How Muscles Work Flashcards
Agonist
Muscle controlling the movement
What are the 2 parts of an Agonist?
Prime mover and synergist
Antagonist
Muscle opposing the agonist
Co-contraction
Both agonist and antagonist are acting at the same time; stabilize/stiffen a joint to prevent movement
Neutralization
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
Stabilization
Specific recruitment of antagonist or use of external forces that counteract unwanted movement of proximal or distal attachment
Muscles move the segment with ______ inertia
Less
What are the 3 types of Lever Systems
First-class lever
Second-class lever
Third-class lever
What is the order of External force/load, AOR, and Internal/Muscle effort in a First-class Lever
LAE
(External Force/Load—AOR—Internal/Muscle Effort)
What is the order of External force/load, AOR, and Internal/Muscle effort in a Second-class Lever
ALE
(AOR—External force/load—Internal/Muscle Effort)
What is the order of External force/load, AOR, and Internal/Muscle effort in a Third-class Lever
LEA
(External force/load—Internal/Muscle effort—AOR)
What are the 2 types of forces that act on the Musculoskeletal System
Internal and External Forces
What are the active internal forces of the musculoskeletal system?
Muscles
What are the passive internal forces of the musculoskeletal system?
Joint capsules and ligaments
What are the two external forces of the musculoskeletal system?
Gravity and external object
Torque
Tendency of a force to create a rotation
Torque = ________ x ________ _____
Force x moment arm
Moment arm
Perpendicular distance from axis of rotation to line of applied force
Torque:
Internal > external :
Concentric
Torque:
Internal = external :
Isometric
Torque:
Internal < external :
Eccentric
What are the 3 rules of Shortening/Concentric Muscle Action
- Movement is in the OPPOSITE direction as the external force/gravity. Speed doesn’t matter.
- Movement is across gravity.
- Movement is in the SAME direction as the external force/gravity but is FASTER than the movement produced by the external force alone.
Rule for Lengthening/Eccentric Muscle Action
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!)
Rule for Isometric Action
There is NO movement but the joint position is held in opposition to an external force.
What are the 6 steps for Identifying Muscle Action
- Identify the joint movement and plane
- Identify the effect of external force on the movement.
- Identify the type of action based on #1 and #2
(1. If opposite directions-shortening : concentric - If same direction - speed matters: Faster = shortening; slower = lengthening)
- If no movement but external force would produce it - isometric)
- Identify the AOR.
- Determines which side of the joint axis the muscles are lengthening and which side they are shortening.
- Combine steps #3 & #5 to determine muscles that are controlling the movement.
