Branched-chain amino acid supplementation improves cycling performance in untrained cyclists

J Sci Med Sport. 2021 Apr;24(4):412-417. doi: 10.1016/j.jsams.2020.10.014. Epub 2020 Oct 28.


Objectives: To investigate the effects of acute branched-chain amino acid (BCAA) supplementation on cycling performance and neuromuscular fatigue during a prolonged, self-paced cycling time-trial.

Design: Randomised double-blind counterbalanced crossover.

Methods: Eighteen recreationally active men (mean±SD; age: 24.7±4.8 years old; body-weight, BW: 67.1±6.1kg; height: 171.7±4.9cm) performed a cycling time-trial on an electromagnetically-braked cycle ergometer. Participants were instructed to complete the individualised total work in the shortest time possible, while ingesting either BCAAs (pre-exercise: 0.084gkg-1 BW; during exercise: 0.056gkg-1h-1) or a non-caloric placebo solution. Rating of perceived exertion, power, cadence and heart rate were recorded throughout, while maximal voluntary contraction, muscle voluntary activation level and electrically evoked torque using single and doublet stimulations were assessed at baseline, immediately post-exercise and 20-min post-exercise.

Results: Supplementation with BCAA reduced (287.9±549.7s; p=0.04) time-to-completion and ratings of perceived exertion (p≤0.01), while concomitantly increasing heart rate (p=0.02). There were no between-group differences (BCAA vs placebo) in any of the neuromuscular parameters, but significant decreases (All p≤0.01) in maximal voluntary contraction, muscle voluntary activation level and electrically evoked torque (single and doublet stimulations) were recorded immediately following the trial, and these did not recover to pre-exercise values by the 20min recovery time-point.

Conclusions: Compared to a non-caloric placebo, acute BCAA supplementation significantly improved performance in cycling time-trial among recreationally active individuals without any notable changes in either central or peripheral factors. This improved performance with acute BCAA supplementation was associated with a reduced rating of perceived exertion.

Keywords: BCAA; Central activation; Exercise; Fatigue; Physical exertion; Sports.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Amino Acids, Branched-Chain / administration & dosage*
  • Bicycling / physiology*
  • Cross-Over Studies
  • Dietary Supplements*
  • Double-Blind Method
  • Humans
  • Male
  • Muscle Fatigue / drug effects*
  • Physical Endurance / drug effects*
  • Physical Exertion / drug effects*
  • Young Adult


  • Amino Acids, Branched-Chain