Reliability of physical performance tests in four different randomized clinical trials

Objectives: (1) To assess the test-retest reliability of physical performan ce tests in subject groups with different levels of impairment and disabili ty, and (2) to assess the stability of these tests over different time inte rvals. Design: Test-retest, repeated measures reliability design. Setting: (1) A university's center for aging and research center, (2) a con tinuing care retirement community, and (3) an extended care and rehabilitat ion center at a Veterans Affairs medical center. Subjects: Twenty-four community-dwelling elders, 15 community-dwelling elde rs with Parkinson disease, 12 older women with vertebral osteoporosis and c ompression fractures, and 14 elderly nursing home residents. Measures: Lower extremity isometric strength (ankle dorsiflexion, hip abduc tion), spinal configuration (thoracic kyphosis, lumbar lordosis), lumbosacr al motion (flexion, extension), and timed measures of the ability to get in and to get out of bed at a usual pace. Results: Most of the within-group intraclass correlation coefficients (ICCs ) were good to excellent (.70 to .97). Overall, ICCs for all groups combine d were between .70 and .96, and no decrement in reliability was noted after controlling for group membership. In addition, no decrement in the ICC was observed for short (1 day) vs longer (1 week) intervals of testing. Conclusions: These performance-based measures may be used reliably across a wider range of testing environments and elderly populations than has been reported. (C) 1999 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.