title: Leg blood flow and VO2 during peak cycle exercise in younger and older women.
abstract: OBJECTIVE
  To test the hypothesis that leg blood flow and leg O2 extraction during peak exercise are reduced with age in healthy normally active women.
  
  
  METHODS
  Thirteen younger (20-27 yr) and 12 older (60-71 yr) nonendurance trained women performed graded upright leg cycling to maximum exertion (VO2peak), while leg blood flow (femoral vein thermodilution), cardiac output (acetylene rebreathing), mean arterial pressure (MAP, radial artery), and blood O2 contents were measured.
  
  
  RESULTS
  Peak leg VO2 was 32% lower in the older versus younger women (0.81 +/- 0.06 vs 1.18 +/- 0.10 L x min(-1)) and was correlated with peak systemic VO2 (1.33 +/- 0.1 vs 1.78 +/- 0.1 L x min(-1)) in both groups. Peak leg blood flow and estimated leg vascular conductance were 29% and 38% lower, respectively, in the older women (both P < 0.001). Peak leg blood flow and peak estimated cardiac output were correlated in the older (r2 = 0.51, P = 0.02), but not younger (r2 = 0.10, P = 0.35), group. Estimates of peak systemic and leg arterial-venous O2 difference did not differ between groups (both P > 0.28).
  
  
  CONCLUSIONS
  Reduced leg blood flow is a major contributor to the reduced peak systemic VO2 observed in older nonendurance trained women. Diminished leg blood flow during peak exercise in older women, in turn, is due to both central (reduced cardiac output) and peripheral (reduced leg vascular conductance) limitations.
authors.affiliation: Noll Physiological Research Center, The Pennsylvania State University, University Park, PA16802-6900, USA. dnp3@psu.edu
authors.forename: David N
authors.initials: DN
authors.lastname: Proctor
authors.forename: Dennis W
authors.initials: DW
authors.lastname: Koch
authors.forename: Sean C
authors.initials: SC
authors.lastname: Newcomer
authors.forename: Khoi U
authors.initials: KU
authors.lastname: Le
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Smithmyer
authors.forename: Urs A
authors.initials: UA
authors.lastname: Leuenberger
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D015308:Anaerobic Threshold / Q000502:physiology; D002302:Cardiac Output; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D010414:Pennsylvania; D010809:Physical Fitness / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology