title: Caffeine attenuates early post-exercise hypotension in middle-aged subjects.
abstract: BACKGROUND
  Sustained hypotension after an acute dynamic exercise bout is due primarily to peripheral vasodilation. We tested the hypothesis that adenosine-mediated vasodilation contributes to hypotension after exercise, by determining the effect of blocking its actions with caffeine.
  
  
  METHODS
  Fourteen healthy middle-aged subjects (mean age = 51 +/- 3 years), cycled to peak effort on 2 study days, after a randomized double-blind intravenous infusion of caffeine (4 mg/kg) selective for adenosine receptor blockade, or vehicle. Both studies were performed after 72 h of caffeine abstinence.
  
  
  RESULTS
  Infusion achieved 52.0 +/- 6.1 mumol/L caffeine in plasma. Significant reductions in mean and diastolic blood pressure (BP) were elicited by prior exercise on the vehicle day (from 93 +/- 2 to 85 +/- 2 mm Hg v from 79 +/- 2 to 73 +/- 3 mm Hg, respectively; both P < .05), but not after caffeine infusion. Systolic and mean BP, 10 min after exercise, were higher on the caffeine than on the vehicle day (by 9 +/- 3 and 6 +/- 2 mm Hg, respectively; P < .05), as was heart rate (HR) (100 +/- 5 v 93 +/- 4 beats/min; P < .05).
  
  
  CONCLUSIONS
  These data suggest that endogenous adenosine contributes to early hypotension after exercise in healthy middle-aged subjects and underscore the importance of caffeine abstinence if BP or HR immediately after exercise is used to infer cardiovascular risk.
authors.affiliation: University Health Network and Mount Sinai Hospital Division of Cardiology, University of Toronto, Toronto, Ontario, Canada. c.notarius@utoronto.ca
authors.forename: Catherine F
authors.initials: CF
authors.lastname: Notarius
authors.forename: Beverley L
authors.initials: BL
authors.lastname: Morris
authors.forename: John S
authors.initials: JS
authors.lastname: Floras
mesh_terms: D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects; D002110:Caffeine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D004311:Double-Blind Method; D004837:Epinephrine / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007022:Hypotension / Q000097:blood / Q000188:drug therapy* / Q000209:etiology; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood
chemical_list: D015415:Biomarkers; D000697:Central Nervous System Stimulants; D002110:Caffeine; D009638:Norepinephrine; D004837:Epinephrine