Accelerometry-based physical activity assessment for children and adolescents

Abstract

Accurate assessment of physical activity (PA) is important to study the associations between PA and health outcomes, to evaluate the effectiveness of interventions and to derive public health recommendations. Despite limitations, accelerometry-based methods generate the best available measures for epidemiological research involving a large number of children and adults. In this chapter, we review the most important methodological issues pertaining to the use of accelerometers to assess the overall volume of PA. We stress the importance of recording and keeping the raw data whenever possible. We review the validation studies using accelerometry to determine energy expenditure and calibration studies that attempt to derive thresholds (“cut-offs”) for differentiating between activity intensity categories. Conceptual and measurement issues due to the use of different thresholds are reviewed, as well as the temporal resolution issues such as sampling rate and epoch length. Different wear time detection algorithms and inclusion criteria are reviewed as well as options in data reduction (deriving meaningful variables from accelerometer data). We present an R package automatising most of the steps in accelerometer data analysis. The chapter concludes with some insights into the future of accelerometry given the wearable revolution and logistical considerations in using accelerometers in large field studies.