title: The Effects of Caffeine Supplementation on Physiological Responses to Submaximal Exercise in Endurance-Trained Men.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effects of caffeine on physiological responses to submaximal exercise, with a focus on blood lactate concentration ([BLa]).
  
  
  METHODS
  Using a randomised, single-blind, crossover design; 16 endurance-trained, male cyclists (age: 38 ± 8 years; height: 1.80 ± 0.05 m; body mass: 76.6 ± 7.8 kg; [Formula: see text]: 4.3 ± 0.6 L∙min-1) completed four trials on an electromagnetically-braked cycle ergometer. Each trial consisted of a six-stage incremental test (3 minute stages) followed by 30 minutes of passive recovery. One hour before trials 2-4, participants ingested a capsule containing 5 mg∙kg-1 of either caffeine or placebo (maltodextrin). Trials 2 and 3 were designed to evaluate the effects of caffeine on various physiological responses during exercise and recovery. In contrast, Trial 4 was designed to evaluate the effects of caffeine on [BLa] during passive recovery from an end-exercise concentration of 4 mmol∙L-1.
  
  
  RESULTS
  Relative to placebo, caffeine increased [BLa] during exercise, independent of exercise intensity (mean difference: 0.33 ± 0.41 mmol∙L-1; 95% likely range: 0.11 to 0.55 mmol∙L-1), but did not affect the time-course of [BLa] during recovery (p = 0.604). Caffeine reduced ratings of perceived exertion (mean difference: 0.5 ± 0.7; 95% likely range: 0.1 to 0.9) and heart rate (mean difference: 3.6 ± 4.2 b∙min-1; 95% likely range: 1.3 to 5.8 b∙min-1) during exercise, with the effect on the latter dissipating as exercise intensity increased. Supplement × exercise intensity interactions were observed for respiratory exchange ratio (p = 0.004) and minute ventilation (p = 0.034).
  
  
  CONCLUSIONS
  The results of the present study illustrate the clear, though often subtle, effects of caffeine on physiological responses to submaximal exercise. Researchers should be aware of these responses, particularly when evaluating the physiological effects of various experimental interventions.
authors.affiliation: School of Sport, Health, and Applied Sciences, St Mary's University, Strawberry Hill, Twickenham, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Glaister
authors.affiliation: School of Sport, Health, and Applied Sciences, St Mary's University, Strawberry Hill, Twickenham, United Kingdom.
authors.forename: Benjamin Henley
authors.initials: BH
authors.lastname: Williams
authors.affiliation: School of Sport, Health, and Applied Sciences, St Mary's University, Strawberry Hill, Twickenham, United Kingdom.
authors.forename: Daniel
authors.initials: D
authors.lastname: Muniz-Pumares
authors.affiliation: Department of Physical Education, Sport & Human Movement, Autonomous University of Madrid, Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Balsalobre-Fernández
authors.affiliation: Cardiff School of Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Foley
mesh_terms: D056352:Athletes; D001642:Bicycling / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D016552:Ergometry / Q000379:methods; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010465:Perception / Q000187:drug effects; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D010919:Placebos / Q000494:pharmacology; D016037:Single-Blind Method
chemical_list: D000697:Central Nervous System Stimulants; D010919:Placebos; D019344:Lactic Acid; D002110:Caffeine