Prediction of activity energy expenditure using accelerometers

based activity monitors as measures of children’s physical activity using energy expenditure as the criterion measure. Methods: Actiwatch (AW) and Actical (AC) activity monitors were validated against continuous 4-h measurements of energy expenditure (EE) in a respiratory room calorimeter and 1-h measurements in an exercise laboratory using a portable calorimeter and treadmill in 32 children, ages 7–18 yr. The children performed structured activities including basal metabolic rate (BMR), playing Nintendo, using a computer, cleaning, aerobic exercise, ball toss, treadmill walking, and running. Equations were developed to predict activity energy expenditure (AEE EE BMR), and physical activity ratio (PAR EE/BMR) from a power function of AW or AC, and age, sex, weight, and height. Thresholds were determined to categorize sedentary, light, moderate, and vigorous levels of physical activity. Results: Activity counts accounted for the majority of the variability in AEE and PAR, with small contributions of age, sex, weight, and height. Overall, AW equations accounted for 76–79 % and AC equations accounted for 81 % of the variability in AEE and PAR. Relatively wide 95 % prediction intervals suggest the accelerometers are best applied to groups rather than individuals. Sensitivities were higher for the vigorous threshold (97%) than the other thresholds (86–92%). Specificities were on the order of 66–73%. The positive predictive values for sedentary, light, moderate, and vigorous categories were 80, 66, 69, and 74 % for AW, respectively, an