Cellular and molecular mechanisms regulating skeletal muscle mass during strength training

Aims. - To describe the cellular and molecular mechanisms underlying muscle hypertrophy in response to strength training. Current knowledge. - Recent works have delineated these cellular and molecular mechanisms. The fusion of satellite cells with pre-existing myofibers may be required for muscle hypertrophy. Addition of new myonuclei to muscle fibers will ultimately increase the capacity of muscle fiber to express and synthesize muscle proteins. Regulation of the concentration of extracellular factors, such as insulin-like growth factor-1 (IGF-1), mecano-growth factor, hepatocyte growth factor, and myostatin, can participate to the regulation of satellite cell activation and proliferation during heavy resistance exercise. IGF-1/PI3K/Akt signaling pathway also plays an important role by activating protein synthesis and by inhibiting protein degradation through the phosphorylation of Foxo family transcription factor. Conclusion. - The physiological significance of such a mechanism during strength training remains to determine. (c) 2006 Elsevier SAS. Tous droits reserves.