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Monitoring of physical activity among 3- to 7-year-old children was achieved with an electronic motion sensor, the Caltrac accelerometer, for 1,666 days (of 2,030 scheduled) over a 2-year period. Failure of the monitor averaged once for each 45 days of successful monitoring. The total cost of devices, repairs, and batteries over the 2 years averaged $1.31 per day of successful monitoring. It is concluded that use of the Caltrac accelerometer is a feasible and relatively inexpensive approach for monitoring physical activity in young children in epidemiologic studies.
Ellison, Zevallos, White, Marmor, Garrahie, and Moore are with the Section of Preventive Medicine & Epidemiology, Evans Dept. of Medicine, Boston University School of Medicine, Boston, MA 02118. Freedson is with the Dept. of Exercise Science, University of Massachusetts, Amherst, MA 01003. Request reprints from Dr. Ellison.