title: Feasibility and validity of accelerometer measurements to assess physical activity in toddlers.
abstract: BACKGROUND
  Accelerometers are considered to be the most promising tool for measuring physical activity (PA) in free-living young children. So far, no studies have examined the feasibility and validity of accelerometer measurements in children under 3 years of age. Therefore, the purpose of the present study was to examine the feasibility and validity of accelerometer measurements in toddlers (1- to 3-year olds).
  
  
  METHODS
  Forty-seven toddlers (25 boys; 20 ± 4 months) wore a GT1M ActiGraph accelerometer for 6 consecutive days and parental perceptions of the acceptability of wearing the monitor were assessed to examine feasibility. To investigate the validity of the ActiGraph and the predictive validity of three ActiGraph cut points, accelerometer measurements of 31 toddlers (17 boys; 20 ± 4 months) during free play at child care were compared to directly observed PA, using the Observational System for Recording Physical Activity in Children-Preschool (OSRAC-P). Validity was assessed using Pearson and Spearman correlations and predictive validity using area under the Receiver Operating Characteristic curve (ROC-AUC).
  
  
  RESULTS
  The feasibility examination indicated that accelerometer measurements of 30 toddlers (63.8%) could be included with a mean registration time of 564 ± 62 min during weekdays and 595 ± 83 min during weekend days. According to the parental reports, 83% perceived wearing the accelerometer as 'not unpleasant and not pleasant' and none as 'unpleasant'. The validity evaluation showed that mean ActiGraph activity counts were significantly and positively associated with mean OSRAC-P activity intensity (r = 0.66; p < 0.001; n = 31). Further, the correlation among the ActiGraph activity counts and the OSRAC-P activity intensity level during each observation interval was significantly positive (ρ = 0.52; p < 0.001; n = 4218). Finally, the three sedentary cut points exhibited poor to fair classification accuracy (ROC-AUC: 0.56 to 0.71) while the three light PA (ROC-AUC: 0.51 to 0.62) and the three moderate-to-vigorous PA cut points (ROC-AUC: 0.53 to 0.57) demonstrated poor classification accuracy with respect to detecting sedentary behavior, light PA and moderate-to-vigorous PA, respectively.
  
  
  CONCLUSIONS
  The present findings suggest that ActiGraph accelerometer measurements are feasible and valid for quantifying PA in toddlers. However, further research is needed to accurately identify PA intensities in toddlers using accelerometry.
authors.affiliation: Department of Movement and Sport Sciences, University of Ghent, Watersportlaan 2, 9000 Ghent, Belgium. eveline.vancauwenberghe@ugent.be
authors.forename: Eveline
authors.initials: E
authors.lastname: Van Cauwenberghe
authors.forename: Jessica
authors.initials: J
authors.lastname: Gubbels
authors.forename: Ilse
authors.initials: I
authors.lastname: De Bourdeaudhuij
authors.forename: Greet
authors.initials: G
authors.lastname: Cardon
mesh_terms: D056044:Actigraphy / Q000295:instrumentation* / Q000379:methods; D001530:Belgium; D015992:Body Mass Index; D002675:Child, Preschool; D003625:Data Collection; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D018670:Monitoring, Ambulatory / Q000379:methods*; D009043:Motor Activity; D015337:Multicenter Studies as Topic; D010988:Play and Playthings; D015203:Reproducibility of Results; D057185:Sedentary Behavior