Understanding altered contractile properties in advanced age: insights from a systematic muscle modelling approach

Mayfield, Dean L., Cronin, Neil ORCID: 0000-0002-5332-1188 and Lichtwark, Glen A. (2023) Understanding altered contractile properties in advanced age: insights from a systematic muscle modelling approach. Biomechanics and Modeling in Mechanobiology, 22. pp. 309-337. doi:10.1007/s10237-022-01651-9

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Abstract

Age-related alterations of skeletal muscle are numerous and present inconsistently, and the effect of their interaction on contractile performance can be nonintuitive. Hill-type muscle models predict muscle force according to well-characterised contractile phenomena. Coupled with simple, yet reasonably realistic activation dynamics, such models consist of parameters that are meaningfully linked to fundamental aspects of muscle excitation and contraction. We aimed to illustrate the utility of a muscle model for elucidating relevant mechanisms and predicting changes in output by simulating the individual and combined effects on isometric force of several known ageing-related adaptations. Simulating literature-informed reductions in free Ca2+ concentration and Ca2+ sensitivity generated predictions at odds qualitatively with the characteristic slowing of contraction speed. Conversely, incorporating slower Ca2+ removal or a fractional increase in type I fibre area emulated expected changes; the former was required to simulate slowing of the twitch measured experimentally. Slower Ca2+ removal more than compensated for force loss arising from a large reduction in Ca2+ sensitivity or moderate reduction in Ca2+ release, producing realistic age-related shifts in the force-frequency relationship. Consistent with empirical data, reductions in free Ca2+ concentration and Ca2+ sensitivity reduced maximum tetanic force only slightly, even when acting in concert, suggesting a modest contribution to lower specific force. Lower tendon stiffness and slower intrinsic shortening speed slowed and prolonged force development in a compliance-dependent manner without affecting force decay. This work demonstrates the advantages of muscle modelling for exploring sources of variation and identifying mechanisms underpinning the altered contractile properties of aged muscle.

Item Type:	Article
Article Type:	Article
Uncontrolled Keywords:	Ageing; Twitch; Force-frequency relationship; Calcium sensitivity; Specifc force; Calcium uptake and release
Subjects:	G Geography. Anthropology. Recreation > GV Recreation Leisure > GV557 Sports
Divisions:	Schools and Research Institutes > School of Education and Science
Research Priority Areas:	Health, Life Sciences, Sport and Wellbeing
Depositing User:	Anna Kerr
Date Deposited:	21 Nov 2022 15:48
Last Modified:	31 Aug 2023 09:06
URI:	https://eprints.glos.ac.uk/id/eprint/11873

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