Quantifying the velocity-dependent muscle response during gait of children with Cerebral Palsy

A new method is introduced quantifying the velocity-dependent muscle response during gait in spastic muscles of children with Cerebral Palsy. The velocity-dependent muscle activation Index is calculated during a 3-dimensional gait analysis using segment angular velocity and the Instantaneous Mean Frequency calculated from surface electromyography. Typical developed children (n = 11) and children with hemiplegia (n = 11) aging from 8 to 19 years participated in the study. The rectus femoris and the medial gastrocnemius were assessed by calculating the velocity dependent muscle activation Index and the modified Ashworth Scale. Greater velocity-dependent muscle activation Index values for both medial gastrocnemius and rectus femoris muscles were associated with greater Ashworth Scale. Post hoc analysis revealed significant lower velocity-dependent muscle activation Index means in the Typical developed group compared with Ashworth Scale scores of 1, 2, 3, and 5. In addition, velocity-dependent muscle activation Index for Ashworth Scale 0, 1, and 2 were significantly lower than for Ashworth Scale 3 and 5. The velocity dependent muscle activation Index showed negative low correlation with walking speed and cadence. Findings show that spastic muscles can be quantified during dynamic functional task such as walking. Future studies should investigate the reliability of the velocity-dependent muscle activation Index that may be used for the assessment of spasticity management such as Botulinum toxin A interventions.