Superficial And Deep Gluteal Muscle Activation During Common Therapeutic Exercises: A Muscle Functional MRI Analysis

Deep gluteal muscles play an important role in femoral rotation and hip stability; however, they are often neglected in clinical research. PURPOSE: To quantify and compare the changes in activation of superficial and deep gluteal muscles across four common therapeutic exercises. METHODS: Ten healthy, physically active individuals (5 females; 5 males; age = 27.2 ± 1.9 years; body mass index = 23.2 ± 2.8 kg/m2; Tegner Activity Scale = 6.4 ± 0.5) were analyzed. Muscle functional magnetic resonance imaging was conducted before and after one set of 40 repetitions of each exercise: single-leg bridge (BRIDGE), side-lying clamshell (CLAM), side-lying reverse clamshell (R-CLAM), and side-lying hip abduction with external rotation (ABD-ER). The dependent variable was T2 relaxation time, calculating percent changes in superficial and deep muscle activation after each exercise. To compare percent changes in muscle activation across exercises, we used a repeated-measures analysis of variance or Friedman test. Statistical analyses were performed using SPSS, with an alpha level set at p < 0.05. RESULTS: All muscles showed increased activation after each exercise, with 95% confidence intervals that did not cross zero. Our comparison across four exercises revealed that 1) BRIDGE (11.6%) and ABD-ER (13.2%) activated the gluteus medius more than CLAM (4.5%); 2) ABD-ER produced higher activation of the tensor fasciae latae (17.8%) and gluteus minimus (18.1%) compared to all other exercises (2.7%-7.2%), while BRIDGE, CLAM, and ABD-ER (13.1%-23.8%) generated higher activation of the piriformis compared to R-CLAM (5.3%); and 3) CLAM and ABD-ER activated the obturator internus (24.2% and 19.5%, respectively) more than BRIDGE (5.3%) and R-CLAM (7.3%), as well as the gemellus superior (18.7% and 21.4%, respectively) and gemellus inferior (6.7% and 9.2%, respectively) more than R-CLAM (7.7% and 3.4%, respectively). CONCLUSION: While all four exercises increased gluteal muscle activation, ABD-ER was the most effective for activating both superficial and deep gluteal muscles. Our study provides valuable clinical insights into gluteal muscle activation changes before and after therapeutic exercises, aiding clinical decision-making for exercise prescriptions. Supported by: This study was funded by the University of Connecticut Brain Imaging Research Core.