Study Design Case-control.

Objectives Determine if differences in visual utilisation during single-limb balance (SLB) are present between those with and without chronic ankle instability (CAI).

Background Impaired SLB is commonly exhibited by CAI patients and may be related to decreased utilisation of somatosensory information and the upregulation of visual information. However, visual modulation across eyes open and closed conditions has not been thoroughly investigated.

Methods and Measures Seventy-four people with CAI (females=51; age:23.76±5.18, height:171.07±9.96 cm, weight:75.05±15.17 kg) were compared to 74 people without CAI (females=47; age:24.48±5.16, height:168.19±11.67 cm, weight:69.36±13.66 kg). Three 10 s trials of barefoot SLB were collected in eyes open and closed conditions using a forceplate. Centre of pressure data were analysed as velocity, range, time-to-boundary (TTB) mean-minima (MM), and TTB standard deviation (SD) for the anterior-posterior (AP) and medial-lateral (ML) directions. The Romberg Quotient (RQ) was calculated for each variable (eyes closed/eyes open) to assess the contribution of visual information during SLB. Increased reliance on visual information was associated with greater RQ for velocity and range and lower RQ for TTB variables. Mann-Whitney U tests examined group differences (p≤0.05).

Results The CAI group exhibited a lower TTB-SD-ML RQ (CAI: 0.514±0.261, Healthy: 0.625±0.314; p=0.02). However, no differences were identified in the RQ for TTB-MM-ML (CAI: 0.434±0.105, Healthy: 0.468±0.141; p=0.26), TTB-MM-AP (CAI: 0.428±0.104, Healthy: 0.419±0.111; p=0.61), TTB-SD-AP (CAI: 0.436±0.132, Healthy: 0.435±0.159; p=0.62), velocity-ML (CAI: 2.331±0.474, Healthy: 2.307±0.520; p=0.78), velocity-AP (CAI: 2.387±0.557, Healthy: 2.522±0.721; p=0.47), range-ML (CAI: 1.895±0.429, Healthy: 1.971±0.394; p=0.11), or range-AP (CAI: 1.969±0.505, Healthy: 2.216±0.716; p=0.07).

Conclusion The utilisation of visual information during SLB did not differ between groups for a majority of postural control variables based on the RQ. However, CAI patients did exhibit an increased reliance on vision for TTB-SD-ML which indicates these individuals may upregulate visual information to augment the number of strategies used to maintain frontal plane postural control.