Antagonist activity of extensor digitorum brevis and tibialis anterior during child walking

Abstract

Synergic and antagonist actions of intrinsic and extrinsic foot muscles are acknowledged during walking of adult people. Conversely, reciprocal role of these muscles in children walking has not been adequately deepened yet. Purpose of the study was the surface-EMG-based evaluation of mutual recruitment of intrinsic and extrinsic foot muscles during healthy-children walking. Extensor digitorum brevis (EDB) is one of the main intrinsic foot muscles, controlling foot movement and stability. In this study, EDB and tibialis anterior (TA) were considered as representative of intrinsic and extrinsic foot muscles, respectively. Surface-EMG signals during 4-minute walking trial were acquired in eight healthy school-age children (mean±SD: age 8.3±1.7 years; height 136±8 cm; mass 30.9±6.2 kg) to fulfill the goal of the study. Then, Statistical gait analysis, a recent methodology performing a statistical characterization of gait, was applied to process EMG data. Data from an exceptional number of strides were acquired and analyzed to consider the expected variability (mean±SD = 265±30 strides for each child, nearly 2500 in total). Results showed that: 1) the most frequent recruitment of EDB muscle occurred between 25% and 55% of gait cycle, i.e., in Flat foot contact and Push off phases; 2) the most frequent recruitment of TA occurred from 55% to following 10% of gait cycle, i.e., during Swing and Heel strike phases. This indicated that the most significant EDB activity overlapped the region of no activity (or infrequent activity) for TA and vice versa. In conclusion, present study suggests that TA and EDB muscles acted mainly as antagonist muscles for foot/ankle-joint movement during children walking. These findings highlighted the need of measuring the mutual activity of extrinsic vs. intrinsic foot muscles as tool for a deeper understanding of mechanisms regulating ankle-foot stability and as a possible marker of pathology of neuro-muscular system.