Physical inactivity and SKM

Question 1

Explain muscle atrophy during immobilisation?

Answer 1

• More rapid atrophy during the earliest period of immobilisation

Question 2

What are the mechanisms of disuse atrophy?

Answer 2

• Declines in muscle protein synthesis account for short-term muscle disuse atrophy in humans in the absence of increased muscle protein breakdown

Question 2

What is the main driver of disuse induced muscle atrophy?

Answer 2

• A decrease in MPS without any notable change in muscle protein breakdown

Question 3

Summarise what happens during physical inactivity in SKM

Answer 3

• Skeletal muscle undergoes rapid atrophy with inactivity, which eventually plateaus
• Atrophy is primarily driven by an imbalance of MPS and MPB
• Primarily as a result of reduced MPS with little involvement of MPB
• Inactivity also has effects on the neural input to muscle
• Motor unit firing rate reduced. NMJ becomes more unstable
• Effects may preferentially affect different motor units