title: Estimating energy expenditure using heat flux measured at a single body site.
abstract: BACKGROUND
  The Personal Calorie Monitor (PCM) is a portable direct calorimeter that estimates energy expenditure (EE) from measured heat flux (i.e., the sum of conductive, convective, radiative, and evaporative heat).
  
  
  OBJECTIVE
  The primary aim of this study was to compare EE estimated from measures of heat flux with those measured using indirect calorimetry in a thermoneutral environment (26°C). A secondary aim was to determine whether exposure to ambient temperature below thermoneutral condition (19°C) influences the accuracy of the PCM.
  
  
  METHODS
  Thirty-four adults (mean ± SD: age, 28 ± 5 yr; body mass index, 22.9 ± 2.6 kg · m(-2)) were studied for 5 h in a whole-room indirect calorimeter (IC) in thermoneutral and cool conditions. Participants wore the PCM on their upper arm and completed two 20-min treadmill walking bouts (0% grade, 3 mph). The remaining time was spent sedentary (e.g., watching television, using a computer).
  
  
  RESULTS
  In thermoneutral conditions, EE values (mean (95% confidence interval)) measured by IC and PCM were 560.0 (526.5-593.5) and 623.3 (535.5-711.1) kcal, respectively. In cool conditions, EE values measured by IC and PCM were 572.5 (540.9-604.0) and 745.5 (668.1-822.8) kcal, respectively. Under thermoneutral conditions, mean PCM minute-by-minute EE tracked closely with IC, resulting in a small nonsignificant bias (63 kcal (-5.8 to 132.4)). During cool conditions, mean PCM minute-by-minute EE did not track IC, resulting in a large bias (173.0 kcal (93.9-252.1)) (P <; 0.001).
  
  
  CONCLUSIONS
  This study demonstrated the validity of using measured heat flux to estimate EE. However, accuracy may be impaired in cool conditions possibly because of excess heat loss from the exposed limbs.
authors.affiliation: 1Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO; 2Division of Geriatric Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO; 3School of Public Health, University of Colorado Anschutz Medical Campus, Aurora, CO; and 4Necessity Consulting, Mars, PA.
authors.forename: Kate
authors.initials: K
authors.lastname: Lyden
authors.forename: Tracy
authors.initials: T
authors.lastname: Swibas
authors.forename: Victoria
authors.initials: V
authors.lastname: Catenacci
authors.forename: Ruixin
authors.initials: R
authors.lastname: Guo
authors.forename: Neil
authors.initials: N
authors.lastname: Szuminsky
authors.forename: Edward L
authors.initials: EL
authors.lastname: Melanson
mesh_terms: D000328:Adult; D002151:Calorimetry / Q000295:instrumentation* / Q000379:methods*; D002153:Calorimetry, Indirect / Q000379:methods; D003080:Cold Temperature; D018592:Cross-Over Studies; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013696:Temperature; D055815:Young Adult