title: Alterations in amino acid concentrations in the plasma and muscle in human subjects during 24 h of simulated adventure racing.
abstract: This investigation was designed to evaluate changes in plasma and muscle levels of free amino acids during an ultra-endurance exercise and following recovery. Nine male ultra-endurance trained athletes participated in a 24-h standardized endurance trial with controlled energy intake. The participants performed 12 sessions of running, kayaking and cycling (4 × each discipline). Blood samples were collected before, during and after exercise, as well as after 28 h of recovery. Muscle biopsies were taken before the test and after exercise, as well as after 28 h of recovery. During the 24-h exercise, plasma levels of branched-chain (BCAA), essential amino acids (EAA) and glutamine fell 13, 14 and 19% (P < 0.05), respectively, whereas their concentrations in muscle were unaltered. Simultaneously, tyrosine and phenylalanine levels rose 38 and 50% (P < 0.05) in the plasma and 66 and 46% (P < 0.05) in muscle, respectively. After the 24-h exercise, plasma levels of BCAA were positively correlated with muscle levels of glycogen (r (2) = 0.73, P < 0.05), as was the combined concentrations of muscle tyrosine and phenylalanine with plasma creatine kinase (R (2) = 0.55, P < 0.05). Following 28-h of recovery, plasma and muscle levels of amino acids had either returned to their initial levels or were elevated. In conclusion, ultra-endurance exercise caused significant changes elevations in plasma and muscle levels of tyrosine and phenylalanine, which suggest an increase in net muscle protein breakdown during exercise. There was a reduction in plasma concentrations of EAA and glutamine during exercise, whereas no changes were detected in their muscle concentration after exercise.
authors.affiliation: Åstrand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, Stockholm, Sweden.
authors.forename: Marcus
authors.initials: M
authors.lastname: Borgenvik
authors.forename: Marie
authors.initials: M
authors.lastname: Nordin
authors.forename: C
authors.initials: C
authors.lastname: Mikael Mattsson
authors.forename: Jonas K
authors.initials: JK
authors.lastname: Enqvist
authors.forename: Eva
authors.initials: E
authors.lastname: Blomstrand
authors.forename: Björn
authors.initials: B
authors.lastname: Ekblom
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000097:blood / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010649:Phenylalanine / Q000097:blood; D012420:Running / Q000502:physiology*; D014443:Tyrosine / Q000097:blood
chemical_list: D000596:Amino Acids; D014443:Tyrosine; D010649:Phenylalanine; D006003:Glycogen