%0 Journal Article
%T A Calibration Protocol for Population-Specific Accelerometer Cut-Points in Children
%A Kelly A. Mackintosh
%A Stuart J. Fairclough
%A Gareth Stratton
%A Nicola D. Ridgers
%J PLOS ONE
%D 2012
%I Public Library of Science (PLoS)
%R 10.1371/journal.pone.0036919
%X Purpose To test a field-based protocol using intermittent activities representative of children's physical activity behaviours, to generate behaviourally valid, population-specific accelerometer cut-points for sedentary behaviour, moderate, and vigorous physical activity. Methods Twenty-eight children (46% boys) aged 10¨C11 years wore a hip-mounted uniaxial GT1M ActiGraph and engaged in 6 activities representative of children's play. A validated direct observation protocol was used as the criterion measure of physical activity. Receiver Operating Characteristics (ROC) curve analyses were conducted with four semi-structured activities to determine the accelerometer cut-points. To examine classification differences, cut-points were cross-validated with free-play and DVD viewing activities. Results Cut-points of ¡Ü372, >2160 and >4806 counts£¿min£¿1 representing sedentary, moderate and vigorous intensity thresholds, respectively, provided the optimal balance between the related needs for sensitivity (accurately detecting activity) and specificity (limiting misclassification of the activity). Cross-validation data demonstrated that these values yielded the best overall kappa scores (0.97; 0.71; 0.62), and a high classification agreement (98.6%; 89.0%; 87.2%), respectively. Specificity values of 96¨C97% showed that the developed cut-points accurately detected physical activity, and sensitivity values (89¨C99%) indicated that minutes of activity were seldom incorrectly classified as inactivity. Conclusion The development of an inexpensive and replicable field-based protocol to generate behaviourally valid and population-specific accelerometer cut-points may improve the classification of physical activity levels in children, which could enhance subsequent intervention and observational studies.
%U http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0036919