Muscle Mechanics

Question 1

What is muscle-tendon unit

Answer 1

Muscle & tendon move together during contraction

Question 2

Torque

Answer 2

Ability of force to rotate the lever about an axis

Question 3

Moment arm

Answer 3

Distance from line of action to the center of rotation

Question 4

Mechanical advantage

Answer 4

Relative effectiveness of the applied force (muscle) compared with the resistance (body weight, antagonist muscles, etc)
Greater than 1
Equal to 1
Less than 1

Question 5

Greater than 1 mechanical advantage

Answer 5

A force smaller than the resistance is required to maintain equilibrium
Like lifting with a lever

Question 6

Equal to 1 mechanical advantage

Answer 6

A force equal to the resistance is required to maintain equilibrium
Like the force on either side of a teeter totter being equal

Question 7

Less than 1 mechanical advantage

Answer 7

A force larger than the resistance is required to maintain equilibrium
Like a greater force to move the head of a broom

Question 8

First class lever

Answer 8

Fulcrum between applied force and resistance
Mechanical advantage can be less than 1, equal to 1, or greater than 1

Question 9

Second class lever

Answer 9

Resistance between fulcrum and applied force
Mechanical advantage is always greater than 1

Question 10

Third class levers

Answer 10

Applied force between fulcrum and resistance
Mechanical advantage is always less than 1

Question 11

Advantage of third class levers

Answer 11

Most joints in the body are third class lever systems (>1)
Smaller muscle shortening can generate larger resistance displacement

Question 12

EMG (electromyography)

Answer 12

Surface electrodes placed on skin and electrical activity in the muscle is recorded
Records motor unit action potentials