Muscle terminology

Question 1

What is force and how do you calculate force?

Answer 1

Linear changes the motion state of a body of mass

Mass * acceleration

Question 2

What is torque and how do you calculate it?

Answer 2

rotational or angular equivalent of force
Force * moment arm (dma)
Axis of rotation needed

Question 3

What is axis of rotation

Answer 3

A point where things rotate upon/ around

Question 4

Axis or rotation

Answer 4

Frontal, sagittal and longitudinal

Question 5

What is the moment arm?

Answer 5

The moment arm is the perpendicular (90 degrees) distance between the line of action of the force to the axis of rotation.
For skeletal muscle it is the distance from the joint’s axis of rotation to the muscles force vector, drawn at a right angles to the vector.

Question 6

What angle must the moment arm be to the line of action?

Answer 6

90 degrees.

Question 7

Why do people change moment arms?

Answer 7

Damage to the spinal chord at cervical tissue resulting in a loss of function e.g. wrist
Loss of balance at the wrist, flexed and ulnar deviated.
After tendon transfer
Increase in wrist extension
moment arm has an increase in wrist extension strength
• Changed moment arm from ulnar to radial deviator
Increase in radial deviation .strength

Question 8

Muscles develop tension and shorten or attempt to shorten. How do they lengthen?

Answer 8

They can lengthen themselves, external forces are required such as gravity or antagonist muscles of engages muscle.

Question 9

3 types of contractions

Answer 9

Concentric
Eccentric
Isometric

Question 10

Concentric contraction

Answer 10

Where muscles develop tension and shorten resistance to shortening are overcome. Occurring during lifting type actions.

Question 11

Eccentric contraction

Question 11

Eccentric contraction

Answer 11

Occur when muscles develop tension but lengthen. External forces overcome those created by muscles. This occurs when we lover objects.

Question 12

Isometric

Answer 12

Muscles develop tension but remain at the same length. Limb or trunk segments are maintained stationary despite forces that tend to cause
muscle lengthening. Or muscles work against loads that can not be lifted. No mechanical work done (W = F x d)

Question 13

Agonist muscle?

Answer 13

Muscle that contracts to cause desired/observed action.

Question 14

Antagonist muscle?

Answer 14

Muscle that contracts to oppose the desired/observed action.

Question 15

What is a prime mover

Answer 15

The most ‘effective’ muscles in a movement

Pec. major & Ant. Delt. in horizontal shoulder flexion

Question 16

What is an assistant mover?

Answer 16

Less ‘effective’ muscles that ‘help out’.

Coracobrachialis & middle deltoid in horizontal shoulder flexion.

Question 17

What dictates “effectiveness” of muscle at producing a particular movement?

Answer 17

Torque = Force x moment arm

Question 18

What are the 2 key principles of 2 joint muscles

Answer 18

1. When a muscle contracts and shortens it wants to produce all its desired actions
2. Just because a particular joint action is present, dosent mean that all muscles that contribute to that joint action will be activated. This is because the nervous system knows that sometimes it is better to activate some agonists (movement can also occur by gravity and momentum).

Question 19

What are the 2 exceptions for single joint muscles that have principles of 2 joint muscle?

Answer 19

1. biceps brachii during simultaneous shoulder extension and elbow flexion.
2. gastrocnemius during simultaneous ankle plantar-flexion and knee extension

Question 20

Exception of the bicep brachii

Answer 20

Some movements require simultaneous shoulder extension and elbow flexion.
Biceps brachii presents an exception to the two-joint rule
Beneficial effect on elbow flexion substantially outweighs negative
effect on shoulder extension
Net effect of recruiting biceps brachii is greater strength in movement
An example of this is rowing, you are pulling the paddles towards your chest (elbow flexion) as well as pulling your shoulders back (shoulder flexion)

Question 21

2 key principles of stabilization synergy

Answer 21

1. When a muscle contracts and shortens, it “wants” to produce all of its
   actions
2. What a muscle can do is not an indication of what it will do

Question 22

What is stabilization

Answer 22

Muscles acting isometrically to ‘stiffen’ joints & prevent unwanted
movement.
An example is your trunk and vertebrae.
When you are standing upright the mass of your trunk and gravity causes trunk flexion the trunk extensor automatically isometrically oppose gravity.

Question 23

What are some sources of unwanted movement with stabilizers

Answer 23

gravity and muscles

Question 24

What are the 2 types of synergy

Answer 24

Helping and true

Question 25

Helping synergy

Answer 25

Muscles with one or more common & one or more opposing action act together (to create the common action).

Question 26

True synergy

Answer 26

One or more actions of a multi-action muscle is prevented by the action(s)
of another muscle which does not contribute to the observed movement.

Question 27

True synergy in single joint muscle (shoulder pecs)

Answer 27

The pectoralis major performs horizontal shoulder flexion, needed in a bench press.
Also produces shoulder internal rotation which is not desired (unwanted movement).
We need a muscle that performs shoulder external rotation without
interfering with horizontal shoulder flexion.
Shoulder external rotators:
• Infraspinatus
• Teres minor