{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,29]],"date-time":"2026-10-29T17:35:11Z","timestamp":1793295311791,"version":"4.5.0"},"reference-count":48,"publisher":"Human Kinetics","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026]]},"abstract":"<jats:p>\n                    <jats:bold>\n                      <jats:italic>Purpose<\/jats:italic>\n                    <\/jats:bold>\n                    <jats:italic>:<\/jats:italic>\n                    Although caffeine-induced increases in fat oxidation are well established under laboratory conditions, evidence during field-based exercise is limited. Therefore, this study aimed to examine the acute effects of 3\u00a0mg\u00b7kg\n                    <jats:sup>\u22121<\/jats:sup>\n                    of caffeine on fat oxidation during a 1-hour field-based outdoor run performed at the individual intensity eliciting maximal fat oxidation (Fatmax).\n                    <jats:bold>\n                      <jats:italic>Methods<\/jats:italic>\n                    <\/jats:bold>\n                    <jats:italic>:<\/jats:italic>\n                    Fourteen healthy, endurance-trained runners (11 men, 3 women;\n                    <jats:inline-formula\/>\n                    \u2009=\u200958.6 [6.3]\u00a0mL\u00b7kg\n                    <jats:sup>\u22121<\/jats:sup>\n                    \u00b7min\n                    <jats:sup>\u22121<\/jats:sup>\n                    ) participated in a randomized, double-blind, placebo-controlled, crossover experiment. Participants completed 1 preexperimental trial to determine\n                    <jats:inline-formula\/>\n                    and Fatmax, followed by 2 experimental trials. During the experimental trials, participants ingested either caffeine (3\u00a0mg\u00b7kg\n                    <jats:sup>\u22121<\/jats:sup>\n                    ) or a placebo 60 minutes before a 1-hour run at their individual Fatmax intensity covered on a 1.97-km outdoor running course. Substrate oxidation rates and energy expenditure were measured via indirect calorimetry using a portable gas analyzer and calculated through stoichiometric equations while heart rate was continuously monitored and ratings of perceived exertion were recorded using the Borg scale.\n                    <jats:bold>\n                      <jats:italic>Results<\/jats:italic>\n                    <\/jats:bold>\n                    <jats:italic>:<\/jats:italic>\n                    Caffeine significantly increased total fat oxidation during the 1-hour run (33.62 [9.23] vs 40.46 [11.32]\u00a0g;\n                    <jats:italic>P<\/jats:italic>\n                    \u2009=\u2009.018;\n                    <jats:italic>d<\/jats:italic>\n                    \u2009=\u20090.76) and decreased carbohydrate oxidation (93.16 [37.84] vs 77.32 [30.35]\u00a0g;\n                    <jats:italic>P<\/jats:italic>\n                    \u2009=\u2009.036;\n                    <jats:italic>d<\/jats:italic>\n                    \u2009=\u20090.66) compared with placebo, with no effect on total energy expenditure (\n                    <jats:italic>P<\/jats:italic>\n                    \u2009=\u2009.936). Caffeine also reduced the rating of perceived exertion (9 [2] vs 8 [2];\n                    <jats:italic>P<\/jats:italic>\n                    \u2009=\u2009.024;\n                    <jats:italic>d<\/jats:italic>\n                    \u2009=\u20090.75) with no effect on heart rate (\n                    <jats:italic>P<\/jats:italic>\n                    \u2009=\u2009.140).\n                    <jats:bold>\n                      <jats:italic>Conclusion<\/jats:italic>\n                    <\/jats:bold>\n                    <jats:italic>:<\/jats:italic>\n                    Acute ingestion of 3\u00a0mg\u00b7kg\n                    <jats:sup>\u22121<\/jats:sup>\n                    of caffeine enhances fat oxidation during 1 hour of running at Fatmax under field-based conditions, suggesting that caffeine may be an effective nutritional strategy to optimize fat utilization during real-world submaximal endurance exercise.\n                  <\/jats:p>","DOI":"10.1123\/ijspp.2026-0194","type":"journal-article","created":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T01:44:31Z","timestamp":1788313471000},"page":"1-10","source":"Crossref","is-referenced-by-count":0,"title":["Caffeine Shifts Substrate Utilization Toward Fat During Outdoor Running at Fatmax: A Randomized Field-Based Crossover Study"],"prefix":"10.1123","author":[{"given":"Iv\u00e1n","family":"Villalba","sequence":"first","affiliation":[{"name":"Sport Sciences Research Center, Rey Juan Carlos University, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-3734-032X","authenticated-orcid":true,"given":"V\u00edctor","family":"Solano-Lizcano","sequence":"additional","affiliation":[{"name":"Sport Sciences Research Center, Rey Juan Carlos University, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-0104-3430","authenticated-orcid":true,"given":"Adri\u00e1n","family":"Rodr\u00edguez-Casta\u00f1o","sequence":"additional","affiliation":[{"name":"Sport Sciences Research Center, Rey Juan Carlos University, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-8357-3643","authenticated-orcid":true,"given":"Christel","family":"Garc\u00eda-Ortiz","sequence":"additional","affiliation":[{"name":"Sport Sciences Research Center, Rey Juan Carlos University, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1319-3334","authenticated-orcid":true,"given":"Luis E.","family":"Ranieri","sequence":"additional","affiliation":[{"name":"Sport Sciences Research Center, Rey Juan Carlos University, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7668-6844","authenticated-orcid":true,"given":"Arturo","family":"Casado","sequence":"additional","affiliation":[{"name":"Sport Sciences Research Center, Rey Juan Carlos University, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5785-984X","authenticated-orcid":true,"given":"Juan","family":"Del Coso","sequence":"additional","affiliation":[{"name":"Sport Sciences Research Center, Rey Juan Carlos University, Madrid, Spain"},{"name":"Faculty of Health Sciences, Institute of Health and Sport Sciences, Universidad Francisco de Vitoria, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-6383-5787","authenticated-orcid":true,"given":"Daniel","family":"Trujillo-Colmena","sequence":"additional","affiliation":[{"name":"Sport Sciences Research Center, Rey Juan Carlos University, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"100","reference":[{"issue":"1","key":"r1","series-title":"J Int Soc Sports Nutr","doi-asserted-by":"publisher","first-page":"383","DOI":"10.1186\/s12970-020-00383-4","article-title":"International Society of Sports Nutrition position stand: caffeine and exercise performance","volume":"18","author":"Guest NS","year":"2021","unstructured":"Guest NS, VanDusseldorp TA, Nelson MT, et\u00a0al. 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