Module 5

Question 1

How do you achieve maximum activation in a muscle?

Answer 1

You can’t do naturally so must get electrocuted

Question 2

what determines a muscles optimal length

What happens to resting force after you pass a muscles resting length.

Answer 2

where there is the most actin myosin overlap, force generation will be the greatest.

The muscle maintains a base amount of force (its being stretched)

Question 3

what does the force-length relationship of muscle look like when graphed?

What are the three regions

Explain why the regions are the way they are

Answer 3

shows:
- Ascending limb - steep ascent where force increases rapidly due to some lengthening from fully contracted. Because, at certain point must deform myosin to contract further, therefore once myosin no longer deformed, force production increases

• plateau region - optimal overlap, peak of graph. Muscle still contracting but no change in amount of actin/myosin bindings
• descending limb - gradual drop off in force production as muscle lengthens past optimal zone. losing bindings

Question 4

What will the force length relationship look like in frogs as opposed to humans?

Answer 4

same shape, just may be shifted over due to diff’s in filament and sarcomere length etc.

Question 5

describe comparison of human sarcomeres to frogs (3)

Answer 5

humans have longer actin

human sarcomeres can produce active force over larger range of motion

ascending limb section is longer for humans

Question 6

How does the force curve change depending on PCSA

Answer 6

increased PCSA shows sharper peak with higher tension production, but there is no change in active range of motion.

Why?*

Question 7

What is the problem measuring torque in a muscle at different joint angles?

Answer 7

Because a moment is the perpendicular distance. Line of force changes throughout rom, not all forces accounted for.

Torque at different angles in the muscle will be different for same load (force will be greatest when muscle is perpendicular to gravity).

Question 8

Describe how the force length curve changes when passive force is added rather than just active force.

What creates the passive force?

Answer 8

• the ascending and plateau part are the same
• passive force adds exponentially more force at longer lengths therefore, after plateau, there is not much drop off before exponential increase.

Passive force (mostly from titin, also from: tendons, fascia [peri, epi, endo])

Question 9

Describe each term in the sarcomere.

Z-band

M-line

I-band

A-band

Answer 9

Z-band - where actin and titin are attached

M-line - where myosin is attached

I-band - area with just actin (no myosin overlap)

A-band - Area with just myosin overlap

Question 10

where does titin span in the sarcomere?

Answer 10

spans from z-band (boundary of sarcomere) to m-line (middle where myosin is attached to)

Question 11

what is titins role

Answer 11

protects muscle to resist passive stretch and overstretching

Question 12

Which point of the force length relationship are muscles the most active at?

Answer 12

Depends on the muscle. Certain muscles are mroe active at different points of the force-length relationship.

Could this influence body building?

Question 13

How does the force-length curve vary depending on the athlete e.g. cyclists vs runners? e.g. for rectus femoris

Answer 13

essentially the power curve shifts to fit the need of the sport. doesn’t change in shape though.

Cyclists have flexed hip angle and therefore adapt to have a force curve that favours power output in that position.
- adaptation: reducing sarcomeres in series (shorter fibre)

Runners are more upright and adapt to put out power at more stretched positions.
- adaptation: adding sarcomeres in series (longer fibre than cyclist)