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This Article Full Text Full Text (PDF) All Versions of this Article: 586/15/3701    most recent jphysiol.2008.153916v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Wilkinson, S. B. Articles by Rennie, M. J. PubMed PubMed Citation Articles by Wilkinson, S. B. Articles by Rennie, M. J. Related Collections Skeletal Muscle and Exercise

¹ Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
² School of Biomedical Science, Graduate Entry Medical School, University of Nottingham, Derby, UK
³ Department of Internal Medicine, Division of Metabolism, Endocrinology and Lipid Research, Washington University School of Medicine, St Louis, MO, USA
⁴ Departments of Pediatrics and Neurology, McMaster University, Hamilton, Ontario, Canada L8S 4K1

Resistance (RE) and endurance (EE) exercise stimulate mixed skeletal muscle protein synthesis. The phenotypes induced by RE (myofibrillar protein accretion) and EE (mitochondrial expansion) training must result from differential stimulation of myofibrillar and mitochondrial protein synthesis. We measured the synthetic rates of myofibrillar and mitochondrial proteins and the activation of signalling proteins (Akt–mTOR–p70S6K) at rest and after an acute bout of RE or EE in the untrained state and after 10 weeks of RE or EE training in young healthy men. While untrained, RE stimulated both myofibrillar and mitochondrial protein synthesis, 67% and 69% (P < 0.02), respectively. After training, only myofibrillar protein synthesis increased with RE (36%, P = 0.05). EE stimulated mitochondrial protein synthesis in both the untrained, 154%, and trained, 105% (both P < 0.05), but not myofibrillar protein synthesis. Acute RE and EE increased the phosphorylation of proteins in the Akt–mTOR–p70S6K pathway with comparatively minor differences between two exercise stimuli. Phosphorylation of Akt–mTOR–p70S6K proteins was increased after 10 weeks of RE training but not by EE training. Chronic RE or EE training modifies the protein synthetic response of functional protein fractions, with a shift toward exercise phenotype-specific responses, without an obvious explanatory change in the phosphorylation of regulatory signalling pathway proteins.

(Received 11 March 2008; accepted after revision 11 June 2008; first published online 12 June 2008)
Corresponding author S. M. Phillips: Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1.  Email: phillis{at}mcmaster.ca

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