Muscle synergies and complexity of neuromuscular control during gait in cerebral palsy

Abstract

AIM Individuals with cerebral palsy (CP) have impaired movement due to a brain injury near birth. Understanding how neuromuscular control is altered in CP can provide insight into pathological movement. We sought to determine if individuals with CP demonstrate reduced complexity of neuromuscular control during gait compared with unimpaired individuals and if changes in control are related to functional ability. METHOD Muscle synergies during gait were retrospectively analyzed for 633 individuals (age range 3.9–70y): 549 with CP (hemiplegia, n=122; diplegia, n=266; triplegia, n=73; quadriplegia, n=88) and 84 unimpaired individuals. Synergies were calculated using non-negative matrix factorization from electromyography collected during previous clinical gait analyses. Synergy complexity during gait was compared with diagnosis subtype, functional ability, and clinical examination measures. RESULT Fewer synergies were required to describe muscle activity during gait in individuals with CP compared with unimpaired individuals. Changes in synergies were related to functional impairment and clinical examination measures including selective motor control, strength, and spasticity. INTERPRETATION Individuals with CP use a simplified control strategy during gait compared with unimpaired individuals. These results were similar to synergies during walking among adult stroke survivors, suggesting similar neuromuscular control strategies between these clinical populations.

Immature Spinal Locomotor Output in Children with Cerebral Palsy

“…EMG activity in most TD and children with CP was well accounted for by four modules (Figures 6A,B). The smaller number of muscle synergies found in children with CP in some previous studies (Steele et al, 2015; Tang et al, 2015; Shuman et al, 2016) may be a consequence of the criterion used to define the minimum number of synergies sufficient to account for overall EMG activity (Hug et al, 2012; Russo et al, 2014) and/or the limited number of recorded muscles (Steele et al, 2013; Zelik et al, 2014; Damiano, 2015). Nevertheless, it is worth noting that the observed phenomenon of widening of basic activation patterns (Figure 6) does not depend on the exact number of modules retained by the specific non-negative matrix factorization procedure (Martino et al, 2015).…”

“…There are only a few studies that attempted to evaluate the spatiotemporal organization of the spinal locomotor output in CP (Steele et al, 2015; Tang et al, 2015; Shuman et al, 2016) suggesting that individuals with CP may use a simplified control strategy (fewer synergies) compared with unimpaired individuals. However, a more detailed and thorough consideration of multi-muscle coordinated patterns is needed (Damiano, 2015).…”

Selective motor control correlates with gait abnormality in children with cerebral palsy

“…Individuals with CP demonstrate less complexity in their control strategies during gait than their typically developing peers and appear to demonstrate strategies similar to the rhythmic stepping observed in infants [14,15]. This lack of development of mature control strategies may be the underlying mechanism resulting in both impairments in SMC and impairments observed in gait.…”

Are Modular Activations Altered in Lower Limb Muscles of Persons with Multiple Sclerosis during Walking? Evidence from Muscle Synergies and Biomechanical Analysis

“…Through non-negative matrix factorization (NNMF) of EMG signals from 8 leg muscles, three or four muscle synergies have been identified that appear to account for muscle activation during gait in the majority of healthy persons (Clark et al, 2010; Dominici et al, 2011; Fox et al, 2013). Recent studies, focused on muscle synergies during locomotor tasks, have already yielded promising insight into neuromotor control in persons after stroke (Clark et al, 2010; Gizzi et al, 2011; Roh et al, 2013, 2015; Routson et al, 2013, 2014), in children and adults with incomplete spinal cord injuries (Ivanenko et al, 2009; Fox et al, 2013; Hayes et al, 2014), and in children with cerebral palsy (Steele et al, 2015). …”