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Muscle action at the Elbow joint - Coggle Diagram
Muscle action at the Elbow joint
Elbow flexors
Brachialis
Proximally:
Distal half of the anterior surface of humers
Distally:
Tuberosity of ulna
Unaffected by the changes in forearm position brought by the rotation of radius
is Considered a mobility muscle
MA is greatest at
at around 100 degrees of elbow flexion,
troque produced will be greatest
One joint muscle and will not be affected by the position of shoulder
Active in all position of elbow flexion
and in all types of contraction
Biceps Brachii
Long head:
Supraglenoid tubercle to radial tuberosity
has the Largest volume among the flexors
Short Head:
Coracoid process to radial tuberosity
Considered a mobility muscle
MA is largest
between 80 - 100 degrees of elbow flexion,
& troque produced will be greatest
In full extension MA of biceps is relatively small, hence force can only be translatory and
toward joint compression, less effective as a flexor in this position
Functioning of the biceps is affected by the position of shoulder
If shoulder is fully flexed and elbow flexion is attempted
when the arm is supinated, torque production is
diminished
Biceps are active during
Supination
Unresisted elbow flexion with supinated forearm and in
neutral position for both concentric and eccentric
contraction
When magnitude of resistance is increased then active in all position of the forearm
Brachioradialis
Proximally:
lateral aspect of the distal humerus above the lateral epicondyle
Distally:
lateral aspect of the distal radius
Away from the joint axis
Considered a stability muscle
MA peak is at 100-120 degrees of elbow flexion
Not affected by the shoulder position
When speed of motion is increased, Brachioradialis is active moderately
if a load is applied and
when the forearm is pronated or neutral
Active in pronation
Elbow Extensors
Tricpes brachii
Proximally:
long head
Infraglenoid tubercle
lateral head
lateral aspect of the humerus
above the radial groove
medial head
medial aspect of the humerus
below the level of the radial groove
Distally:
All 3 heads
Olecranon of the ulna
Affected by the changes of position of elbow but not the position of forearm
2 joint muscle, hence affected by shoulder position
in unresisted active elbow extension,
Medial head is active
when resisted heavily
all heads are active
is active eccentrically
when the body is lowered to
the ground in a pushup
n concentrically
in the upward
motion
Active during stabilization of elbow joint
Eg. Act as a synergist to prevent flexion when the bicpes is acting as a supinator
the effectiveness of triceps brachii as a whole
is uneffected
by changes in the position of the forearm
because triceps attaches to the ulna
NOT the radius
the influence of long head of triceps
is affected
by changing shoulder positions
cos the long head crosses both the shoulder & the elbow
the long head's ability to produce force will diminish when full elbow extension attempted with simultaneous shoulder hyperextension
because the muscle is shortened over both joints at the same time, thus is approaching active insufficiency
the medial and lateral heads of the triceps are
1 joint muscles
so are not effected by the position of the shoulder
medial head is active
in unrestricted elbow extension
all 3 heads are active
when heavy resistance is given to extension
or when quick extension of elbow is attempted,
even in a gravity assisted position
when the elbow is extended
(triceps shortened at the elbow)
the shoulder is FLEXED
when the elbow is flexed
(long H of triceps is lengthened over the shoulder
the shoulder is EXTENDED
Anconeus
Proximally: Lateral epicondyle of the humerus
Distally: Olecranon process and posterior ulna
Assist in elbow extension
Act as a stabilizer during supination and pronation