The following abstract are in PDF form. 
Validation of the Actiheart Monitor for Combined Heart Rate and Movement in Overweight, Obese and Athlete Child Populations
The objective was to determine if previously published protocols using single-pieced HR and movement sensor in children during treadmill walking and running could be replicated with a combined HR and movement sensor: the Actiheart monitor. This monitor had been validated in healthy children, but not in overweight or athletic children. Resting energy expenditure (EE) and submaximal EE was measured by indirect calorimetry at rest and during a progressive treadmill exercise test.