title: Comparison of caffeine and theophylline ingestion: exercise metabolism and endurance.
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.
authors.affiliation: Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: F
authors.initials: F
authors.lastname: Greer
authors.forename: D
authors.initials: D
authors.lastname: Friars
authors.forename: T E
authors.initials: TE
authors.lastname: Graham
mesh_terms: D000105:Acetyl Coenzyme A / Q000032:analysis; D000255:Adenosine Triphosphate / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D002110:Caffeine / Q000008:administration & dosage*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D019343:Citric Acid / Q000032:analysis; D000242:Cyclic AMP / Q000032:analysis; D004734:Energy Metabolism / Q000187:drug effects*; D004837:Epinephrine / Q000097:blood; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005952:Glucose-6-Phosphatase / Q000032:analysis; D005990:Glycerol / Q000097:blood; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000187:drug effects*; D013806:Theophylline / Q000008:administration & dosage*; D014665:Vasodilator Agents / Q000008:administration & dosage*; D014970:Xanthines / Q000097:blood
chemical_list: D001786:Blood Glucose; D000697:Central Nervous System Stimulants; D005230:Fatty Acids, Nonesterified; D014665:Vasodilator Agents; D014970:Xanthines; C008514:methylxanthine; D019343:Citric Acid; D019344:Lactic Acid; D002110:Caffeine; D000105:Acetyl Coenzyme A; D000255:Adenosine Triphosphate; D006003:Glycogen; D013806:Theophylline; D000242:Cyclic AMP; D005952:Glucose-6-Phosphatase; D005990:Glycerol; D009638:Norepinephrine; D004837:Epinephrine