Relative reliability of three objective tests of limb muscle strength.

If measures of muscle strength are to be broadly applied, they should be objective, portable, quick, and reliable. Through this component of the NIH Toolbox study we sought to compare the test-retest reliability of 3 tests of muscle strength that are objective, portable, and quick: the five-repetition sit-to-stand test (FRSTST), hand-grip dynamometry (HGD), and belt-stabilized hand-held dynamometry (BSHHD) of knee extension. Three sets of each test were performed- 1 warm-up and 2 maximal. Measures from the maximal tests obtained 4 to 10 days apart were compared. Reliability was described using descriptive statistics, intraclass correlation coefficients (ICCs) and 4 measures of response stability: standard error of measurement (SEM), method error (ME), coefficient of variation of SEM (SEM CV ), and coefficient of variation of variation of ME (ME CV ). The ICCs of all tests were good (≥ 0.853). Measures of response stability showed less variability between test and retest for FRSTST and HGD than for BSHHD. In conclusions all 3 tests demonstrated good test-retest reliability. However, greater differences would need to be observed between tests sessions to conclude that a real change had occurred in measures obtained by BSHHD.