Muscle Function pt2 Flashcards
active tension
tension developed by the contractile elements of the muscle
what is active tension initiated by
cross bridge formation and movement of the actin and myosin
passive tension
tension developed in the passive non-contractile components of the muscle
where is passive tension developed
the parallel elastic components of the muscle
what is w/in the connective tissue that surrounds the muscle
titin (protein)
nerves and vessels
what is the length-tension relationship
there is a direct relationship b/w tension development in a muscle and length of a muscle
there is an optimal length at which a muscle is capable of developing maximal tension
optimal length
where a muscle is capable of developing maximal tension
optimal length is close to what is called “resting length”
1.2 times resting length
when do muscles develop maximal tension
at optimal length
b/w the actin and myosin are positioned for the maximum number of cross bridges
what happens when a muscle is shortened or lengthened beyond optimal length
force producing capabilities are decreased
too long –> minimal cross bridging, no tension generated
too short –> unable to shorten anymore, no cross bridging, no tension
what happens at optimal length
maximal number of cross bridges
maximal shortening
maximal tension (optimal tension)
what position will the body tend to put the muscles at when maximal tension is required
optimal length
optimal length = optimal tension
why is positioning of our patients while they perform their exercises important?
the position we place our patients in can alter the tension-length relationship
we allow the patient’s muscle to be @ an advantage to produce the optimal amount of tension
single joint muscles
muscles that cross only one joint
ex: brachialis
multi joint muscles
muscles that cross two or more joints
more efficient than 1 joint muscles
why are multi-joint muscles more efficient than single joint muscles
they can maintain an optimal length tension relationship throughout the range of motion
where do muscle insufficiencies primarily occur
multi-joint muscles
2 types of muscle insufficiencies
active insufficiency and passive insufficiency
2 types of active insufficiency
too long
too short
active insufficiency
TENSION
the diminished ability of a muscle to produce or maintain active tension
occurs when a muscle is too short or too long
too long active insufficiency
the muscle is elongated to a point at which there is no overlap b/w the actin and myosin
no cross bridges
no cross bridges = no active tension
example of too long active insufficiency
hip flexion and knee extension
too short active insufficiency
the muscle has shortened to a point at which no further sliding of the filaments can take place
cross bridges are maximally overlapped
no sliding –> no active tension
when does too short active insufficiency occur
when the full AROM is attempted simultaneously at all joints by the muscle
too short active insufficiency example
hip extension and knee flexion
what positions do you avoid with patients
every muscle has 2 positions of active insufficiency
these positions are those to avoid
passive insufficiency
ROM
occurs when a muscle is of insufficient length to permit completion of the full ROM available @ the joints crossed by the muscle
the muscle isn’t long enough to provide full ROM @ all joints the muscle crosses
what happens when the muscle develops passive tension
may be enough to pull the bony lever in the direction of passive pull
tendinosis
what is tendinosis
muscle creates enough passive tension to pull the bony lever
example of passive insufficiency
hamstrings
in the supine position, when the hip is being pushed into flexion, there is a point the knee will begin to flex d/t the amount of passive tension
active v. passive insufficiency
while both are related to the length of the muscle…
passive involves elastic or passive elements
active involves the contractile or active elements
a position of passive insufficiency will…
always be one of the positions of active insufficiencies
when the muscle is too long
types of muscle action
isometric contraction
isotonic contraction
isometric contraction
constant length (length never changes)
the distal and proximal attachments are fixed (distance =0)
shortening occurs at the myofibril level (visible length remains unchanged)
no mechanical work is performed
isotonic contraction
constant tension
tension never changed
2 types of isotonic contraction
concentric and eccentric
concentric contraction
shortening contraction
origin and insertion move closer together
positive work is being done by the muscle
eccentric contraction
lengthening contraction
origin and insertion move apart
muscle lengthens while it maintains tension
negative work is done
tends to be about control
when does eccentric contraction occur
when the forced that the muscle generates is insufficient to offset an opposing force on a lever or the resisting force of gravity
force production according to contraction type
eccentric contraction will produce the most tension
concentric contraction produces the least tension
reverse muscle action
occurs when the muscles distal attachment is fixed and the proximal is free
proximal bony component is pulled towards the distal bony component
origin moves towards the insertion
can occur in a concentric or eccentric contraction
agonist muscle
muscle that is responsible for producing a desired motion at a joint
types of agonist muscles
prime movers
secondary mover
prime movers
agonists
the muscle that plays the greatest role in completing the movement
secondary mover
agonist
does not consistently work in completing the movement but may be recruited to assist
antagonist
the muscle that has an action directly opposed to that of the agonist
synergist
refers to those muscles that help the agonist to perform a desired action
may assist the agonist directly or indirectly
how does a synergist directly assist the agonist
helping to perform the desired action
how does a synergist indirectly assist the agonist
stabilizing a part or by preventing an undesired action
types of synergists
conjoint synergy
neutralizing synergy
stabilizing synergy or co-contraction
conjoint synergy
when 2 or more muscles act together to produce a movement that neither muscle could do alone
example of conjoint synergy
radial deviation
flexor carpi radialis and extensor carpi radialis longus
there is no specific muscle or muscle group that performs radial deviation
neutralizing synergy
when a 2 joint muscle contracts, there may be an undesired motion at one of the joints
so another muscle will contract to “neutralize” that undesired motion
example of neutralizing synergy
finger flexion
during finer flexion, wrist extensors neutralize the finger flexion
they prevent the wrist from flexion to preserve the tension-length relationship
if the wrist were to flex, there would be active insufficiency and we wouldn’t be able to produce as much tension
stabilizing synergy or co-contraction
the contraction of agonists and antagonists of a proximal joint to allow
1) highly coordinated movements
OR
2) forceful contraction of a more distal joint
example of stabilizing synergy or co-contraction
finger flexion
elbow flexors and extensors stabilize the elbow while we flex our fingers to produce more force
proximal stability to produce force distally
stabalizing or co-contraction involves
an agonist and antagonist
neutralizing synergy involves
an agonist and some other muscle group
spurt muscles
a muscle whose proximal attachment (origin) is far from the joint axis
insertion is close tot he axis
results in large ROM
what happens when the insertion is close to the axis
has a large rotary or mobility component
shunt muscles
a muscle whose proximal attachment (origin) is close to the joint axis
insertion is far from the joint axis
ex: brachioradialis during elbow flexion
what happens when insertion is far from the joint axis
has a large translatory or stability component
shunt v. spurt
shunt –> stability
spurt –> mobility
