Intrafoot Coordination and Its Variability During Walking in Males with and Without Chronic Ankle Instability.

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). Because the "giving way" of the ankle joint (episodes of excessive inversion of the rearfoot that do not result in an acute lateral ankle sprain) usually occurs during walking, investigating the intrafoot coordination during walking is necessary. This study aimed to identify intrafoot coordination and its variability in copers while walking.

METHODS

The study included 12 copers, 13 patients with CAI, and ten control patients. The participants were required to walk on a treadmill at a fixed speed of 1.3 m/sec. Using the modified vector coding technique, the coupling angle between the intrafoot joints, representing interjoint 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 antiphase with proximal dominance in the coper group than in the CAI and control groups during midstance (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 dominance than the CAI group during midstance (P < .05). For coordination between the midfoot and forefoot in the frontal plane, the coper group also showed a significantly lower proportion of antiphase with distal dominance than the CAI group during 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 midstance (P < .05).

CONCLUSIONS

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