{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T23:30:49Z","timestamp":1783467049694,"version":"3.55.0"},"reference-count":38,"publisher":"American Physiological Society","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2000,11,1]]},"abstract":"<jats:p>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<jats:sub>2<\/jats:sub>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 \u00b1 4.8 min) and Theo (37.4 \u00b1 5.0 min) trials compared with placebo (32.6 \u00b1 3.4 min) ( P &lt; 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<jats:sub>2<\/jats:sub>consumption (identical treatment protocol as in part A). Neither methylxanthines (MX) affected muscle glycogen utilization ( P &gt; 0.05). Only Caff increased plasma epinephrine ( P &lt; 0.05), but both MX increased blood glycerol levels ( P &lt; 0.05). Muscle cAMP was increased ( P &lt; 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.<\/jats:p>","DOI":"10.1152\/jappl.2000.89.5.1837","type":"journal-article","created":{"date-parts":[[2017,12,23]],"date-time":"2017-12-23T03:03:06Z","timestamp":1513998186000},"page":"1837-1844","source":"Crossref","is-referenced-by-count":100,"title":["Comparison of caffeine and theophylline ingestion: exercise metabolism and endurance"],"prefix":"10.1152","volume":"89","author":[{"given":"F.","family":"Greer","sequence":"first","affiliation":[{"name":"Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"D.","family":"Friars","sequence":"additional","affiliation":[{"name":"Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"T. 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