Effects of Different Hip Rotations on Gluteus Medius and Tensor Fasciae Latae Muscle Activity During Isometric Side-Lying Hip Abduction

Context: Gluteus medius (Gmed) weakness is associated with some lower-extremity injuries. People with Gmed weakness might compensate by activating the tensor fasciae latae (TFL). Different hip rotations in the transverse plane may affect Gmed and TFL muscle activity during isometric side-lying hip abduction (S HA). Objectives: To compare Gmed and TFL muscle activity and the Gmed:TFL muscle-activity ratio during SHA exercise with 3 different hip rotations. Design: The effects of different hip rotations on Gmed, TFL, and the Gmed:TFL muscle-activity ratio during isometric SHA were analyzed with 1-way, repeated-measures analysis of variance. Setting: University research laboratory. Participants: 20 healthy university students were recruited in this study. Interventions: Participants performed isometric SHA: frontal SHA with neutral hip (frontal SHA-N), frontal SHA with hip medial rotation (frontal SHA-MR), and frontal SHA with hip lateral rotation (frontal SHA-LR). Main Outcome Measures: Surface electromyography measured the activity of the Gmed and the TFL. A 1-way repeated-measures analysis of variance assessed the statistical significance of Gmed and TFL muscle activity. When there was a significant difference, a Bonferroni adjustment was performed. Results: Frontal SHA-MR showed significantly greater Gmed muscle activation than frontal SHA-N (P = .000) or frontal SHA-LR (P = .015). Frontal SHA-LR showed significantly greater TFL muscle activation than frontal SHA-N (P = .002). Frontal SHA-MR also resulted in a significantly greater Gmed:TFL muscle-activity ratio than frontal SHA-N (P = .004) or frontal SHA-LR (P = .000), and frontal SHA-N was significantly greater than frontal SHA-LR (P = .000). Conclusions: Frontal SHA-MR results in greater Gmed muscle activation and a higher Gmed:TFL muscle ratio.