Reliability and responsiveness of two physical performance measures examined in the context of a functional training intervention

Abstract

Background and Purpose. The reliability and responsiveness of 2 physical performance measures were assessed in this nonrandomized, controlled pilot exercise intervention. Subjects. Forty-five older individuals with mobility impairment (mean age=77.9 years, SD=5.9, range=70-92) were sequentially assigned to participate in an exercise program (intervention group) or to a control group. Methods. The intervention group performed exercise 3 times a week for 12 weeks that targeted muscle force, endurance, balance, and flexibility: Outcome measures were the 8-item Physical Performance Test (PPT- 8) and the 6-minute walk test. Test-retest reliability and responsiveness indexes were determined for both tests; interrater reliability was measured for the PPT-8. Results. The intraclass correlation coefficient for interrater reliability for the PPT-8 was .96. Intraclass correlation coefficients for test-retest reliability, were .88 for the PPT-8 and .93 for the 6-minute walk test. The intervention group improved 2.4 points and the control group improved 0.7 point on the PPT-8, as compared with baseline measurements. There was no change in 6-minute walk test distance in the intervention group when compared with the control group. The responsiveness index was .8 for the PPT-8 and .6 for the 6-minute walk test. Conclusion and Discussion. Measurements for both the PPT-8 and the 6-minute walk test appeared to be highly reliable. The PPT-8 was more responsive than the 6-minute walk test to change in performance expected with this functional training intervention.