title: Caffeine is ergogenic after supplementation of oral creatine monohydrate.
abstract: OBJECTIVE
  The purpose of this investigation was to assess the acute effects of caffeine ingestion on short-term, high-intensity exercise (ST) after a period of oral creatine supplementation and caffeine abstinence.
  
  
  METHODS
  Fourteen trained male subjects performed treadmill running to volitional exhaustion (T(lim)) at an exercise intensity equivalent to 125% VO(2max). Three trials were performed, one before 6 d of creatine loading (0.3 g x kg x d(-1) baseline), and two further trials after the loading period. One hour before the postloading trials, caffeine (5 mg x kg(-1)) or placebo was orally ingested in a cross-over, double-blind fashion. Four measurements of rating of perceived exertion were taken, one every 30 s, during the first 120 s of the exercise. Blood samples were assayed for lactate, glucose, potassium, and catecholamines, immediately before and after exercise.
  
  
  RESULTS
  Body mass increased (P < 0.05) over the creatine supplementation period, and this increase was maintained for both caffeine and placebo trials. There was no increase in the maximal accumulated oxygen deficit between trials; however, total VO(2) was significantly increased in the caffeine trial in comparison with the placebo trial (13.35 +/- 3.89 L vs 11.67 +/- 3.61 L). In addition, caffeine T(lim) (222.1 +/- 48.9 s) was significantly greater (P < 0.05) than both baseline (200.8 +/- 33.4 s) and placebo (198.3 +/- 45.4 s) T(lim). RPE was also lower at 90 s in the caffeine treatment (13.8 +/- 1.8 RPE points) in comparison with baseline (14.6 +/- 1.9 RPE points).
  
  
  CONCLUSIONS
  As indicated by a greater T(lim), acute caffeine ingestion was found to be ergogenic after 6-d of creatine supplementation and caffeine abstinence.
authors.affiliation: Department of Sport, Exercise and Biomedical Sciences, University of Luton, United Kingdom. mike.doherty@luton.ac.uk
authors.forename: Mike
authors.initials: M
authors.lastname: Doherty
authors.forename: Paul M
authors.initials: PM
authors.lastname: Smith
authors.forename: R C Richard
authors.initials: RC
authors.lastname: Davison
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hughes
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold / Q000187:drug effects / Q000502:physiology; D000704:Analysis of Variance; D001774:Blood Chemical Analysis; D001784:Blood Gas Analysis; D002110:Caffeine / Q000008:administration & dosage*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage; D003401:Creatine / Q000008:administration & dosage*; D019587:Dietary Supplements; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D010807:Physical Endurance / Q000187:drug effects; D005082:Physical Exertion / Q000187:drug effects* / Q000502:physiology; D011336:Probability; D012016:Reference Values; D012420:Running / Q000502:physiology*; D012680:Sensitivity and Specificity
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine; D003401:Creatine