{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T18:30:57Z","timestamp":1790793057131,"version":"4.1.0"},"reference-count":86,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2022,1,4]],"date-time":"2022-01-04T00:00:00Z","timestamp":1641254400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Physiol."],"abstract":"<jats:p>Using metadata from previously published research, this investigation sought to explore: (1) whole-body total carbohydrate and fat oxidation rates of endurance (e.g., half and full marathon) and ultra-endurance runners during an incremental exercise test to volitional exhaustion and steady-state exercise while consuming a mixed macronutrient diet and consuming carbohydrate during steady-state running and (2) feeding tolerance and glucose availability while consuming different carbohydrate regimes during steady-state running. Competitively trained male endurance and ultra-endurance runners (<jats:italic>n<\/jats:italic>\u2009=\u200928) consuming a balanced macronutrient diet (57\u2009\u00b1\u20096% carbohydrate, 21\u2009\u00b1\u200916% protein, and 22\u2009\u00b1\u20099% fat) performed an incremental exercise test to exhaustion and one of three 3\u2009h steady-state running protocols involving a carbohydrate feeding regime (76\u201390\u2009g\/h). Indirect calorimetry was used to determine maximum fat oxidation (MFO) in the incremental exercise and carbohydrate and fat oxidation rates during steady-state running. Gastrointestinal symptoms (GIS), breath hydrogen (H<jats:sub>2<\/jats:sub>), and blood glucose responses were measured throughout the steady-state running protocols. Despite high variability between participants, high rates of MFO [mean (range): 0.66 (0.22\u20131.89) g\/min], Fat<jats:sub>max<\/jats:sub> [63 (40\u201394) % <jats:italic>V\u0307<\/jats:italic>O<jats:sub>2max<\/jats:sub>], and Fat<jats:sub>min<\/jats:sub> [94 (77\u2013100) % <jats:italic>V\u0307<\/jats:italic>O<jats:sub>2max<\/jats:sub>] were observed in the majority of participants in response to the incremental exercise test to volitional exhaustion. Whole-body total fat oxidation rate was 0.8\u2009\u00b1\u20090.3\u2009g\/min at the end of steady-state exercise, with 43% of participants presenting rates of \u22651.0\u2009g\/min, despite the state of hyperglycemia above resting homeostatic range [mean (95%CI): 6.9 (6.7\u20137.2) mmol\/L]. In response to the carbohydrate feeding interventions of 90\u2009g\/h 2:1 glucose\u2013fructose formulation, 38% of participants showed breath H<jats:sub>2<\/jats:sub> responses indicative of carbohydrate malabsorption. Greater gastrointestinal symptom severity and feeding intolerance was observed with higher carbohydrate intakes (90 vs. 76\u2009g\/h) during steady-state exercise and was greatest when high exercise intensity was performed (i.e., performance test). Endurance and ultra-endurance runners can attain relatively high rates of whole-body fat oxidation during exercise in a post-prandial state and with carbohydrate provisions during exercise, despite consuming a mixed macronutrient diet. Higher carbohydrate intake during exercise may lead to greater gastrointestinal symptom severity and feeding intolerance.<\/jats:p>","DOI":"10.3389\/fphys.2021.773054","type":"journal-article","created":{"date-parts":[[2022,1,4]],"date-time":"2022-01-04T06:47:04Z","timestamp":1641278824000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":25,"title":["Feeding Tolerance, Glucose Availability, and Whole-Body Total Carbohydrate and Fat Oxidation in Male Endurance and Ultra-Endurance Runners in Response to Prolonged Exercise, Consuming a Habitual Mixed Macronutrient Diet and Carbohydrate Feeding During Exercise"],"prefix":"10.3389","volume":"12","author":[{"given":"Christopher E.","family":"Rauch","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alan J.","family":"McCubbin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stephanie K.","family":"Gaskell","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ricardo J. S.","family":"Costa","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2022,1,4]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"92","DOI":"10.1097\/00005768-200201000-00015","article-title":"Determination of the exercise intensity that elicits maximal fat oxidation","volume":"34","author":"Achten","year":"","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref2","doi-asserted-by":"publisher","first-page":"1017","DOI":"10.1080\/02640410310001641403","article-title":"The effect of pre-exercise carbohydrate feedings on the intensity that elicits maximal fat oxidation","volume":"21","author":"Achten","year":"2003","journal-title":"J. Sports Sci."},{"key":"ref3","doi-asserted-by":"publisher","first-page":"747","DOI":"10.1016\/s0026-0495(03)00068-4","article-title":"Fat oxidation rates are higher during running compared with cycling over a wide range of intensities","volume":"52","author":"Achten","year":"","journal-title":"Metabolism"},{"key":"ref4","doi-asserted-by":"publisher","first-page":"508","DOI":"10.1016\/j.wem.2018.06.004","article-title":"CASE STUDY. Nutritional support for self-sufficient multi-stage ultra-marathon: rationed versus full energy provisions","volume":"29","author":"Alcock","year":"2018","journal-title":"Wilderness Environ. Med."},{"key":"ref5","doi-asserted-by":"publisher","first-page":"2091","DOI":"10.1007\/s40279-018-0941-1","article-title":"Skeletal muscle glycogen content at rest and during endurance exercise in humans: a meta-analysis","volume":"48","author":"Areta","year":"2018","journal-title":"Sports Med."},{"key":"ref6","doi-asserted-by":"publisher","first-page":"318","DOI":"10.1097\/MEG.0b013e32832b20e8","article-title":"Benefits of breath hydrogen testing after lactulose administration in analysing carbohydrate malabsorption","volume":"22","author":"Bate","year":"2010","journal-title":"Eur. J. Gastroenterol. Hepatol."},{"key":"ref7","doi-asserted-by":"publisher","first-page":"479","DOI":"10.1152\/jappl.1999.86.2.479","article-title":"Respiratory gas-exchange ratios during graded exercise in fed and fasted trained and untrained men","volume":"86","author":"Bergman","year":"1999","journal-title":"J. Appl. Physiol."},{"key":"ref8","doi-asserted-by":"publisher","first-page":"154041","DOI":"10.1016\/j.metabol.2019.154041","article-title":"Serum endotoxin, gut permeability and skeletal muscle metabolic adaptations following a short term high fat diet in humans","volume":"103","author":"Bowser","year":"2020","journal-title":"Metabolism"},{"key":"ref85","doi-asserted-by":"publisher","first-page":"377","DOI":"10.1249\/00005768-198205000-00012","article-title":"Psychophysical bases of perceived exertion","volume":"14","author":"Borg","year":"1982","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref9","doi-asserted-by":"publisher","first-page":"73","DOI":"10.1123\/ijsnem.2019-0065","article-title":"International association of athletics federations consensus statement 2019: nutrition for athletics","volume":"29","author":"Burke","year":"2019","journal-title":"Int. J. Sport Nutr. Exerc. Metab."},{"key":"ref10","doi-asserted-by":"publisher","first-page":"451","DOI":"10.1123\/ijsnem.2018-0289","article-title":"Toward a common understanding of diet-exercise strategies to manipulate fuel availability for training and competition preparation in endurance sport","volume":"28","author":"Burke","year":"2018","journal-title":"Int. J. Sport Nutr. Exerc. Metab."},{"key":"ref11","doi-asserted-by":"publisher","first-page":"2785","DOI":"10.1113\/JP273230","article-title":"Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers","volume":"595","author":"Burke","year":"2017","journal-title":"J. Physiol."},{"key":"ref12","doi-asserted-by":"publisher","first-page":"e0234027","DOI":"10.1371\/journal.pone.0238342","article-title":"Crisis of confidence averted: impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible","volume":"15","author":"Burke","year":"2020","journal-title":"PLoS One"},{"key":"ref13","doi-asserted-by":"publisher","first-page":"771","DOI":"10.1113\/JP280221","article-title":"Adaptation to a low carbohydrate high fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability","volume":"599","author":"Burke","year":"2021","journal-title":"J. Physiol."},{"key":"ref14","doi-asserted-by":"publisher","first-page":"115","DOI":"10.1152\/jappl.2001.91.1.115","article-title":"Effects of fat adaptation and carbohydrate restoration on prolonged endurance exercise","volume":"91","author":"Carey","year":"2001","journal-title":"J. Appl. Physiol."},{"key":"ref15","doi-asserted-by":"publisher","first-page":"1281","DOI":"10.1152\/japplphysiol.01032.2018","article-title":"The impact of exercise-induced hypohydration on intestinal integrity, function, symptoms, and systemic endotoxin and inflammatory responses","volume":"126","author":"Costa","year":"","journal-title":"J. Appl. Physiol."},{"key":"ref16","doi-asserted-by":"publisher","first-page":"237","DOI":"10.1123\/ijsnem.2019-0349","article-title":"The impact of a dairy milk recovery beverage on bacterially-stimulated neutrophil function and gastrointestinal tolerance in response to hypohydration inducing exercise stress","volume":"30","author":"Costa","year":"","journal-title":"Int. J. Sport Nutr. Exerc. Metab."},{"key":"ref17","doi-asserted-by":"publisher","first-page":"58","DOI":"10.1080\/23328940.2019.1597676","article-title":"Exertional-heat stress-associated gastrointestinal perturbations during Olympic sports: management strategies for athletes preparing and competing in the 2020 Tokyo Olympic games","volume":"7","author":"Costa","year":"","journal-title":"Temperature"},{"key":"ref18","doi-asserted-by":"publisher","first-page":"428","DOI":"10.1017\/S0007114514000907","article-title":"Perturbed energy balance and hydration status in ultra-endurance runners during a 24 h ultra-marathon","volume":"112","author":"Costa","year":"2014","journal-title":"Br. J. Nutr."},{"key":"ref19","doi-asserted-by":"publisher","first-page":"166","DOI":"10.1080\/15438627.2018.1502188","article-title":"Considerations for ultra-endurance activities: part 1 - nutrition","volume":"27","author":"Costa","year":"2018","journal-title":"Res. Sports Med."},{"key":"ref20","doi-asserted-by":"publisher","first-page":"130","DOI":"10.1123\/ijsnem.2018-0255","article-title":"Nutrition for ultramarathon running: trail, track, and road (IAAF statement)","volume":"29","author":"Costa","year":"","journal-title":"Int. J. Sport Nutr. Exerc. Metab."},{"key":"ref21","doi-asserted-by":"publisher","first-page":"547","DOI":"10.1139\/apnm-2016-0453","article-title":"Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance","volume":"42","author":"Costa","year":"","journal-title":"Appl. Physiol. Nutr. Metab."},{"key":"ref22","doi-asserted-by":"publisher","first-page":"366","DOI":"10.1123\/ijsnem.19.4.366","article-title":"Influence of timing of postexercise carbohydrate-protein ingestion on selected immune indices","volume":"19","author":"Costa","year":"2009","journal-title":"Int. J. Sport Nutr. Exerc. Metab."},{"key":"ref23","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1186\/s40798-015-0041-9","article-title":"The impact of gastrointestinal symptoms and dermatological injuries on nutritional intake and hydration status during ultramarathon events","volume":"2","author":"Costa","year":"2016","journal-title":"Sports Med."},{"key":"ref24","doi-asserted-by":"publisher","first-page":"246","DOI":"10.1111\/apt.14157","article-title":"Systematic review: exercise-induced gastrointestinal syndrome\u2014implication for health and disease","volume":"46","author":"Costa","year":"","journal-title":"Aliment. Pharmacol. Ther."},{"key":"ref25","doi-asserted-by":"publisher","first-page":"51","DOI":"10.5923\/j.sports.20130302.03","article-title":"Compromised energy and nutritional intake of ultra-endurance runners during a multi-stage ultra-marathon conducted in a hot ambient environment","volume":"3","author":"Costa","year":"2013","journal-title":"Int. J. Sports Sci."},{"key":"ref26","doi-asserted-by":"publisher","first-page":"834","DOI":"10.1152\/jappl.1971.31.6.834","article-title":"Muscle glycogen utilisation during prolonged exercise on successive days","volume":"31","author":"Costill","year":"1971","journal-title":"J. Appl. Physiol."},{"key":"ref27","doi-asserted-by":"publisher","first-page":"126","DOI":"10.1152\/japplphysiol.00950.2009","article-title":"Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling","volume":"109","author":"Cox","year":"2010","journal-title":"J. Appl. Physiol."},{"key":"ref28","first-page":"E268","article-title":"Fatty acid oxidation is directly regulated by carbohydrate metabolism during exercise","volume":"273","author":"Coyle","year":"1997","journal-title":"Am. J. Phys."},{"key":"ref29","doi-asserted-by":"publisher","first-page":"110","DOI":"10.1249\/JES.0000000000000224","article-title":"Exercise and GLUT4","volume":"48","author":"Flores-Opazo","year":"2020","journal-title":"Exerc. Sport Sci. Rev."},{"key":"ref30","doi-asserted-by":"publisher","first-page":"1056","DOI":"10.1249\/MSS.0000000000002546","article-title":"Diurnal versus nocturnal exercise-impact on the gastrointestinal tract","volume":"53","author":"Gaskell","year":"","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref31","first-page":"36","article-title":"Gastrointestinal assessment and management procedures for exercise-associated gastrointestinal symptoms","volume":"10","author":"Gaskell","year":"","journal-title":"Aspetar Sports Med. J."},{"key":"ref32","doi-asserted-by":"publisher","first-page":"719142","DOI":"10.3389\/fphys.2021.719142","article-title":"Gastrointestinal assessment and therateutic intervention for the management of exercise-associated gastrointestinal symptoms: a case series translational and professional practice approach","volume":"12","author":"Gaskell","year":"","journal-title":"Front. Physiol."},{"key":"ref33","doi-asserted-by":"publisher","first-page":"411","DOI":"10.1123\/ijsnem.2018-0215","article-title":"Test re-test reliability of a modified visual analogue scale assessment tool for determining incidence and severity of gastrointestinal symptom in response to exercise stress","volume":"29","author":"Gaskell","year":"2019","journal-title":"Int. J. Sport Nutr. Exerc. Metab."},{"key":"ref34","doi-asserted-by":"publisher","first-page":"569","DOI":"10.1139\/apnm-2019-0187","article-title":"Impact of 24-h high and low fermentable oligo-, di-, monosaccharide, and polyol diets on markers of exercise-induced gastrointestinal syndrome in response to exertional heat stress","volume":"45","author":"Gaskell","year":"2020","journal-title":"Appl. Physiol. Nutr. Metab."},{"key":"ref35","doi-asserted-by":"publisher","first-page":"37","DOI":"10.1186\/s12970-021-00435-3","article-title":"Performance effects of periodized carbohydrate restriction in endurance trained athletes - a systematic review and meta-analysis","volume":"18","author":"Gejl","year":"2021","journal-title":"J. Int. Soc. Sports Nutr."},{"key":"ref36","doi-asserted-by":"publisher","first-page":"379","DOI":"10.1055\/s-0031-1271763","article-title":"Maximal fat oxidation rate and cross-over point with respect to lactate thresholds do not have good agreement","volume":"32","author":"Gonz\u00e1lez-Haro","year":"2011","journal-title":"Int. J. Sports Med."},{"key":"ref37","doi-asserted-by":"publisher","first-page":"817","DOI":"10.1038\/s42255-020-0251-4","article-title":"Skeletal muscle energy metabolism during exercise","volume":"2","author":"Hargreaves","year":"2020","journal-title":"Nat. Metab."},{"key":"ref38","doi-asserted-by":"publisher","first-page":"194","DOI":"10.1152\/japplphysiol.00813.2005","article-title":"Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance","volume":"100","author":"Havemann","year":"2006","journal-title":"J. Appl. Physiol."},{"key":"ref39","doi-asserted-by":"publisher","first-page":"1031","DOI":"10.1007\/s40279-018-0867-7","article-title":"Fuel for the work required: a theoretical framework for carbohydrate periodization and the glycogen threshold hypothesis","volume":"48","author":"Impey","year":"2018","journal-title":"Sports Med."},{"key":"ref40","doi-asserted-by":"publisher","first-page":"1551","DOI":"10.1249\/01.mss.0000139796.07843.1d","article-title":"High oxidation rates from combined carbohydrates ingested during exercise","volume":"36","author":"Jentjens","year":"","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref41","doi-asserted-by":"publisher","first-page":"485","DOI":"10.1079\/BJN20041368","article-title":"High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise","volume":"93","author":"Jentjens","year":"2005","journal-title":"Br. J. Nutr."},{"key":"ref42","doi-asserted-by":"publisher","first-page":"1277","DOI":"10.1152\/japplphysiol.00974.2003","article-title":"Oxidation of combined ingestion of glucose and fructose during exercise","volume":"96","author":"Jentjens","year":"","journal-title":"J. Appl. Physiol."},{"key":"ref43","doi-asserted-by":"publisher","first-page":"807","DOI":"10.1152\/japplphysiol.00322.2005","article-title":"Exogenous carbohydrate oxidation rates are elevated after combined ingestion of glucose and fructose during exercise in the heat","volume":"100","author":"Jentjens","year":"2006","journal-title":"J. Appl. Physiol."},{"key":"ref44","doi-asserted-by":"publisher","first-page":"452","DOI":"10.1097\/MCO.0b013e328339de9f","article-title":"Carbohydrate and exercise performance: the role of multiple transportable carbohydrates","volume":"13","author":"Jeukendrup","year":"2010","journal-title":"Curr. Opin. Clin. Nutr. Metab. Care"},{"key":"ref45","doi-asserted-by":"publisher","first-page":"S25","DOI":"10.1007\/s40279-014-0148-z","article-title":"A step towards personalized sports nutrition: carbohydrate intake during exercise","volume":"44","author":"Jeukendrup","year":"2014","journal-title":"Sports Med."},{"key":"ref46","doi-asserted-by":"publisher","first-page":"S101","DOI":"10.1007\/s40279-017-0690-6","article-title":"Training the gut for athletes","volume":"47","author":"Jeukendrup","year":"2017","journal-title":"Sports Med."},{"key":"ref47","doi-asserted-by":"publisher","first-page":"407","DOI":"10.2165\/00007256-200029060-00004","article-title":"Oxidation of carbohydrate feedings during prolonged exercise: current thoughts, guidelines and directions for future research","volume":"29","author":"Jeukendrup","year":"2000","journal-title":"Sports Med."},{"key":"ref48","doi-asserted-by":"publisher","first-page":"1134","DOI":"10.1152\/japplphysiol.00981.2004","article-title":"Exogenous carbohydrate oxidation during ultraendurance exercise","volume":"100","author":"Jeukendrup","year":"2006","journal-title":"J. Appl. Physiol."},{"key":"ref49","doi-asserted-by":"publisher","first-page":"209","DOI":"10.1123\/ijsnem.11.2.209","volume":"11","author":"Lambert","year":"2001","journal-title":"Int. J. Sport Nutr. Exerc. Metab."},{"key":"ref50","doi-asserted-by":"crossref","first-page":"G196","DOI":"10.1152\/ajpgi.1990.258.2.G196","article-title":"Human pancreatic secretion and intestinal motility: effects of ileal nutrient perfusion","volume":"258","author":"Layer","year":"1990","journal-title":"Am. J. Physiol. Gastrointest. Liver Physiol."},{"key":"ref51","doi-asserted-by":"publisher","first-page":"1255","DOI":"10.1007\/s00421-021-04609-4","article-title":"Exogenous carbohydrate and regulation of muscle carbohydrate utilisation during exercise","volume":"121","author":"Malone","year":"2021","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref52","doi-asserted-by":"publisher","first-page":"15075","DOI":"10.1073\/pnas.0706678104","article-title":"T1R3 and gustducin in gut sense sugars to regulate expression of Na+-glucose cotransporter 1","volume":"104","author":"Margolskee","year":"2007","journal-title":"Proc. Natl. Acad. Sci."},{"key":"ref53","doi-asserted-by":"publisher","first-page":"663","DOI":"10.1249\/MSS.0000000000000823","article-title":"Enhanced endurance performance by periodization of carbohydrate intake: \"sleep low\" strategy","volume":"48","author":"Marquet","year":"","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref54","doi-asserted-by":"publisher","first-page":"755","DOI":"10.3390\/nu8120755","article-title":"Periodization of carbohydrate intake: short-term effect on performance","volume":"8","author":"Marquet","year":"","journal-title":"Nutrients"},{"key":"ref55","doi-asserted-by":"publisher","first-page":"25","DOI":"10.1123\/ijsnem.2019-0090","article-title":"Hydrogel carbohydrate-electrolyte beverage does not improve glucose availability, substrate oxidation, gastrointestinal symptoms or exercise performance, compared with a concentration and nutrient-matched placebo","volume":"30","author":"McCubbin","year":"2020","journal-title":"Int. J. Sport Nutr. Exerc. Metab."},{"key":"ref56","doi-asserted-by":"publisher","first-page":"395","DOI":"10.1111\/j.1440-1681.2006.04362.x","article-title":"Exercise and skeletal muscle glucose transporter 4 expression: molecular mechanisms","volume":"33","author":"McGee","year":"2006","journal-title":"Clin. Exp. Pharmacol. Physiol."},{"key":"ref57","doi-asserted-by":"publisher","first-page":"630","DOI":"10.1111\/sms.12912","article-title":"Two weeks of repetitive gut-challenge reduces exercise associated gastrointestinal symptoms and malabsorption","volume":"28","author":"Miall","year":"2018","journal-title":"Scand. J. Med. Sci. Sports"},{"key":"ref58","doi-asserted-by":"publisher","first-page":"594150","DOI":"10.3389\/fimmu.2020.594150","article-title":"Role of metabolic endotoxemia in systemic inflammation and potential interventions","volume":"11","author":"Mohammad","year":"2021","journal-title":"Front. Immunol."},{"key":"ref59","doi-asserted-by":"crossref","first-page":"882","DOI":"10.1152\/jappl.1991.70.2.882","article-title":"Exercise metabolism at different time intervals after a meal","volume":"70","author":"Montain","year":"1991","journal-title":"J. Appl. Physiol."},{"key":"ref60","first-page":"23","article-title":"Table of nonprotein respiratory quotient: an update","volume":"16","author":"P\u00e9ronnet","year":"1991","journal-title":"Can. J. Sport Sci."},{"key":"ref61","doi-asserted-by":"publisher","first-page":"344","DOI":"10.1249\/MSS.0b013e31822dc809","article-title":"Nutritional intake and gastrointestinal problems during competitive endurance events","volume":"44","author":"Pfeiffer","year":"2012","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref62","doi-asserted-by":"publisher","first-page":"769","DOI":"10.1016\/0026-0495(83)90106-3","article-title":"The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation","volume":"32","author":"Phinney","year":"1983","journal-title":"Metabolism"},{"key":"ref63","doi-asserted-by":"publisher","first-page":"G171","DOI":"10.1152\/ajpgi.00073.2006","article-title":"Taste receptors in the gastrointestinal tract. I. Bitter taste receptors and alpha-gustducin in the mammalian gut","volume":"291","author":"Rozengurt","year":"2006","journal-title":"Am. J. Physiol. Gastrointest. Liver Physiol."},{"key":"ref64","doi-asserted-by":"publisher","first-page":"628863","DOI":"10.3389\/fphys.2021.628863","article-title":"Assessing overall exercise recovery processes using carbohydrate and carbohydrate-protein containing recovery beverages","volume":"12","author":"Russo","year":"","journal-title":"Front. Physiol."},{"key":"ref65","doi-asserted-by":"publisher","DOI":"10.1123\/ijspp.2020-0847","article-title":"The effects of an acute \u2018train-low\u2019 nutritional protocol on markers of recovery optimisation in endurance trained male athletes","author":"Russo","year":"","journal-title":"Int. J. Sports Physiol."},{"key":"ref66","doi-asserted-by":"publisher","first-page":"467","DOI":"10.1007\/s40279-017-0751-x","article-title":"Assessment of metabolic flexibility by means of measuring blood lactate, fat, and carbohydrate oxidation responses to exercise in professional endurance athletes and less-fit individuals","volume":"48","author":"San-Millan","year":"2018","journal-title":"Sports Med."},{"key":"ref67","doi-asserted-by":"publisher","first-page":"275","DOI":"10.1055\/a-1096-0980","article-title":"Defining off-road running: a position statement from the ultra sports science foundation","volume":"41","author":"Scheer","year":"2020","journal-title":"Int. J. Sports Med."},{"key":"ref68","doi-asserted-by":"publisher","first-page":"280","DOI":"10.1055\/s-0033-1349106","article-title":"Limited benefit of Fatmax-test to derive training prescriptions","volume":"35","author":"Schwindling","year":"2014","journal-title":"Int. J. Sports Med."},{"key":"ref69","doi-asserted-by":"publisher","first-page":"27","DOI":"10.1093\/ajcn\/57.1.27","article-title":"Dietary carbohydrate, muscle glycogen, and exercise performance during 7 d of training","volume":"57","author":"Sherman","year":"1993","journal-title":"Am. J. Clin. Nutr."},{"key":"ref70","doi-asserted-by":"publisher","first-page":"114","DOI":"10.1016\/j.physbeh.2013.07.008","article-title":"Lipids: can all macronutrients put a \u2018brake\u2019 on eating?","volume":"120","author":"Shin","year":"2013","journal-title":"Physiol. Behav."},{"key":"ref71","doi-asserted-by":"publisher","first-page":"185","DOI":"10.1017\/S0029665111000103","article-title":"Glucose sensing and signalling; regulation of intestinal glucose transport","volume":"70","author":"Shirazi-Beechey","year":"2011","journal-title":"Proc. Nutr. Soc."},{"key":"ref72","doi-asserted-by":"publisher","first-page":"771","DOI":"10.1016\/j.jsams.2017.12.014","article-title":"Does the temperature of water ingested during exertional-heat stress influence gastrointestinal injury, symptoms, and systemic inflammatory profile?","volume":"21","author":"Snipe","year":"2018","journal-title":"J. Sci. Med. Sport"},{"key":"ref73","doi-asserted-by":"publisher","first-page":"1283","DOI":"10.1139\/apnm-2017-0361","article-title":"Carbohydrate and protein intake during exertional-heat stress ameliorates intestinal epithelial injury and small intestine permeability","volume":"42","author":"Snipe","year":"2017","journal-title":"Appl. Physiol. Nutr. Metab."},{"key":"ref74","doi-asserted-by":"publisher","first-page":"389","DOI":"10.1007\/s00421-017-3781-z","article-title":"The impact of exertional-heat stress on gastrointestinal integrity, gastrointestinal symptoms, systemic endotoxin and cytokine profile","volume":"118","author":"Snipe","year":"","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref75","doi-asserted-by":"publisher","first-page":"255","DOI":"10.1055\/s-0043-122742","article-title":"Mild heat stress during prolonged running results in exacerbated intestinal epithelial injury and gastrointestinal symptoms","volume":"39","author":"Snipe","year":"","journal-title":"Int. J. Sports Med."},{"key":"ref76","doi-asserted-by":"publisher","first-page":"998","DOI":"10.1139\/apnm-2014-0027","article-title":"Systematic review: carbohydrate supplementation in exercise performance or capacity of varying durations","volume":"39","author":"Stellingwerff","year":"2014","journal-title":"Appl. Physiol. Nutr. Metab."},{"key":"ref77","doi-asserted-by":"publisher","first-page":"E380","DOI":"10.1152\/ajpendo.00268.2005","article-title":"Decreased PDH activation and glycogenolysis during exercise following fat adaptation with carbohydrate restoration","volume":"290","author":"Stellingwerff","year":"2006","journal-title":"Am. J. Physiol. Endocrinol. Metab."},{"key":"ref78","doi-asserted-by":"publisher","first-page":"497","DOI":"10.1007\/s00421-006-0290-x","article-title":"Maximal fat oxidation rates in endurance trained and untrained women","volume":"98","author":"Stisen","year":"2006","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref86","doi-asserted-by":"publisher","first-page":"543","DOI":"10.1249\/MSS.0000000000000852","article-title":"American college of sports medicine joint position statement. Nutrition and athletic performance","volume":"48","author":"Thomas","year":"2016","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref79","doi-asserted-by":"publisher","first-page":"235","DOI":"10.1038\/ijo.2014.112","article-title":"Ileal brake activation: macronutrient-specific effects on eating behavior?","volume":"39","author":"van Avesaat","year":"2015","journal-title":"Int. J. Obes."},{"key":"ref80","doi-asserted-by":"publisher","first-page":"367","DOI":"10.1007\/s11894-006-0021-9","article-title":"Ileal brake: neuropeptidergic control of intestinal transit","volume":"8","author":"Van Citters","year":"2006","journal-title":"Curr. Gastroenterol. Rep."},{"key":"ref81","doi-asserted-by":"publisher","first-page":"1367","DOI":"10.3390\/nu12051367","article-title":"Effects of 120 g\/h of carbohydrates intake during a mountain marathon on exercise-induced muscle damage in elite runners","volume":"12","author":"Viribay","year":"2020","journal-title":"Nutrients"},{"key":"ref82","doi-asserted-by":"publisher","first-page":"100","DOI":"10.1016\/j.metabol.2015.10.028","article-title":"Metabolic characteristics of keto-adapted ultra-endurance runners","volume":"65","author":"Volek","year":"2016","journal-title":"Metabolism"},{"key":"ref83","doi-asserted-by":"publisher","first-page":"4389","DOI":"10.1113\/JP271934","article-title":"Gluconeogenesis during endurance exercise in cyclists habituated to a long-term low carbohydrate high-fat diet","volume":"594","author":"Webster","year":"2016","journal-title":"J. Physiol."},{"key":"ref84","doi-asserted-by":"publisher","first-page":"510","DOI":"10.1123\/ijsnem.16.5.510","article-title":"A low glycemic index meal before exercise improves endurance running capacity in men","volume":"16","author":"Wu","year":"2006","journal-title":"Int. J. Sport Nutr. Exerc. Metab."}],"container-title":["Frontiers in Physiology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fphys.2021.773054\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,1,4]],"date-time":"2022-01-04T06:47:11Z","timestamp":1641278831000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fphys.2021.773054\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,1,4]]},"references-count":86,"alternative-id":["10.3389\/fphys.2021.773054"],"URL":"https:\/\/doi.org\/10.3389\/fphys.2021.773054","relation":{},"ISSN":["1664-042X"],"issn-type":[{"value":"1664-042X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,1,4]]},"article-number":"773054"}}