Effects of glucose, glucose plus branched-chain amino acids, or placebo on bike performance over 100 km.
This study was undertaken to determine the effects of ingesting either glucose (trial G) or glucose plus branched-chain amino acids (BCAA: trial B), compared with placebo (trial P), during prolonged exercise. Nine well-trained cyclists with a maximal oxygen uptake of 63.1 +/- 1.5 ml O2. min-1.kg-1 performed three laboratory trials consisting of 100 km of cycling separated by 7 days between each trial. During these trials, the subjects were encouraged to complete the 100 km as fast as possible on their own bicycles connected to a magnetic brake. No differences in performance times were observed between the three trials (160.1 +/- 4.1, 157.2 +/- 4.5, and 159.8 +/- 3.7 min, respectively). In trial B, plasma BCAA levels increased from 339 +/- 28 microM at rest to 1,026 +/- 62 microM after exercise (P < 0.01). Plasma ammonia concentrations increased during the entire exercise period for all three trials and were significantly higher in trial B compared with trials G and P (P < 0.05). The respiratory exchange ratio was similar in the three trials during the first 90 min of exercise; thereafter, it tended to drop more in trial P than in trials G and B. These data suggest that neither glucose nor glucose plus BCAA ingestion during 100 km of cycling enhance performance in well-trained cyclists.
Madsen
K
K
Department of Physical Education, Odense University, Denmark.
MacLean
D A
DA
Kiens
B
B
Christensen
D
D
D000328:Adult; D000597:Amino Acids, Branched-Chain / Q000494:pharmacology; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D013647:Task Performance and Analysis
D000597:Amino Acids, Branched-Chain; D005947:Glucose