Ten weeks of branched-chain amino acid supplementation improves select performance and immunological variables in trained cyclists

Amino Acids. 2016 Mar;48(3):779-789. doi: 10.1007/s00726-015-2125-8. Epub 2015 Nov 9.


We examined if supplementing trained cyclists (32 ± 2 year, 77.8 ± 2.6 kg, and 7.4 ± 1.2 year training) with 12 g/day (6 g/day L-Leucine, 2 g/day L-Isoleucine and 4 g/day L-Valine) of either branched-chain amino acids (BCAAs, n = 9) or a maltodextrin placebo (PLA, n = 9) over a 10-week training season affected select body composition, performance, and/or immune variables. Before and after the 10-week study, the following was assessed: (1) 4-h fasting blood draws; (2) dual X-ray absorptiometry body composition; (3) Wingate peak power tests; and (4) 4 km time-trials. No group × time interactions existed for total lean mass (P = 0.27) or dual-leg lean mass (P = 0.96). A significant interaction existed for body mass-normalized relative peak power (19 % increase in the BCAA group pre- to post-study, P = 0.01), and relative mean power (4 % increase in the BCAA group pre- to post-study, P = 0.01). 4 km time-trial time to completion approached a significant interaction (P = 0.08), as the BCAA group improved in this measure by 11 % pre- to post-study, though this was not significant (P = 0.15). There was a tendency for the BCAA group to present a greater post-study serum BCAA: L-Tryptophan ratio compared to the PLA group (P = 0.08). A significant interaction for neutrophil number existed (P = 0.04), as there was a significant 18 % increase within the PLA group from the pre- to post-study time point (P = 0.01). Chronic BCAA supplementation improves sprint performance variables in endurance cyclists. Additionally, given that BCAA supplementation blunted the neutrophil response to intense cycling training, BCAAs may benefit immune function during a prolonged cycling season.

Keywords: Cycling; Immunity; Isoleucine; Leucine; Peak power; Valine.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Amino Acids, Branched-Chain / metabolism*
  • Athletes*
  • Body Composition
  • Dietary Supplements / analysis*
  • Humans
  • Male
  • Middle Aged
  • Muscle, Skeletal / metabolism
  • Neutrophils / immunology*
  • Physical Endurance*
  • Young Adult


  • Amino Acids, Branched-Chain