title: Effects of different interval-training programs on cycling time-trial performance.
abstract: OBJECTIVE
  We have investigated the effect of varying the intensity of interval training on 40-km time-trial performance in 20 male endurance cyclists (peak oxygen uptake 4.8+/-0.6 L x min(-1), mean +/- SD).
  
  
  METHODS
  Cyclists performed a 25-kJ sprint test, an incremental test to determine peak aerobic power (PP) and a simulated 40-km time-trial on a Kingcycle ergometer. They were then randomly assigned to one of five types of interval-training session: 12x30 s at 175% PP, 12x60 s at 100% PP, 12x2 min at 90% PP, 8x4 min at 85% PP, or 4x8 min at 80% PP. Cyclists completed 6 sessions over 3 wk, in addition to their usual aerobic base training. All laboratory tests were then repeated.
  
  
  RESULTS
  Performances in the time trial were highly reliable when controlled for training effects (coefficient of variation = 1.1%). The percent improvement in the time trial was modeled as a polynomial function of the rank order of the intensity of the training intervals, a procedure validated by simulation. The cubic trend was strong and statistically significant (overall correlation = 0.70, P = 0.005) and predicted greatest enhancement for the intervals performed at 85% PP (2.8%, 95% CI = 4.3-1.3%) and at 175% PP (2.4%, 95% CI = 4.0-0.7%). Intervals performed at 100% PP and 80% PP did not produce statistically significant enhancements of performance. Quadratic and linear trends were weak or insubstantial.
  
  
  CONCLUSIONS
  Interval training with work bouts close to race-pace enhance 1-h endurance performance; work bouts at much higher intensity also appear to improve performance, possibly by a different mechanism.
authors.affiliation: Department of Physiology, University of Cape Town Medical School, South Africa.
authors.forename: N K
authors.initials: NK
authors.lastname: Stepto
authors.forename: J A
authors.initials: JA
authors.lastname: Hawley
authors.forename: S C
authors.initials: SC
authors.lastname: Dennis
authors.forename: W G
authors.initials: WG
authors.lastname: Hopkins
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D013997:Time Factors