Hip Strength and Activation in Individuals With Ankle Instability During the Single-Leg Squat Test

Context: Hip muscle function has been reported to be altered in individuals with chronic ankle instability (CAI). The purpose of this study was to determine whether the single-leg squat test (SLST) could be used to detect differences in proximal muscle activation between individuals with and without CAI and to determine if there were differences in strength of the hip lateral rotators, extensors, and abductors between individuals with and without CAI. Design: A case-control study design was used to compare hip muscle activation and strength during the SLST between individuals with CAI, lateral ankle sprain copers, and healthy controls. Methods: Forty-eight participants (14 males, 34 females; median age = 22.00 y) participated in this study. Participants were separated into CAI (n =18), coper (n =15), and control (n = 15) groups based on published criteria. Surface electromyography was used to measure muscle activation of the gluteus maximus and gluteus medius during the SLST. Strength of the hip lateral rotators, extensors, and abductors was measured using handheld dynamometry and quantified using maximum isometric body weight normalized torque. Results: The CAI group utilized significantly more gluteus maximus muscle activation during the SLST than both the coper (P < .001) and control (P < .001) groups. The CAI group had weaker hip lateral rotators when compared with the coper (P = .001) and control (P < .001) groups, and weaker hip extensors strength when compared with the control group (P < .001). Conclusion: The results support existing literature demonstrating that there are proximal neuromuscular changes in individuals with CAI and suggest that the SLST has potential for use as a clinical measure of gluteus maximus activation in individuals with CAI. Further study is needed to determine whether the differences in activation are clinically detectable.