Function of the spindle dynamic response in stiffness regulation—a predictive mechanism provided by non-linear feedback
Autogenetic reflex responses that act to regulate muscle stiffness are initiated too soon and are too large to be explained solely on the basis of linear feedback from muscle spindle receptors and Golgi tendon organs. In this article we present several lines of evidence that the unexpected efficacy is due to the unique non-linear response properties of primary endings. Several of these non-linear features of spindle dynamic responses are well matched to assist in the maintenance of stiffness during the transient phases of response to muscle stretch and release. As a consequence of these spindle and muscle properties, appropriate reflex actions can actually occur in advance of the failures in stiffness for which they provide compensation. This result is interpreted to mean that the system is endowed with a predictive mechanism.
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