Muscle Stiffness During Transient and Continuous Movements of Cat Muscle: Perturbation Characteristics and Physiological Relevance

Robert F. Kirsch, Djordje Boskov, William Z. Rymer

Research output: Contribution to journalArticlepeer-review

74 Scopus citations

Abstract

Continuous stochastic position perturbations are an attractive alternative to transient perturbations in muscle and reflex studies because they allow efficient characterization of system properties. However, the relevance of the results obtained from stochastic perturbations remains unclear because they may induce a state change in muscle properties. We addressed this concern by comparing the force and stiffness responses of isolated muscles of the decerebrate cat elicited by stochastic perturbations to those evoked by “step” stretches of similar amplitudes. Muscle stiffness during stochastic perturbations was found to be predominantly linear and elastic in nature for a given operating point, showing no evidence of instantaneous amplitude-dependent nonlinearities, even during large movements. In contrast, force responses evoked by step stretches were found to be mainly viscous in nature and nonlinear for larger stretches, with only a small maintained (elastic) component. Stiffness magnitude decreased with displacement amplitude for both stochastic and step perturbations. Our results are largely consistent with the crossbridge theory of muscle contraction, indicating that transient and continuous displacements evoke different, although functionally relevant, aspects of muscle behavior. These differences have several implications for the neural control of posture and movement, and for the design of perturbations appropriate for its study.

Original languageEnglish (US)
Pages (from-to)758-770
Number of pages13
JournalIEEE Transactions on Biomedical Engineering
Volume41
Issue number8
DOIs
StatePublished - Aug 1994

ASJC Scopus subject areas

  • Biomedical Engineering

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