Variations in Gluteus Medius Activity During Clam Exercise: Differences Due to Hip Flexion Angle During Exercise and Maximum Passive Internal Rotation Range

OBJECTIVE: To assess differences in the activity of each gluteus-medius segment in response to variations in the maximum passive hip internal-rotation range and across ranges of hip flexion angle during clam exercises. DESIGN: Cross-sectional study METHODS: The participants were healthy women. The maximum passive range of hip internal rotation was measured in prone with the hip in a neutral position and the knee flexed to 90°. Based on these values, participants were classified into two groups (excessive-range group; normal-range group). Differences in the activity of 3 gluteus-medius segments (anterior, middle, and posterior) during the clam exercise, performed at hip flexion angles of 30°, 45°, and 60°, were compared between groups. Analysis of variance for a split-plot factorial design was used to assess statistical differences (p = 0.05). RESULTS: Activity in the posterior gluteus-medius segment was significantly higher when the hip flexion angle was 60° or 45°, than when it was 30° during clam exercises (p = 0.042 and 0.035, 95% confidence intervals = 0.10–6.4 and 0.1–4.2, effect size = 0.32 and 0.20, respectively p = 0.042 and 0.035, respectively). CONCLUSION: Deeper hip flexion angles during the clam exercise were associated with increased posterior gluteus-medius activity, regardless of individual differences in hip internal rotation range.