The gluteus medius muscle is an important frontal plane stabilizer of the pelvis. Although its primary function is pelvic stabilization in single leg stance (closed-chain), many therapists and trainers continue to strengthen the gluteus medius in an open chain using hip abduction. The addition of an unstable surface such as a Thera-Band® Stability Trainer is thought to increase muscle activation due to the increased challenge of stabilizing the pelvis in the frontal plane while balancing on a labile surface.
Researchers found that single leg stance exercises produced significantly greater glute med EMG activity compared to bilateral stance. In addition, single leg squats produced significantly more EMG activity than single leg stance. While not statistically significant, performing single-leg exercises on a foam pad did produce more EMG activity of the gluteus medius than a stable surface.