Description of a weight-bearing method to assess hip abductor and external rotator muscle performance.

STUDY DESIGN Measurements, descriptive. OBJECTIVES To describe a weight-bearing method to assess bilateral hip abductor and external rotator muscle performance. BACKGROUND The hip abductors and external rotators are important in maintaining lower extremity alignment during weight-bearing tasks. As such, there is a need for a method to assess hip muscle performance in weight bearing. METHODS The weight-bearing method of assessing hip muscle performance utilized a force transducer connected to a nonstretchable fabric strap positioned around the distal ends of both thighs (proximal to the lateral epicondyles). The force generation capacity was recorded with the participants in a semi-squat position (30° of hip flexion and 50° of knee flexion). To establish the reliability of the measurement, 20 participants were tested on 2 separate days, and intraclass correlation coefficient (model 3,1) and standard error of measurement were calculated to evaluate test-retest reliability and intersession consistency. The level of agreement between the muscle performance values obtained using the weight-bearing method and the traditional non-weight-bearing method of testing hip abduction in sidelying (dynamometer) was assessed using a linear correlation model. RESULTS The weight-bearing method of assessing hip muscle performance was reliable (intraclass correlation coefficient = 0.99; 95% confidence interval: 0.97, 0.99) and consistent (standard error of measurement, 0.02 N/kg). The measured strength using the weight-bearing method was moderately associated with hip abduction strength values measured in non-weight bearing (r = 0.75, P<.01). CONCLUSION The proposed weight-bearing method of assessing hip abductor and external rotator muscle performance can be used as a simple, economic, and reliable method to assess hip muscle strength.