Comparison of caffeine and theophylline ingestion: exercise metabolism and endurance.

F Greer, D Friars, T E Graham

Journal: Journal of applied physiology (Bethesda, Md. : 1985) 2001;89(5):1837-44

PMID: 11053334

Abstract

This two-part investigation compared the ergogenic and metabolic effects of theophylline and caffeine. Initially (part A), the ergogenic potential of theophylline on endurance exercise was investigated. Eight men cycled at 80% maximum O(2) consumption to exhaustion 90 min after ingesting either placebo (dextrose), caffeine (6 mg/kg; Caff), or theophylline (4.5 mg/kg Theolair; Theo). There was a significant increase in time to exhaustion in both the Caff (41.2+/-4.8 min) and Theo (37.4+/-5.0 min) trials compared with placebo (32.6+/-3.4 min) (P<0.05). In part B, the effects of Theo on muscle metabolism were investigated and compared with Caff. Seven men cycled for 45 min at 70% maximum O(2) consumption (identical treatment protocol as in part A). Neither methylxanthines (MX) affected muscle glycogen utilization (P>0.05). Only Caff increased plasma epinephrine (P<0.05), but both MX increased blood glycerol levels (P<0.05). Muscle cAMP was increased (P<0.05) by both MX at 15 min and remained elevated at 45 min with Theo. This demonstrates that both MX are ergogenic and that this can be independent of muscle glycogen.

Address: Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.

DOI: 10.1152/jappl.2000.89.5.1837

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MeSH Terms: Acetyl Coenzyme A, Adenosine Triphosphate, Blood Glucose, Caffeine, Central Nervous System Stimulants, Citric Acid, Cyclic AMP, Energy Metabolism, Epinephrine, Fatty Acids, Nonesterified, Glucose-6-Phosphatase, Glycerol, Glycogen, Humans, Lactic Acid, Male, Muscle, Skeletal, Norepinephrine, Oxygen Consumption, Physical Endurance, Theophylline, Vasodilator Agents, Xanthines