How Muscles Work

Question 1

Agonist

Answer 1

Muscle controlling the movement

Question 2

What are the 2 parts of an Agonist?

Answer 2

Prime mover and synergist

Question 3

Antagonist

Answer 3

Muscle opposing the agonist

Question 4

Co-contraction

Answer 4

Both agonist and antagonist are acting at the same time; stabilize/stiffen a joint to prevent movement

Question 5

Neutralization

Answer 5

Specific recruitment of agonist that counteract unwanted movements in other planes

(Ex. Hamstring curls; seated - biceps femoris (lateral) and semi tendinosus/membranosus (medial) neutralize to just cause flexion

Question 6

Stabilization

Answer 6

Specific recruitment of antagonist or use of external forces that counteract unwanted movement of proximal or distal attachment

Question 7

Muscles move the segment with ______ inertia

Answer 7

Less

Question 8

What are the 3 types of Lever Systems

Answer 8

First-class lever
Second-class lever
Third-class lever

Question 9

What is the order of External force/load, AOR, and Internal/Muscle effort in a First-class Lever

Answer 9

LAE
(External Force/Load—AOR—Internal/Muscle Effort)

Question 10

What is the order of External force/load, AOR, and Internal/Muscle effort in a Second-class Lever

Answer 10

ALE

(AOR—External force/load—Internal/Muscle Effort)

Question 11

What is the order of External force/load, AOR, and Internal/Muscle effort in a Third-class Lever

Answer 11

LEA

(External force/load—Internal/Muscle effort—AOR)

Question 12

What are the 2 types of forces that act on the Musculoskeletal System

Answer 12

Internal and External Forces

Question 13

What are the active internal forces of the musculoskeletal system?

Answer 13

Muscles

Question 14

What are the passive internal forces of the musculoskeletal system?

Answer 14

Joint capsules and ligaments

Question 15

What are the two external forces of the musculoskeletal system?

Answer 15

Gravity and external object

Question 16

Torque

Answer 16

Tendency of a force to create a rotation

Question 17

Torque = ________ x ________ _____

Answer 17

Force x moment arm

Question 18

Moment arm

Answer 18

Perpendicular distance from axis of rotation to line of applied force

Question 19

Torque:
Internal > external :

Answer 19

Concentric

Question 20

Torque:
Internal = external :

Answer 20

Isometric

Question 21

Torque:
Internal < external :

Answer 21

Eccentric

Question 22

What are the 3 rules of Shortening/Concentric Muscle Action

Answer 22

1. Movement is in the OPPOSITE direction as the external force/gravity. Speed doesn’t matter.
2. Movement is across gravity.
3. Movement is in the SAME direction as the external force/gravity but is FASTER than the movement produced by the external force alone.

Question 23

Rule for Lengthening/Eccentric Muscle Action

Answer 23

Movement is in the SAME direction as the external force/gravity but is SLOWER than the movement produced by the external force alone.
(*speed matters!)

Question 24

Rule for Isometric Action

Answer 24

There is NO movement but the joint position is held in opposition to an external force.

Question 25

What are the 6 steps for Identifying Muscle Action

Answer 25

1. Identify the joint movement and plane
2. Identify the effect of external force on the movement.
3. Identify the type of action based on #1 and #2
   (1. If opposite directions-shortening : concentric
4. If same direction - speed matters: Faster = shortening; slower = lengthening)
5. If no movement but external force would produce it - isometric)
6. Identify the AOR.
7. Determines which side of the joint axis the muscles are lengthening and which side they are shortening.
8. Combine steps #3 & #5 to determine muscles that are controlling the movement.