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Summary & References

  • Mechanotransduction: Muscle growth begins with physical deformation of the fibers—the weight on the bar only matters if it creates enough internal tension to trigger integrins and release Phosphatidic Acid. Fast or light movements fail because they don’t generate that deformation.
  • mTORC1: This protein complex is the master regulator of muscle protein synthesis, activated primarily by mechanical tension (via Phosphatidic Acid) and amino acids (especially leucine).
  • Growth Capacity: Long-term hypertrophy is supported by ribosome biogenesis (increasing the cell’s protein-building machinery) and the recruitment of satellite cells (donating new nuclei to support larger muscle volumes).
  • Muscle Memory: Once satellite cells donate nuclei to a fiber, those nuclei are retained even during periods of detraining, allowing for faster muscle regain in the future.

References

Section titled “References”
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[1]Klossner S, Durieux AC, Freyssenet D, Flueck M. Mechano-transduction to muscle protein synthesis is modulated by FAK. Eur J Appl Physiol. 2009;106(3):389–398.PMID: 19294408
[2]Hornberger TA, Chu WK, Mak YW, et al. The role of phospholipase D and phosphatidic acid in the mechanical activation of mTOR signaling in skeletal muscle. Proc Natl Acad Sci USA. 2006;103(12):4741–4746.PMID: 17090540
[3]Drummond MJ, Fry CS, Glynn EL, et al. Rapamycin administration in humans blocks the contraction-induced increase in skeletal muscle protein synthesis. J Physiol. 2009;587(Pt 7):1535–1546.PMID: 19228591
[4]Drummond MJ, Rasmussen BB. Leucine-enriched nutrients and the regulation of mammalian target of rapamycin signalling and human skeletal muscle protein synthesis. Curr Opin Clin Nutr Metab Care. 2008;11(3):222–226.PMID: 18403916
[5]Figueiredo VC, McCarthy JJ. Regulation of ribosome biogenesis in skeletal muscle hypertrophy. Physiology (Bethesda). 2019;34(1):30–42.PMID: 30540235
[6]Snijders T, Nederveen JP, McKay BR, et al. Satellite cells in human skeletal muscle plasticity. Front Physiol. 2015;6:283.PMID: 26557092
[7]Gundersen K. Muscle memory and a new cellular model for muscle atrophy and hypertrophy. J Exp Biol. 2016;219(Pt 2):235–242.PMID: 26792335
[8]Bhasin S, Storer TW, Berman N, et al. The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men. N Engl J Med. 1996;335(1):1–7.PMID: 8637535