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Effects of changing wrist positions on finger flexor hypertonia in stroke survivors
Author(s) -
Li Sheng,
Kamper Derek G.,
Rymer William Zev
Publication year - 2006
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.20453
Subject(s) - hypertonia , stretch reflex , wrist , spastic , physical medicine and rehabilitation , reflex , medicine , muscle spindle , electromyography , anatomy , spasticity , cerebral palsy , anesthesia , afferent
We sought to establish whether spastic hypertonia results from changes in intrinsic muscle properties or from altered stretch reflex properties. We hypothesized that finger flexor spastic hypertonia is primarily of neural origin, and that the dynamics of spastic muscle responses to stretch should therefore reflect the dynamics of muscle spindle receptor responses. In 12 stroke survivors, we recorded torque and electromyographic (EMG) responses of extrinsic finger flexors to constant‐velocity rotation of the metacarpophalangeal (MCP) joints of the affected hand, over a range of initial muscle lengths. Stretch velocity was set to 6°, 50°, 150°, or 300° per second. Muscle length changes were imposed by changing wrist angle between 0°, 25°, and 50° of flexion. We found that reflex torque and EMG responses exhibited both velocity and length dependence, and there were significant interactions between velocity and length, replicating known characteristics of muscle spindle receptors. Our results support the hypothesis that finger flexor hypertonia is primarily of neural origin, and that it accurately reflects spindle receptor firing properties. Muscle Nerve 2006