[Reproducibility of lower limb loading force in healthy elderly and mobility-impaired elderly]

The aim of this study was to investigate the reproducibility of lower limb loading force measurements by comparing changes of measurement value and the error of measurement value in healthy elderly and mobility impaired elderly.

Seventeen healthy elderly (8 men and 9 women aged 71.8+/-6.1 years [mean+/-SD]) and 43 mobility impaired elderly (17 men and 26 women aged 80.2+/-8.7 years) were enrolled in this study. All subjects provided their informed consent to participate in this study. The healthy elderly were Health groups, and the mobility impaired elderly were classified into Low and High groups based on each subject's Functional Independence Measure score. Lower limb loading force was measured three times and the lower limb loading force to body weight ratio was calculated as a percentage. We statistically analyzed the change of measurement value using intraclass correlation coefficients (ICC) and the standard error of mean (SEM), and the error of measurement value using Bland-Altman analysis.

In all groups, the change of measurement value produced a high ICC value and a low SEM value. Systematic errors in Bland-Altman analysis were observed in Low groups for measurement value of the first and third as well as second and third, and also High groups for that of the second and third.

This study suggests that reliable lower limb loading force measurements can be obtained. The results also suggest that the reliability of lower limb loading force measurements is independent from the extent or kind of impairment. We advise that one or two measurements be taken in the clinical setting.