biomechanics

Basic muscle functions

Create movement

Maintain posture

Stabilize joints

Generate heat through contraction

Muscle properties

Contractillity: shorten

Extensibility: stretched beyond resting length

Elasticity: ability to return to resting length

Muscle nomenclature

Shape, size, number of heads, action, location, direction of fiber, attachment points.

Parallel muscle

Fibers run parallel to length of muscle

Great range of motion, less force

panate muscle

Fibers run at an angle to the tendon

Greater force less rom

Types of parallel muscles

Flat, fusiform, strap, radiate, sphincter

Types of pennate muscles

Unipennate: fibers on one side of tendon

Bipennate: fibers on both sides

Multipennate: several tendons with fibers

origin

proximal/stable attachment point

Insertion

Distal/movable attachment

Apineurosis

Flat, tendon like connective tissue

Retinaculum

Band that holds tendon in place

Fascia

Connective tissue surrounding muscles and groups

Muscle structure

Muscle-fascicle-muscle fiber-myofibrils-sarcomeres

Innervation

CNS

PNS

Force and velocity relationship

Faster contractions-less force

Eccentric contractions - greater force

Length and tension relationship

Optimal force at mid range muscle length

Isometric contraction

Muscle contracts but no movement

Stabilization

Concentric contraction

Muscle shortens, overcomes resistance

Acceleration

Eccentric contractions

Muscle lengthens under tension

Deceleration and control

muscle role: agonist

Prime mover ( main action )

Muscle role: antagonist

Opposes movement

Muscle roles: synergist

Assists agonist

Muscle role: neutralizer

Cancels unwanted motion

Muscle roles: stabilizer

Supports a joint

Muscle roles: force couple

Two+ muscles produce movement in the same direction

Proprioception

Body’s ability to sense position and movement

Kinesthesia

Awareness of motion itself

Muscle fiber type 1

Slow

High endurance

Posture

Muscle fiber type iia

Some endurance

Intermediate

Muscle type iix

High force quick fatigue

Explosive

Active insufficiency

Muscle cannot shorten enough to produce full range

Passive insufficiency

Opposing muscle too stretched to allow full rom

Lever class 1

A-R-F

Head neck

Balance

Levers class 2

A-R-F

Calf raise

Force advantage

Lever class 3

A-F-R

Bicep curl

Speed Rom advantage

Force arm

Distance from axis point of force application

Resistance arm

Distance from axis to resistance

Mechanical advantage

MA= force arm / resistance arm

MA > 1 more force

MA < 1 great speed and rom

Axis (A)

Pivot point or joint

Force (F)

Muscle effort applied

Resistance (R)

Weight or external load

Pulley

Change direction of force

Wheel and axle

Enhances force or speed

Law of inertia

Body stays at rest or motion unless acted upon

Law of acceleration

Force = mass x acceleration

Law of action

Every action has an equal and opposite reaction

Balance and stability

Balance: ability to control equilibrium

Stability: resistance to change in equilibrium