title: Physical activity related energy expenditure in children by doubly labeled water as compared with the Caltrac accelerometer.
abstract: OBJECTIVE
  The objective of this study was to determine whether the Caltrac accelerometer was a meaningful predictor of physical activity related energy expenditure (AEE) in free-living, pre-adolescent children.
  
  
  METHODS
  The sample consisted of 31 children (14 girls, 17 boys; 22 Caucasian, 9 Mohawk) with a mean age of 8.3 (+/- 2.0) y.
  
  
  METHODS
  AEE was measured by subtracting postprandial resting metabolic rate (RMR), measured via indirect calorimetry, from total daily energy expenditure (TDEE), derived from the doubly labeled water (DLW) method. Average daily activity counts (AC) were measured using a Caltrac accelerometer, which was worn for three days, two weekdays and one weekend day, within the DLW dosing period.
  
  
  RESULTS
  AEE was related to gender (r = 0.42, P = 0.02), fat mass (FM, r = 0.32; P = 0.07), and fat free mass (FFM, r = 0.32; P = 0.07), but not to AC (r = -0.09; P = 0.63). After adjusting for gender, race, FM and FFM using multiple correlation regression analysis (R = 0.53), AC did not significantly increase the amount of variation explained in AEE. An estimate of the calories expended in physical activity was derived from AC using a formula developed by Sallis et al. This estimate was significantly higher than AEE (956 kcal/d vs 469 kcal/d, respectively, t = 5.9, P < 0.001).
  
  
  CONCLUSIONS
  The Caltrac was not a meaningful predictor of AEE in our sample. The caloric estimates of energy expended in physical activity derived from the Caltrac AC, were significantly higher in comparison with measured AEE in these free-living children.
authors.affiliation: Department of Nutrition and Food Sciences, University of Vermont, Burlington 05405, USA.
authors.forename: R K
authors.initials: RK
authors.lastname: Johnson
authors.forename: J
authors.initials: J
authors.lastname: Russ
authors.forename: M I
authors.initials: MI
authors.lastname: Goran
mesh_terms: D044466:Asian People; D001834:Body Water / Q000378:metabolism; D002153:Calorimetry, Indirect; D002648:Child; D003903:Deuterium; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D007198:Indians, North American; D007553:Isotope Labeling; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation; D009518:New York; D005082:Physical Exertion / Q000502:physiology*; D013686:Telemetry; D044465:White People
chemical_list: D003903:Deuterium