Meilak E A, Gostling N J, Palmer C, Heller M O
Bioengineering Research Group, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, United Kingdom.
Faculty of Environmental and Life Sciences, University of Southampton, Southampton, United Kingdom.
Front Bioeng Biotechnol. 2021 Jun 29;9:676894. doi: 10.3389/fbioe.2021.676894. eCollection 2021.
Take-off is a critical phase of flight, and many birds jump to take to the air. Although the actuation of the hindlimb in terrestrial birds is not limited to the sagittal plane, and considerable non-sagittal plane motion has been observed during take-off jumps, how the spatial arrangement of hindlimb muscles in flying birds facilitates such jumps has received little attention. This study aims to ascertain the 3D hip muscle function in the magpie (), a bird known to jump to take-off. A musculoskeletal model of the magpie hindlimb was developed using μCT scans (isotropic resolution of 18.2 μm) to derive bone surfaces, while the 3D muscle path definition was further informed by the literature. Function was robustly characterized by determining the 3D moment-generating capacity of 14 hip muscles over the functional joint range of motion during a take-off leap considering variations across the attachment areas and uncertainty in dynamic muscle geometry. Ratios of peak flexion-extension (FE) to internal-external rotation (IER) and abduction-adduction (ABD) moment-generating capacity were indicators of muscle function. Analyses of 972 variations of the 3D muscle paths showed that 11 of 14 muscles can act as either flexor or extensor, while all 14 muscles demonstrated the capacity to act as internal or external rotators of the hip with the mean ratios of peak FE to IER and ABD moment-generating capacity were 0.89 and 0.31, respectively. Moment-generating capacity in IER approaching levels in the FE moment-generating capacity determined here underline that the avian hip muscle function is not limited to the sagittal plane. Together with previous findings on the 3D nature of hindlimb kinematics, our results suggest that musculoskeletal models to develop a more detailed understanding of how birds orchestrate the use of muscles during a take-off jump cannot be restricted to the sagittal plane.
起飞是飞行的关键阶段，许多鸟类通过跳跃来升空。尽管陆生鸟类后肢的驱动不限于矢状面，并且在起飞跳跃过程中已观察到相当多的非矢状面运动，但飞行鸟类后肢肌肉的空间排列如何促进此类跳跃却很少受到关注。本研究旨在确定喜鹊（ ）的三维髋部肌肉功能，喜鹊是一种已知通过跳跃起飞的鸟类。利用μCT扫描（各向同性分辨率为18.2μm）建立了喜鹊后肢的肌肉骨骼模型以获取骨表面，同时通过文献进一步明确三维肌肉路径定义。通过确定14块髋部肌肉在起飞跳跃功能关节活动范围内的三维力矩产生能力，并考虑附着区域的变化和动态肌肉几何形状的不确定性，对功能进行了稳健的表征。屈伸（FE）与内外旋转（IER）以及外展内收（ABD）力矩产生能力的峰值比值是肌肉功能的指标。对三维肌肉路径的972种变化进行分析表明，14块肌肉中有11块既可以作为屈肌也可以作为伸肌，而所有14块肌肉都表现出作为髋部内旋或外旋肌的能力，FE与IER和ABD力矩产生能力的峰值平均比值分别为0.89和0.31。此处确定的IER力矩产生能力接近FE力矩产生能力的水平，这强调了鸟类髋部肌肉功能不限于矢状面。结合先前关于后肢运动学三维性质的研究结果，我们的结果表明，为了更详细地了解鸟类在起飞跳跃过程中如何协调肌肉的使用而建立的肌肉骨骼模型不能局限于矢状面。
