title: Comparing physical activity assessment methods in the Seasonal Variation of Blood Cholesterol Study.
abstract: OBJECTIVE
  This paper evaluated three measures of physical activity employed in the Seasonal Variation of Blood Cholesterol Study (Seasons), and it had two objectives: 1) To examine the laboratory validity of the Actillume activity monitor, and 2) To examine the relative validity of three 24-h physical activity recalls (24HR) in quantifying short-term physical activity behaviors.
  
  
  METHODS
  Nineteen healthy middle-age adults completed seven activity trials (reading, typing, box moving, stepping, and walking (3.5, 4.25, 5.0 km x h(-1))) while oxygen consumption and Actillume measures were obtained. ANOVA, linear regression, and a scatter plot were employed to examine the validity of the Actillume. In relative validity analyses of the 24HR in the Seasons study, participants (N = 481) completed two or three 24HR (MET-h x d(-1)) and a modified Baecke Questionnaire. A subset of the cohort (N = 41) wore the Actillume for 3-8 d (counts x min(-1) x d(-1)). The relative validity of the 24HR method was examined by comparison to these criterion measures.
  
  
  RESULTS
  In laboratory validation analyses, the monitor was found to discriminate between sedentary and moderate intensity activities, changes in walking speed, and to account for 79% of the variance in oxygen consumption across sedentary and walking trials. In relative validity analyses, correlations between the 24HR and the modified Baecke ranged from 0.29 to 0.52 (P < 0.01) across total, household, occupational, and leisure-time activities.
  
  
  CONCLUSIONS
  In laboratory testing, the Actillume monitor discriminated between sedentary and moderate intensity activities and was highly correlated with oxygen consumption. Three 24HR of physical activity were observed to have a relative validity that was comparable to published data from other short-term activity assessments that also employed the Baecke Questionnaire and activity monitors as criterion measures.
authors.affiliation: University of Massachusetts Medical School and School of Public Health and Health Sciences, Worcester, USA. cematthe@sph.sc.edu
authors.forename: C E
authors.initials: CE
authors.lastname: Matthews
authors.forename: P S
authors.initials: PS
authors.lastname: Freedson
authors.forename: J R
authors.initials: JR
authors.lastname: Hebert
authors.forename: E J
authors.initials: EJ
authors.lastname: Stanek
authors.forename: P A
authors.initials: PA
authors.lastname: Merriam
authors.forename: I S
authors.initials: IS
authors.lastname: Ockene
mesh_terms: D000328:Adult; D002784:Cholesterol / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D015203:Reproducibility of Results; D012621:Seasons; D011795:Surveys and Questionnaires
chemical_list: D002784:Cholesterol