Surface Electromyography of Wrist Flexors and Extensors in Children With Hemiplegic Cerebral Palsy

Objective: To investigate the characteristics of motor unit recruitment and coordination function of the wrist during maximum isometric voluntary contraction (MIVC) using surface electromyography (EMG) in children with hemiplegic cerebral palsy (CP). Design: A cross-sectional trial. Setting: Hospital neurology and rehabilitation department. Participants: Sixty-eight children with spastic hemiplegic CP. Methods: The signals of wrist flexors and extensors in unaffected and affected hands of children with hemiplegic cerebral palsy were measured with surface EMG. The characteristics of integrated EMG (iEMG), root mean square (RMS), and co-contraction ratio of surface EMG were analyzed. Results: The RMS and iEMG in the affected hand during MIVC were higher than that of the unaffected hand (P <. 001). The RMS and iEMG of wrist extensors and the iEMG of wrist flexors of the affected hand had a good correlation with the unaffected hand (P < .01). The RMS and iEMG of the unaffected hand during MIVC were higher than that of the affected hand (P < .001), and the iEMG of the unaffected hand had a good correlation with the affected hand (P < .05). The RMS and iEMG in the unaffected hand during MIVC were significantly higher than that of the affected hand during MIVC (P < .001). The co-contraction ratio of the unaffected hand was significantly lower than that of the affected hand (P < .001). Conclusions: The affected side shows more co-contractions than the unaffected side in children with hemiplegic CP. However, the unaffected side demonstrates stronger motor unit recruitment at maximal effort than the affected side. In addition, this study demonstrates the successful use of surface EMG for assessment of motor unit activation in young children with CP.