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Research project: Quantitative measurements of impairment and how they relate to activity in the upper limb of the older adult post-stroke

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Loss of upper-limb function is a problem following stroke. Recent research has identified potential for recovery with intensive practice and has led to the emergence of new treatments. Progress is hampered by lack of: reliable objective measures of impairment, understanding of the relationship between impairments and activity limitation and underlying mechanisms associated with loss and recovery of function. An instrumented rig has been designed, built and validated to measure impairments: muscle weakness, motor control, spasticity, muscle co-activation and passive stiffness. Signal processing and data analysis techniques generate useful indices and metrics to quantify impairments and evaluate their relative contribution to loss of arm activity.

Aims: - Identify and characterise key elements of wrist motor impairments early and late after stroke, including the development of appropriate signal processing and data analysis techniques. - Identify motor impairment correlates of activity limitation in the upper limb of sub-acute and chronic stroke survivors. This is a cross-sectional observational measurement study using an instrumented wrist rig which measures force, joint angle and electromyography during active and passive tests. Forty volunteers with stroke recruited from three NHS sites in Southampton and Southwest Surrey and 20 age and sex matched healthy volunteers undergo rig assessments involving tests of strength, range of movement, active and passive tracking. Wrist angle and EMG signals from the wrist flexor and extensor muscles are recorded, and maximum voluntary contraction and stiffness can be measured via a strain-gauge mounted in the lever arm of the rig. The signals are all acquired simultaneously to a computer (using the Matlab signal acquisition toolbox), which also controls the tracking target made up of a set of 80 LEDs, mounted in an arc at 2o intervals. An adjustable slip-clutch is used to set resistance to movement as a fixed percentage of subjects’ maximum voluntary contraction. In-house software has been developed to extract parameters from the recorded signals. These include indexes of accuracy in tracking, co-activation in the EMGs calculated during wrist extension, onset timing of muscle activity, flexor stretch response and resistance at the wrist joint with passive movements. In addition, subjects perform the Wolf motor function test (WMFT), to evaluate their ability to carry out functional movements with their impaired (patient) or dominant (healthy controls) upper limb. Statistical tests will identify: differences in the impairment indices between sub-acute and chronic patients and healthy individuals; and impairment correlates with activity (WMFT) scores.
Collaborations: J H Burridge [School of Health Professions and Rehabilitation Sciences], V Pomeroy [University of East Anglia], M Donavan-Halls [School of Health Sciences]

Related research groups

Signal Processing, Audio and Hearing Group
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