title: Validity of physical activity measures in individuals after total knee arthroplasty.
abstract: OBJECTIVE
  To determine the concurrent criterion-related validity of 2 activity monitors in comparison with the criterion method of indirect calorimetry in older adults after total knee arthroplasty (TKA).
  
  
  METHODS
  Validation study.
  
  
  METHODS
  Subjects completed 9 increasingly demanding daily activities in a research laboratory; each activity was performed for 7 minutes, for a total of 80 minutes, while the activity monitors and criterion method were used concurrently.
  
  
  METHODS
  Subjects (N=21, 67% women) had a mean age ± SD of 68±7 years and a body mass index of 29±4.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Energy expenditure (in kcal/min) measured by accelerometer-based and multisensor-based monitors and by a criterion method. Validity was assessed by the paired t test, intraclass correlation coefficient (ICC), and Bland-Altman plots comparing the measurements from the activity monitors with those of the criterion method.
  
  
  RESULTS
  Measurements from the accelerometer-based monitor were significantly lower than those of the criterion method across all walking and nonwalking activities. The underestimations ranged from 40% to 100%. The accelerometer-based monitor demonstrated small to moderate agreement compared with the criterion method (ICCs from 0 to .38). Measurements from the multisensor-based monitor were significantly lower than those of the criterion method during several nonwalking activities; yet, the differences were minor (2%-19%). Measurements from the multisensor-based monitor during walking activities were not different compared with the criterion method. The multisensor-based monitor demonstrated moderate to excellent agreement with the criterion method (ICCs from .48 to .81).
  
  
  CONCLUSIONS
  The multisensor-based monitor showed better criterion-related validity than the accelerometer-based monitor and should be considered as a tool to measure physical activity in individuals after TKA.
authors.affiliation: Department of Physical Therapy, University of Pittsburgh, Pittsburgh, PA. Electronic address: gja4@pitt.edu.
authors.forename: Gustavo J
authors.initials: GJ
authors.lastname: Almeida
authors.affiliation: Department of Physical Therapy, University of Pittsburgh, Pittsburgh, PA.
authors.forename: David M
authors.initials: DM
authors.lastname: Wert
authors.affiliation: School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Kelly S
authors.initials: KS
authors.lastname: Brower
authors.affiliation: Department of Physical Therapy, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Sara R
authors.initials: SR
authors.lastname: Piva
mesh_terms: D061725:Accelerometry; D000203:Activities of Daily Living; D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D002153:Calorimetry, Indirect; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D009043:Motor Activity; D020370:Osteoarthritis, Knee / Q000601:surgery; D011795:Surveys and Questionnaires
keywords: Accelerometry; Activities of daily living; Arthroplasty; Energy metabolism; Reference standards; Rehabilitation; Validation studies; knee; replacement