Inactivity and SKM

Question 1

Muscle study, inactivity

at what stage does percentage change in cross-sectional area occur the most in a period of immobilisation?

Answer 1

in the initial/Early stages

Question 2

what would a graph of disuse muscle atrophy due to immbolisation against muscle cross-sectional area (size) look like?

Answer 2

rapid decline initially (ten days) then decline slows down, and then levels off/plateaus

Question 3

mechanisms of disuse atrophy

what is the main driver of disuse muscle atrophy?

Answer 3

• decrease increase in MPS, with no noticable difference in MPB, creating a NET Loss

Question 4

True or false, normal, untrained muscle has been seen to show no change in muscle size or strength versus an immobilised leg?

Answer 4

True, studies have shown that a normal leg exhibits no change in muscle size or strength, but an immobilisation of a leg causes noticeable loss in muscle strength and size

Question 5

functional loss

how much greater is the functional loss in immobilised muscle compared to muscle size loss

Answer 5

3 times greater

Question 6

functional loss

what 2 things mean that the functional loss greater than the muscle size loss in immobilised muscle?

Answer 6

• decrease/suppression in motor unit firing rate
• decrease in motor neurons

Question 7

when you immbolise someone, how can you know for sure there is an absolute lower force production from the muscle due to the immbolisation?

Answer 7

• you use the same weight used before the immbolisation started to be certain there is an absolute lower force production

Question 8

further neural adaptation to inactivity

what can happen to the Neuromuscular Junction after severe inactivity?

Answer 8

• NMJ fragmentation

Question 9

what deterioates faster in muscle immobilisation, muscle size or muscle function?

Answer 9

muscle function

Question 10

what is retrograde feedback

Answer 10

when the muscle sends signals to/back up the motor neurone to message that it is not receiving any neuronal input

Question 11

what is cramping

Answer 11

when motor units are firing so fast that there is never an opportunity for the muscle to relax, leading to disregulated motor unit firing rate

Question 12

what is an implication NMJ fragmentation?

Answer 12

if there is NMJ fragmentation, there is no/less ACh neurotransmitter crossing the synaptic cleft and propagating action potentials in the muscle fibre, so there is no/less contraction