Limits of the MSK System - Muscle

Question 1

what his the maximal isometric force of muscle ?

Answer 1

approx. 30 N/cm²

Question 2

state 3 basic facts about muscle force

Answer 2

• actin and myosin form cross bridges
• force related to the number of cross-bridges formed
• additional force from the passive elastic structures of the MTU

Question 3

explain concentric contractions

Answer 3

force generated by the muscle exceeds the external force and so the muscle shortens

Question 4

explain isometric contractions

Answer 4

force generated by muscle matches the external force and muscle fibres remain the same length

Question 5

explain eccentric contraction

Answer 5

force generated by muscle is less than the external force and muscle fibres are lengthened by the external force

Question 6

what causes muscle strain

Answer 6

if the lengthening of the muscle cannot be controlled by the muscle, it will be strained too much and the muscle will fail

Question 7

what type of muscles is strain more likely to occur ?

Answer 7

biarticular muscles

Question 8

state 2 additional facts about muscle tears

Answer 8

• damage occurs when sarcomeres lengthen too much

- muscles said to be ‘unstable’ when operating on the descending limb of the F-L curve

Question 9

where does failure to the muscle usually occur ?

Answer 9

tearing usually occurs at the muscle fascicle - aponeurosis junction

Question 10

what can be used to image muscles ?

Answer 10

both MRI and Ultrasound are methods of imaging muscles

Question 11

what is the inflammatory response to muscle healing ?

Answer 11

• influx of neutrophils to the injured area

- oxidative burst of neutrophils causes more damage to fascicles to enable their release

Question 12

what happens 24 and above hours post injury ?

Answer 12

• 24 hours post injury there is an increase in the number of fascicles at the injured site
• protein synthesis is up-regulated
• loading stimulates this response - so controlled and progressive loading is essential to recovery