OBJECTIVE: To determine how gluteus medius (Gmed) and maximus (Gmax) activate during closed-chain functional rehabilitative exercises in those with and without chronic ankle instability (CAI).

DESIGN: Cohort study. Subjects performed ten repetitions of a rotational lunge and single-leg rotational squat while surface electromyography was used to collect mean muscle activity of the Gmed and Gmax.

MAIN OUTCOME MEASURES: Mean electromyography activity of the Gmed and Gmax at maximum excursion was compared between Groups and Exercises using a separate 2-way repeated measures analysis of variance design for each muscle.

SETTING: University biomechanics lab.

PARTICIPANTS: Nine healthy (8F, 1M) and nine CAI subjects (8F, 1M) RESULTS: For Gmax activation, there was a statistically significant Group by Exercise interaction (F(3,48) = 4.84, p = 0.043). A Scheffe's post-hoc test revealed that during the rotational squat, the CAI group had significantly lower Gmax activation (51.1 ± 31.0%) than the healthy group (78.6 ± 44.8%). There were no statistically significant findings for the Gmed. In the healthy group, the Gmax produced significantly higher activation during rotational squat (78.6 ± 44.8%) compared to the rotational lunge (57.6 ± 31.9%).

CONCLUSION: Because the CAI group had significantly less Gmax activation than the healthy group during the rotational squat at the point of maximum excursion, and because the rotational squat showed significantly higher Gmax activation compared to the rotational lunge, it may be important for clinicians to implement the rotational squat during rehabilitation for those with CAI. Future prospective and intervention research involving hip musculature in those with CAI is recommended.