Number of Synergies Is Dependent on Spasticity and Gait Kinetics in Children With Cerebral Palsy.

PURPOSE: Children with cerebral palsy have motor dysfunctions, which are mainly associated with the loss of motor coordination. For the assessment of motor coordination, muscle synergies calculated by nonnegative matrix factorization have been investigated. However, the characteristics of muscle synergies in children with cerebral palsy are not understood. METHODS: This study compared the number of muscle synergies during gait between children with cerebral palsy and children with typical development and clarified whether certain clinical parameters differed according to the number of synergies. RESULTS: Children with cerebral palsy had significantly fewer synergies than children developing typically. The extent of spasticity and gait kinetics differed according to the number of synergies. CONCLUSION: Increases in the number of synergies are limited by severe spasticity. The muscle synergies calculated by nonnegative matrix factorization have the potential to enable the quantification of motor coordination during gait.

Merging and Fractionation of Muscle Synergy Indicate the Recovery Process in Patients with Hemiplegia: The First Study of Patients after Subacute Stroke.

Loss of motor coordination is one of the main problems for patients after stroke. Muscle synergy is widely accepted as an indicator of motor coordination. Recently, the characteristics of muscle synergy were quantitatively evaluated using nonnegative matrix factorization (NNMF) with surface electromyography. Previous studies have identified that the number and structure of synergies were associated with motor function in patients after stroke. However, most of these studies had a cross-sectional design, and the changes in muscle synergy during recovery process are not clear. In present study, two consecutive measurements were conducted for subacute patients after stroke and the change of number and structure of muscle synergies during gait were determined using NNMF. Results showed that functional change did not rely on number of synergies in patients after subacute stroke. However, the extent of merging of the synergies was negatively associated with an increase in muscle strength and the range of angle at ankle joint. Our results suggest that the neural changes represented by NNMF were related to the longitudinal change of function and gait pattern and that the merging of synergy is an important marker in patients after subacute stroke.