Journal
FASEB JOURNAL
Volume 19, Issue 13, Pages 190-+Publisher
FEDERATION AMER SOC EXP BIOL
DOI: 10.1096/fj.05-4809fje
Keywords
adaptation; endurance; hypertrophy; plasticity
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Skeletal muscle from strength- and endurance-trained individuals represents diverse adaptive states. In this regard, AMPK-PGC-1 alpha signaling mediates several adaptations to endurance training, while up-regulation of the Akt-TSC2-mTOR pathway may underlie increased protein synthesis after resistance exercise. We determined the effect of prior training history on signaling responses in seven strength- trained and six endurance-trained males who undertook 1 h cycling at 70% VO2peak or eight sets of five maximal repetitions of isokinetic leg extensions. Muscle biopsies were taken at rest, immediately and 3 h postexercise. AMPK phosphorylation increased after cycling in strength- trained (54%; P<0.05) but not endurance-trained subjects. Conversely, AMPK was elevated after resistance exercise in endurance-(114%; P<0.05), but not strength-trained subjects. Akt phosphorylation increased in endurance- (50%; P<0.05), but not strength-trained subjects after cycling but was unchanged in either group after resistance exercise. TSC2 phosphorylation was decreased (47%; P<0.05) in endurance- trained subjects following resistance exercise, but cycling had little effect on the phosphorylation state of this protein in either group. p70S6K phosphorylation increased in endurance- (118%; P<0.05), but not strength- trained subjects after resistance exercise, but was similar to rest in both groups after cycling. Similarly, phosphorylation of S6 protein, a substrate for p70 S6K, was increased immediately following resistance exercise in endurance- (129%; P<0.05), but not strength- trained subjects. In conclusion, a degree of response plasticity is conserved at opposite ends of the endurance-hypertrophic adaptation continuum. Moreover, prior training attenuates the exercise specific signaling responses involved in single mode adaptations to training.
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