Document Detail


Effects of caffeine on muscle glycogen utilization and the neuroendocrine axis during exercise.
MedLine Citation:
PMID:  10852448     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
To examine the effect of caffeine ingestion on muscle glycogen utilization and the neuroendocrine axis during exercise, we studied 20 muscle glycogen-loaded subjects who were given placebo or caffeine (6 mg/kg) in a double blinded fashion 90 min before cycling for 2 h at 65% of their maximal oxygen consumption. Exercise-induced glycogen depletion in the thigh muscle was noninvasively measured by means of 13C nuclear magnetic resonance spectroscopy (NMR) spectroscopy, and plasma concentrations of substrates and neuroendocrine hormones, including beta-endorphins, were also assessed. Muscle glycogen content was increased 140% above normal values on the caffeine trial day (P < 0.001). After cycling for 2 h, caffeine ingestion was associated with a greater increase in plasma lactate (caffeine: +1.0 +/- 0.2 mmol/L; placebo, +0.1 +/- 0.2 mmol/L; P < 0.005), epinephrine (caffeine, +223 +/- 82 pg/mL; placebo, +56 +/- 26 pg/mL; P < 0.05), and cortisol (caffeine, +12 +/- 3 mg/mL; placebo, +2 +/- 2 mg/mL; P < 0.001) levels. However, plasma free fatty acid concentrations increased (caffeine, +814 +/- 133 mmol/L; placebo, +785 +/- 85 mmol/L; P = NS), and muscle glycogen content decreased (caffeine, -57 +/- 6 mmol/L muscle; placebo, -53 +/- 5 mmol/L muscle; P = NS) to the same extent in both groups. At the same time, plasma beta-endorphin levels almost doubled (from 30 +/- 5 to 53 +/- 13 pg/mL; P < 0.05) in the caffeine-treated group, whereas no change occurred in the placebo group. We conclude that caffeine ingestion 90 min before prolonged exercise does not exert a muscle glycogen-sparing effect in athletes with high muscle glycogen content. However, these data suggest that caffeine lowers the threshold for exercise-induced beta-endorphin and cortisol release, which may contribute to the reported benefits of caffeine on exercise endurance.
Authors:
D Laurent; K E Schneider; W K Prusaczyk; C Franklin; S M Vogel; M Krssak; K F Petersen; H W Goforth; G I Shulman
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Publication Detail:
Type:  Clinical Trial; Controlled Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of clinical endocrinology and metabolism     Volume:  85     ISSN:  0021-972X     ISO Abbreviation:  J. Clin. Endocrinol. Metab.     Publication Date:  2000 Jun 
Date Detail:
Created Date:  2000-06-23     Completed Date:  2000-06-23     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0375362     Medline TA:  J Clin Endocrinol Metab     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2170-5     Citation Subset:  AIM; IM; S    
Affiliation:
Department of Internal Medicine and the Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
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MeSH Terms
Descriptor/Qualifier:
Adult
Caffeine / pharmacology*
Epinephrine / blood
Exercise / physiology*
Exercise Test
Fatty Acids, Nonesterified / blood
Glycogen / metabolism*
Humans
Hydrocortisone / blood
Lactates / blood
Magnetic Resonance Spectroscopy
Male
Muscle Fatigue / drug effects,  physiology
Muscle, Skeletal / drug effects,  physiology*
Neurosecretory Systems / drug effects,  physiology*
Oxygen Consumption
Running
beta-Endorphin / blood
Grant Support
ID/Acronym/Agency:
MO1-RR-00125/RR/NCRR NIH HHS; P30-DK-45735/DK/NIDDK NIH HHS; R01-DK-49230/DK/NIDDK NIH HHS
Chemical
Reg. No./Substance:
0/Fatty Acids, Nonesterified; 0/Lactates; 50-23-7/Hydrocortisone; 51-43-4/Epinephrine; 58-08-2/Caffeine; 60617-12-1/beta-Endorphin; 9005-79-2/Glycogen
Comments/Corrections
Comment In:
J Clin Endocrinol Metab. 2000 Jun;85(6):2167-9   [PMID:  10852447 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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