title: Exercise at given percentages of VO2max: heterogeneous metabolic responses between individuals.
abstract: OBJECTIVE
  Given percentages of VO(2max) are widely used for training and study purposes although they might not result in homogeneous metabolic strain. Therefore, the homogeneity of metabolic responses to prolonged exercise at fixed percentages of VO(2max) should be investigated.
  
  
  METHODS
  Twenty-one healthy male subjects (29+/-5 years, 77+/-8 kg, VO(2max): 59.9+/-11.8 ml min(-1)kg(-1)) performed two incremental tests to exhaustion on a cycle ergometer to determine VO(2max). Subsequently, two 60 min tests at 60 and 75% VO(2max) were conducted in randomised order. VO(2) was kept constant by adjusting the work rate. Blood lactate (La) responses as primary outcome variable to quantify metabolic strain were assessed.
  
  
  RESULTS
  Mean La was 2.1+/-1.1 mmol l(-1) (min-max: 0.7-5.6 mmol l(-1)) during the 60% VO(2max) test and 4.6+/-1.9 mmol l(-1) (min-max: 2.2-8.0 mmol l(-1)) during the 75% VO(2max) test. The coefficients of variation of La amounted for 52.4 and 41.3% during the 60 and 75% VO(2max) test, respectively. La responses did not differ significantly between three subgroups of the subjects (N=7 with VO(2max)<55 ml min(-1)kg(-1), N=7 with VO(2max) 55-65 ml min(-1)kg(-1), and N=7 with VO(2 max)>65 ml min(-1)kg(-1); P>or=0.08).
  
  
  CONCLUSIONS
  Altogether, prolonged exercise at given percentages of VO(2max) leads to inhomogeneous metabolic strain as indicated by the large variability of La responses. This holds true even in subgroups of similar aerobic capacity. Thus, intensity prescription for endurance training and study purposes should not be solely based upon percentages of VO(2max) when a comparable metabolic strain is intended.
authors.affiliation: Institute of Sports and Preventive Medicine, University of Saarland, Saarbrücken, Germany. friederike.scharhag-rosenberger@uni-potsdam.de
authors.forename: Friederike
authors.initials: F
authors.lastname: Scharhag-Rosenberger
authors.forename: Tim
authors.initials: T
authors.lastname: Meyer
authors.forename: Nina
authors.initials: N
authors.lastname: Gässler
authors.forename: Oliver
authors.initials: O
authors.lastname: Faude
authors.forename: Wilfried
authors.initials: W
authors.lastname: Kindermann
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008448:Maximal Expiratory Flow Rate; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011897:Random Allocation; D055815:Young Adult
chemical_list: D019344:Lactic Acid