Intra-Foot Coordination and Its Variability During Walking in Males With and Without Chronic Ankle Instability.

Abstract

Background: Investigating the kinematics of copers, who are individuals with no recurrent ankle sprains, is necessary to prevent the development of chronic ankle instability (CAI). Since the "giving way" of the ankle joint (episodes of excessive inversion of the rearfoot, which do not result in an acute lateral ankle sprain) usually occurs during walking, investigating the intra-foot coordination during walking is necessary. This study aims to identify intra-foot coordination and its variability in copers while walking.

Methods: The study included 12 copers, 13 CAIs, and 10 controls. The participants were required to walk on a treadmill at a fixed speed of 1.3 m/s. Using the modified vector coding technique, the coupling angle between the intra-foot joints, representing inter-joint coordination, was calculated and categorized into four coordination patterns. The coupling angle standard deviation represented the coordination variability during the stance phase.

Results: The coordination between the rearfoot and midfoot in the frontal plane showed a significantly lower proportion of anti-phase with proximal dominance in the coper group than in the CAI and control groups during mid-stance (p < .05). Regarding coordination between the midfoot and forefoot in the sagittal plane, the coper group also showed a significantly lower proportion of in-phase coordination with distal dominancy than the CAI group during mid-stance (p < .05). For coordination between the midfoot and forefoot in the frontal plane, the coper group also showed a significantly lower proportion of anti-phase with distal dominance than the CAI group during the late stance (p < .05).The coordination variability between the sagittal midfoot and forefoot in the coper group was significantly lower than that in the CAI group and similar to that in the control group during mid-stance (p < .050).

Conclusions: These differences may explain why copers do not experience ankle sprain recurrence.