The Alteration of Neuromuscular Control Strategies During Gait Initiation in Individuals with Chronic Ankle Instability

Background: Providing a clear picture of neuromuscular control mechanisms and deficits in patients with chronic ankle instability (CAI) requires further investigation. Gait initiation (GI) is a perfect task to evaluate concurrent open-loop (planned GI) and closedloop (unplanned GI) neuromuscular control mechanisms in patients with CAI. Objectives: The current study aimed at evaluating neuromuscular control mechanisms via assessment of the center of pressure (COP) displacements during planned and unplanned GI in patients with CAI and healthy individuals. Methods: It was a case-control study. Twenty-two subjects with unilateral CAI and 22 healthy subjects stood on a force plate and initiated gait with maximal velocity under 2 conditions: i) planned (initiated gait after hearing the "all set" signal, when subjects felt ready to walk) and ii) unplanned (initiated gait "as soon as possible" after hearing acoustic signal). The COP parameters were assessed during the preparatory and the execution phase of GI. Results: The peak COP displacement toward swing leg decreased significantly, with P value = 0.003, in the preparatory phase of GI under planned and unplanned conditions in patients with CAI (0.028 +/- 0.002) in comparison with the control group (0.038 +/- 0.002). Forward velocity of the COP displacement increased in CAI patients (0.026 +/- 0.003) compared with the control group (0.018 +/- 0.002) in the execution phase of GI, with P value = 0.039. Conclusions: According to the findings of the current study, both open-loop and closed-loop neuromuscular control mechanisms altered in patients with CAI.