Background Static postural control impairments are often identified in people with chronic ankle instability (CAI).
Objective To examine the effect of trial duration on the assessment of postural control in people with CAI.
Participants Twenty-five individuals with self-reported CAI (7 Males; age = 23.86 ± 3.90 years; height = 170.33 ± 11.69 cm; body mass = 76.33 ± 15.28 kg) participated. Inclusion criteria included ≥1 previous ankle sprain, ≥2 episodes of “giving way” in the previous three months, and ≤ 24 on the Cumberland Ankle Instability Tool.
Interventions Barefoot single-limb stance on a forceplate was used to assess postural control. Three 10-second trials were collected in eyes open and closed conditions. Data collected during each trial were analysed as the initial 2.5 s (2.5 sec), the initial 5 s (5 sec) and 10 s (10 sec).
Main outcome measurements Independent variables included vision (open, closed) and duration (2.5 sec, 5 sec, 10 sec). Dependent variables included time-to-boundary (TTB) variables: mean of TTB minima (TTB-mean) and standard deviation of TTB minima (TTB-SD) in the anterior-posterior (AP) and medial-lateral (ML) directions. For each TTB variable, a 2 × 3 ANOVA with Fisher’s LSD post hoc comparisons examined differences between vision and duration. Alpha level was set at p ≤ 0.05.
Results Significant vision and duration main effects and vision-by-duration interactions were identified for all TTB variables (p < 0.015). Post-hoc analyses revealed differences in eyes open between 2.5 sec and 5 sec durations for TTB-mean AP and TTB-SD AP; 2.5 sec and 10 sec for TTB-mean ML, TTB-mean AP, TTB-SD ML, and TTB-SD AP; 5 sec and 10 sec for TTB-mean ML, TTB-SD ML, and TTB-SD AP (p < 0.011). Eyes closed conditions revealed differences between 5 sec and 10 sec for TTB-mean ML and TTB-SD ML (p < 0.020).
Conclusions Postural control improved with longer trial durations during eyes open conditions but not during eyes closed conditions. This suggests people with CAI may not recover from the perturbation of moving into single-limb stance during eyes closed conditions.
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