Merging Analysis of Muscle Synergies for Cerebral Palsy Gait

Cerebral palsy (CP) is a common motor impairment caused by primary brain lesion. Investigation of the altered motor control strategies in CP individuals can lead to a deeper understanding of their neuromuscular disorders. This study sought to evaluate the motor complexity of CP gait, in comparison with that of the TD using synergy analysis. The muscle synergies of 80 children with CP and five healthy children, as the control group, were extracted using the non-negative matrix factorization algorithm from the surface electromyography data of the lower limbs. For each group, the muscle synergies were clustered to find the characteristic muscle modulus which were then analyzed to explore the existence of the merging patterns. The number of muscle synergies was 5 for the control group, and 4, 3, 2, and 2 for the true, jump, apparent and crouch groups, respectively, in accordance with their level of involvement. Merging patterns were observed in the stance phase and swing phase modules of the CP groups with contributions from non-corresponding modules of the control group. The sparsity in the CP gait, demonstrated by merging pattern, indicates a strategy for reducing the required neural command signals. This strategy, however, causes interference in the gait sub-phases which leads to an abnormally awkward gait.