{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T22:02:22Z","timestamp":1781128942328,"version":"3.54.1"},"reference-count":60,"publisher":"Human Kinetics","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2025,9,1]]},"abstract":"\n The ergogenic effects of caffeine for endurance performance at sea level are well established. However, whether caffeine enhances exercise capacity or modulates cardiorespiratory responses in hypoxia remains unclear. Twenty-nine healthy, active volunteers (14 women) completed four tests in a pseudorandomized order, comprising 10\u00a0min of steady-state cycling (40% normoxic maximal aerobic power) followed by incremental exercise tests to exhaustion. Participants consumed 6\u00a0mg\/kg body mass anhydrous caffeine, or placebo, 45\u00a0min before exercise. Tests were performed while breathing room air or a hypoxic gas mixture (simulating \u223c3,500\u00a0m). At peak exercise intensity, oxygen uptake was affected by condition (hypoxia vs. normoxia; 44.8\u2009\u00b1\u20097.3 vs. 51.4\u2009\u00b1\u20097.9\u00a0ml\u00b7kg\n \u22121<\/jats:sup>\n \u00b7min\n \u22121<\/jats:sup>\n ;\n p<\/jats:italic>\n \u2009<\u2009.001) but not supplement (caffeine vs. placebo; 48.2\u2009\u00b1\u20098.2 vs. 48.0\u2009\u00b1\u20098.4\u00a0ml\u00b7kg\n \u22121<\/jats:sup>\n \u00b7min\n \u22121<\/jats:sup>\n ;\n p<\/jats:italic>\n \u2009=\u2009.501). Maximal aerobic power and pulse oxygen saturation were lower in hypoxia (both\n p<\/jats:italic>\n \u2009<\u2009.001), but unaffected by caffeine (\n p<\/jats:italic>\n \u2009=\u2009.061 and .898, respectively). Pulmonary ventilation was unaffected by hypoxia (\n p<\/jats:italic>\n \u2009=\u2009.154) or caffeine (\n p<\/jats:italic>\n \u2009=\u2009.117). Heart rate was higher in normoxia and with caffeine (both\n p<\/jats:italic>\n \u2009<\u2009.001). During steady-state cycling, hypoxia (\n p<\/jats:italic>\n \u2009<\u2009.001) and caffeine (\n p<\/jats:italic>\n \u2009=\u2009.026) increased pulmonary ventilation. However, the hypoxia-induced pulse oxygen saturation decrease (\n p<\/jats:italic>\n \u2009<\u2009.001) was not attenuated with caffeine (interaction\n p<\/jats:italic>\n \u2009=\u2009.283). Perceived exertion was higher in hypoxia (\n p<\/jats:italic>\n \u2009<\u2009.001) and lower with caffeine (\n p<\/jats:italic>\n \u2009=\u2009.026). Caffeine increased\n vastus lateralis<\/jats:italic>\n oxygenation in hypoxia (caffeine vs. placebo; 52\u2009\u00b1\u20098 vs. 50\u2009\u00b1\u200910%;\n p<\/jats:italic>\n \u2009=\u2009.020) but not in normoxia (caffeine vs. placebo; 59\u2009\u00b1\u20097 vs. 59\u2009\u00b1\u20098%;\n p<\/jats:italic>\n \u2009>\u2009.999). Overall, caffeine did not enhance exercise capacity in either environmental condition. However, during steady-state cycling, caffeine enhanced pulmonary ventilation, reduced perceived exertion, and mitigated hypoxia-induced muscle oxygenation reductions.\n <\/jats:p>","DOI":"10.1123\/ijsnem.2025-0024","type":"journal-article","created":{"date-parts":[[2025,7,16]],"date-time":"2025-07-16T17:53:39Z","timestamp":1752688419000},"page":"385-393","source":"Crossref","is-referenced-by-count":0,"title":["The Acute Effects of Caffeine and Normobaric Hypoxia on Cardiorespiratory Exercise Responses in Healthy Adults: A Randomized Controlled Trial"],"prefix":"10.1123","volume":"35","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7812-5626","authenticated-orcid":true,"given":"Benjamin Jonathan","family":"Narang","sequence":"first","affiliation":[{"name":"Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia"},{"name":"Department of Automatics, Biocybernetics and Robotics, Jo\u017eef Stefan Institute, Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ana","family":"\u0160tritof","sequence":"additional","affiliation":[{"name":"Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7053-3978","authenticated-orcid":true,"given":"Tadej","family":"Debevec","sequence":"additional","affiliation":[{"name":"Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia"},{"name":"Department of Automatics, Biocybernetics and Robotics, Jo\u017eef Stefan Institute, Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"100","reference":[{"issue":"12","key":"r1","series-title":"Medicine & Science in Sports & Exercise,","doi-asserted-by":"publisher","first-page":"2159","DOI":"10.1249\/01.mss.0000233805.56315.a9","article-title":"Placebo effects of caffeine on cycling performance","volume":"38","author":"Beedie, C.J.","year":"2006","unstructured":"Beedie, C.J., Stuart, E.M., Coleman, D.A., & Foad, A.J. 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