title: Exploring Metrics to Express Energy Expenditure of Physical Activity in Youth.
abstract: BACKGROUND
  Several approaches have been used to express energy expenditure in youth, but no consensus exists as to which best normalizes data for the wide range of ages and body sizes across a range of physical activities. This study examined several common metrics for expressing energy expenditure to determine whether one metric can be used for all healthy children. Such a metric could improve our ability to further advance the Compendium of Physical Activities for Youth.
  
  
  METHODS
  A secondary analysis of oxygen uptake (VO2) data obtained from five sites was completed, that included 947 children ages 5 to 18 years, who engaged in 14 different activities. Resting metabolic rate (RMR) was computed based on Schofield Equations [Hum Nutr Clin Nut. 39(Suppl 1), 1985]. Absolute oxygen uptake (ml.min-1), oxygen uptake per kilogram body mass (VO2 in ml.kg-1.min-1), net oxygen uptake (VO2 - resting metabolic rate), allometric scaled oxygen uptake (VO2 in ml.kg-0.75.min-1) and YOUTH-MET (VO2.[resting VO2] -1) were calculated. These metrics were regressed with age, sex, height, and body mass.
  
  
  RESULTS
  Net and allometric-scaled VO2, and YOUTH-MET were least associated with age, sex and physical characteristics. For moderate-to-vigorous intensity activities, allometric scaling was least related to age and sex. For sedentary and low-intensity activities, YOUTH-MET was least related to age and sex.
  
  
  CONCLUSIONS
  No energy expenditure metric completely eliminated the influence of age, physical characteristics, and sex. The Adult MET consistently overestimated EE. YOUTH-MET was better for expressing energy expenditure for sedentary and light activities, whereas allometric scaling was better for moderate and vigorous intensity activities. From a practical perspective, The YOUTH-MET may be the more feasible metric for improving of the Compendium of Physical Activities for Youth.
authors.affiliation: Exercise and Sport Science and Nutrition, University of North Carolina, Chapel Hill, NC, United States of America.
authors.forename: Robert G
authors.initials: RG
authors.lastname: McMurray
authors.affiliation: USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX, United States of America.
authors.forename: Nancy F
authors.initials: NF
authors.lastname: Butte
authors.affiliation: Department of Kinesiology, Recreation and Sport Studies, University of Tennessee, Knoxville, TN, United States of America.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Crouter
authors.affiliation: Exercise and Nutrition Sciences, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.
authors.forename: Stewart G
authors.initials: SG
authors.lastname: Trost
authors.affiliation: Department of Kinesiology, Michigan State University, East Lansing, MI, United States of America.
authors.forename: Karin A
authors.initials: KA
authors.lastname: Pfeiffer
authors.affiliation: Department of Kinesiology, Recreation and Sport Studies, University of Tennessee, Knoxville, TN, United States of America.
authors.forename: David R
authors.initials: DR
authors.lastname: Bassett
authors.affiliation: USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX, United States of America.
authors.forename: Maurice R
authors.initials: MR
authors.lastname: Puyau
authors.affiliation: Centers for Disease Control and Prevention/National Cancer Institute/National Collaborative on Childhood Obesity Research, Washington, DC, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Berrigan
authors.affiliation: Division of Nutrition, Physical Activity, and Obesity, CDC, Atlanta, GA, United States of America.
authors.forename: Kathleen B
authors.initials: KB
authors.lastname: Watson
authors.affiliation: Division of Nutrition, Physical Activity, and Obesity, CDC, Atlanta, GA, United States of America.
authors.forename: Janet E
authors.initials: JE
authors.lastname: Fulton
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001827:Body Height; D015992:Body Mass Index; D049628:Body Size; D002648:Child; D002675:Child, Preschool; D004734:Energy Metabolism / Q000502:physiology*; D005006:Ethnicity / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007899:Leisure Activities; D008297:Male; D009043:Motor Activity; D010101:Oxygen Consumption; D012016:Reference Values; D012420:Running; D012727:Sex Characteristics; D013177:Sports; D014481:United States; D016138:Walking