Dance Anatomy & Kinesiology

The Muscular System 63

electrodes) to help record the electrical activity of
muscles during various movements or conditions
(see Basmajian and DeLuca, 1985). The greater the
contraction of the muscle, the greater the frequency
and amplitude of the recorded potentials. Results of
some of these studies will be referred to in ensuing
chapters, and additional research methods helpful for
movement analysis will be addressed in chapter 8.

4. Determine the muscles that could produce
   a given joint movement. In addition to learning
   the action(s) of a given muscle, it is important to
   reverse that process and learn which muscles could
   produce a given joint movement. This is impor-
   tant for movement analysis. A summary table for
   each region is provided in chapters 3 through 7
   to help with this process. A cumulative summary
   is also provided in chapter 8. When performing this

process, for now focus on just the prime movers. A

more detailed analysis can take into account second-

ary muscles, synergists, and stabilizers; this more

detailed approach will be reserved for chapter 8.

Furthermore, simplify this process of analysis by

first identifying the functional group of muscles that

would perform the movement (e.g., hip flexors, hip

extensors, hip abductors) as seen in table 2.5, and

then selecting one to three specific primary muscles

that perform this desired joint movement.

5. Take into account the influence of gravity
   and the type of muscle contraction. When one is
   practicing this process of analyzing a movement, it is
   important to remember that the influence of gravity
   must be taken into account. In many phases of dance
   movements, gravity is fundamental in producing
   the movement, and muscles are used to control this

Deducing Muscle Actions From Their Attachments

Use figures 2.19 and 2.20 for reference.

• Action of the middle deltoid muscle. Find the middle deltoid in figure 2.20, and use this to
  locate the muscle on your body or a skeleton. Place your thumb on the estimated midpoint of the
  proximal attachment and your little finger of the same hand on the estimated midpoint of the distal
  attachment to establish the line of pull of the muscle. Now bring the distal attachment toward the
  proximal attachment and see what shoulder joint movement occurs. Check this action with that listed
  on figure 2.20.


• Action of the anterior deltoid and posterior deltoid. Repeat this procedure with the anterior
  deltoid (figure 2.19) and posterior deltoid (figure 2.20).


• Reversal of customary action. This procedure demonstrates the customary actions of muscles
  (with concentric contractions) in which the distal segment is the moving end. This is the easiest way
  to learn muscle actions. However, keep in mind that in instances such as when the hand is fixed
  (closed kinematic chain), these muscles can produce movement of the proximal segment (reversal of
  customary action) or both segments simultaneously (e.g., push-up, pull-up, dips).

CONCEPT DEMONSTRATION 2.6

Attachments and Primary Actions of the Deltoid Muscle

Muscle

Proximal

attachment(s)

Distal

attachment(s) Primary action(s)

Deltoid

(DEL-toid)

Anterior: clavicle

(lateral aspect)

Middle: scapula

(acromion process)

Posterior: scapula

(spine)

Humerus (deltoid

tuberosity)

Anterior: Shoulder flexion

Shoulder horizontal adduction

Shoulder internal rotation

Middle: Shoulder abduction

Shoulder horizontal abduction

Posterior: Shoulder extension

Shoulder horizontal abduction

Shoulder external rotation

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