title: The effect of age-related differences in body size and composition on cardiovascular determinants of VO2max.
abstract: BACKGROUND
  A reduction in maximal stroke volume (SVmax) and total blood volume (TBV) has been hypothesized to contribute to the decline in maximal oxygen uptake (VO2max) with healthy aging. However, these variables have rarely been collected simultaneously in a board age range to support or refute this hypothesis. It is also unclear to what extent scaling size-related cardiovascular determinants of VO2max affects the interpretation of age-related differences.
  
  
  METHODS
  A retrospective analysis of VO2max, maximal cardiac output (QCmax), TBV, and body composition including fat-free mass (FFM) in 95 (51% M) healthy adults ranging from 19-86 years.
  
  
  RESULTS
  Absolute and indexed VO2max, QCmax, and maximal heart rate decreased in both sexes with age (p ≤ .031). SVmax declined with age when scaled to total body mass or body surface area (p ≤ .047) but not when expressed in absolute levels (p = .120) or relative to FFM (p = .464). Absolute and indexed TBVs (mL/kg; mL/m(2)) were not significantly affected by age but increased with age in both sexes when scaled to FFM (p ≤ .013). A lower arteriovenous oxygen difference (a-vO2diff) contributed to the reduction in VO2max with age in treadmill exercisers (p = .004) but not in the entire cohort (p = .128).
  
  
  CONCLUSIONS
  These results suggest (a) a reduction in absolute SVmax, and TBV do not contribute substantially to the age-related reduction in VO2max, which instead results from a smaller QCmax due to a lower maximal heart rate, and (b) body composition scaling methods should be used to accurately describe the effect of aging on physical function and cardiovascular variables.
authors.affiliation: University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Graeme
authors.initials: G
authors.lastname: Carrick-Ranson
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Hastings
authors.forename: Paul S
authors.initials: PS
authors.lastname: Bhella
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shibata
authors.forename: Naoki
authors.initials: N
authors.lastname: Fujimoto
authors.forename: Dean
authors.initials: D
authors.lastname: Palmer
authors.forename: Kara
authors.initials: K
authors.lastname: Boyd
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Levine
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition; D049628:Body Size; D002320:Cardiovascular Physiological Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D012189:Retrospective Studies; D055815:Young Adult