Comparison of Kenz Lifecorder EX and ActiGraph accelerometers in 10-yr-old children

Purpose: This study compared the LC and AG accelerometers and the Yamax SW-200 pedometer (DW) under free-living conditions with regard to children's steps taken and time in light-intensity physical activity (PA) and moderate to vigorous PA (MVPA). Methods: Participants (N = 31, age = 10.2 +/- 0.4 yr) wore LC, AG, and DW monitors from arrival at school (7:45 a.m.) until they went to bed. Time in light and MVPA intensities were calculated using two separate intensity classifications for the LC (LC_4 and LC 5) and four classifications for the AG (AG_Treuth, AG_Puyau, AG_Trost, and AG_Freedson). Both accelerometers provided steps as outputs. DW steps were self recorded. Repeated-measures ANOVA was used to assess overlapping monitor outputs. Results: There was no difference between DW and LC steps (Delta = 200 steps), but a nonsignificant trend was observed in the pairwise comparison between DW and AG steps (Delta = 1001 steps, P = 0.058). AG detected significantly greater steps than the LC (Delta = 801 steps, P = 0.001). Estimates of light-intensity activity minutes ranged from a low of 75.6 +/- 18.4 min (LC-4) to a high of 309 +/- 69.2 min (AG-Treuth). Estimates of MVPA minutes ranged from a low of 25.9 +/- 9.4 min (LC_5) to a high of 112.2 +/- 34.5 min (AG-Freedson). No significant differences in MVPA were seen between LC_5 and AG-Treuth (Delta = 4.9 min) or AG-Puyau (Delta = 1.7 min). Conclusion: The LC detected a comparable number of steps as the DW but significantly fewer steps than the AG in children. Current results indicate that the LC_5 and either AG-Treuth or AG Puyau intensity derivations provide similar mean estimates of time in MVPA during-free living activity in 10-yr-old children.