title: Effect of caffeine on LT, VT and HRVT.
abstract: Caffeine has many diverse physiological effects including central nervous system stimulation. Ventilatory threshold and a recently described heart rate variability threshold both have a relationship with autonomic control that could be altered by caffeine consumption. The purpose of this investigation was to determine the influence of caffeine on lactate, ventilatory, and heart rate variability thresholds during progressive exercise. Using a randomized placebo controlled, double-blind study design, 10 adults performed 2 graded maximal cycle ergometry tests with and without caffeine (5 mg·kg⁻¹). Respiratory gas exchange, blood lactate concentrations, and heart rate variability data were obtained at baseline and throughout exercise.
  
  
  RESULTS
  At rest, caffeine (p<0.05) increased blood lactate, oxygen consumption, carbon dioxide production, and minute ventilation. For indices of heart rate variability at rest, caffeine increased (p<0.05) the coefficient of variation, while standard deviation, and mean successive difference displayed non-significant increases. During progressive exercise, minute ventilation volumes were higher in caffeine trials but no other parameters were significantly different compared to placebo tests.
  
  
  CONCLUSIONS
  These data demonstrate the robustness of the lactate, ventilatory and heart rate variability thresholds when challenged by a physiological dose of caffeine.
authors.affiliation: Department of Biology, Henry Ford Community College, Dearborn, USA.
authors.forename: G K
authors.initials: GK
authors.lastname: Karapetian
authors.forename: H J
authors.initials: HJ
authors.lastname: Engels
authors.forename: K A
authors.initials: KA
authors.lastname: Gretebeck
authors.forename: R J
authors.initials: RJ
authors.lastname: Gretebeck
mesh_terms: D000293:Adolescent; D000328:Adult; D015308:Anaerobic Threshold; D002110:Caffeine / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D011659:Pulmonary Gas Exchange; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D002245:Carbon Dioxide; D019344:Lactic Acid; D002110:Caffeine