Adolescent physical activity levels: discrepancies with accelerometer data analysis

作者：Logan Greig R M^*; Duncan Scott; Harris Nigel K; Hinckson Erica A; Schofield Grant

来源：Journal of Sports Sciences, 2016, 34(21): 2047-2053.

DOI：10.1080/02640414.2016.1150599

• ActiGraph
• epoch
• cut points
• vector magnitude
• youth

This study investigated the effects of epoch length and cut point selection on adolescent physical activity intensity quantification using vertical axis and vector magnitude (VM) measurement with the ActiGraph GT3X+ accelerometer. Four hundred and nine adolescents (211 males; 198 females) aged 12-16years of age wore accelerometers during waking hours. The GT3X+ acceleration counts were reintegrated into 1, 5, 15, 30 and 60s epoch lengths for both vertical axis and VM counts. One cut point was applied to vertical axis counts and three different cut points were applied to VM counts for each epoch length. Significant differences (P<0.01) in mean total counts per day were observed between vertical axis and VM counts, and between epoch lengths for VM only. Differences in physical activity levels were observed between vertical and VM cut points, and between epoch lengths across all activity intensities. Our findings illustrate the magnitude of differences in physical activity outcomes that occur between axis measurement, cut points and epoch length. The magnitude of difference across epoch length must be considered in the interpretation of accelerometer data and seen as a confounding variable when comparing physical activity levels between studies.

• 出版日期2016-11