Neuromuscular constraints on muscle coordination during overground walking in persons with chronic incomplete spinal cord injury

Abstract

h i g h l i g h t s Persons with chronic incomplete spinal cord injury (iSCI) exhibit significant reduced muscle coordination during overground walking as compared to age-matched adults. Neuromuscular constraints following iSCI contribute to person-specific deficits in overground walking. Neuromuscular mechanisms underlying gait deficits may provide guidance for targeted SCI rehabilitation. a b s t r a c t 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