Coper has altered foot joint coordination pattern compared to individuals with chronic ankle instability during running.

BACKGROUND

There is limited information regarding the cause for the different etiologies in individuals with initial lateral ankle sprains (LAS) who have chronic ankle instability (CAI) and no recurrence or instability for > 12 months (copers) following initial LAS. Assessing the movement patterns of copers and individuals with CAI and LAS recurrence is essential for identifying the mechanical factors that affect patient outcomes.

RESEARCH QUESTION

Does coordination and coordination variability of rearfoot, midfoot, and forefoot present a potentially causative pattern for CAI or coper?

METHODS

This cross-sectional study included 35 males who were divided into the CAI (n = 13), coper (n = 12), and control group (n = 10). Participants performed rearfoot strike running on the treadmill at a fixed speed of 3.5 m/s. The coupling angle between the rearfoot, midfoot, and forefoot, representing intersegmental coordination, was calculated using the modified vector coding technique and categorized into four coordination patterns. The coupling angle standard deviation served represented coordination variability during the stance phase.

RESULTS

One control participant and one CAI participant were excluded, and final analyses were performed on the CAI (n = 12), coper (n = 12), and control (n = 9) groups. During late stance, the coper group showed a significantly greater proportion of in-phase with distal dominancy (p = 0.02, effect size=0.17) and a significantly lower proportion of in-phase with proximal dominancy (p = 0.05, effect size=0.17), than the CAI group. During the early stance, the coper group showed a significantly lower proportion of anti-phase with distal dominancy than the CAI group (p = 0.03, effect size=0.18). There were no differences in intra-foot variability among the groups.

SIGNIFICANCE

The intra-foot coordination observed in the coper group suggests that this movement pattern may reduce the risk of ankle sprains.