Assessment of physical function and exercise tolerance in older adults: Reproducibility and comparability of five measures

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Abstract
This study examined the reproducibility and comparability of five measures of function and exercise tolerance. The test battery and questionnaire on function and physical activity were administered twice, 7–10 days apart to 38 men and 12 women aged 54–80 years at the Baltimore Veterans Affairs Medical Center. Tests included fast pace 4 and 20-meter walks, 6-minute and graded treadmill walks, and a seated step test. All tests demonstrated good reproducibility with Pearson and intraclass correlation coefficients ranging from 0.84 to 0.98, and percent differences on retest ranging from 4 to 11%. Although correlations between different tests were all significant (range 0.34–0.89), comparison of performance ranks and linear regression analyses indicated that the short fast walks and seated step test may not be suitable substitutes for treadmill or long self-paced corridor walks. Only 28% had the same quintile performance ranking on the step test as on the treadmill walk, and 36% had rankings 2 or more points apart. The fast 20m walk shows the most promise as a low-level alternative to the 6-minute walk; performances had a correlation of 0.73, 82% of ranks were within one point, and 20m speed explained 42% of the variance in distance covered. More development is needed for comprehensive assessment of exercise tolerance in older adults; the 6-minute walk did not adequately discriminate fitness level in persons who walk regularly, and the treadmill posed problems for those with walking difficulty.