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.
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The authors thank the participants for devoting time to this study. Reagent costs and participant compensation costs were paid through a contract awarded to M.D.R. through MusclePharm Corp. (Denver, CO). B.N. and R.D.A were supported in part by funding from NIH R01 EB016100.
Besides J.R.M., none of the authors have conflicts of interest. J.R.M. is a Ph.D. scientist employed by the MusclePharm Research Institute, but he substantially contributed to the study design and data write-up. Therefore, all co-authors agreed that his work into this project warranted co-authorship. It should also be noted that all participants gave their informed consent in writing prior to inclusion in the study. Identifying details (names, dates of birth, identity numbers and other information) of the participants are not published in the current work.
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Kephart, W.C., Wachs, T.D., Mac Thompson, R. et al. Ten weeks of branched-chain amino acid supplementation improves select performance and immunological variables in trained cyclists. Amino Acids 48, 779–789 (2016). https://doi.org/10.1007/s00726-015-2125-8
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