Quiz 1.5

Question 1

Concentric Action

Answer 1

Shortening of fibers to cause movement

Question 2

Eccentric action

Answer 2

Lengthening of fibers to control or resist movement, slower movement but still produces force
EX: walking down stairs, hamstring

Question 3

Isometric action

Answer 3

No change in fiber length, no movement, still produce force

Question 4

Mechanical factors affecting muscle force

Answer 4

Length and velocity

Question 5

Force- length relationship

Answer 5

Optimal is resting length b/c max crossbridges
Shortened –> cross bridge overlap so not a lot of room for additional shortening/ more CB
Lengthened –> crossbridges pulled apart, no room for more to form

Question 6

Concentric vs. Eccentric force

Answer 6

At same length,
Force Ecc > Force Con
This is because stability and safety are controlled by ecc
KNOW GRAPH

Question 7

When stretched beyond resting length…

Answer 7

Active tension decrease and passive tension increases
More passive tension in 2 joint muscles
Total tension = active + passive
(Max total at end of motion)
KNOW GRAPH

Question 8

Force velocity relationship for concentric

Answer 8

The slower the more force
Faster contraction is less force
Force decreases exponentially as velocity increases
KNOW GRAPH

Question 9

Force velocity relationship for eccentric

Answer 9

Faster contraction produces more force, slower = less force
At faster speed, max muscle force increases to 1.4-1.8x max isometric force
KNOW GRAPH

Question 10

Why do fast eccentric contractions produce more force

Answer 10

Allows it to slow and control the muscles/movement over the concentric

Question 11

Why concentric F-V relationship

Answer 11

Increase velocity –> increase CB cycling rate –> more crossbridges in release stage at a given time –> decrease crossbridge formation = decrease force

Question 12

Velocity and force impact

Answer 12

At any given activation, slowly contracting muscles produce greater force than quick contracting muscles
KNOW GRAPH

Question 13

Velocity-force impact on Activation

Answer 13

To achieve a given force, muscles contracting more slowly need less activation than those contracting quickly
KNOW GRAPH

Question 14

Stretch shorten cycle

Answer 14

More muscle force produce when shortening immediately follows stretching
ex: jump higher in counter movement jump vs squat jump
If stretch held for too long the effects are lost
explanation is not well known, possibilities: stored elastic energy, reflex activation