Usherwood 27Jul2021

Usherwood, James

Abstract

Considerable attention has been given to the spring-like behaviour of stretching and recoiling tendons, and how this can reduce the work demanded from muscle for a given loss-return cycling of mechanical energy during high-speed locomotion. However, even completely isometric muscle-tendon units have the potential to act as tension struts, forming links in linkages that avoid the demand for mechanical work cycling in the first place. Here, hind and forelimb structures and geometries of quadrupeds are considered in terms of linkages that avoid mechanical work at the level of both the whole limb and the individual muscles. The scapula and serratus muscles of the forelimb form a modified Roberts’ straight-line mechanism, facilitating more horizontal motion with more vertically orientated forces, and so low limb work, with near-isometric muscles, so low muscle work. Modelled isometric triceps brachii inserting to the olecranon form part of a series of 4-bar linkages (forelimb) and isometric biceps femoris cranial, rectus femoris and tensor fascia latae form part of a series of 6-bar linkages (hindlimb), in both cases potentially resulting in straight-line horizontal motion, generating appropriate moments about shoulder and hip to maintain vertical ground reaction forces and again low mechanical work demand from the limb. Analysing part of the complexity of animal limb structure as linkages that avoid work at the level of both the whole limb and the supporting muscles suggests a new paradigm with which to appreciate the role of isometric muscle-tendon units and multiple muscle origins.

Citation

Usherwood, J. (2022). Usherwood 27Jul2021. Journal of Experimental Biology, https://doi.org/10.1242/jeb.243254

• Journal Article Type: Article
• Acceptance Date: Feb 22, 2022
• Publication Date: Mar 8, 2022
• Deposit Date: Jul 28, 2021
• Publicly Available Date: Jul 15, 2022
• Print ISSN: 0022-0949
• Publisher: The Company of Biologists
• Peer Reviewed: Not Peer Reviewed
• DOI: https://doi.org/10.1242/jeb.243254