Measuring physical activity using accelerometry in 13–15-year-old adolescents: the importance of including non-wear activities

摘要

ObjectiveThe present study aimed to examine the impact of non-wear activities registered in diaries when using accelerometers to assess physical activity (PA) in young adolescents.DesignData arise from a large-scale cross-sectional study on PA. PA was objectively assessed using Actigrapha?￠ accelerometers (Actigraph MTI, Manufacturing Technology Inc., Pensacola, FL, USA) during seven consecutive days. Non-wear time activity diaries were provided to register the activities for which the accelerometer was removed. After correction to deal with over-reporting, the registered minutes of PA were used to replace periods of non-wear time measured by the accelerometer.SettingBetween October 2008 and May 2009 adolescents were recruited by home visits in Ghent (Belgium).SubjectsYoung adolescents (n 513; 48?·6 % boys) aged 13 to 15 years.ResultsOf the total sample, 49?·9 % registered at least one activity of moderate to vigorous intensity in the non-wear time activity diary. More adolescents registered an activity performed on a weekday than on a weekend day and the registered mean number of minutes of moderate to vigorous PA were higher on weekend days. Repeated-measures (M)ANOVA tests revealed a significant difference between the mean minutes with and without non-wear activities for all PA intensities, regardless of adolescentsa€? socio-economic status or gender. More adolescents achieved the PA recommendations after inclusion of the non-wear activities irrespective of accelerometer thresholds used.ConclusionsThe collection of information regarding non-wear time by non-wear time activity diaries when using accelerometers in 13a€“15-year-old adolescents can lead to different PA outcomes at the individual level and therefore can improve the ability to accurately measure PA.