Superficial and Deep Gluteal Muscle Activation During Common Therapeutic Exercises: A Muscle Functional Magnetic Resonance Imaging Analysis

Abstract

Background: Deep gluteal muscles play an important role in femoral rotation and hip stability, but are often neglected in clinical research. We quantified and compared activation changes of superficial and deep gluteal muscles across 4 common therapeutic exercises: single-leg bridge (BRIDGE), side-lying clamshell (CLAM), side-lying reverse clamshell (R-CLAM), and side-lying hip abduction with external rotation (ABD-ER). Hypothesis: ABD-ER activates both superficial and deep gluteal muscles more effectively than other exercises. Study Design: Controlled laboratory study. Level of Evidence: Level 2. Methods: Ten healthy, physically active people (5 women and 5 men; age, 27.2 ± 1.9 years; Tegner activity scale, 6.4 ± 0.5) participated. Muscle functional magnetic resonance imaging was conducted before and after 1 set of 40 repetitions of each exercise type. Percent changes in T2 relaxation time in superficial and deep gluteal muscle activation were assessed before and after each exercise using repeated-measures analysis of variance or Friedman test. Results: All muscles showed increased activation after exercise. BRIDGE (11.6%) and ABD-ER (13.2%) activated the gluteus medius more than CLAM (4.5%). ABD-ER activated the tensor fasciae latae (17.8%) and gluteus minimus (18.1%) more than other exercises (2.7% to 7.2%). BRIDGE (13.1%), CLAM (14.5%), and ABD-ER (23.8%) activated the piriformis more than R-CLAM (5.3%). CLAM (24.2%) and ABD-ER (19.5%) activated the obturator internus more than BRIDGE (5.3%) and R-CLAM (7.3%). CLAM and ABD-ER activated 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: Of the exercises studied, ABD-ER was most effective in activating both superficial and deep gluteal muscles. BRIDGE and CLAM demonstrated selective activation advantages for specific muscles, supporting an individualized approach to exercise selection. Clinical Relevance: These insights into gluteal muscle activation changes before and after therapeutic exercises will aid clinical decision-making for exercise prescriptions.