Understanding the effects of a sudden directional shift in somatosensory feedback and increasing task complexity on postural adaptation in individuals with and without chronic ankle instability

Individuals with chronic ankle instability (CAI) present somatosensory dysfunction following an initial ankle sprain. However, little is known about how individuals with CAI adapt to a sudden sensory perturbation of instability with increasing task and environmental constraints to maintain postural stability. Forty-four individuals with and without unilateral CAI performed the Adaptation Test to a sudden somatosensory inversion and plantarflexion perturbations (environment) in double-, injured-, and uninjured- limbs. Mean sway energy scores were analyzed using 2 (group) × 2 (somatosensory perturbations) × 3 (task) repeated measures analysis of variance. There were significant interactions between the group, environment, and task (P=.025). The CAI group adapted faster than healthy controls to a sudden somatosensory inversion perturbation in the uninjured- (P=.002) and injured- (P