Sensing mechanical signals for muscle hypertrophy

Question 1

How does force application lead to muscle hypertrophy?

Answer 1

• Force modifies mechanoreceptor
• This triggers an early signalling response
• This initiates hypertrophic signalling (mTORC1) and muscle hypertrophy (mechano-receptor)

Question 2

According to O’neil et al 2009, what does mechanical stimulus activate, which subsequently activates mTORC1?

Answer 2

Mechanical stimulus can activate phospholipases, these synthesize phosphatidic acid (PA), PA binds to mTOR which then activates mTORC1.

Question 3

What is the ‘pump’ - according to O’neil et al 2009

Answer 3

whole muscle swelling (changes in thickness) occurs after RT - very little evidence for muscle fibre swelling

Question 4

Lengthening contractions lead to greater levels of what, compared to shortening contractions

Answer 4

Z-line (boundaries between sarcomeres) streaming - Moore et al 2005

Z-line streaming is a structural damage signal. It indicates micro-damage. This damage triggers inflammatory and anabolic signalling cascades, including mTOR pathway activation - a key regulator of MPS.

Eccentric (lengthening) contractions activate mTORC1, leading to higher MPS rate both acutely and chronically

Question 5

What does repeated bouts of same exercise stimulus lead to?

Answer 5

Decrease levels of exercise-induced muscle damage Nosaka + Clarkson 1995

Question 6

What key finding does Moberg et al 2020 find?

Answer 6

Provides data not supporting hypothesis that blood lactate is anabolic signalling molecules