Mechanics of MovementMechanics of Movement

Muscle Structure ReviewMuscle Structure Review

• Muscle fiberMuscle fiber = = muscle cellmuscle cell• Fibers lined up = direction of pullFibers lined up = direction of pull• TendonTendon attaches to attaches to bonebone• Muscle pulls on boneMuscle pulls on bone

Muscle Origin Muscle Origin and Insertionand Insertion

• OriginOrigin– ProximalProximal– FixedFixed

• InsertionInsertion– DistalDistal– MovesMoves

• (usually!!)(usually!!)

What is the origin?What is the origin?

Origin- is the point where the muscle Origin- is the point where the muscle attaches to a stationary bone.attaches to a stationary bone.

What is the insertion?What is the insertion?

Insertion- is the point where the Insertion- is the point where the muscle attaches to the moving muscle attaches to the moving bone.bone.

Muscle PhysicsMuscle Physics• Length Length of muscle is of muscle is

proportional to ability to proportional to ability to shorten (strain)shorten (strain)– Number of Number of sarcomeressarcomeres in series in series

gives shortening abilitygives shortening ability

• Short, fat musclesShort, fat muscles– Lots of forceLots of force– Less shortening rangeLess shortening range

• Long, skinny musclesLong, skinny muscles– Less forceLess force– More shortening rangeMore shortening range

Muscular movement of bonesMuscular movement of bones

Generally skeletal muscles are attached to one Generally skeletal muscles are attached to one end of a bone, stretch across a joint, and are end of a bone, stretch across a joint, and are fastened to the end of another bone.fastened to the end of another bone.

Muscular movement of bonesMuscular movement of bones

Muscles are attached to bones to form Muscles are attached to bones to form lever systems to create movementlever systems to create movement

Types of Types of fasciclefascicle arrangements arrangements

• Affects length Affects length and cross section and cross section of muscleof muscle

• Thus affects force Thus affects force and shortening and shortening properties of properties of musclemuscle

MUSCLES & LEVERSMUSCLES & LEVERS

LEVERLEVER – simple machine – simple machine for making work easierfor making work easier

Three factors influence a Three factors influence a lever:lever:

1.1. Load – to be movedLoad – to be moved2.2. Effort – needed to move Effort – needed to move

the loadthe load3.3. Fulcrum – point of balanceFulcrum – point of balance

Muscle movement across joints is Muscle movement across joints is like lever systemlike lever system

First-class leverFirst-class lever

Second-class leverSecond-class lever

Third-class leverThird-class lever

Muscles attach to bone by tough Muscles attach to bone by tough connective tissue called what?connective tissue called what?

Muscles attach to bone by tough Muscles attach to bone by tough connective tissue called what?connective tissue called what?

TendonsTendons

Movement of the limbsMovement of the limbs

Movement of the limbsMovement of the limbs

Muscles work in pairs to move a limbMuscles work in pairs to move a limb

• 1) Agonist1) Agonist

• 2) Antagonist2) Antagonist

AgonistAgonist

"prime movers""prime movers" responsible for generating a specific responsible for generating a specific

movement through its own movement through its own contractioncontraction

AntagonistAntagonist

acts in opposition to the specific acts in opposition to the specific movement generated by the agonistmovement generated by the agonist

responsible for returning a limb to its responsible for returning a limb to its initial position.initial position.

Stabilization and Control Stabilization and Control AroundAround Joint Joint

Agonist Main Mover E.g. biceps

Antagonist Opposite motion E.g. triceps

Synergist Aids agonist E.g. brachialis

Antagonist often “fires” or contracts or is stimulated simultaneously with agonist to stabilize around joint during movement

NOTE: Muscle “contraction” or stimulus to “fire” does not always result in muscle shortening

Agonist/AntagonistAgonist/Antagonist