Abstract

The importance of proteins and amino acids as sources of energy during muscle efforts is well known. With a view to assessing their role during intense prolonged efforts, serum concentrations of individual amino acids were determined in 31 amateur sportsmen before, at the end of and one hour after three competitive footracers: a 12 km race, a marathon und a 100 km race. At the control times, no significant variations were recorded for any of the amino acids, with the exception of phenylalanine in the marathon (baseline = 58 +/- 12 vs end = 78 +/- 20 micro-mol/l; p < 0.05) and tyrosine in the 100 km race (baseline = 86 +/- 16 micro-mol/l vs end = 120 +/- 30; p < 0.05). Variations recorded for the latter amino acid showed that the statistical profile of its overall trend was different to the one observed for the 12 km race and for the marathon for this nitrogen compound. On the basis of data published in the literature and of our results, our conclusions point to the difficulty of carrying out a correct assessment of protein metabolism during endurance sports by determining serum amino acids. Verf.-Referat