Mechanics and Energetics of Force Production in Muscle

van der Zee, Tim Jonathan

Mechanics and Energetics of Force Production in Muscle

dc.contributor.advisor	Kuo, Arthur D.
dc.contributor.author	van der Zee, Tim Jonathan
dc.contributor.committeemember	Bertram, John Edward Arthur
dc.contributor.committeemember	Herzog, Walter
dc.contributor.committeemember	Fletcher, Jared R.
dc.contributor.committeemember	MacIntosh, Brian Robert
dc.contributor.committeemember	Campbell, Kenneth S.
dc.date.accessioned	2023-09-27T15:14:14Z
dc.date.available	2023-09-27T15:14:14Z
dc.date.issued	2023-09-22
dc.description.abstract	The mechanics and energetics of skeletal muscle force production are important for many movements, including locomotion. But they have been characterized primarily for steady conditions such as constant shortening velocity and fixed muscle length, rather than dynamic or cyclic conditions that resemble daily movements. Although musculoskeletal models are intended to predict how muscles behave during movement, there have been few quantitative experiments to inform such models. In this thesis, I experimentally examine muscle mechanics and energetics for cyclic conditions, and then apply those data to develop a new computational model of muscle. The model reproduces activation and force development dynamics observed experimentally, is more mechanistic than current Hill-type models, and better matches energy expenditure for cyclic conditions. A simple summary of these effects is that muscle behaves like a low-pass filter with respect to excitatory input. A filter predicts a sharp increase in energetic cost with faster cyclic conditions, in agreement with empirical data (Chapter 2). To facilitate quantification of muscle mechanics in vivo, I developed an algorithm to track muscle fascicles in ultrasound images, named ‘TimTrack’ (Chapter 3). Much of the energetic cost of cyclic force production was not explained by traditional measures of work or force, but by rate of force development (termed ‘force-rate’). To expand on the low-pass filter, I proposed a model that combines muscle dynamics with steady relations and series elasticity. Unlike existing models, the proposed model predicts muscle force development across a broad range of conditions in a self-consistent manner (Chapter 4). An essential aspect is a set of dynamics intermediate to calcium activation and muscle cross-bridges, here termed force facilitation. These dynamics help explain the energetic cost of both steady and cyclic muscle contractions, in qualitative agreement with the simple low-pass filter (Chapter 5). Model simulations suggest that most of the force-rate cost is due to increased calcium transport at higher muscle excitation levels. The experiments and computational modeling presented here demonstrate energetic costs not previously identified or modeled and have potential to improve understanding of how muscles contribute to daily movements.
dc.identifier.citation	van der Zee, T. J. (2023). Mechanics and energetics of force production in muscle (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.
dc.identifier.uri	https://hdl.handle.net/1880/117242
dc.language.iso	en
dc.publisher.faculty	Graduate Studies
dc.publisher.institution	University of Calgary
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subject	muscle energetics
dc.subject	SERCA
dc.subject	calcium transport
dc.subject	biomechanics
dc.subject	metabolic cost
dc.subject	cross-bridge model
dc.subject	musculoskeletal modelling
dc.subject	muscle force production
dc.subject	rate of muscle force development
dc.subject.classification	Engineering--Biomedical
dc.subject.classification	Physiology
dc.title	Mechanics and Energetics of Force Production in Muscle
dc.type	doctoral thesis
thesis.degree.discipline	Engineering – Biomedical
thesis.degree.grantor	University of Calgary
thesis.degree.name	Doctor of Philosophy (PhD)
ucalgary.thesis.accesssetbystudent	I do not require a thesis withhold – my thesis will have open access and can be viewed and downloaded publicly as soon as possible.