title: Test-retest reliability of a portable gas analysis system under free living conditions.
abstract: BACKGROUND
  K4b2 (COSMED Srl Italy) is a portable device that is considered valid and reliable for measuring oxygen uptake (VO2) and carbon dioxide production (VCO2) under laboratory conditions.
  
  
  OBJECTIVE
  Evaluate the test-retest reliability of K4b2 during walking, stair climbing and descending stairs under free living conditions.
  
  
  METHODS
  Twelve participants completed two self-selected comfortable paced walking tests and 20 participants completed two self-selected comfortable paced stair climbing and descending tests. VO2 and VCO2 were measured during the tests using K4b2.
  
  
  RESULTS
  ICCs for VO2 (ICC & 95% Cl: 0.91, 0.72-0.97) and VCO2 (0.91, 0.72-0.97) of walking demonstrated high reliability whereas reliability was moderate for stair climbing (VO2: 0.82, 0.6-0.93; VCO2: 0.73, 0.44 - 0.88) and low for descending stairs (VO2: 0.67, 0.33-0.85; VCO2: 0.51, 0.1-0.77).
  
  
  CONCLUSIONS
  K4b2 is a highly reliable device for VO2 and VCO2 measurement during self-paced walking in free living environment.
authors.forename: Sundar Kumar
authors.initials: SK
authors.lastname: Veluswamy
authors.forename: Vasudeva
authors.initials: V
authors.lastname: Guddattu
authors.forename: Arun G
authors.initials: AG
authors.lastname: Maiya
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D015203:Reproducibility of Results; D016138:Walking / Q000502:physiology
chemical_list: D002245:Carbon Dioxide