Biomechanics of Muscular System pt 2

longitudinal arrangement

longitudinal arrangement

• Long, strap like muscle with fibers in parallel to its long axis

• Allows increased ROM but less power

Examples:

• Sartorius – longest fibers

•Sternocleidomastoid – turn head

quadrilateral arrangement

• Four sided and usually flat

• Consists of parallel fibers that allow increased power but smaller range of movement

Examples:

• Rhomboids

• Masseter

fusiform arrangement

• Rounded muscle that tapers at either end

• Allows for power and range of movement

Examples:

• Biceps brachii

• Brachioradialis

triangular or fan shaped arrangement

• Origin of the muscle is broad

• Fascicles converge toward the tendon of insertion

• Occurs if a large powerful muscle has to be focused at a restricted point of leverage

Examples:

• Pectoralis major

• Half a feather

pennate arrangements

•“Feathery” in appearance

•Seem to offer strength without bulk

•Muscles are usually quite flat or are found operating within confined spaces

unipennate arrangement

• A series of short, parallel, feather like fibers extends diagonally for side of a long tendon

Examples:

• Tibialis posterior

• Flexor pollicis lonus

bipennate arrangement

• Has a long central tendon with fibers extending diagonally in pairs from either side of the tendon

Example:

• Rectus femoris

multipennate arrangemnt

• Several tendons are present, with fibers running diagonally between them

Example:

• Middle deltoid

proportional

the force a muscle can exert is _ to its physiological cross

more

A broad, thick, longitudinal muscle exerts _ force than a thin one

greater

A pennate muscle of the same thickness as a longitudinal muscle can exert _ force

less; more

long muscles have _ range of motion

pennate muscles have _ range of motion but has greater force

effects of age on fiber types

In most individuals, there is a progressive age-related loss of Type II motor units and muscle fibers

effects of obesity on fiber types

Significantly lower proportions of Type IIB fibers are found in obese than in non-obese adults

• lipotoxicity

concentric contraction

Muscle force is sufficient to overcome a resistance and move the body segment

• Shortening of the muscle by you causing the movement

eccentric contraction

When a muscle lengthens as it gives in to an external force that is greater than the contractile force it is exerting

• Muscle “controls” movement like the brakes in your car when going down a hill

isometric or static contraction

Isometric means “equal length” thus no movement 

• Tension in the muscle without any appreciable change in length

Occurs under two conditions:

1.  Antagonistic muscles contract with equal strength

2.  Muscle is held against another force

isotonic

means “equal tension” and the tension remains constant while muscle shortens or lengthens

• Can be concentric or eccentric

isokentic

Isokinetic means “equal speed”

• Maximum muscle effort at the same speed; form of strength testing

• Can be concentric or eccentric

concentric

Lifting against gravity is a _ contraction of the agonist

eccentric

slower lowering with gravity is an _ contraction of the same muscle

movers or agonists

muscles directly responsible for producing a movement

prime movers

large impact on movement

assistant movers

only help when needed

synergists

muscles that work together

concentric

A forceful downward motion uses antagonist muscles is a _ contraction, since gravitational pull is being exceeded

antagonist

a role played by a muscle acting to slow or stop a movement

• primarily relaxed at the start of the movement

• primarily most active to slow a movement, at the end of the movement

stabilizer

is a role played by a muscle acting to stabilize a body part against some other force

• Muscles that contract statically/isometrically to sturdy or to support some part of the body against the pull of the contracting muscles

neutralizer

a role played by a muscle acting to eliminate an unwanted action produced by an agonist

• when muscle does more than one action, it counteracts unwanted action