Absolute reliability of measurements of muscle strength and physical performance measures in older people with high functional capacities.

Abstract

The purpose of this study was to clarify the absolute reliability of muscle strength and physical performance measures in older people. The participants were 718 community-dwelling older people who were living independently. Muscle strength and physical performance tests were administered twice for all participants by the same rater. Grip and knee extension strength during isometric contractions were used as muscle strength tests, and the five-times chair stand test (FCST), 5-m walking time at comfortable pace, and the timed up and go test (TUG) as physical performance tests. Bland-Altman analysis was performed to determine the systematic errors for each muscle strength and physical performance test, and the amount of errors was estimated using the minimum detectable change (MDC). Further, %MDC was calculated by dividing the MDC with the mean of two measurement values for each test. No systematic errors were found in any of the muscle strength or physical performance tests, except for the FCST, for which MDC and %MDC could not be calculated. The %MDC of grip strength, 5-m walking time, and the TUG were estimated at < 10%, whereas that of knee extension strength was 12%. Age and gender were not found to affect any systematic errors or MDC and %MDC. Grip strength, 5-m walking time, and the TUG, which all have excellent reliability, were suggested to be appropriate indexes as outcome measures of muscle strength and physical performance in community-dwelling older people.