Everything you wanted to know about selecting the "right" Actigraph accelerometer cut-points for youth, but…: a systematic review.

OBJECTIVES The purpose of this study is to provide an overview of the evidence on the calibration of ActiGraph accelerometers to quantify moderate-to-vigorous physical activity (MVPA) for youth through the use of cut-points and describe the independent validation studies comparing the accuracy of the developed cut-points to a criterion measure. DESIGN A systematic review. METHODS Studies were identified that: (a) developed ActiGraph accelerometer cut-points for children and youth (calibration study); or (b) performed an independent validation of already established cut-points (validation study). Both calibration studies and independent validation studies were retrieved through a systematic search of online databases. According to proposed guidelines for designing accelerometer calibration studies, each calibration study was evaluated on the following criteria: quality of a criterion measure employed; epoch length; inclusion of a variety of activities; and sample size. RESULTS A total of 11 calibration studies were identified. Two studies met all four criteria for a calibration study. A total of 4 independent validation studies were identified. Three of them reported that no cut-points accurately classified moderate-to-vigorous physical activity (MVPA) across all ranges of physical activity intensity levels in comparison to a criterion measure. The fourth study reported two sets of cut-points that under laboratory conditions, accurately classified moderate-to-vigorous physical activity (MVPA) compared to indirect calorimetry. CONCLUSIONS Limited evidence suggests that two sets of cut-points correctly classify ActiGraph counts into moderate-to-vigorous physical activity (MVPA). However, limitations with calibration and validation studies indicate greater efforts aimed at designing high quality studies are needed to confirm these findings.