{"id":{"repo_id":"birmingham","oai_identifier":"oai:etheses.bham.ac.uk:1091"},"canonical_url":"https://search.dev.ndltd.org/etd/birmingham/oai:etheses.bham.ac.uk:1091","repository":{"repo_id":"birmingham","name":"University of Birmingham","base_url":"https://etheses.bham.ac.uk/cgi/oai2"},"display":{"title":"Carbohydrate intake and metabolism during prolonged endurance exercise","abstract":"It is well accepted that CHO ingestion can improve endurance performance. However, a number of questions remain open regarding fine-tuning CHO intake recommendations during prolonged endurance events. A way to measure the bioavailability of ingested CHO is to measure exogenous CHO oxidation with the use of \\(^{13}\\)C or \\(^{14}\\)C tracers. This, however, has been studied only with CHO solutions, predominantly during cycling. In this thesis, we demonstrated that glucose+fructose ingested in the form of gel (1.8 g/min) is as effectively oxidized as an isocarbohydrate solution (1.44±0.29 g/min vs 1.42±0.23 g/min, respectively). Accordingly, the ingestion of glucose+fructose in a solid bar (1.55 g CHO/min) was demonstrated to be oxidized at high rates (1.25±0.15 g/min), comparable to a solution (1.34±0.27 g/min). A comparison of CHO ingestion (1.5 g/min) during cycling and running at the same relative, moderate-intensity (~60% exercise-specific VO\\(_2\\)max) resulted in similar exogenous CHO oxidation rates (1.25±0.10 g/min vs 1.19±0.08 g/min, respectively). The present thesis also tested the gastrointestinal (GI) tolerance of high CHO ingestion rates (1.4 g CHO/min), previously recommended to athletes. High intakes in the form of a glucose+fructose gel were, on average, well tolerated during a 16-km run, and there was no difference between tolerance of glucose and glucose+fructose gel. A questionnaire-based field study of 221 athletes during prolonged endurance events (running, cycling and triathlon) revealed that voluntary CHO intake rates vary greatly between events and individuals (6-136 g/h). High CHO intakes were related to increased scores for nausea and flatulence as well as to better performance. GI distress during all studies was correlated with a reported history of GI distress. Findings from those studies suggest a need for more individualized nutritional advice that optimizes CHO and fluid delivery to enhance performance, while minimizing GI discomfort","abstract_html":"It is well accepted that CHO ingestion can improve endurance performance. However, a number of questions remain open regarding fine-tuning CHO intake recommendations during prolonged endurance events. A way to measure the bioavailability of ingested CHO is to measure exogenous CHO oxidation with the use of <span class=\"etd-inline-math\"><sup>13</sup></span>C or <span class=\"etd-inline-math\"><sup>14</sup></span>C tracers. This, however, has been studied only with CHO solutions, predominantly during cycling. In this thesis, we demonstrated that glucose+fructose ingested in the form of gel (1.8 g/min) is as effectively oxidized as an isocarbohydrate solution (1.44±0.29 g/min vs 1.42±0.23 g/min, respectively). Accordingly, the ingestion of glucose+fructose in a solid bar (1.55 g CHO/min) was demonstrated to be oxidized at high rates (1.25±0.15 g/min), comparable to a solution (1.34±0.27 g/min). A comparison of CHO ingestion (1.5 g/min) during cycling and running at the same relative, moderate-intensity (~60% exercise-specific VO<span class=\"etd-inline-math\"><sub>2</sub></span>max) resulted in similar exogenous CHO oxidation rates (1.25±0.10 g/min vs 1.19±0.08 g/min, respectively). The present thesis also tested the gastrointestinal (GI) tolerance of high CHO ingestion rates (1.4 g CHO/min), previously recommended to athletes. High intakes in the form of a glucose+fructose gel were, on average, well tolerated during a 16-km run, and there was no difference between tolerance of glucose and glucose+fructose gel. A questionnaire-based field study of 221 athletes during prolonged endurance events (running, cycling and triathlon) revealed that voluntary CHO intake rates vary greatly between events and individuals (6-136 g/h). High CHO intakes were related to increased scores for nausea and flatulence as well as to better performance. GI distress during all studies was correlated with a reported history of GI distress. Findings from those studies suggest a need for more individualized nutritional advice that optimizes CHO and fluid delivery to enhance performance, while minimizing GI discomfort","abstract_has_math":true,"creators":["Pfeiffer, Beate"],"institution":"University of Birmingham","degree_name":"d_ph","degree_level":"d_ph","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2010,"date_issued":"2010-12","date_published":"2010-12","updated_at":"2026-07-24T01:11:23Z","subjects":["QP Physiology"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.sponsor","label":"Sponsor","values":["na"]},{"key":"dc:creator","label":"Author","values":["Pfeiffer, Beate"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2010-12"]},{"key":"dc:date.issued","label":"Date","values":["2010-12"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["College of Life & Environmental Sciences","School of Sport, Exercise and Rehabilitation Sciences"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Birmingham"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["http://etheses.bham.ac.uk//id/eprint/1091/"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["d_ph"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["d_ph"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["QP Physiology"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://etheses.bham.ac.uk//id/eprint/1091/1/Pfeiffer10PhD.pdf","http://etheses.bham.ac.uk//id/eprint/1091/2/Decl_IS_Pfeiffer10PhD.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["It is well accepted that CHO ingestion can improve endurance performance. However, a number of questions remain open regarding fine-tuning CHO intake recommendations during prolonged endurance events. A way to measure the bioavailability of ingested CHO is to measure exogenous CHO oxidation with the use of \\(^{13}\\)C or \\(^{14}\\)C tracers. This, however, has been studied only with CHO solutions, predominantly during cycling. In this thesis, we demonstrated that glucose+fructose ingested in the form of gel (1.8 g/min) is as effectively oxidized as an isocarbohydrate solution (1.44±0.29 g/min vs 1.42±0.23 g/min, respectively). Accordingly, the ingestion of glucose+fructose in a solid bar (1.55 g CHO/min) was demonstrated to be oxidized at high rates (1.25±0.15 g/min), comparable to a solution (1.34±0.27 g/min). A comparison of CHO ingestion (1.5 g/min) during cycling and running at the same relative, moderate-intensity (~60% exercise-specific VO\\(_2\\)max) resulted in similar exogenous CHO oxidation rates (1.25±0.10 g/min vs 1.19±0.08 g/min, respectively). The present thesis also tested the gastrointestinal (GI) tolerance of high CHO ingestion rates (1.4 g CHO/min), previously recommended to athletes. High intakes in the form of a glucose+fructose gel were, on average, well tolerated during a 16-km run, and there was no difference between tolerance of glucose and glucose+fructose gel. A questionnaire-based field study of 221 athletes during prolonged endurance events (running, cycling and triathlon) revealed that voluntary CHO intake rates vary greatly between events and individuals (6-136 g/h). High CHO intakes were related to increased scores for nausea and flatulence as well as to better performance. GI distress during all studies was correlated with a reported history of GI distress. Findings from those studies suggest a need for more individualized nutritional advice that optimizes CHO and fluid delivery to enhance performance, while minimizing GI discomfort"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Carbohydrate intake and metabolism during prolonged endurance exercise"]}]}],"canonical_facts":{"dc:contributor.sponsor":["na"],"dc:creator":["Pfeiffer, Beate"],"dc:date":["2010-12"],"dc:date.issued":["2010-12"],"dc:description.abstract":["It is well accepted that CHO ingestion can improve endurance performance. However, a number of questions remain open regarding fine-tuning CHO intake recommendations during prolonged endurance events. A way to measure the bioavailability of ingested CHO is to measure exogenous CHO oxidation with the use of \\(^{13}\\)C or \\(^{14}\\)C tracers. This, however, has been studied only with CHO solutions, predominantly during cycling. In this thesis, we demonstrated that glucose+fructose ingested in the form of gel (1.8 g/min) is as effectively oxidized as an isocarbohydrate solution (1.44±0.29 g/min vs 1.42±0.23 g/min, respectively). Accordingly, the ingestion of glucose+fructose in a solid bar (1.55 g CHO/min) was demonstrated to be oxidized at high rates (1.25±0.15 g/min), comparable to a solution (1.34±0.27 g/min). A comparison of CHO ingestion (1.5 g/min) during cycling and running at the same relative, moderate-intensity (~60% exercise-specific VO\\(_2\\)max) resulted in similar exogenous CHO oxidation rates (1.25±0.10 g/min vs 1.19±0.08 g/min, respectively). The present thesis also tested the gastrointestinal (GI) tolerance of high CHO ingestion rates (1.4 g CHO/min), previously recommended to athletes. High intakes in the form of a glucose+fructose gel were, on average, well tolerated during a 16-km run, and there was no difference between tolerance of glucose and glucose+fructose gel. A questionnaire-based field study of 221 athletes during prolonged endurance events (running, cycling and triathlon) revealed that voluntary CHO intake rates vary greatly between events and individuals (6-136 g/h). High CHO intakes were related to increased scores for nausea and flatulence as well as to better performance. GI distress during all studies was correlated with a reported history of GI distress. Findings from those studies suggest a need for more individualized nutritional advice that optimizes CHO and fluid delivery to enhance performance, while minimizing GI discomfort"],"dc:format":["application/pdf"],"dc:identifier.uri":["http://etheses.bham.ac.uk//id/eprint/1091/1/Pfeiffer10PhD.pdf","http://etheses.bham.ac.uk//id/eprint/1091/2/Decl_IS_Pfeiffer10PhD.pdf"],"dc:publisher.department":["College of Life & Environmental Sciences","School of Sport, Exercise and Rehabilitation Sciences"],"dc:publisher.institution":["University of Birmingham"],"dc:relation.isreferencedby":["http://etheses.bham.ac.uk//id/eprint/1091/"],"dc:subject":["QP Physiology"],"dc:title":["Carbohydrate intake and metabolism during prolonged endurance exercise"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["d_ph"],"dc:type.qualificationname":["d_ph"]},"updated_at":"2026-07-24T01:11:23Z"}