Background: The purpose of this study was to compare gluteus medius (Gmed) and quadratus lumborum (QL) muscle activities and the Gmed/QL activity ratio, during five hip abduction exercises in individuals with Gmed weakness. Objects: Nineteen participants with clinically identified Gmed weakness performed five hip abduction exercises: side-lying hip abduction (SHA), side-bridge (SB), SB using sling (SB-sling), SB with hip abduction (SB-HA), and SB-HA using sling (SB-HA-sling). Surface electromyography recorded Gmed and QL, normalized to %maximum voluntary isometric contraction (%MVIC). A repeated-measures ANOVA was used to assess differences across conditions. Results: Significant differences were found in Gmed (F = 68.980, p = 0.001) and QL (F = 10.676, p = 0.001) activation across exercises. Gmed activity was highest in SB-HA (61.77 ± 14.46 %MVIC), while SHA produced the highest Gmed/QL activity ratio (1.70 ± 0.26), indicating more selective Gmed activation. SB and SB-sling showed lower Gmed activity and higher QL activation. SB-HA-sling resulted in moderate Gmed activation without significantly increasing QL activation. Conclusion: The SB-HA exercise is effective for co-activating Gmed and QL, while SHA and SB-HA-sling are better suited for selectively targeting Gmed with minimal QL compensation. These findings support exercise selection based on specific rehabilitation goals.

INTRODUCTION
MATERIALS AND METHODS
    1. Subjects
    2. Surface Electromyography Recording and DataProcessing
    3. Experimental Procedures
    4. Statistical Analysis
RESULTS
    1. Gmed and QL Muscle Activity
    2. Gmed/QL Muscle Activity Ratio
DISCUSSION
CONCLUSIONS
FUNDING
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTION
ORCID
REFERENCES

• Kyung-hee Jung(Department of Physical Therapy, The Graduate School, Yonsei University, Wonju, TBCS, Hotel Shilla VANTT, Seoul)
• Il-young Moon(Department of Rehabilitation Medicine, Wonju Severance Christian Hospital, Wonju)
• One-bin Lim(Department of Physical Therapy, Mokpo Science University, Mokpo)
• Chung-hwi Yi(Department of Physical Therapy, College of Software and Digital Healthcare Convergence, Yonsei University, Wonju, Korea) Corresponding author