Children with autism display altered ankle strategies when changing speed during over-ground gait.

Background: Examining gait mechanics when altering speed has been used in various clinical populations to understand the pervasiveness of neurological impairments. Few studies have examined whether different gait mechanics exist when altering speed in children with Autism Spectrum Disorder, although autism may present as a movement disorder due to abnormalities in the central nervous system. Most autism gait-related research has used preferred walking speed, while different speeds may yield discernible patterns that can be used for future interventions. The purpose of this study was to examine kinematic strategies used by children with autism in preferred, fast, and slow walking speeds.

Methods: Three-dimensional kinematic data were obtained on 14 children (aged 8-17 years) during preferred, fast, and slow walking. Hip, knee, and ankle angular joint positions were examined at loading response, pre-swing, and terminal swing sub-phases due to their importance on forward propulsion and weight transfer. Repeated measures analyses of variance (α = 0.05) were used to test for statistical differences and effect sizes were interpreted with Cohen's d.

Findings: Although significant differences were observed for each joint and sub-phase, the left and right ankle joints during pre-swing displayed the most consistent differences among conditions (p < 0.001, and p < 0.001), respectively. Additionally, the left ankle displayed a moderate effect size (η = 0.71) and the right ankle displayed a large effect size (η = 0.80).

Interpretations: These findings reveal that the ankle joint, during pre-swing, is the primary kinematic strategy used by children with autism when altering gait speed, whereas previous evidence suggests that the hip joint was the primary strategy.