The intra- and interrater reliability of hip muscle strength assessments using a handheld versus a portable dynamometer anchoring station

Objective: To compare the inter- and intrarater reliability of a portable dynamometer anchoring station (DAS) to a handheld dynamometer (HHD). Design: Repeated-measures design. Setting: Human performance and movement analysis laboratory. Participants: Fifteen healthy participants, ages 23 to 44 years. Interventions: Not applicable. Main Outcome Measures: Three consecutive measures of peak bilateral isometric strength were obtained for hip abduction, extension, and flexion by 2 investigators by using the DAS and the HHD after a 1-hour rest period. This testing scenario was repeated I week later. Intraclass correlation coefficients (ICCs) were used to determine reliability. Results: Interrater ICCs of average peak strength ranged from .84 to .92 (hip flexors), .69 to .88 (hip abductors), and .56 to .80 (hip extensors). Intrarater ICCs ranged from .59 to .89 for tester A and from .72 to .89 for tester B using the DAS, and from .67 to .81 for the HHD across muscle groups. Conclusions: The DAS showed good intrarater reliability for hip flexion and abduction, whereas the HHD demonstrated higher reliability for hip extension. The results support the use of dynamometers that are quick and reliable and that reduce tester bias during hip strength assessment.