Myoelectric activity of antagonist ankle-muscles in 6-to-8-year-old children during walking

Great co-contraction, i.e. simultaneous contraction of agonist and antagonist muscles crossing a joint, of ankle muscles during the stance phase has been identified as one of the typical features of the immature gait. The goal of the present study was the assessment of the co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL) during walking in 20 healthy 6-to-8-year-old children, critical age for the maturation of gait. To this aim, Statistical gait analysis, a recent methodology performing a statistical characterization of gait by averaging spatial-temporal and surface-EMG-based parameters over numerous strides, was performed in each subject. Co-contractions were assessed as the period of overlap between activation intervals of TA and GL. Results showed that GL and TA act as pure antagonists for ankle plantar/dorsiflexion (no co-contractions) in only 18.7% of strides. In the remaining strides, statistically significant (p<0.05) co-contractions were detected in early stance (45.0% of the strides), mid-stance (27.7%), pre-swing (14.6%), and swing (74.1%). The presence of all these different kinds of ankle-muscle co-contractions seems to suggest the need of a stabilizing control in children, supporting the hypothesis that a young neurocontrol system can operate on more degrees of freedom. In conclusion, the present analysis represents the first attempt for providing a quantitative assessment for ankle-muscle co-contraction in healthy 6-to-8-year-old children, in order to give further information on the maturation of gait in children.