Muscle glycogen and glucose have been suggested to be carbon-chain precursors for
glutamine synthesis in skeletal muscle. Therefore, the aim of the present study is
to investigate whether carbohydrate supplementation affects plasma glutamine and other
amino acids during exercise and 7 h of recovery. Eight well-trained subjects cycled
at an alternating workload of 50 and 80 % Wmax until exhaustion (59 to 140 min). During the exercise bout the subjects received
either water (control) or a carbohydrate (CHO) drink (83 g CHO · l-1, 2 ml · kg-1 per kg body weight every 15 min). Plasma glutamine concentration appeared not to
be affected by exercise, as a significant increase was only observed at some points
in time during the control test. During recovery, however, plasma glutamine concentration
decreased from 682 + 24 and 685 ± 19 μmol · l-1 at exhaustion to 552 ± 19 and 534 ± 12 μmol · l-1 after 2 h of recovery for the control and CHO test, respectively. Plasma glutamine
concentration returned to pre-exercise values after 7 h of recovery. Alanine concentration
increased during exercise in both tests. During the recovery period the concentration
of alanine (48 %), and total amino acids (23 %) decreased below the pre-exercise level.
The plasma alanine and the total amino acid concentration was still suppressed after
7 h of recovery. In conclusion, carbohydrate supplementation had neither an effect
during exercise nor during recovery on the concentration of plasma glutamine or other
amino acids. Exercise, however, causes a substantial decrease in the plasma amino
acid concentration during recovery.
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