Ageing alters ankle mechanics and muscle co-contraction patterns across the gait cycle

BACKGROUND: The ankle plays a central role in stability and propulsion during walking. Ageing alters muscle-tendon properties and neural coordination, disrupting the relationship between neuromuscular control and mechanical output. RESEARCH QUESTION: What are the age-related changes in tibialis anterior and gastrocnemius normalised electromyography signals, sagittal-plane ankle angle and moment, and braking-propulsive ground reaction force across the walking gait cycle? METHODS: A secondary analysis was conducted on 107 healthy able-bodied adults aged 26-86 years who walked overground at self-selected speed while three-dimensional motion capture, force platforms and surface electromyography recorded movement data. Time-normalised gait cycle data were analysed using one-dimensional Statistical Parametric Mapping simple linear regressions to examine continuous age-related effects. RESULTS: Increasing age was associated with increased tibialis anterior-gastrocnemius co-contraction during early and mid-stance and reduced co-contraction in terminal stance. Older adults exhibited greater dorsiflexion in late stance and pre-swing, reduced plantarflexion moments in mid-stance, and lower braking and propulsive ground reaction forces. With increasing age, normalised gastrocnemius electromyography signal within the gait cycle increased in early stance even as plantarflexion moments declined, reflecting a stabilising motor-control strategy that compensates for reduced proprioceptive acuity. SIGNIFICANCE: Ageing induces phase-specific ankle motor-control adaptations that maintain stability but reduce mechanical efficiency and propulsion. These changes likely contribute to slower gait, greater fatigue and elevated fall risk. Interventions should target neuromuscular timing, phase-specific coordination, proprioception and muscle-tendon function to restore propulsion without compromising stability.