title: Physiological effects of constant versus variable power during endurance cycling.
abstract: OBJECTIVE
  Previous theoretical research found that varying power slightly to counter external conditions may result in improved performance during cycling time trialing, but it is not known whether such power variations result in added physiological stress. Thus, the purpose of this study was to determine whether variable power (VP) cycling produced greater physiological stress than constant power (CP) cycling of the same mean intensity.
  
  
  METHODS
  Eight trained male cyclists (age 28 +/- 2 yr, mass 74.4 +/- 2.3 kg, VO2max 4.24 +/- 0.13 L x min(-1), weekly training 277 +/- 44 km) performed three 1-h ergometer trials. The first trial was performed at a self-paced maximal effort. The mean power from that trial was used to determine the power for the CP trial (constant effort at mean power) and the VP trial (alternating +/- 5% of mean power every 5 min).
  
  
  RESULTS
  No differences were found between the CP and VP trials in mean VO2 (CP 3.33 +/- 0.11 L x min(-1), VP 3.26 +/- 0.12 L x min(-1)), mean heart rate (CP 158 +/- 3 min(-1), VP 159 +/- 3 min(-1)), mean blood lactate concentration (CP 4.2 +/- 0.7 mM, VP 4.3 +/- 0.7 mM), or mean RPE (CP 13.9 +/- 0.4, VP 14.1 +/- 0.4).
  
  
  CONCLUSIONS
  Therefore, during a strenuous 1-h effort (78% of VO2max), subjects experienced no additional physiological stress by varying power +/- 5% compared with that during a constant power effort.
authors.affiliation: Wellness Institute and Research Center, Old Dominion University, Norfolk, VA 23529-0196, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Liedl
authors.forename: D P
authors.initials: DP
authors.lastname: Swain
authors.forename: J D
authors.initials: JD
authors.lastname: Branch
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*
chemical_list: D019344:Lactic Acid