Objective： Chronic Ankle Instability (CAI) involves decreased muscle activity not only around the ankle but also around knee and hip joints. Observing posture control of upper joints in CAI patients can aid in providing preventative guidance against sprain recurrence. Previous studies observed whole body motion patterns in three groups: healthy limbs with no trauma history, limbs with a history of ankle sprain without subjective instability, and limbs with a history of ankle sprain with subjective instability. Using the Redcord system to cancel gravitational effects while exerting ankle pronator strength, movements were classified into three types: the ideal type (consistent trunk stability), sway type (temporary stability followed by instability), and abnormal type (absence of an upper kinetic chain). The ideal type was predominant in the healthy group, while the abnormal type was observed in both the CAI group and the group with past injuries, indicating a risk of sprain recurrence.
Methods： 44 limbs from 22 healthy adults were categorized into ideal, sway, and abnormal types based on movement patterns. Differences among groups were examined using Kruskal-Wallis tests and multiple comparisons, focusing on surface electromyography of the fibularis muscle, gluteus medius, and external oblique muscles, as well as ankle pronation output.
Results： The ideal type exhibited significantly higher values in fibularis muscle electromyography and ankle pronation output, with no differences between sway and abnormal types. No significant differences were found in external oblique muscle electromyography.
Discussion： Evaluating trunk muscles, including the transversus abdominis, using only surface electromyography is difficult. A comprehensive interpretation that combines visual evaluation of posture control during movement is needed.
Keywords： CAI, kinetic chain, evaluation method, Redcord, ankle sprain recurrence prevention
