title: Within- and between-individual variability in estimated energy expenditure and habitual physical activity among young adults.
abstract: OBJECTIVE
  To examine the within- and between-individual variability in the estimated total energy expenditure (TEE) and habitual physical activity (PA) in free-living young adults. We were specifically interested in the day-to-day variation.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  University.
  
  
  METHODS
  A total of 277 (125 males, 152 females) participants aged 18-24 years.
  
  
  METHODS
  None.
  
  
  METHODS
  Subjects recorded their daily PA with the Bouchard 3-day diary. Descriptive statistics for TEE, moderate-to-vigorous physical activity (MVPA), inactivity (IA), and activity energy expenditure (AEE) were calculated and presented as a frequency distribution. Within- and between-individual variability were tested by RMANOVA and also presented as the coefficient of variation (CV).
  
  
  RESULTS
  Mean values for TEE, MVPA, AEE, and IA were comparable between males and females; however, considerable between-individual variability existed. Only MVPA showed a significant difference between sexes (P<0.05), due to slightly greater vigorous PA in males compared to females (8.0 and 6.8 kcal/kg/day, respectively; P=0.12). Results from the RMANOVA revealed no significant day-to-day variability in any TEE or PA variable and the CVs were not significantly different between males and females. TEE and IA displayed mean CVs of approximately 12% while mean CVs for AEE and MVPA approximated 32 and 84%, respectively.
  
  
  CONCLUSIONS
  Results from this study suggest (1) a limited day-to-day variability in TEE and (2) a large degree of between-individual variation for TEE and PA exist. This study highlights the importance of understanding the variability associated with TEE, which is important for PA measurement and proper PA and nutritional recommendations.
  
  
  BACKGROUND
  None.
authors.affiliation: Department of Health and Human Performance, Iowa State University, Ames, IA 50010, USA.
authors.forename: E E
authors.initials: EE
authors.lastname: Wickel
authors.forename: J C
authors.initials: JC
authors.lastname: Eisenmann
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001481:Basal Metabolism / Q000502:physiology*; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009751:Nutritional Requirements; D009765:Obesity / Q000378:metabolism