• Geon Woo Lee, Juseong Lee, Seung Woo Shin, and Junghoon Kim.
• Sports and Exercise Medicine Laboratory, Korea Maritime and Ocean University, Busan, Republic of Korea.
• Medicine (Baltimore). 2024 Dec 13; 103 (50): e40902e40902.

BackgroundLimited evidence exists regarding the movement control patterns of individuals with chronic ankle instability (CAI) during sand walking. This study aimed to analyze gait characteristics and muscle activation in patients with CAI while walking on sand.MethodsThis study recruited 30 participants, including 15 patients with CAI and 15 healthy controls. Patients with CAI were selected based on having experienced at least a lateral ankle sprain within 12 months before recruitment. They also had to scoring ≤ 27 on the Cumberland ankle instability tool. This study was conducted using a randomized crossover trial. All participants were asked to walk three times each at their natural speed on both sand and paving blocks for a distance of 50m. There was at least a week between each trial.ResultsThe lower limb gait kinematics, spatiotemporal, and muscle activity parameters while walking on sand and paving blocks were compared between both groups. Significant differences in knee angle were observed between 60.83% and 75.34% of the gait cycle during walking on sand in the patients with CAI. Regarding spatiotemporal parameters, cadence (P = .001) and stride length (P = .049) showed significant differences as the main effect. In the CAI group, the recruitment threshold for the peroneus longus muscle was significantly lower during walking on sand than on paving blocks (P < .001). In contrast, the motor unit action potential (MUAP) was significantly higher (P < .001). For the tibialis anterior muscle, the recruitment threshold and number of motor units were significantly lower during walking on sand than on paving blocks (P = .006 and P = .003, respectively), and the MUAP was significantly higher (P < .001). During walking on sand, patients with CAI exhibited increased knee flexion angle, stride length, and MUAP, along with decreased cadence and recruitment thresholds.ConclusionThese results suggest that sand can influence gait characteristics and muscle activation in patients with CAI. Our findings indicate that gait characteristics and muscle activation changes in patients with CAI could potentially benefit CAI rehabilitation.Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.

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