Free-living energy expenditure in children using multi-sensor activity monitors

Aims: To improve the energy expenditure algorithm of the activity monitor ActiReg, and to validate ActiReg and the activity monitor SenseWear in free-living children. Methods: The development of the ActiReg algorithm was performed in 20 healthy 11-13 years old children on treadmill walking and running with indirect calorimetry as reference. The original and new ActiReg algorithms and SenseWear using software versions InnerView 5.1 and 6.1 were validated in 20 healthy 14-15 years old children against doubly labelled water. Results: The new ActiReg algorithm improved the assessment of energy expenditure during walking and running, but the response from the monitor levelled off after 7 km h(-1). The new algorithm and InnerView 6.1 decreased the mean (sd) difference to doubly labelled water from 11 (25) (P < 0.05) to 0 (22) kJ kg(-1) d(-1) for ActiReg, and from 17 (20) (P < 0.01) to -10 (21) (P < 0.05) kJ kg(-1) d(-1) for SenseWear. However, the correlations between energy expenditure and the individual error for the new ActiReg algorithm and InnerView 6.1 were r = -0.50 (P < 0.05) and r = -0.73 (P < 0.01). Conclusions: The new ActiReg algorithm and InnerView 6.1 improved the activity monitors at group level, but the error was dependent on physical activity level. Both activity monitors need further developments for use in children. (C) 2009 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.