Heather B Hayes1, Stacie A Chvatal2, Margaret A French1, Lena H Ting2, Randy D Trumbower3. 1. Dept. of Rehabilitation Medicine, Emory University, Atlanta, GA, USA. 2. Dept. of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA. 3. Dept. of Rehabilitation Medicine, Emory University, Atlanta, GA, USA; Dept. of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA. Electronic address: randy.trumbower@emory.edu.
Abstract
OBJECTIVE: Incomplete spinal cord injury (iSCI) disrupts motor control and limits the ability to coordinate muscles for overground walking. Inappropriate muscle activity has been proposed as a source of clinically observed walking deficits after iSCI. We hypothesized that persons with iSCI exhibit lower locomotor complexity compared to able-body (AB) controls as reflected by fewer motor modules, as well as, altered module composition and activation. METHODS: Eight persons with iSCI and eight age-matched AB controls walked overground at prescribed cadences. Electromyograms of fourteen single leg muscles were recorded. Non-negative matrix factorization was used to identify the composition and activation of motor modules, which represent groups of consistently co-activated muscles that accounted for 90% of variability in muscle activity. RESULTS: Motor module number, composition, and activation were significantly altered in persons with iSCI as compared to AB controls during overground walking at self-selected cadences. However, there was no significant difference in module number between persons with iSCI and AB controls when cadence and assistive device were matched. CONCLUSIONS: Muscle coordination during overground walking is impaired after chronic iSCI. SIGNIFICANCE: Our results are indicative of neuromuscular constraints on muscle coordination after iSCI. Altered muscle coordination contributes to person-specific gait deficits during overground walking.
OBJECTIVE: Incomplete spinal cord injury (iSCI) disrupts motor control and limits the ability to coordinate muscles for overground walking. Inappropriate muscle activity has been proposed as a source of clinically observed walking deficits after iSCI. We hypothesized that persons with iSCI exhibit lower locomotor complexity compared to able-body (AB) controls as reflected by fewer motor modules, as well as, altered module composition and activation. METHODS: Eight persons with iSCI and eight age-matched AB controls walked overground at prescribed cadences. Electromyograms of fourteen single leg muscles were recorded. Non-negative matrix factorization was used to identify the composition and activation of motor modules, which represent groups of consistently co-activated muscles that accounted for 90% of variability in muscle activity. RESULTS: Motor module number, composition, and activation were significantly altered in persons with iSCI as compared to AB controls during overground walking at self-selected cadences. However, there was no significant difference in module number between persons with iSCI and AB controls when cadence and assistive device were matched. CONCLUSIONS: Muscle coordination during overground walking is impaired after chronic iSCI. SIGNIFICANCE: Our results are indicative of neuromuscular constraints on muscle coordination after iSCI. Altered muscle coordination contributes to person-specific gait deficits during overground walking.
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