Peroneus longus muscle activation pattern during gait cycle in athletes affected by functional ankle instability: a surface electromyographic study.

BACKGROUND: Functional ankle instability is a clinical syndrome that may develop after acute lateral ankle sprain. Although several causes of this functional instability have been suggested, it is still unclear what the activation pattern of the peroneus longus muscle is in patients with functional ankle instability. HYPOTHESIS: Peroneus longus activation patterns differ in the injured side and the uninjured side in subjects with functional ankle instability. STUDY DESIGN: Descriptive laboratory study. METHODS: The authors examined 14 subjects with functional ankle instability by using surface electromyography during walking. Activation time of the peroneus longus muscle was expressed as a percentage of the stance phase of the gait cycle. RESULTS: A statistically significant decrease in peroneus longus muscle activity was found in the injured side compared with the uninjured side (22.8% +/- 4.25% vs 37.6% +/- 3.5%, respectively). CONCLUSIONS: Results obtained in this study show a change in peroneus longus muscle activation time after injury. Independent of the origin of this change, which could only be surmised, the decrease in peroneus longus muscle activity may result in reduced protection against lateral sprains. CLINICAL RELEVANCE: The assessment of peroneus longus activation pattern during gait is useful to design an appropriate rehabilitation program in athletes suffering from functional ankle instability.