Reliability of Physical Activity Measures During Free-Living Activities in XXXX After Total Knee Arthroplasty.

@entity1 @entity497
BACKGROUND: Few instruments that measure physical activity (PA) can accurately quantify PA performed at light and moderate intensities, which is particularly relevant in older adults. The evidence of their reliability in free-living conditions is limited. OBJECTIVE: The study objectives were: (1) to determine the test-retest reliability of the Actigraph (ACT), SenseWear Armband (SWA), and @entity497 ( @entity497 ) questionnaire in assessing free-living PA at light and moderate intensities in @entity1 after total knee arthroplasty; (2) to compare the reliability of the 3 instruments relative to each other; and (3) to determine the reliability of commonly used monitoring time frames (24 hours, waking hours, and 10 hours from awakening). DESIGN: A one-group, repeated-measures design was used. METHODS: @entity1 wore the activity monitors for 2 weeks, and the @entity497 questionnaire was completed at the end of each week. Test-retest reliability was determined by using the intraclass correlation coefficient (ICC [2,k]) to compare PA measures from one week with those from the other week. RESULTS: Data from 28 @entity1 who reported similar PA during the 2 weeks were included in the analysis. The mean age of these @entity1 was 69 years (SD=8), and 75% of them were @entity1 . Reliability ranged from moderate to excellent for the ACT (ICC=.75-.86) and was excellent for the SWA (ICC=.93-.95) and the @entity497 questionnaire (ICC=.86-.92). The 95% confidence intervals (95% CI) of the ICCs from the SWA were the only ones within the excellent reliability range (.85-.98). The @entity497 questionnaire showed systematic bias, with less PA being reported in week 2. The reliability of PA measures in the waking-hour time frame was comparable to that in the 24-hour time frame and reflected most PA performed during this period. LIMITATIONS: Reliability may be lower for time intervals longer than 1 week. CONCLUSIONS: All PA measures showed good reliability. The reliability of the ACT was lower than those of the SWA and the @entity497 questionnaire. The SWA provided more precise reliability estimates. Wearing PA monitors during waking hours provided sufficiently reliable measures and can reduce the burden on @entity1 wearing them.
