Reliability of lower extremity strength measurements using the belt-resisted method

The objectives of this study were to standardize measurement procedures and study the test-retest and interrater reliability of the belt-resisted method for measuring the lower extremity isometric strength of three muscle groups. The strength of 33 healthy, elderly, community-dwelling subjects was evaluated with a hand-held dynamometer using the belt-resisted method. Isometric strength testing of three muscle groups (hip flexors, knee extensors, and ankle dorsiflexors) was performed on two separate occasions, 1 week apart, by the Same tester to determine test-retest reliability. The test results of two different examiners testing on different days were used to determine interrater reliability. Test-retest reliability was higher than interrater reliability. Test-retest reliability coefficients of the three muscle groups were high (.79-.95). For interrater reliability, intraclass correlation coefficients varied from .64 to .92, depending on the muscle group and side. For the two kinds of reliability, intraclass correlation coefficients increased from proximal to distal. The method for the hip muscle group should be modified to increase reliability of the measure.