Limb work and joint work minimization reveal an energetic benefit to the elbows-back, knees-forward limb design in parasagittal quadrupeds

Usherwood, James R.; Granatosky, Michael C.

Abstract

Quadrupedal animal locomotion is energetically costly. We explore two forms of mechanical work that may be relevant in imposing these physiological demands. Limb work, due to the forces and velocities between the stance foot and the centre of mass, could theoretically be zero given vertical limb forces and horizontal centre of mass path. To prevent pitching, skewed vertical force profiles would then be required, with forelimb forces high in late stance and hindlimb forces high in early stance. By contrast, joint work—the positive mechanical work performed by the limb joints—would be reduced with forces directed through the hip or shoulder joints. Measured quadruped kinetics show features consistent with compromised reduction of both forms of work, suggesting some degree of, but not perfect, inter-joint energy transfer. The elbows-back, knees-forward design reduces the joint work demand of a low limb-work, skewed, vertical force profile. This geometry allows periods of high force to be supported when the distal segment is near vertical, imposing low moments about the elbow or knee, while the shoulder or hip avoids high joint power despite high moments because the proximal segment barely rotates—translation over this period is due to rotation of the distal segment.

Citation

Usherwood, J. R., & Granatosky, M. C. (2020). Limb work and joint work minimization reveal an energetic benefit to the elbows-back, knees-forward limb design in parasagittal quadrupeds. Proceedings of the Royal Society B: Biological Sciences, 287(1940), 20201517. https://doi.org/10.1098/rspb.2020.1517

• Journal Article Type: Article
• Acceptance Date: Nov 13, 2020
• Online Publication Date: Dec 9, 2020
• Publication Date: Dec 9, 2020
• Deposit Date: Dec 9, 2020
• Publicly Available Date: Dec 9, 2020
• Journal: Proceedings of the Royal Society B: Biological Sciences
• Print ISSN: 0962-8452
• Electronic ISSN: 1471-2954
• Publisher: The Royal Society
• Peer Reviewed: Peer Reviewed
• Volume: 287
• Issue: 1940
• Pages: 20201517
• DOI: https://doi.org/10.1098/rspb.2020.1517
• Keywords: General Biochemistry, Genetics and Molecular Biology; General Immunology and Microbiology; General Agricultural and Biological Sciences; General Environmental Science; General Medicine
• Public URL: https://rvc-repository.worktribe.com/output/1442059
• Publisher URL: https://royalsocietypublishing.org/doi/10.1098/rspb.2020.1517
• Additional Information: Received: 2020-06-26; Accepted: 2020-11-13; Published: 2020-12-09