Endurance training alters alanine and glutamine release from muscle during contractions

The release of alanine and glutamine from perfused muscle of trained and control animals was investigated. Release rates did not differ between trained and control muscle at rest. During contractions in trained muscle, alanine release was higher than at rest, while glutamine release was transiently increased. Phenylalanine release did not differ between trained and control muscle, implying that protein degradation was not increased in trained muscle. The muscle cellular adaptations to training include a selective modification of amino acid output, which could potentially influence gluconeogenic flux and alter muscle ammonia levels during contractions.