Muscle adaptation notes

TANGENT : ... Mechanotransduction ...

90a. Endurance training -> thyroid etc. hormones -> AMPK-SIRT1-PGC-1a (protein) axis -> mitochondrial biogenesis -> adaptation towards slow, type-1 fibres

90b. Power training -> androgens ( testosterone etc. ) -> hypertrophy of existing fast, type-2a/2b fibres

90c. localised myostatin suppression -> hypertrophy in all of type-1/2a/2b fibres

91a. AMPK-SIRT1-PGC-1a Triggers :

• - AMP/ATP ratio increases (during ATP consumption)
• - cytosolic calcium increases (Ca released from SR)
• - ROS increases (pollution from burning)

91b. Activated PGC-1a moves to the nucleus, where it coordinates BOTH nuclear and mitochondrial genomes!

92a. Hypertrophy Triggers :

• - [ titin, filamin-C, BAG3 proteins are mechanosensory complexes, at the (Z-disc) edges of sarcomeres; sarcomeres are intra-cellular structures ] -> [ cell membrane enzyme activation ] -> mTORC1 activation -> [ mRNA builds more actin and myosin; ribosome biogenesis increases ]

92b. satellite cell fusion

• - day 0 to 1 : sarcolemma ( cell membrane ) damage,  satellite cell activation
• - day 1 to 5 : satellite cell proliferation, differentiation
• - day 4 to 10 : fusion into more nuclei per muscle cell to facilitate control over larger cells
• - day 14 to 28 : maturation, and full functional repair