Role of muscles

Question 1

Agonist muscles

Answer 1

• Cause joint motion through a specified plane of motion when contracting concentrically
• known as prime movers, or muscles most involved

Question 2

Antagonist muscles

Answer 2

• located at the opposite side of the joint from agonist
• have opposite concentric action
• known as contralateral muscles

Question 3

How does antagonist muscle work with the agonist muscle?

Answer 3

• work in cooperation with agonist muscle by relaxing and allowing movement
• when contracting concentrically perform the opposite joint motion of agonist

Question 4

Stabilizers

Answer 4

• surround joint or body part
• known as fixators
• contract to stabilize the area to enable another limb or body segment to exert force & move

Question 5

Stabilizers are essential for ____

Answer 5

establishing a relatively firm base for the more distal joints to work from when carrying out movements

Question 6

Synergists

Answer 6

• assists in action of agonists
• known as guiding muscles
• assist in refined movement and rule out undesired motions

Question 7

Neutralizers

Answer 7

• counteract or neutralize the action of another muscle to prevent undesirable movements such as inappropriate muscle substitutions
• contract to resist specific actions of other muscles

Question 8

What does muscles with multiple agonist actions do?

Answer 8

• attempt to perform all of their actions when contracting

- cannot determine which actions are appropriate for the task at hand

Question 9

Actions performed are dependent upon which factors?

Answer 9

• the motor units activated
• joint position
• muscle length
• relative contraction or relaxation of other muscles acting on the joint

Question 10

Reversal of Muscle Function

Answer 10

A muscle group described to perform as given function can contract to control the exact opposite motion

Question 11

Determination of muscle action

Answer 11

• consideration of anatomical lines of pull
• anatomical dissection
• palpation
• models
• electromyography
• electrical stimulation

Question 12

Palpation

Answer 12

• using to sense of touch to feel a muscle as it is contracted
• limited to superficial muscles
• helpful in furthering one’s understanding of joint mechanics

Question 13

Electromyography (EMG)

Answer 13

• utilizes surface electrodes which are placed over muscles or fine wire/needle electrodes
• most accurate way of detecting presence & extent of muscle activity

Question 14

Electrical muscle stimulation

Answer 14

• reverse approach to EMG
• use electricity to cause muscle activity
• surface electrodes are placed over muscle to contract

Question 15

Lines of pull

Answer 15

7 things to consider

1. Exact locations of bony landmarks
2. Planes of motion
3. Muscle’s relationship to the joint’s axes of rotation
4. Change in line of pull and cause opposite action
5. Effect of other muscles
6. Effect of a muscle’s relative length on its ability to generate force
7. Effect of the position of other joints on the ability of bi/multiarticular muscle to generate force or allow lengthening