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

Research output: Contribution to journalArticle

  • John O'Hara
  • Lauren C. Duckworth
  • Alistair Black
  • David Woods
  • Adrian Mellor
  • Christopher Boos
  • Liam Gallagher
  • Costas Tsakirides
  • Nicola Arjomandkhah
  • Douglas J. Morrison
  • Thomas Preston
  • Rod F. King
Original languageEnglish
Pages (from-to)2586–2594
Number of pages9
JournalMedicine and Science in Sports and Exercise
Issue number12
Publication statusPublished - 1 Dec 2019
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.

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External organisations

  • Leeds Beckett University
  • Northumbria Healthcare NHS Foundation Trust
  • Poole Hospital NHS Foundation Trust
  • Defence Medical Services
  • Scottish Universities Environmental Research Centre

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