title: Fat mass modifies the association of fat-free mass with symptom-limited treadmill duration in the Coronary Artery Risk Development in Young Adults (CARDIA) Study.
abstract: BACKGROUND
  The assessment of fat mass and fat-free mass in relation to the symptom-limited maximal exercise duration (Max(dur)) of a treadmill test allows for insight into the association of body composition with treadmill performance potential.
  
  
  OBJECTIVE
  We investigated the complex associations between fat mass and fat-free mass and Max(dur) in a population setting.
  
  
  METHODS
  The Max(dur) of a graded exercise treadmill test and body composition by dual-energy X-ray absorptiometry were estimated in 2413 black and white men and women aged 38-50 y from the Coronary Artery Risk Development in Young Adults (CARDIA) cohort.
  
  
  RESULTS
  The mean Max(dur) was ≈7.5 s shorter per kilogram of fat mass in both men and women and independent of fat-free mass, height, race, television watching, physical activity, systolic blood pressure, lung function, and education. Fat mass modified the association of fat-free mass with the Max(dur) (2-way interaction P < 0.001), and the interaction was stronger in women than in men. In men in the lowest fat-mass quartile, the Max(dur) was 1.3 s longer per kilogram of fat-free mass and was 0.5 s shorter per kilogram of fat-free mass in the highest fat-mass quartile. In contrast, in women with the least fat mass, the Max(dur) was 2.7 s longer per kilogram of fat-free mass and was 2.8 s shorter per kilogram of fat-free mass in the highest fat-mass quartile.
  
  
  CONCLUSIONS
  The Max(dur) was negatively related to fat mass. Fat-free mass in obese people contributed little to the treadmill performance potential as assessed by the Max(dur), although the contribution of fat-free mass was positive in thinner people.
authors.affiliation: Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis, MN 55454, USA.
authors.forename: Na
authors.initials: N
authors.lastname: Zhu
authors.forename: David R
authors.initials: DR
authors.lastname: Jacobs
authors.forename: Stephen
authors.initials: S
authors.lastname: Sidney
authors.forename: Barbara
authors.initials: B
authors.lastname: Sternfeld
authors.forename: Mercedes
authors.initials: M
authors.lastname: Carnethon
authors.forename: Cora E
authors.initials: CE
authors.lastname: Lewis
authors.forename: Christina M
authors.initials: CM
authors.lastname: Shay
authors.forename: Akshay
authors.initials: A
authors.lastname: Sood
authors.forename: Claude
authors.initials: C
authors.lastname: Bouchard
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000293:Adolescent; D000328:Adult; D001823:Body Composition; D015992:Body Mass Index; D015331:Cohort Studies; D003324:Coronary Artery Disease / Q000209:etiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010809:Physical Fitness; D012307:Risk Factors; D055815:Young Adult