¹³C labelled glucose-fructose show greater exogenous and whole-body CHO oxidation and lower O₂ cost of running at 120 vs 60 & 90 g·h⁻¹ in elite male marathoners

Ravikanti, S, Silang, KG ORCID: 0009-0009-1200-7326, Martyn, HJ, Johnson, KO ORCID: 0000-0002-7395-5129, Louis, JB ORCID: 0000-0002-9109-0958, Bampouras, TM ORCID: 0000-0002-8991-4655, Owens, DJ ORCID: 0000-0002-1908-8677, Jones, AM, Morton, JP ORCID: 0000-0003-2776-2542 and Pugh, JN ORCID: 0000-0002-5930-4709 ¹³C labelled glucose-fructose show greater exogenous and whole-body CHO oxidation and lower O₂ cost of running at 120 vs 60 & 90 g·h⁻¹ in elite male marathoners. Journal of Applied Physiology. ISSN 8750-7587 (Accepted)

Text ravikanti-et-al-2025-13c-labelled-glucose-fructose-show-greater-exogenous-and-whole-body-cho-oxidation-and-lower-o2.pdf - Accepted Version Access Restricted Download (2MB)

Abstract

We evaluated the effects of carbohydrate (CHO) ingestion at rates of 60 (maltodextrin:fructose ratio 1:0), 90 (2:1), and 120 (1:1) g·h⁻¹ on whole body substrate metabolism, exogenous CHO oxidation (via U-13 C enriched glucose-fructose drinks) and gastrointestinal (GI) symptoms in elite male marathon runners (n<=8; marathon PB, 02:22:54 ± 00:05:37). After 24 h of a high-CHO (8 g·kg-1) diet and pre-exercise meal (2 g·kg-1), participants completed 120-minute running trials comprising 15 mins at 95% lactate threshold (LT), 90 mins at 94% lactate turnpoint and a final 15 mins at 95% LT. Mean whole body CHO oxidation (120 g·h⁻1, 3.06 ± 0.19; 90 g·h⁻1, 2.46 ± 0.12; 60 g·h⁻1, 2.08 ± 0.03 g·min⁻1) and hour 2 mean exogenous CHO oxidation (120 g·h⁻1, 1.68 ± 0.16; 90 g·h⁻1, 1.31 ± 0.18; 60 g·h⁻1, 0.89 ± 0.11 g·min⁻1) were different between all trials (P<0.01 for all pairwise comparisons), such that 120 g·h⁻1 > 90 g·h⁻1 > 60 g·h⁻1. Running economy was improved in the 120 g·h⁻¹ condition, with a 2.6% lower O₂ cost compared to 60 g·h⁻¹ (P = 0.021). The incidence of moderate or severe (≥4) GI symptoms was high in all trials, though peak symptoms of nausea, stomach fullness and abdominal cramps were greatest for 120 g·h⁻1. We report for the first time that CHO ingestion at 120 g·h⁻1 confers a metabolic advantage to male marathoners by better maintaining whole-body rates of CHO oxidation, increasing exogenous CHO oxidation and improving running economy. However, gut training strategies, preceding practical application, are warranted.

Item Type:	Article
Uncontrolled Keywords:	Fructose; Maltodextrin; Marathon; Metabolism; Stable Isotopes; 06 Biological Sciences; 11 Medical and Health Sciences; Physiology; 31 Biological sciences; 32 Biomedical and clinical sciences; 42 Health sciences
Subjects:	T Technology > TX Home economics > TX341 Nutrition. Foods and food supply R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions:	Sport and Exercise Sciences
Publisher:	American Physiological Society
Date of acceptance:	28 August 2025
Date Deposited:	13 Nov 2025 10:34
Last Modified:	13 Nov 2025 10:34
DOI or ID number:	10.1152/japplphysiol.00665.2025
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27554

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