title: Resistance exercise-induced S6K1 kinase activity is not inhibited in human skeletal muscle despite prior activation of AMPK by high-intensity interval cycling.
abstract: Combining endurance and strength training in the same session has been reported to reduce the anabolic response to the latter form of exercise. The underlying mechanism, based primarily on results from rodent muscle, is proposed to involve AMPK-dependent inhibition of mTORC1 signaling. This hypothesis was tested in eight trained male subjects who in randomized order performed either resistance exercise only (R) or interval cycling followed by resistance exercise (ER). Biopsies taken from the vastus lateralis before and after endurance exercise and repeatedly after resistance exercise were assessed for glycogen content, kinase activity, protein phosphorylation, and gene expression. Mixed muscle fractional synthetic rate was measured at rest and during 3 h of recovery using the stable isotope technique. In ER, AMPK activity was elevated immediately after both endurance and resistance exercise (∼90%, P < 0.05) but was unchanged in R. Thr(389) phosphorylation of S6K1 was increased severalfold immediately after exercise (P < 0.05) in both trials and increased further throughout recovery. After 90 and 180 min recovery, S6K1 activity was elevated (∼55 and ∼110%, respectively, P < 0.05) and eukaryotic elongation factor 2 phosphorylation was reduced (∼55%, P < 0.05) with no difference between trials. In contrast, markers for protein catabolism were differently influenced by the two modes of exercise; ER induced a significant increase in gene and protein expression of MuRF1 (P < 0.05), which was not observed following R exercise only. In conclusion, cycling-induced elevation in AMPK activity does not inhibit mTOR complex 1 signaling after subsequent resistance exercise but may instead interfere with the hypertrophic response by influencing key components in protein breakdown.
authors.affiliation: Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden; Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden; william.apro@gih.se.
authors.forename: William
authors.initials: W
authors.lastname: Apró
authors.affiliation: Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden;
authors.forename: Marcus
authors.initials: M
authors.lastname: Moberg
authors.affiliation: Health and Exercise Sciences Research Group, University of Stirling, Stirling, United Kingdom;
authors.forename: D Lee
authors.initials: DL
authors.lastname: Hamilton
authors.affiliation: Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden;
authors.forename: Björn
authors.initials: B
authors.lastname: Ekblom
authors.affiliation: Department of Biomedical Sciences, Rigshospitalet, University of Copenhagen, Denmark;
authors.forename: Gerrit
authors.initials: G
authors.lastname: van Hall
authors.affiliation: Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden; and.
authors.forename: Hans-Christer
authors.initials: HC
authors.lastname: Holmberg
authors.affiliation: Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Blomstrand
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004789:Enzyme Activation; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D011485:Protein Binding; D055070:Resistance Training / Q000379:methods; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015854:Up-Regulation; D055815:Young Adult
chemical_list: D006003:Glycogen; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; D055372:AMP-Activated Protein Kinases
keywords: AMPK; S6K1; concurrent exercise; mTORC1