title: Effect of Creatine Loading on Oxygen Uptake during a 1-km Cycling Time Trial.
abstract: OBJECTIVE
  For the first time, we investigated the effects of altering cellular metabolic capacitance, via a 5-d creatine (Cr) loading protocol (20 g·d⁻¹), on oxygen uptake (VO2), accumulated oxygen deficit, muscle recruitment, and performance during a 1-km cycling time trial.
  
  
  METHODS
  In a double-blind, randomized, placebo-controlled design, 19 amateur cyclists were allocated to a Cr (n = 10, VO2peak = 56.0 ± 7.8 mL·kg⁻¹·min⁻¹) or placebo (n = 9, VO2peak = 56.0 ± 8.4 mL·kg⁻¹·min⁻¹) group, and performed a 1-km cycling time trial before and after the supplementation period.
  
  
  RESULTS
  Body mass was significantly increased in the Cr group (P < 0.05), but not in the placebo group. Participants adopted an "all-out" pacing strategy in both groups. However, Cr loading reduced VO2 immediately after the beginning (12th to 23th seconds), and this was accompanied by a reduced aerobic and increased anaerobic contribution. The VO2 mean response time was slower (pre: 17.2 ± 5.6 s vs post: 19.9 ± 4.6 s), the total O2 uptake was reduced (pre: 4.64 ± 0.59 L vs post: 4.47 ± 0.53 L), and the oxygen deficit was increased (pre: 0.82 ± 0.27 L vs post: 0.98 ± 0.25 L) after Cr loading. No differences were observed in the placebo group for these variables. Plasma lactate and integrated electromyography were not altered in either group, nor was the time to complete the trial (Cr group: pre: 89.1 ± 6.7 s vs post 89.1 ± 6.2 s and placebo group: pre 85.9 ± 4.9 s vs post 87.0 ± 5.4 s).
  
  
  CONCLUSIONS
  Cr loading slows the V˙O2 response and increases the anaerobic contribution during a 1-km cycling time trial.
authors.affiliation: 1Sports Science Research Group, Department of Physical Education and Sports Science CAV, Federal University of Pernambuco, BRAZIL; 2Endurance Performance Research Group, School of Physical Education and Sport, University of São Paulo, São Paulo, BRAZIL; 3School of Physical Education and Sport, University of São Paulo, BRAZIL; 4Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, AUSTRALIA.
authors.forename: Kleiner Marcio
authors.initials: KM
authors.lastname: De Andrade Nemezio
authors.forename: Romulo
authors.initials: R
authors.lastname: Bertuzzi
authors.forename: Carlos Rafaell
authors.initials: CR
authors.lastname: Correia-Oliveira
authors.forename: Bruno
authors.initials: B
authors.lastname: Gualano
authors.forename: David John
authors.initials: DJ
authors.lastname: Bishop
authors.forename: Adriano Eduardo
authors.initials: AE
authors.lastname: Lima-Silva
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D050218:Body Fat Distribution; D015992:Body Mass Index; D003401:Creatine / Q000008:administration & dosage*; D019587:Dietary Supplements; D004311:Double-Blind Method; D004576:Electromyography; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation / Q000502:physiology
chemical_list: D019344:Lactic Acid; D003401:Creatine