title: Reliability of Physical Activity Measures During Free-Living Activities in People After Total Knee Arthroplasty.
abstract: 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 Community Healthy Activities Model Program for Seniors (CHAMPS) questionnaire in assessing free-living PA at light and moderate intensities in people 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).
  
  
  METHODS
  A one-group, repeated-measures design was used.
  
  
  METHODS
  Participants wore the activity monitors for 2 weeks, and the CHAMPS 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 participants who reported similar PA during the 2 weeks were included in the analysis. The mean age of these participants was 69 years (SD=8), and 75% of them were women. Reliability ranged from moderate to excellent for the ACT (ICC=.75-.86) and was excellent for the SWA (ICC=.93-.95) and the CHAMPS 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 CHAMPS 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.
  
  
  CONCLUSIONS
  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 CHAMPS questionnaire. The SWA provided more precise reliability estimates. Wearing PA monitors during waking hours provided sufficiently reliable measures and can reduce the burden on people wearing them.
authors.affiliation: G.J. Almeida, PT, PhD, Department of Physical Therapy, University of Pittsburgh, 100 Technology Dr, Ste 210, Pittsburgh, PA 15219 (USA). gja4@pitt.edu.
authors.forename: Gustavo J
authors.initials: GJ
authors.lastname: Almeida
authors.affiliation: J.J. Irrgang, PT, PhD, ATC, FAPTA, Department of Orthopaedic Surgery, University of Pittsburgh.
authors.forename: James J
authors.initials: JJ
authors.lastname: Irrgang
authors.affiliation: G.K. Fitzgerald, PT, PhD, FAPTA, Department of Physical Therapy, University of Pittsburgh.
authors.forename: G Kelley
authors.initials: GK
authors.lastname: Fitzgerald
authors.affiliation: J.M. Jakicic, PhD, FACSM, FTOS, Department of Health and Physical Activity, University of Pittsburgh.
authors.forename: John M
authors.initials: JM
authors.lastname: Jakicic
authors.affiliation: S.R. Piva, PT, PhD, OCS, FAAOMPT, Department of Physical Therapy, University of Pittsburgh.
authors.forename: Sara R
authors.initials: SR
authors.lastname: Piva
mesh_terms: D056044:Actigraphy / Q000295:instrumentation*; D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D015444:Exercise; D005260:Female; D006801:Humans; D057187:Independent Living; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D013997:Time Factors