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Cited by 108Muscle metabolism and nutritionCardiovascular and exercise physiologySports Performance and Training

Effect of training status on fuel selection during submaximal exercise with glucose ingestion

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van Loon, Luc J. C., Jeukendrup, Asker E., Saris, Wim H. M., Wagenmakers, Anton J. M.·1999·Journal of Applied Physiology
DOI 10.1152/jappl.1999.87.4.1413
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Abstract

In this study, an oral glucose load was enriched with a [U-(13)C]glucose tracer to determine differences in substrate utilization between endurance-trained (T) and untrained (UT) subjects during submaximal exercise at the same relative and absolute workload when glucose is ingested. Six highly trained cyclists/triathletes [maximal workload (Wmax), 400 +/- 9 W] and seven UT subjects (Wmax, 296 +/- 8 W) were studied during 120 min of cycling exercise at 50% Wmax ( approximately 55% maximal O(2) consumption). The T subjects performed a second trial at the mean workload of the UT group (148 +/- 4 W). Before exercise, 8.0 ml/kg of a (13)C-enriched glucose solution (80 g/l) was ingested. During exercise, boluses of 2.0 ml/kg of the same solution were administered every 15 min. Measurements were made in the 90- to 120-min period when a steady state was present in breath (13)CO(2) and plasma glucose (13)C enrichment. Energy expenditure was higher in T than in UT subjects (58 vs. 47 kJ/min, respectively; P < 0.001) at the same relative intensity. This was completely accounted for by an increased fat oxidation (0.57 vs. 0.40 g/min; P < 0.01). At the same absolute intensity, fat oxidation contributed more to energy expenditure in the T compared with the UT group (44 vs. 33%, respectively; P < 0.01). The reduction in carbohydrate oxidation in the T group was explained by a diminished oxidation rate of muscle glycogen (indirectly assessed by using tracer methodology at 0.72 +/- 0.1 and 1.03 +/- 0.1 g/min, respectively; P < 0.01) and liver-derived glucose (0.15 +/- 0.03 and 0.22 +/- 0.02 g/min, respectively; P < 0.05). Exogenous glucose oxidation rates were similar during all trials (+/-0.70 g/min).

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Authors
van Loon, L. J. C., Jeukendrup, A. E., Saris, W. H. M., & Wagenmakers, A. J. M.
Affiliations
  • Department of Human Biology, Maastricht University, 6200 MD Maastricht, The Netherlands
  • Maastricht University (NL)
ORCID
Venue
Journal of Applied Physiology
Publisher
American Physiological Society
Published
1999-10-01
Volume
87
Issue
4
Pages
1413-1420
ISSN
  • 0161-7567 (ISSN-L)
  • 8750-7587
  • 1522-1601
DOI
10.1152/jappl.1999.87.4.1413
OpenAlex
W2161826939
Cited by
108
References
37
Citations by year
2025: 2 · 2024: 3 · 2023: 3 · 2022: 7 · 2021: 6 · 2020: 3 · 2019: 4 · 2018: 11 · 2017: 4 · 2016: 4 · 2015: 5 · 2014: 3 · 2013: 5 · 2012: 4
FWCI
0.82
Type
journal article
Language
en
Open access
Licence
other-oa
Locations
  • Journal of Applied Physiology (publishedVersion)
  • PubMed (publishedVersion)
  • Research Publications (Maastricht University) (publishedVersion, other-oa)
  • Research Publications (Maastricht University) (submittedVersion, other-oa)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
  • Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
  • Health Sciences › Medicine › Orthopedics and Sports Medicine › Sports Performance and Training
Keywords
endurance training, fuel selection, substrate utilization, submaximal exercise, glucose ingestion, fat oxidation, carbohydrate oxidation, muscle glycogen, energy expenditure, 13C-glucose tracer
MeSH terms
Adult, Bicycling, Dietary Carbohydrates, Dietary Fats, Energy Metabolism, Glucose, Humans, Oxidation-Reduction, Physical Education and Training, Reference Values, Exercise, Carbohydrate Metabolism

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