Effects of Examiner Strength on Reliability of Hip-Strength Testing Using a Handheld Dynamometer

Context: Hip-muscle impairments are associated with a variety of lower-extremity dysfunctions. Accurate assessment in the clinical setting can be challenging due to the strength of hip muscles relative to examiner strength. Objective: To examine the influence of examiner strength and technique on manual hip-strength testing using a handheld dynamometer. Design: Repeated measures. Setting: Research laboratory. Participants: 30 active adults (age 24 +/- 1.4 y). Interventions: Three examiners of different strength performed manual muscle tests (MMT) in 2 different positions for hip extension, abduction, and external rotation using a MicroFet handheld dynamometer. Examiner strength was quantified via a 1-repetition-maximum leg press and chest press with a Keiser A420 pneumatic resistance machine. Main Outcome Measures: Intrarater reliability (ICC3,1), interrater reliability (ICC2,1), and measured torque values. Results: Intrarater reliability for all measurements ranged from .82 to .97. Interrater reliability ranged from .81 to .98. Main effects for hip extension revealed a significant difference in torque values between examiners and between techniques. For the short-lever hip-abduction and seated hip-external-rotation tests, there was a significant difference between examiners. There was no significant difference in measured torque values between examiners with the long-lever hip-abduction or the prone hip-external-rotation tests. Conclusions: MMT of the hip may be performed with high reliability by examiners of different strength. To obtain valid MMT measurements of hip muscles, examiners must consider their own strength and testing techniques employed. The authors recommend a long-lever technique for hip abduction and a prone position for testing hip external rotation to minimize the influence of examiner strength. Both positions appear to provide mechanical advantages to the examiner compared with the alternative techniques. The authors are unable to recommend a preferred hip-extension-testing technique to minimize the influence of examiner strength.