ABSTRACT
Assessment of physical activity in youth is a complex problem. Typically, questionnaires or activity check lists are used to characterize physical activity among youth. Numerous concerns arise with this type of evaluation including inaccurate recall of activity and the inability of these measures to capture all types of physical activity in this population. Accelerometer based motion sensors appear to be attractive alternatives as they can be used to directly measure movement. The first generation of this type of motion sensor was the Caltrac which is a single plane accelerometer that accumulates counts or kilocalories over time. Total activity is quantified as counts or kilocalories resulting in a generalized measure of physical activity. This monitor has been validated in both laboratory[1, 2] and field settings[3, 4].
