Quantitative assessment of somatic muscle tone.

An operational definition and a method for the evaluation of somatic muscle tone are presented. The relation between the applied perturbation (pseudo-random sequence of torque pulses) and the resulting changes in joint angular position defines a mechanical admittance. The usefulness of this and related concepts for the quantitative assessment of pathologic changes in muscle tone is illustrated with an example of an experimental lesion of the internal capsule in the monkey. The identification of time-varying reflex responses is discussed in relation to a catching task in human subjects.