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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