History-dependent muscle resistance to stretch remains high after small, posturally relevant pre-movements.

Autor:	Horslen BC; Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, ON, Canada, N2L 3G1.; Wallace H. Coulter Department of Biomedical Engineering, Emory University and The Georgia Institute of Technology, Atlanta, GA 30332, USA., Milburn GN; Department of Physiology, University of Kentucky, Lexington, KY 40536, USA., Blum KP; Wallace H. Coulter Department of Biomedical Engineering, Emory University and The Georgia Institute of Technology, Atlanta, GA 30332, USA.; Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA., Simha SN; Wallace H. Coulter Department of Biomedical Engineering, Emory University and The Georgia Institute of Technology, Atlanta, GA 30332, USA., Campbell KS; Department of Physiology, University of Kentucky, Lexington, KY 40536, USA., Ting LH; Wallace H. Coulter Department of Biomedical Engineering, Emory University and The Georgia Institute of Technology, Atlanta, GA 30332, USA.; Department of Rehabilitation Medicine, Division of Physical Therapy, Emory University, Atlanta, GA 30322, USA.
Jazyk:	angličtina
Zdroj:	The Journal of experimental biology [J Exp Biol] 2023 Sep 15; Vol. 226 (18). Date of Electronic Publication: 2023 Sep 27.
DOI:	10.1242/jeb.245456
Abstrakt:	The contributions of intrinsic muscle fiber resistance during mechanical perturbations to standing and other postural behaviors are unclear. Muscle short-range stiffness is known to vary depending on the current level and history of the muscle's activation, as well as the muscle's recent movement history; this property has been referred to as history dependence or muscle thixotropy. However, we currently lack sufficient data about the degree to which muscle stiffness is modulated across posturally relevant characteristics of muscle stretch and activation. We characterized the history dependence of muscle's resistance to stretch in single, permeabilized, activated, muscle fibers in posturally relevant stretch conditions and activation levels. We used a classic paired muscle stretch paradigm, varying the amplitude of a 'conditioning' triangular stretch-shorten cycle followed by a 'test' ramp-and-hold imposed after a variable inter-stretch interval. We tested low (<15%), intermediate (15-50%) and high (>50%) muscle fiber activation levels, evaluating short-range stiffness and total impulse in the test stretch. Muscle fiber resistance to stretch remained high at conditioning amplitudes of <1% optimal fiber length, L0, and inter-stretch intervals of >1 s, characteristic of healthy standing postural sway. An ∼70% attenuation of muscle resistance to stretch was reached at conditioning amplitudes of >3% L0 and inter-stretch intervals of <0.1 s, characteristic of larger, faster postural sway in balance-impaired individuals. The thixotropic changes cannot be predicted solely on muscle force at the time of stretch. Consistent with the disruption of muscle cross-bridges, muscle resistance to stretch during behavior can be substantially attenuated if the prior motion is large enough and/or frequent enough. Competing Interests: Competing interests The authors declare no competing or financial interests. (© 2023. Published by The Company of Biologists Ltd.)
Databáze:	MEDLINE
Externí odkaz:	Zobrazit plný text záznamu