The effect of series elasticity on the force-length relationship of skeletal muscle

Hamilton, Brian S (2023) The effect of series elasticity on the force-length relationship of skeletal muscle. Masters thesis, Northern Arizona University.

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Abstract

Skeletal muscle contains molecular motors that allow for voluntary movement in vertebrate organisms. It has been widely accepted that skeletal muscle has a narrow range of operating lengths that provide peak force and that this force-length relationship is dictated by the amount of overlap of thick and thin myofilaments. However, much remains unknown about the molecular mechanics of skeletal muscle. This is especially true in dynamic movement, where the isometric force-length relationship tends to fall short in accurately predicting optimum length, the length at which peak force is produced. When attempting to predict in vivo muscle behavior with the isometric force-length relationship, systematic errors may occur due to varying activation levels, active length changes, and lack of structural homogeneity between organisms and within an organism. To elucidate a potential mechanism for observed experimental shifts in optimum length with varying activation levels, experiments were performed on muscles with parallel fiber orientation that were sutured to an external in-series artificial elastic component with considerable compliance. These muscles were attached to a stationary clamp on one side and a force-measuring ergometer on the other. Maximal contractions were elicited at a wide range of starting lengths both with and without the artificial tendon and force-length graphs were constructed. Optimum length with an artificial tendon and resultant shortening decreases to approximately 89.26 ± 5.21% compared to the optimum length of purely isometric contractions. This lends support to the hypothesis that a purely mechanical mechanism driven by shortening may be responsible for the majority of the shifts in optimum length and that, similar to observations in experiments with varying activation levels, this shift may not be driven solely by the length dependence of calcium sensitivity.

Item Type:	Thesis (Masters)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	anatomy; force; length; Muscle; physiology
Subjects:	Q Science > QM Human anatomy
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited:	05 May 2025 16:57
Last Modified:	05 May 2025 16:57
URI:	https://openknowledge.nau.edu/id/eprint/6123

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