Chapter 12: Types of Muscle Contractions

Stability does what?

Fix or stabilize Stop movement or hold it still,

Isometric Contractions-def.

Force of muscle contraction-Resistance force Muscle will neither shorten or lengthen Contraction occurs, but length stays the same No movers and no antagonists to identify

Contraction

Myosin grabbing actin and attempting to pull the sarcomeres closer to each other

Is all lengthening a contraction? Ex.

No, Ex. Muscle attachments moving away from eachother

Muscle Structure is:

organ attaching from bone to bone-tendon Composed on muscle fibers, which are composed of myofibrils, which is composed of sarcomeres-sliding filament

When do eccentric contractions occur?

when force is needed to slow down a movement caused by gravity or another external force

Three Types of Muscle Contractions

Concentric, Eccentric and Isometric

Scenario 3- Slowing Momentum of a Vertical Upward Motion

Controlled, basketball

Muscles:

Create forces to increase mobility and stability of joints

Concentric Contractions-movement

Create movement

Resistance Exercises & Example

Adds to the resistive force the contracting muscles must work against. May also want to reduce resistive forces. Ex.-Therapy

Three Scenarios-gravity

Against gravity, gravity neutral( doesn't exist), with gravity

Against Gravity

Basic, concentric, move against, vertically upward, most common

If contraction doesn't happen what happens?

Eccentric or isometric. Must ask what type of tensile force is created

What is it caused by?

External force

With Gravity

Gravity does its own work, want down motion to be faster-golf

Scenario 2- Against any Force other Than Gravity

Hold body part in position

Scenario 1-Against Gravity

Holding body part up

Gravity Neutral

Horizontal, not moving against or with gravity, rotational movements

Eccentric Contractions do what to movement?

Modify movement

Scenario 1-Slowing Gravity's Vertical Downward Motion

Most common, setting cup down

Mobility

Movement

Eccentric Contraction-def.

Muscle contraction that is lengthening, keep going until signaled to stop

Eccentric contractions

Muscle contracts and lengthens, opposes concentric contractions

Concentric contractions-def.

Muscle contracts and shortens, muscle is termed the mover

Isometric Contractions def.

Muscle stays the same length

Fixator (Stabilizer)

Muscle that acts to fix or stabilize a body part-isometic muscle contractions

Three Scenarios: Eccentric

Slowing Gravity's vertical downward motion, Slowing momentum of horizontal motion, Slowing momentum of vertical upward motion

Isometic Contractions do what with movement?

Stop movement

Must consider any additional forces

Weight, resistance

When do Concentric contractions occur?

When force is needed to move a body part

When do they occur?

When force is needed to stop a body part form moving

Resistance force

antagonist

Eccentrically contracting muscles

antagonists, negative contraction

Motor unit sizes

are as big as its branches

Must also consider any additional forces exist beyond that of the body part itself

beyond gravity

A Mover is a muscle that

concentrically contracts

what does a muscle mover do

creates the movement of the joint action

Nervous system control

muscle is innervated by a motor nerve, messages are sent to all fibers of a motor unit

Eccentric contraction is the result of

slowing down the movement of the external force

Opposing force:

stops muscle from contracting-gravity or internal force such as another muscle within our own bodies