Comparison of Actical and activPAL measures of sedentary behaviour in preschool children

Objectives: The purpose of this study was to examine the convergent validity of the Actical and activPAL to measure sedentary behaviour (SB) and non-SB in preschoolers in a free-living environment. Design: A convenience sample of 49 preschoolers (22 boys; 4.0 +/- 0.5 years) from six early childhood centres in Auckland, New Zealand were included in data analysis. Methods: Participants wore a hip-mounted Actical and a thigh-mounted activPAL accelerometer simultaneously during centre attendance for one day and data were collected in 15 s epochs. Bland-Altman tests were used to assess differences in group mean minutes and percentage of time in (non-)SB between both monitors. Agreement between binary coded (SB vs. non-SB) 15 s-by-15 s Actical and activPAL data was evaluated by calculating percentage agreement and kappa statistic. Results: The monitors were worn on average for 294.8 +/- 46.3 min resulting in a total of 57,780 15 s epochs. Bland-Altman tests suggested a small group mean difference in (non-)SB (1.3 min; 0.1%) and a wide prediction interval (121.3 min; 39.2%). No obvious systematic bias was observed in the Bland-Altman plot. Percentage agreement between the 15 s-by-15 s Actical and activPAL data of all participants was 73.0% (inter-child range: 36.8-93.8%). The kappa statistic showed moderate agreement with a value of 0.46(95% Cl: 0.45-0.47). Conclusions: Although the group mean estimate of (non-)SB was similar between the Actical and activPAL, the output of both monitors cannot be considered convergent as meaningful random disagreement was found between both monitors. (C) 2012 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.