title: Does net energy cost of swimming affect time to exhaustion at the individual's maximal oxygen consumption velocity?
abstract: OBJECTIVE
  The purpose of the present study was to examine the relationship between time limit at the minimum velocity that elicits the individual's maximal oxygen consumption (TLim-v VO2max) and three swimming economy related parameters: the net energy cost corresponding to v VO2max (Cv VO2max), the slope of the regression line obtained from the energy expenditure (E) and corresponding velocities during an incremental test (C(slope)) and the ratio between the mean E value and the velocity mean value of the incremental test (C(inc)). Complementarily, we analysed the influence of Cv VO2max, C(slope) and C(inc) on TLim-v VO2max by swimming level.
  
  
  METHODS
  Thirty swimmers divided into 10 low-level (LLS) (4 male and 6 female) and 20 highly trained swimmers (HTS) (10 of each gender) performed an incremental test for v VO2max assessment and an all-out TLim-v VO2max test.
  
  
  RESULTS
  TLim-v VO2max, v VO2max, Cv fVO2max, C(slope) and C(inc) averaged, respectively, 313.8+/-63 s, 1.16+/-0.1 m x s(-1), 13.2+/-1.9 J x kg(-1) x m(-1), 28+/-3.2 J x kg(-1) x m(-1) and 10.9+/-1.8 J x kg(-1) x m(-1) in the LLS and 237.3+/-54.6 s, 1.4+/-0.1 m x s(-1), 15.6+/-2.2 J x kg(-1) x m(-1), 36.8+/-4.5 J x kg(-1) x m(-1) and 13+/-2.3 J x kg(-1) x m(-1) in the HTS. TLim-v VO2max was inversely related to C(slope) (r = -0.77, P < 0.001), and to v VO2max (r = -0.35, P = 0.05), although no relationships with the Cv VO2max and the C(inc) were observed.
  
  
  CONCLUSIONS
  The findings of this study confirmed exercise economy as an important factor for swimming performance. The data demonstrated that the swimmers with higher and v VO2max performed shorter time in TLim-v VO2max efforts.
authors.affiliation: Faculty of Sport Sciences and Physical Education, Swimming Department, University of Porto, Porto, Portugal. ricfer@fcdef.up.pt
authors.forename: R J
authors.initials: RJ
authors.lastname: Fernandes
authors.forename: V L
authors.initials: VL
authors.lastname: Billat
authors.forename: A C
authors.initials: AC
authors.lastname: Cruz
authors.forename: P J
authors.initials: PJ
authors.lastname: Colaço
authors.forename: C S
authors.initials: CS
authors.lastname: Cardoso
authors.forename: J P
authors.initials: JP
authors.lastname: Vilas-Boas
mesh_terms: D000293:Adolescent; D000328:Adult; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D010806:Physical Education and Training; D010807:Physical Endurance / Q000502:physiology*; D012044:Regression Analysis; D013550:Swimming