The Upper Extremity 417been shown to be least with the forearm pronated and most with the forearm supinated (Hamilton and
Luttgens, 2002). At the shoulder, the biceps brachii can assist with shoulder flexion (and abduction
when the shoulder is externally rotated with the elbow straight). Hence, performing elbow flexion with
the shoulder in a position of flexion, such as in partnering or the kneeling biceps lift (table 7.10M,
p. 442), will increase the difficulty for the biceps brachii, without influencing the difficulty for elbow
flexors that do not cross the shoulder such as the brachialis. In addition, the biceps brachii can assist
other muscles with adduction of the shoulder.
Palpation: The biceps brachii can be easily seen and palpated on the front of the upper arm. Sit with
the fingers of the left hand on the front of your right upper arm, with the right elbow bent and the right
palm under the top of a desk. You can feel the biceps brachii contracting when you press your right
palm up against the desk as if to bend the elbow (isometric elbow flexion). Move your fingers distally
on the biceps, and you will find its tendon standing out prominently at the fold of the elbow. Note that
the biceps brachii attaches proximally on the scapula and attaches distally below the elbow, and has no
actual attachment onto the humerus. Thus, when you relax this muscle, it can more readily be moved
from side to side than the underlying brachialis, which has extensive attachments onto the humerus.Attachments and Primary Actions of Brachialis
Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)
Brachialis
(BRA-kee-al-is)Anterior aspect of lower half of humerus Upper ulna Elbow flexionBrachialis
The brachialis (brachium, arm) is located on the
front of the arm beneath the biceps brachii (figure
7.42). It arises proximally from the anterior por-
tion of the lower half of the humerus and attaches
distally to the upper ulna. Due to its attachment on
the ulna, the brachialis does not produce supination
or pronation of the forearm and is not influenced
by the position of the forearm. The brachialis is
sometimes termed the “workhorse of the elbow”
because it appears to work in almost all conditions
of elbow flexion, regardless of speed, resistance, or
forearm position.
Palpation: Sit with the fingers of the left hand on
the front of your right arm (about 1 inch [2.5 centi-
meters] above the crease of the elbow and to the
sides of the biceps brachii) while the right elbow is
bent and the forearm pronated such that the right
dorsum of the hand is under the top of a desk. You
can feel the brachialis contracting just medial and
lateral to the biceps when you press your right hand
up against the desk as if to further bend the elbow
(isometric elbow flexion).FIGURE 7.42 Brachialis and coracobrachialis (right
arm, deep anterior view).