Abstract
The influence of exercise training on plasma amino acid concentrations at rest and
after exercise was examined in a highly trained group of humans and compared with
the response of a control group of nontrained healthy humans. After a bout of intense
exercise at the same relative work load, the trained group exhibited significantly
(28%) higher plasma concentrations of alanine compared with the nontrained group (nontrained
= 313.4 µM, trained = 401.3 µM). Other differences in plasma amino acid concentrations
after exercise were related to initial differences present at rest before exercise.
At rest, the trained group exhibited significantly higher plasma concentrations of
leucine, isoleucine, and tyrosine. Post-exercise ammonia and lactate levels were not
significantly different between the two groups when any pre-exercise differences were
statistically accounted for. Alanine plays a central role as a primary gluconeogenic
substrate and as an ammonia carrier. Therefore, in light of the results presented
here, we propose that the higher alanine levels observed in the endurance-trained
athletes after exercise may play a physiologically relevant role in accommodation
to the metabolic demands of exercise.
Key words
exercise - alanine - amino acids - gluconeo-genesis - energy metabolism
