Effect of caffeinated drinks on substrate metabolism, caffeine excretion, and performance

• Published in: Journal of applied physiology (1985) Vol. 85; no. 2; pp. 709 - 715
• Main Authors: Kovacs, Eva M. R, Stegen, Jos H. C. H, Brouns, Fred
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01-08-1998; American Physiological Society
• Subjects: Adult; Anatomy & physiology; Beverages; Biological and medical sciences; Blood Volume - drug effects; Blood Volume - physiology; Caffeine; Caffeine - pharmacokinetics; Caffeine - pharmacology; Central Nervous System Stimulants - pharmacokinetics; Central Nervous System Stimulants - pharmacology; Dietary Carbohydrates - metabolism; Exercise; Exercise Test; Fatty Acids, Nonesterified - blood; Humans; Male; Medical sciences; Metabolism; Neuropharmacology; Oxygen Consumption - drug effects; Oxygen Consumption - physiology; Pharmacology. Drug treatments; Psychoanaleptics: cns stimulant, antidepressant agent, nootropic agent, mood stabilizer..., (alzheimer disease); Psychology. Psychoanalysis. Psychiatry; Psychopharmacology; Sweat - metabolism; Sweating - physiology; Physical exercise; Human; Excretion; CNS stimulant; Physical performance; Stimulative beverage; Doping; Xanthine derivatives; Metabolism; Caffeine; Dose activity relation
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1998.85.2.709

1  Department of Human Biology
and 2  Novartis Nutrition Research
Unit, Maastricht University, The Netherlands
The effect of
addition of different dosages of caffeine (Caf) to a
carbohydrate-electrolyte solution (CES) on metabolism, Caf excretion,
and performance was examined. Subjects
( n  = 15) ingested 8 ml/kg of water
placebo (Pla-W), 7% CES (Pla-CES), or 7% CES with 150, 225, and 320 mg/l Caf (CES-150, CES-225, and CES-320, respectively) during a warm-up
protocol (20 min) and 3 ml/kg at one-third and two-thirds of a 1-h time
trial. Performance was improved with Caf supplementation: 62.5 ± 1.3, 61.5 ± 1.1, 60.4 ± 1.0, 58.9 ± 1.0, and 58.9 ± 1.2 min for Pla-W, Pla-CES, CES-150, CES-225, and CES-320, respectively.
The postexercise urinary Caf concentration (range 1.3-2.5 µg/ml)
was dose dependent and always far below the doping level of the
International Olympic Committee (12 µg/ml) in all subjects. Sweat Caf
excretion during exercise exceeded postexercise early-void urinary Caf
excretion. Caffeinated CES did not enhance free fatty acid
availability, ruling out the fact that performance improvement resulted
from enhanced fat oxidation. It is concluded that addition of
relatively low amounts of Caf to CES improves performance and that
postexercise urinary Caf concentration remained low.
caffeine; exercise; dose-response; doping