Dance Anatomy & Kinesiology

424 Dance Anatomy and Kinesiology

posterolaterally on the lower humerus and upper ulna to wrap around the radius and attach to the

anterolateral aspect of the upper radius (figure 7.41, p. 416). A way of picturing this action more clearly

is to consider a position of pronation in which the radius would be moving forward and in front of the

ulna. The supinator is in an appropriate position to pull the radius back (supination) toward anatomi-

cal position, in which the radius and ulna are approximately parallel. The supinator appears to actively

produce supination of the forearm under all conditions (Hamilton and Luttgens, 2002).

Palpation: Sit with the fingertips of the left hand about 1 inch (2.5 centimeters) distal to the lateral

epicondyle of the humerus while the right elbow is bent and resting against your waist. You can feel the

supinator contracting under your fingertips when the forearm is slowly supinated.

Summary of Attachments, Actions,

and Movement Roles of the Muscles of the Radioulnar Joints

A summary of the attachments and actions of the primary muscles that act to produce forearm prona-

tion and supination was included in table 7.6. As with elbow flexion and extension, some of the other

muscles whose primary action is at the wrist or hand can also assist with pronation and supination,

but for purposes of simplicity they are not included in table 7.7.

In functional movement, the movements of pronation and supination are often used to appropri-

ately position or assist with the action of the hand. For example, concentric contraction of the prona-

tors—including the pronator quadratus and teres—is used in movements such as turning a screw

counterclockwise (to loosen it) and dribbling a basketball. In dance, the pronators would be used in arm

movements that involve facing the palm backward as in jazz. In contrast, concentric contraction of the

supinators is used in tightening a screw, an underhand pitch, and a tennis backhand drive. In dance,

the supinators—including the supinator and biceps brachii—would work when the dancer raises the

arms from the sides with the palms facing upward.

In functional movement, the movements of the forearm are also often linked with motions at the

shoulder joint. So, when the elbow is straight, forearm supination is often accompanied by external

rotation of the shoulder, while forearm pronation is often linked with internal rotation of the shoulder.

This combination allows a greater range of motion for the hand and more forceful movements such as

used in turning a doorknob. In dance movements, these movements can also be combined to enhance

range or provide a desired aesthetic, as in modern or jazz dance when the front arm is externally rotated

with the palm facing up and the back arm is internally rotated with the palm facing back.

Note that this is a different arrangement than occurs in the lower leg, where the tibia and fibula are

firmly connected and almost no motion is allowed between them. In the lower extremity, changing the

facing of the foot occurs more distally within the bones of the feet rather than at the more proximal

site of the forearm in the upper extremity.

Structure and Movements

of the Wrist and Hand

The hand is a highly specialized structure that con-

tains 27 bones and over 20 joints, and the wrist-hand

complex involves the use of 25 key muscles. There

are many parallels between the foot and hand, but

one key distinction is that while the foot is designed

primarily for strength to support the body weight,

the hand is designed for manipulation.

The bones of the hand include eight carpals

(which are arranged in two rows of four), five meta-

carpals (numbered from 1 through 5 starting from

the thumb), and 14 phalanges as seen in figure 7.46.

However, while there is a parallel with respect to the

numbers and sequence of these bones, the tarsals

and metatarsals of the foot are much larger than the

corresponding carpals and metacarpals in the hand

(to better serve their weight-bearing function), while

in the hand the phalanges are larger than the pha-

langes in the foot (to better meet their manipulation

function). The distal row of carpals articulates with

the proximal end, or base, of the metacarpals. The

shaft of the metacarpal is termed the body; and the

distal rounded head of the metacarpal articulates

anteriorly with its respective phalanges. The heads of

the metacarpals can easily be palpated at the knuck-

les of the hand while the phalanges make up the

digits of the fingers. The fingers are numbered like

the corresponding metacarpals, with 1 correspond-