title: Endurance Training and V˙O2max: Role of Maximal Cardiac Output and Oxygen Extraction.
abstract: OBJECTIVE
  Although endurance training (ET) commonly augments maximal oxygen consumption (V˙O2max), it remains unclear whether such increase is associated with that of maximal cardiac output (Qmax) alone or along with arteriovenous oxygen difference (a-V˙O2diff). Herein, we sought to systematically review and determine the effects of ET on V˙O2max, Qmax, and a-V˙O2diff at maximal exercise, and on their associations, in healthy young subjects.
  
  
  METHODS
  We conducted a systematic search of MEDLINE, Scopus, and Web of Science (from their inception until September 2014) for articles assessing the effects of ET lasting ≥3 wk on V˙O2max and Qmax and/or a-V˙O2diff at maximal exercise in healthy young adults (mean age <40 yr). Meta-analyses were performed to determine standardized mean differences (SMD) in V˙O2max, Qmax, and a-V˙O2diff at maximal exercise between posttraining and pretraining measurements. Subgroup and meta-regression analyses were used to evaluate associations among SMD and potential moderating factors.
  
  
  RESULTS
  Thirteen studies were included after systematic review, comprising a total of 130 untrained or moderately trained healthy young subjects (mean age, 22-28 yr). Duration of ET programs ranged from 5 to 12.9 wk. After data pooling, V˙O2max (SMD = 0.75, P < 0.0001) and Qmax (SMD = 0.64, P < 0.0001), but not a-V˙O2diff at maximal exercise (SMD = 0.21, P = 0.23), were increased after ET. No significant heterogeneity was detected. With meta-regression, the SMD in Qmax was positively associated with the SMD in V˙O2max (B = 0.91, P = 0.007). The SMD in a-V˙O2diff at maximal exercise was not associated with the SMD in V˙O2max (B = 0.20, P = 0.40).
  
  
  CONCLUSIONS
  Based on a relatively small number of studies, improvement in V˙O2max following 5-13 wk of ET is associated with increase in Qmax, but not in a-V˙O2diff, in previously untrained to moderately trained healthy young individuals.
authors: 1Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, SWITZERLAND; 2Institute of Physiology, University of Zurich, Zurich, SWITZERLAND; and 3Center for Molecular Cardiology, University of Zurich, Schlieren, SWITZERLAND.
authors: David
authors: D
authors: Montero
authors: Candela
authors: C
authors: Diaz-Cañestro
authors: Carsten
authors: C
authors: Lundby
mesh_terms: D000328:Adult; D002302:Cardiac Output; D006801:Humans; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010806:Physical Education and Training / Q000379:methods*; D010807:Physical Endurance / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen