Electromyographic analysis of ankle muscles in chronic ankle instability during sudden inversion according to visual information provision

Summary Background Chronic ankle instability is a condition in which the ankle is repetitively giving way, with symptoms such as pain, muscle weakness, and proprioceptive deficits. Therefore, people with chronic ankle instability require complex and systematic interactions between sensory association and the musculoskeletal system. The purpose of this study was to examine changes in ankle muscle activities and reaction times during sudden ankle inversion in chronic ankle instability patients under different visual conditions. Material and Methods Twenty-eight subjects with chronic ankle instability were recruited for the study. All subjects performed a trapdoor platform that was inversion by 25 degrees. This study assessed muscle activity and muscle reaction time during sudden ankle inversion three times with a 60-second rest period between tests with eyes-open and eyes-closed conditions. Results Muscle activities of tibialis anterior, peroneus longus, and peroneus brevis were significantly diminished with eyes closed, whereas that of gastrocnemius was not significantly different. No significant changes in tibialis anterior, peroneus longus, and peroneus brevis, and gastrocnemius reaction times were observed during sudden ankle inversion in the eyes-open and eyes-closed conditions. Conclusions Blocking visual information can lower tibialis anterior, peroneus longus, and peroneus brevis muscle activities during postural perturbation in subjects with chronic ankle instability. These results provide insight into the injury mechanism and causes of injury, and thus to improve the existing preventive appliances.