Muscular Activity during Elevation of the Arm

Question 1

Which muscle contracts to initiate shoulder abduction? How many degrees is this responsible for?

Answer 1

Supraspinatus; 0-15 degrees

Question 2

After the first 0-15 degrees of Shoulder Abduction, which muscles take over and to what degree?

Answer 2

(0-15 Supraspinatus)

• Deltoid Provides the remainder (15-90 degrees)

Question 3

Above 90 degrees of abduction which muscles are active and to what extent? (degrees of ROM)

Answer 3

Serratus Anterior, Trapezius (force couple; upper and lower traps) at the scapulothoracic joint

• Provides upward rotation of the scapula
• 90 - 150 degrees abduction

Question 4

Bilateral Abduction of the shoulder requires recruitment from which body region. Adaptations that are made?

Answer 4

• Thoracic Spine Extension
• Increased Lumbar Lordosis

Question 5

In Shoulder Abduction is the Trapezius or Serratus Anterior Predominate?

Answer 5

Trapezius Mainly, but SA still active

Question 6

In Shoulder Flexion is the Trapezius or Serratus Anterior Predominate?

Answer 6

Serratus Anterior Mainly, but Trapezius is still active

Question 7

Muscles Associated with Downward Rotation of the Scapulae?

Answer 7

• Rhomboids
• Levator Scapulae
• Pectoralis Minor

Question 8

If Upward rotation of the Scapula is Lacking, what strength deficits may cause this limitation?

Answer 8

Concentric Motion is Lacking:

• Upward Rotators or Weak

Question 9

If Upward rotation of the Scapula is Excessive, what muscle weakness may cause this limitation?

Answer 9

Eccentric Control is Lacking:

• Downward Rotators are Weak