title: Biophysical Determinants of Front-Crawl Swimming at Moderate and Severe Intensities.
abstract: OBJECTIVE
  To conduct a biophysical analysis of the factors associated with front-crawl performance at moderate and severe swimming intensities, represented by anaerobic-threshold (vAnT) and maximal-oxygen-uptake (vV̇O2max) velocities.
  
  
  METHODS
  Ten high-level swimmers performed 2 intermittent incremental tests of 7 × 200 and 12 × 25 m (through a system of underwater push-off pads) to assess vAnT, and vV̇O2max, and power output. The 1st protocol was videotaped (3D reconstruction) for kinematic analysis to assess stroke frequency (SF), stroke length (SL), propelling efficiency (ηP), and index of coordination (IdC). V̇O2was measured and capillary blood samples (lactate concentrations) were collected, enabling computation of metabolic power. The 2nd protocol allowed calculating mechanical power and performance efficiency from the ratio of mechanical to metabolic power.
  
  
  RESULTS
  Neither vAnT nor vV̇O2max was explained by SF (0.56 ± 0.06 vs 0.68 ± 0.06 Hz), SL (2.29 ± 0.21 vs 2.06 ± 0.20 m), ηP(0.38 ± 0.02 vs 0.36± 0.03), IdC (-12.14 ± 5.24 vs -9.61 ± 5.49), or metabolic-power (1063.00 ± 122.90 vs 1338.18 ± 127.40 W) variability. vV̇O2max was explained by power to overcome drag (r = .77, P ≤ .05) and ηP(r = .72, P ≤ .05), in contrast with the nonassociation between these parameters and vAnT; both velocities were well related (r = .62, P ≤ .05).
  
  
  CONCLUSIONS
  The biomechanical parameters, coordination, and metabolic power seemed not to be performance discriminative at either intensity. However, the increase in power to overcome drag, for the less metabolic input, should be the focus of any intervention that aims to improve performance at severe swimming intensity. This is also true for moderate intensities, as vAnT and vV˙O2max are proportional to each other.
authors.forename: João
authors.initials: J
authors.lastname: Ribeiro
authors.forename: Argyris G
authors.initials: AG
authors.lastname: Toubekis
authors.forename: Pedro
authors.initials: P
authors.lastname: Figueiredo
authors.forename: Kelly
authors.initials: K
authors.lastname: de Jesus
authors.forename: Huub M
authors.initials: HM
authors.lastname: Toussaint
authors.forename: Francisco
authors.initials: F
authors.lastname: Alves
authors.forename: João P
authors.initials: JP
authors.lastname: Vilas-Boas
authors.forename: Ricardo J
authors.initials: RJ
authors.lastname: Fernandes
mesh_terms: D015308:Anaerobic Threshold / Q000502:physiology; D054874:Athletic Performance / Q000502:physiology; D001696:Biomechanical Phenomena; D004734:Energy Metabolism / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D012119:Respiration; D013550:Swimming / Q000502:physiology*; D013996:Time and Motion Studies; D034941:Upper Extremity / Q000502:physiology; D055815:Young Adult
chemical_list: D019344:Lactic Acid
keywords: coordination; energy expenditure; kinematics; power; propelling efficiency