Validity And Reliability Of Hand-held Dynamometer In Assessing Isometric Leg Strength In Older Adults

Abstract

The hand-held dynamometer (HHD) is portable in measuring an isometric muscle strength at multiple angles and limbs. The accuracy and consistency of the HHD in measuring muscle strength in older adults remains less explored. PURPOSE:We investigated the sex-specific and overall concurrent validity and interclass reliability of the HHD (microFET 2) in assessing isometric leg muscle strength in older men and women. We also constructed the prediction model for isometric leg strength using HHD, gait-speed, sit-to-stand, handgrip strength, and sex. METHODS: Forty-eight older adults (12 males and 36 females), aged 60-85 years, were recruited for this study. All participants had anthropometric, dual-energy x-ray absorptiometry, gait speed, sit-to-stand, handgrip, and hand-held dynamometer measurements. All participants also had both isometric and isokinetic leg strengths assessed by a Biodex isokinetic dynamometer. Pearson partial correlations were used to investigate the concurrent validity of HHD compared with an isokinetic dynamometer after adjustment for age and race and additional adjustment for sex. Cronbach alpha coefficients (α) were used to estimate the interclass reliability of HHD. Multiple regression with stepwise selection procedures were used to develop the prediction models for isometric leg strength with HHD, gait-speed, sit-to-stand, handgrip strength, and sex. RESULTS: Age-, sex-, and race-adjusted partial Pearson correlation coefficients were 0.62 for isokinetic leg strength (p < 0.001) and 0.90 for isometric leg strength (p < 0.001) with the HHD. Age- and race-adjusted partial Pearson correlations between isometric leg strength and HHD were 0.93 for men and 0.81 for women, and between isokinetic leg strength and HHD were 0.45 for men and 0.59 for women. Stepwise regression procedures documented the prediction model for isometric leg strength with HHD, gait-speed, and sex (R2 = 0.93, SEE = 5.01). Cronbach α coefficients showed high interclass reliabilities in estimating the leg muscle strength using the HHD in men (α = 0.99) and women (α = 0.97). CONCLUSIONS: The HHD (microFET 2) had high concurrent validity and interclass reliability in assessing the isometric leg muscle strength in older adults.