muscles of the elbow Flashcards
elbow flexion primary movers
brachialis
biceps brachii
brachioradialis
pronator teres
secondary or assist muscles for elbow flexion
extensor carpi radialis longus and brevis
flexor carpi radialis
palmaris longus
flexor carpi ulnaris
pass anterior to the elbow axis
used when needed to move a larger load
how do we determine whether a muscle is or isnt active during elbow flexion
location of muscle
position of the elbow or adjacent points
position of forearm
magnitude of applied load
type of muscle contraction
speed of motion
location of muscle
refers to its insertion
is it close to the joint or is it far from the joint (spurt v. shunt muscle, stability v. mobility)
position of the elbow or adjacent joints
fully extended v. fully flexed
affects angle of insertion and what muscles we recruit
shoulder position will dictate what elbow flexors we recruit
position of forearm
pronated or supinated
magnitude of applied load
what is the resistance
how much are we trying to move
type of muscle contraction
isometric
eccentric
concentric
speed of motion
are we moving quickly or are we moving slowly
brachialis
is a 1 joint muscle
inserts close to the joint axis and is considered a spurt muscle (mobility muscle)
“work horse” of the elbow flexors
not affected by shoulder position (b/c it is a one joint muscle)
produces greatest torque at approximately 100 degrees of elbow flexion (length tension relationship is optimized)
how is the brachialis the “work horse”
always active, despite forearm position, with or without resistance, fast or slow movements and during all types of contractions
is the biceps brachii a spurt or shunt muscle
spurt or mobility muscle
how many joints does the biceps brachii cross
2 joints
the position of the shoulder will effect its function at the elbow
when is the biceps brachii active
during unresisted elbow flexion as long as the forearm is supinated or in mid position
quick or slower movements
concentric and eccentric contractions (except when the forearm is pronated)
when is the biceps brachii active despite forearm position
when the resistance is great
when does the biceps produce the greatest force
b/w 80-100 degrees of elbow flexion
functions at the shoulder of the biceps
assisting in shoulder flexion
abduction when the shoulder is in ER
effects of shoulder position on biceps function
when the shoulder is slightly extended, the length tension relationship is maximized
biceps are actively insufficient when the shoulder is in the too short or too long position
biceps are passively insufficient when its in the too long position
too short biceps brachii
shoulder is flexed
elbow is flexed
forearm is supinated
too long biceps brachii
shoulder is extended
elbow is extended
forearm is pronated
is the brachioradialis a shunt or spurt muscle
shunt muscle
acts for joint stability
when is the brachioradialis active
when the forearm is neutral or pronated
when the speed of the motion increased
when resistance is applied
is the brachioradialis affected by shoulder position
no
it doesnt cross the shoulder
pronator teres
will assist with elbow flexion when resistance is applied
elbow extension primary movers
triceps with assist from the anconeus
what is the overall effectiveness is affected by
changes in elbow position
BUT NOT CHANGES IN THE FOREARM
how many joints does the triceps cross
2 joints
is affected by shoulder position
when does the triceps produce the greatest force
at 90 degrees of flexion
parts of the triceps
medial head
lateral head
long head
medial head
“work horse” of the extensors
active all the time
lateral head
strongest of the 3 heads
only recruited w/ resistance
long head
only active during resisted elbow extension
effects of shoulder position on the triceps
when the shoulder is slightly flexed, the length tension relationship is maximized
when its actively insufficient and passively insufficient
actively insufficient –> triceps
too short –> elbow extension and shoulder extension
too long –> elbow flexion and shoulder flexion
passively insufficient –> triceps
elbow flexion and shoulder flexion
anconeus
assists in elbow extension
acts as a stabilizer during pronation and supination
supination primary movers
supinator
biceps brachii
supinator
is always active during forearm supination
not affected by forearm position
biceps brachii (supination)
is active with resisted supination, including when elbow is extended
at 90 degrees of elbow flexion –> is the primary supinator
pronation primary movers
pronator quadratus and pronator teres
pronator quadratus
active in any position of the forearm or elbow regardless of speed of motion
with or without resistance
will maintain compression of the distal radioulnar joint
pronator teres (pro)
is active during resisted or fast pronation regardless of elbow position
also works as an elbow flexor
synergies at the elbow
biceps and triceps
biceps and triceps synergy (1)
when a forceful grip is made they will work synergistically to stabilize the elbow
also prevent movement that could be caused by strong contraction of the wrist and finger flexors and extensors
co-contraction
biceps and triceps synergy (2)
actions of turning a door knob or using a screw driver
triceps will stabilize the elbow and prevent elbow flexion that could be caused by the biceps or pronator teres as they participate in supinator or pronation
