Caffeine vs caffeine-free sports drinks : Effects on urine production at rest and during prolonged exercise

We compared the effects of caffeinated vs non-caffeinated carbohydrate electrolyte (CE) drinks on urine volume (UV), free water clearance (CH2O), fractional excretion of water (FEH2O), and osmolar excretion during 4 h of rest or 1 h rest followed by 3 h of cycling at 60% VO2max in six subjects. We a...

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Bibliographic Details
Published in:International journal of sports medicine 1997, Vol.18 (1), p.40-46
Main Authors: WEMPLE, R. D, LAMB, D. R, MCKEEVER, K. H
Format: Article
Language:English
Subjects:
Adult
Beverages
Biological and medical sciences
Caffeine - pharmacology
Catecholamines - blood
Creatinine - metabolism
Exercise
Female
Glomerular Filtration Rate
Heart Rate - physiology
Humans
Male
Medical sciences
Neuropharmacology
Osmolar Concentration
Pharmacology. Drug treatments
Psychoanaleptics: cns stimulant, antidepressant agent, nootropic agent, mood stabilizer..., (alzheimer disease)
Psychology. Psychoanalysis. Psychiatry
Psychopharmacology
Rest
Urine
Water - metabolism
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Summary:We compared the effects of caffeinated vs non-caffeinated carbohydrate electrolyte (CE) drinks on urine volume (UV), free water clearance (CH2O), fractional excretion of water (FEH2O), and osmolar excretion during 4 h of rest or 1 h rest followed by 3 h of cycling at 60% VO2max in six subjects. We also tested maximal performance at 85% VO2max following the 3-h exercise trials. Throughout the two resting trials and the two rest + exercise trials, subjects ingested CE (total volume = 35 ml/kg) without (PLAC) or with (CAFF) caffeine (25 mg/dl). Blood samples were collected, and body weight and UV were recorded every hour. Urine and blood were analyzed for osmolality and creatinine, and plasma catecholamine concentrations were determined. At rest, mean (+/-SE) UV between 60 min and 240 min was greater for CAFF (1843 +/- 166 ml) vs PLAC (1411 +/- 181 ml) (p < 0.01); during exercise the difference in UV between CAFF (398 +/- 32 ml) and PLAC (490 +/- 57 ml) was not significant. Cycling performance was unaffected by caffeine. Plasma catecholamine concentrations were not different between PLAC and CAFF but were greater during exercise than rest (p < 0.01) and may have counteracted the diuretic effect of caffeine observed at rest. Thus, CAFF consumed in CE during moderate endurance exercise apparently does not compromise bodily hydration status.
ISSN:0172-4622
1439-3964
DOI:10.1055/s-2007-972593