Muscle coactivation during postural adjustments in subjects with chronic ankle instability

To evaluate muscle coactivation synergies during postural adjustments associated to single leg drop landing in athletes with CAITo evaluate muscle coactivation synergies during postural adjustments associated to single leg drop landing in athletes with CAI.

A cross-sectional observational study was carried out with a sample of 28 athletes distributed into two groups, one with and one without CAI, according to the criteria of the International Ankle Consortium. The participants performed the single leg drop landing from a stable support surface onto an unstable surface in a dual task context. The ground reaction forces and the center of pressure (CoP) were monitored through two force plates on the two support surfaces to access the time instant of the beginning of CoP displacement to the starting limb and the supporting limb, the instant of contact with the unstable surface and the CoP displacement toward the starting limb, to the support limb and during single leg support. The position of the center of pressure (CoP) was calculated to identify the time instant where its stabilization occurred. At intervals up to and after the CoP stabilization, the range of CoP displacement and the related rambling and trembling variables and the ankle and hip muscle coactivation were used for analysis. 

The CAI group presented in the limb with CAI decreased time required for CoP stabilization compared to the control group. After CoP stabilization participants with CAI presented decreased CoP anteroposterior displacement, decreased rambling amplitude and velocity and decreased ankle muscle coactivation in the mediolateral direction. 

Individuals with CAI present deregulation in ankle muscle coactivation in mediolateral direction associated with changes in postural stability in the limb with CAI.

Rehabilitation of chronic ankle instability should include strategies to improve ankle muscle coactivation in the mediolateral direction to improve postural stability as decreased CoP displacement and related variables could increase the risk of reinjury.