Muscle force-stiffness characteristics influence joint stability: a spine example.

Stephen H M Brown; Stuart M McGill

doi:10.1016/j.clinbiomech.2005.06.002

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Muscle force-stiffness characteristics influence joint stability: a spine example.

Stephen H M Brown·Stuart M McGill

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Abstract

BACKGROUND: The muscle force-stiffness relationship has often been modeled as linear, while in situ muscle research has clearly demonstrated non-linearity. Estimation of rotational joint stability relies on both a muscle's instantaneous pre-perturbation force and stiffness. Under conditions of static equilibrium, a muscle's stiffness will function in a stabilizing manner, while its force can function in either a stabilizing or destabilizing manner depending on the muscle's orientation about the joint. METHODS: A single muscle (rectus abdominis) was modeled and its individual direct stabilizing potential about the L4-L5 spine joint was analyzed. Three force-stiffness relationships were examined: (1) linear; (2) non-linear with moderate stiffness magnitudes; (3) non-linear with higher stiffness magnitudes. FINDINGS: With a linear force-stiffness relationship, stability increased proportional to muscle force; with a non-linear relationship, stability peaked and subsequently decreased at submaximal muscle forces. When considering the lower, as opposed to the higher non-linear stiffness magnitudes, the stabilizing potential of the muscle peaked at a lower muscle force level and actually became negative (destabilizing) at a critical stiffness magnitude. INTERPRETATION: It was concluded that a non-linear muscle force-stiffness relationship greatly alters the individual stabilizing potential of the muscle throughout its progression of force development. A muscle's stabilizing contribution may actually peak at and subsequently decrease above a critical submaximal force level. Incorporating this knowledge into stability models may assist in recognizing unstable events that lead to injury at higher levels of muscle activation.

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Biomechanical Phenomena Humans Lumbar Vertebrae Mathematics Muscle, Skeletal Reflex, Stretch Rotation Spine Journal Article Research Support, Non-U.S. Gov't

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Stephen H M Brown, Stuart M McGill. 2005. Muscle force-stiffness characteristics influence joint stability: a spine example.. https://doi.org/10.1016/j.clinbiomech.2005.06.002

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