Addition of Fructose to a Carbohydrate-Rich Breakfast Improves Cycling Endurance Capacity in Trained Cyclists

• Tim Podlogar ^[1] ; Simon Cirnski ^[2] ; Špela Bokal ^[3] ; Nina Verdel ^[4] ; Javier T. González ^[5]
  1. [1] School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
  2. [2] Human Performance Centre, Ljubljana, Slovenia
  3. [3] Faculty of Health Sciences, University of Primorska, Izola, Slovenia
  4. [4] Faculty of Sports, University of Ljubljana, Ljubljana, Slovenia
  5. [5] Centre for Nutrition, Exercise and Metabolism, University of Bath, Bath, United Kingdom

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• Localización: International journal of sport nutrition and exercise metabolism, ISSN 1526-484X, ISSN-e 1543-2742, Vol. 32, Nº. 6, 2022, págs. 439-445
• Idioma: inglés
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• Resumen

  • It was previously demonstrated that postexercise ingestion of fructose–glucose mixtures can lead to superior liver and equal muscle glycogen synthesis as compared with glucose-based carbohydrates (CHOs) only. After an overnight fast, liver glycogen stores are reduced, and based on this we hypothesized that addition of fructose to a glucose-based breakfast would lead to improved subsequent endurance exercise capacity. In this double-blind cross-over randomized study (eight males, peak oxygen uptake: 62.2 ± 5.4 ml·kg−1·min−1), participants completed two experimental trials consisting of two exercise bouts. In the afternoon of Day 1, they completed a cycling interval training session to normalize glycogen stores after which a standardized high-CHO diet was provided for 4 hr. On Day 2, in the morning, participants received 2 g/kg of CHOs in the form of glucose and rice or fructose and rice, both in a CHO ratio of 1:2. Two hours later they commenced cycling exercise session at the intensity of the first ventilatory threshold until task failure. Exercise capacity was higher in fructose and rice (137.0 ± 22.7 min) as compared with glucose and rice (130.06 ± 19.87 min; p = .046). Blood glucose and blood lactate did not differ between the trials (p > .05) and neither did CHO and fat oxidation rates (p > .05). However, due to the duration of exercise, total CHO oxidation was higher in fructose and rice (326 ± 60 g vs. 298 ± 61 g, p = .009). Present data demonstrate that addition of fructose to a glucose-based CHO source at breakfast improves endurance exercise capacity. Further studies are required to determine the mechanisms and optimal dose and ratio.