Gait termination strategies differ between those with and without ankle instability.

BACKGROUND

Chronic ankle instability is a common occurrence after an ankle sprain. Yet, some people (copers) possess a mechanism that limits recurrent injury and disability. During gait termination, those with chronic ankle instability exhibit altered feed-forward and feedback control but little is known about alterations in copers. Therefore, the purpose of this investigation was to determine the biomechanical control alterations present in controls, copers, and those with chronic ankle instability during planned and unplanned gait termination.

METHODS

Twenty subjects with chronic ankle instability, 20 copers, and 20 uninjured controls completed planned and unplanned gait termination tasks. Unplanned gait termination required subjects to stop, when cued, during randomly selected trials. Planned gait termination required intended stopping. A total of 10 trials were recorded for each condition. Normalized propulsive and braking force magnitudes and dynamic postural stability indices were calculated and compared among the groups.

FINDINGS: Normalized maximum braking forces were significantly higher in the chronic ankle instability group (Mean: 2.82 SD: 0.93N/kg), relative to copers (Mean: 2.59 SD: 0.84N/kg) and controls (Mean: 2.51 SD: 0.78N/kg). Similarly, the antero-posterior postural stability index revealed higher scores in the chronic ankle instability group (Mean: 0.15 SD: 0.03) compared to the coper (Mean: 0.14 SD: 0.02) and control group (Mean: 0.14 SD: 0.02). Copers did not differ from controls.

INTERPRETATION: The findings suggest that the ability of copers to terminate gait in a manner similar to uninjured controls may represent part of the underlying mechanism that limits recurrent injury and disability in copers.