Stroke is a leading cause of long-term adult disability. Due to abnormal timing and magnitude of muscle activation, and altered muscle force generating capacity, performance of gait is disrupted and asymmetric kinematics and kinetics emerge. The proposed work will investigate the relationship between altered muscle morphology, muscle activation, and muscle coordination following stroke. Our technical objectives include the development and implementation of tools to facilitate the creation of subject-specific simulations of human movement using the SimTK framework introduced by the Simbios investigators. We propose to apply this simulation toolkit to understand muscle coordination in post-stroke hemiparesis by achieving the following specific aims: (1) Identify morphological characteristics of paretic and non-paretic muscles in chronic stroke and differences with healthy age- matched subjects, (2) Determine whether reductions in muscle force and net joint torque following stroke are due to altered morphology or impaired activation, (3) Identify factors that limit gait speed in persons post-stroke, and (4) Identify differences between self-selected and fastest possible gait speed for healthy persons and those post-stroke. In the proposed series of studies, static MRI will be used to assess physiological cross-sectional area of key lower extremity muscles. Measurements of muscle activity and net joint torque will be taken during a range of isometric and isokinetic dynamometer tasks. Experimental gait data will be collected on healthy and post-stroke individuals and used to generate subject-specific simulations. A variety of analysis techniques will be employed to assess differences between groups, such as muscle excitation patterns, limb configuration, and the potential effect of muscle forces on joint accelerations, and to address clinically relevant hypotheses.

Public Health Relevance

Stroke is a leading cause of long-term adult disability. The relationship between altered muscle force- generating capacity, activation and coordination during walking after stroke is unclear. Through coupled experiments and simulations, we can identify factors that limit gait speed post-stroke and assist rehabilitation professionals in designing treatment interventions that address the specific impairments of an individual subject.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Special Emphasis Panel (ZRG1-BST-E (51))
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Liu, Yuan
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University of Delaware
Biomedical Engineering
Schools of Engineering
United States
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Stanhope, Victoria A; Knarr, Brian A; Reisman, Darcy S et al. (2014) Frontal plane compensatory strategies associated with self-selected walking speed in individuals post-stroke. Clin Biomech (Bristol, Avon) 29:518-22
Knarr, Brian A; Reisman, Darcy S; Binder-Macleod, Stuart A et al. (2014) Changes in predicted muscle coordination with subject-specific muscle parameters for individuals after stroke. Stroke Res Treat 2014:321747
Knarr, Brian A; Reisman, Darcy S; Binder-Macleod, Stuart A et al. (2013) Understanding compensatory strategies for muscle weakness during gait by simulating activation deficits seen post-stroke. Gait Posture 38:270-5
Knarr, Brian A; Ramsay, John W; Buchanan, Thomas S et al. (2013) Muscle volume as a predictor of maximum force generating ability in the plantar flexors post-stroke. Muscle Nerve 48:971-6
Knarr, Brian A; Kesar, Trisha M; Reisman, Darcy S et al. (2013) Changes in the activation and function of the ankle plantar flexor muscles due to gait retraining in chronic stroke survivors. J Neuroeng Rehabil 10:12
Knarr, Brian A; Higginson, Jill S; Binder-Macleod, Stuart A (2012) Validation of an adjustment equation for the burst superimposition technique in subjects post-stroke. Muscle Nerve 46:267-9
Knarr, Brian A; Zeni Jr, Joseph A; Higginson, Jill S (2012) Comparison of electromyography and joint moment as indicators of co-contraction. J Electromyogr Kinesiol 22:607-11
Higginson, Jill S; Ramsay, John W; Buchanan, Thomas S (2012) Hybrid models of the neuromusculoskeletal system improve subject-specificity. Proc Inst Mech Eng H 226:113-9
Ramsay, John W; Barrance, Peter J; Buchanan, Thomas S et al. (2011) Paretic muscle atrophy and non-contractile tissue content in individual muscles of the post-stroke lower extremity. J Biomech 44:2741-6
Hakansson, Nils A; Kesar, Trisia; Reisman, Darcy et al. (2011) Effects of fast functional electrical stimulation gait training on mechanical recovery in poststroke gait. Artif Organs 35:217-20

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