Fuel use during exercise at altitude in women with glucose–fructose ingestion

O'Hara, J. P. et al. (2019) Fuel use during exercise at altitude in women with glucose–fructose ingestion. Medicine and Science in Sports and Exercise, 51(12), pp. 2586-2594. (doi: 10.1249/MSS.0000000000002072) (PMID:31206498)

Abstract

Purpose: This study compared the co-ingestion of glucose and fructose on exogenous and endogenous substrate oxidation during prolonged exercise at terrestrial high altitude (HA) versus sea level, in women. Method Five women completed two bouts of cycling at the same relative workload (55% Wmax) for 120 minutes on acute exposure to HA (3375m) and at sea level (~113m). In each trial, participants ingested 1.2 g.min-1 of glucose (enriched with 13C glucose) and 0.6 g.min-1 of fructose (enriched with 13C fructose) before and every 15 minutes during exercise. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total and exogenous carbohydrate oxidation, plasma glucose oxidation and endogenous glucose oxidation derived from liver and muscle glycogen. Results The rates and absolute contribution of exogenous carbohydrate oxidation was significantly lower at HA compared with sea level (ES>0.99, P<0.024), with the relative exogenous carbohydrate contribution approaching significance (32.6±6.1 vs. 36.0±6.1%, ES=0.56, P=0.059) during the second hour of exercise. In comparison, no significant differences were observed between HA and sea level for the relative and absolute contributions of liver glucose (3.2±1.2 vs. 3.1±0.8%, ES=0.09, P=0.635 and 5.1±1.8 vs. 5.4±1.7 grams, ES=0.19, P=0.217), and muscle glycogen (14.4±12.2% vs. 15.8±9.3%, ES=0.11, P=0.934 and 23.1±19.0 vs. 28.7±17.8 grams, ES=0.30, P=0.367). Furthermore, there was no significant difference in total fat oxidation between HA and sea level (66.3±21.4 vs. 59.6±7.7 grams, ES=0.32, P=0.557). Conclusion In women, acute exposure to HA reduces the reliance on exogenous carbohydrate oxidation during cycling at the same relative exercise intensity.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Preston, Professor Tom and Morrison, Professor Douglas
• Authors: O'Hara, J. P., Duckworth, L., Black, A., Woods, D. R., Mellor, A., Boos, C., Gallagher, L., Tsakirides, C., Arjomandkhah, N. C., Morrison, D. J., Preston, T., and King, R. F.G.J.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Medicine and Science in Sports and Exercise
• Publisher: Lippincott, Williams & Wilkins
• ISSN: 0195-9131
• ISSN (Online): 1530-0315
• Copyright Holders: Copyright © 2019 American College of Sports Medicine
• First Published: First published in Medicine and Science in Sports and Exercise 51912): 2586-2594
• Publisher Policy: Reproduced in accordance with the publisher copyright policy