作用在脚踝上的每​​块肌肉的浅层和深层羽状角之间的差异，并预测差异如何影响肌肉骨骼建模中计算的肌肉力。第二个目的是研究生理横截面积和羽状角的受试者间变异性如何影响计算出的脚踝接触力。八条尸体腿被解剖以切除作用在脚踝上的肌肉。测量了平均表面和深羽化角、纤维长度和生理横截面积。应用聚类分析根据肌肉的结构特征对肌肉进行分组。之前经过验证的 OpenSim 模型用于使用来自所有八个肢体的架构数据来估计脚踝肌肉力和接触载荷。比目鱼肌的平均表面羽化角明显大于 (54%) 平均深羽化角。聚类分析揭示了三组具有相似结构和功能的肌肉：深跖屈肌和腓骨，浅跖屈肌和背屈肌。预计脚踝接触力峰值出现在脚趾离地之前，幅度大于体重的五倍。接触力的样本间变异性在峰值力时最小。这些发现将通过提供数据来估计基于表面和深羽状角的力，从而有助于改进实验和计算肌肉骨骼模型的开发。肌肉结构的受试者间差异仅轻微影响脚踝肌肉和接触负荷。肌肉结构和功能之间的联系有助于理解肌肉结构和功能之间的关系。接触力的样本间变异性在峰值力时最小。这些发现将通过提供数据来估计基于表面和深羽状角的力，从而有助于改进实验和计算肌肉骨骼模型的开发。肌肉结构的受试者间差异仅轻微影响脚踝肌肉和接触负荷。肌肉结构和功能之间的联系有助于理解肌肉结构和功能之间的关系。接触力的样本间变异性在峰值力时最小。这些发现将通过提供数据来估计基于表面和深羽化角的力，从而有助于改进实验和计算肌肉骨骼模型的开发。肌肉结构的受试者间差异仅轻微影响脚踝肌肉和接触负荷。肌肉结构和功能之间的联系有助于理解肌肉结构和功能之间的关系。