Abstract
AimTo determine if muscle synergy structure (activations and weights) differs between gait patterns in children with spastic cerebral palsy (CP).MethodIn this cross‐sectional study, we classified 188 children with unilateral (n=82) or bilateral (n=106) spastic CP (mean age: 9y 5mo, SD: 4y 3mo, range: 3y 9mo–17y 7mo; 75 females; Gross Motor Function Classification System [GMFCS] level I: 106, GMFCS level II: 55, GMFCS level III: 27) into a minor deviations (n=34), drop foot (n=16), genu recurvatum (n=26), apparent equinus (n=53), crouch (n=39), and jump gait pattern (n=20). Surface electromyography recordings from eight lower limb muscles of the most affected side were used to calculate synergies with weighted non‐negative matrix factorization. We compared synergy activations and weights between the patterns.ResultsSynergy structure was similar between gait patterns, although weights differed in the more impaired children (crouch and jump gait) when compared to the other patterns. Variability in synergy structure between participants was high.InterpretationThe similarity in synergy structure between gait patterns suggests a generic motor control strategy to compensate for the brain lesion. However, the differences in weights and high variability between participants indicate that this generic motor control strategy might be individualized and dependent on impairment level.
Highlights
Synergy structure was similar between gait patterns, weights differed in the more impaired children when compared to the other patterns
Two basic muscle activity patterns are already present in neonates during stepping movements.[3,4]. These locomotor primitives are modified and the number of muscle synergies increases.[3,4]. These findings suggest that, a part of the muscle synergies of gait appears to be present in the central nervous system (CNS) at birth, muscle synergies have the ability to adapt.[3,4]
N is the number of synergies, m is the number of muscles, t is the number of data points of the concatenated signal (404), and error is the difference between the measured surface electromyography (sEMG) and reconstructed muscle activity signals computed using the corresponding synergy structure.[15]
Summary
Based on missing or poor quality sEMGs of the required muscle groups, we excluded 35 children. The 3D gait analyses of the remaining 195 children were grouped per gait pattern (Table 1). Of those 195 children, 170 children had good quality sEMGs of all eight muscles for all four gait cycles. The true equinus group did not meet the sample size requirements and was excluded, leaving 188 children for subsequent analyses Minor deviations 34 I=33 II=1 III=0 10:11 (8:6–12:10) 33.3 (27.0–50.7) 1.46 (1.32–1.67) 0.42 (0.39–0.46) 0.72 (0.69–0.78)
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