Effects of protein intake prior to carbohydrate-restricted endurance exercise: a randomized crossover trial

Mads S Larsen, Lars Holm, Mads V Svart, Astrid J Hjelholt, Mads B Bengtsen, Ole L Dollerup, Line B Dalgaard, Mikkel H Vendelbo, Gerrit van Hall, Niels Møller, Ulla R Mikkelsen, Mette Hansen

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3 Citations (Scopus)
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Deliberately training with reduced carbohydrateavailability, a paradigm coined training low, has shown to promoteadaptations associated with improved aerobic capacity. In this contextresearchers have proposed that protein may be ingested prior to training as ameans to enhance the protein balance during exercise without spoiling theeffect of the low carbohydrate availability. Accordingly, this is beingpracticed by world class athletes. However, the effect of protein intake onmuscle protein metabolism during training low has not been studied.

This study aimed to examine if protein intake prior toexercise with reduced carbohydrate stores benefits muscle protein metabolism inexercising and non-exercising muscles.


Nine well-trained subjects completed two trials in randomorder both of which included a high-intensity interval ergometer bike ride (day1), a morning (day 2) steady state ride (90 min at 65% VO2peak, 90ss), and a4-h recovery period. An experimental beverage was consumed before 90ss andcontained either 0.5 g whey protein hydrolysate [WPH]/ kg lean body mass orflavored water [PLA]. A stable isotope infusion (L-[ring-13C6]-phenylalanine)combined with arterial-venous blood sampling, and plasma flow rate measurementswere used to determine forearm protein turnover. Myofibrillar protein synthesiswas determined from stable isotope incorporation into the vastus lateralis.



Forearm protein net balance was not different from zeroduring 90ss exercise (nmol/100 ml/min, PLA: 0.5 ± 2.6; WPH: 1.8, ± 3.3) butnegative during the 4 h recovery (nmol/100 ml/min, PLA: − 9.7 ± 4.6; WPH: − 8.7 ± 6.5);no interaction (P = 0.5) or main effect of beverage (P = 0.11) was observed.Vastus lateralis myofibrillar protein synthesis rates were increased during90ss exercise (+ 0.02 ± 0.02%/h) and recovery (+ 0.02 ± 0.02%/h); nointeraction (P = 0.3) or main effect of beverage (P = 0.3) was observed.



We conclude that protein ingestion prior to enduranceexercise in the energy- and carbohydrate-restricted state does not increasemyofibrillar protein synthesis or improve net protein balance in the exercisingand non-exercising muscles, respectively, during and in the hours afterexercise compared to ingestion of a non-caloric control.

Trial registration

clinicaltrials.gov, NCT01320449. Registered 10 May 2017 –Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03147001

Original languageEnglish
Article number7
Pages (from-to)1-13
Number of pages13
JournalJournal of the International Society of Sports Nutrition
Issue number1
Publication statusPublished - 28 Jan 2020


  • Carbohydrate restriction
  • Dietary protein
  • Endurance training
  • Protein metabolism

ASJC Scopus subject areas

  • Food Science
  • Nutrition and Dietetics


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