Distinguishing active from passive components of ankle plantar flexor stiffness in stroke, spinal cord injury and multiple sclerosis

J Lorentzen, Michael Grey, C Crone, D Mazevet, F Biering-Sørensen, JB Nielsen

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79 Citations (Scopus)

Abstract

OBJECTIVE Spasticity is a common manifestation of lesion of central motor pathways. It is essential for correct anti-spastic treatment that passive and active contributions to increased muscle stiffness are distinguished. Here, we combined biomechanical and electrophysiological evaluation to distinguish the contribution of active reflex mechanisms from passive muscle properties to ankle joint stiffness in 31 healthy, 10 stroke, 30 multiple sclerosis and 16 spinal cord injured participants. The results were compared to routine clinical evaluation of spasticity. METHODS A computer-controlled robotic device applied stretches to the ankle plantar flexor muscles at different velocities (8-200deg/s; amplitude 6°). The reflex threshold was determined by soleus EMG. Torque and EMG data were normalized to the maximal torque and EMG evoked by supramaximal stimulation of the tibial nerve. Passive resistance (the torque response to stretches) was confirmed to be a good representation of the passive stiffness also at higher velocities when transmission in the tibial nerve was blocked by ischemia. RESULTS Passive torque tended to be larger in the neurological than in the healthy participants, but it did not reach statistical significance, except in the stroke group (p
Original languageEnglish
Pages (from-to)1939-1951
Number of pages13
JournalClinical Neurophysiology
Volume121
Issue number11
DOIs
Publication statusPublished - 1 Nov 2010

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