RESUMO
BACKGROUND: Evidence of neuroplasticity after joint injury has suggested that individuals with chronic ankle instability (CAI) may have degraded movement when facing cognitive demand. To date, research into these effects have been limited to static balance models, and typically only incorporate a single type of cognitive demands. RESEARCH QUESTION: We aimed to determine the effects of multiple modalities of cognitive load (quantitative, verbal-memory, visuospatial) on dynamic postural control strategies in a sample of patients with CAI compared to uninjured controls. METHODS: Thirty-two participants (16 CAI, 16 healthy) performed a series of 20 hops-to-stabilization while either under no cognitive load (CON), or while performing Benton's judgment of line orientation (JLO), the symbol digit modalities test (SDM), or a serial seven task (SVN). Dynamic postural stability indices and mean muscle activation from the lower leg muscles were extracted and assessed via analysis of variance. RESULTS: Healthy subjects demonstrated better vertical and dynamic postural stability indices under JLO (P ≤ 0.017) and SVN (P ≤ 0.010) conditions compared to CON. Postural stability was unaffected in CAI (P > 0.050). Peroneus longus and lateral gastrocnemius activation was lowest in SVN across all subjects (P ≤ 0.033). Lateral gastrocnemius activation was greatest in SDM (P ≤ 0.033). SIGNIFICANCE: These results suggest improvements in postural stability under cognitive demand in healthy individuals that did not occur in CAI, suggesting less movement optimization. Quantitative tasks appear to impede stabilizing muscle activation in the leg, while verbal-memory tasks result in a more protective landing strategy.