Branched-chain amino acid supplementation lowers perceived exertion but does not affect performance in untrained males

Beau Kjerulf Greer, Jim P. White, Eric M. Arguello, Emily M. Haymes

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32 Scopus citations


The purpose of this study was to determine whether branched-chain amino acid (BCAA) supplementation affects aerobic performance, ratings of perceived exertion (RPE), or substrate utilization as compared with an isocaloric, carbohydrate (CHO) beverage or a noncaloric placebo (PLAC) beverage. Nine untrained males performed three 90-minute cycling bouts at 55% •VO 2 peak followed by 15-minute time trials. Subjects, who were blinded to beverage selection, ingested a total of 200 kcal via the CHO or BCAA beverage before and at 60 minutes of exercise or the PLAC beverage on the same time course. RPE and metabolic measurements were taken every 15 minutes during steadystate exercise, and each of the trials was separated by 8 weeks. Plasma glucose and BCAA concentrations were measured preand post-exercise. A greater distance (4.6 ± 0.6 km) was traveled in the time-trial during the CHO trial than the PLAC trial (3.9 ± 0.4 km) (p < 0.05). There was no difference between the BCAA (4.4 < 0.5 km) and PLAC trials. RPE was reduced at the 75-minute and 90-minute mark during the BCAA trial as compared with the PLAC trial. There were no significant differences found for the trial vs. time interaction in regard to respiratory exchange ratio. Thus, CHO supplementation improves performance in a loaded time-trial as compared with a PLAC beverage. BCAA supplementation, although effective at increasing blood concentrations of BCAA, did not influence aerobic performance but did attenuate RPE as compared with a PLAC beverage.

Original languageEnglish
Pages (from-to)539-544
Number of pages6
JournalJournal of Strength and Conditioning Research
Issue number2
StatePublished - Feb 2011


  • Amino acids
  • Central fatigue
  • Ergogenics aids


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