Variation in plasma amino acid concentrations during a cycling competition.
OBJECTIVE
The variations in plasma concentrations of 24 amino acids (AAs) were measured, taking into account modifications in plasma volume, in 7 male subjects, professional cyclists, during the first 2 stages (EI and EII) of the competition "4 Days of Dunkirk 1999".


METHODS
Blood samples were taken before the start and at the end of each stage. At the end of EI a significant reduction (p<0.02) in alpha-aminobutyric acid was observed (-38%) and a significant increase (Wilcoxon 0.01<p<0.05) in cystine (+28%), phenylalanine (+21%), taurine (+33%) and tyrosine (+42%). Alanine in particular, and also the ramified AAs, remained relatively stable at this stage. At the end vs start of EII there was a significant reduction in several AAs, alpha-aminobutyric acid (33%), arginine (-21%), cystine (-15%), glycocholic acid (26%), hydroxyproline (-28%), leucine (-17%), lysine (-26%), methionine (-19%), threonine (-15%) and valine (-16%).


RESULTS
The recovery period was characterised by increases in previously reduced AAs and vice versa.


CONCLUSIONS
These results show that cellular use of plasma AAs in the endurance cyclist could differ between the first hours of competition and the subsequent stages, possibly in relation to the gradual increase in stress level as the stages progress; they also suggest that appropriate consideration should be given to the quality of protein inputs in the nutrition of cyclists involved in a high-level stage competition.
Medelli
J
J
Biology and Sports Medicine Unit, CHU-Hôpital-Nord, Amiens, France. medelli.jean@chu-amiens.fr
Lounana
J
J
Hill
D
D
D000328:Adult; D000596:Amino Acids / Q000097:blood*; D001642:Bicycling; D001798:Blood Proteins / Q000032:analysis; D003404:Creatinine / Q000097:blood; D006801:Humans; D008297:Male; D010806:Physical Education and Training; D010807:Physical Endurance; D012709:Serum Albumin / Q000032:analysis; D013997:Time Factors; D014508:Urea / Q000097:blood
D000596:Amino Acids; D001798:Blood Proteins; D012709:Serum Albumin; D014508:Urea; D003404:Creatinine