Physical activity assessed by activity monitor and doubly labeled water inchildren

Purpose: To validate the Computer Science and Application's (CSA)activity m onitor for assessment of the total amount of physical activity during two s chool-weeks in 9-yr-old children and to develop equations to predict total energy expenditure (TEE) and activity energy expenditure (AEE) from activit y counts and anthropometric variables. Methods: A total of 26 children (15 boys and 11 girls, mean age 9.1 +/- 0.3 yr) were monitored for 14 consecuti ve days. TEE was simultaneously measured by the doubly labeled water method . Averaged activity counts (counts min(-1)) were compared with data on: 1) TEE, 2) AEE = TEE minus basal metabolic rate (BMR; estimated from predictiv e equations), and 3) daily physical activity level (PAL = TEE/BMR). Results : Physical activity determined by activity counts was significantly related to the data on energy expenditures: TEE (r = 0.39; P < 0.05), AEE (r = 0.5 4; P < 0.01), and PAL (r = 0.58; P < 0.01). Multiple stepwise regression an alysis showed that TEE was significantly influenced by gender, body composi tion (body weight or fat free mass), and activity counts (R-2 = 0.54-0.60). AEE was significantly influenced by activity counts and gender (R-2 = 0.45 ). There were no significant differences between activity counts and PAL in discriminating among activity levels with "low" (PAL < 1.56), "moderate" ( 1.57 less than or equal to PAL greater than or equal to 1.81), and "high" ( PAL > 1.81) intensity. Conclusion: Activity counts from the CSA activity mo nitor seems to be a useful measure of the total amount of physical activity in 9-yr-old children. Activity counts contributed significantly to the exp lained variation in TEE and was the best predictor of AEE.