Question

Agonists: Levator Scapulae and Trapezius (upper fibers) // Antagonists: Serratus Anterior and Trapezius (lower fibers)

Describe the starting position, direction of movement, and end position of the shoulder girdle when the prime movers named in above are performing an isotonic eccentric contraction, with reference to the muscle attachments and direction of fibres.

Describe an exercise (starting position, movement, end position) that works the antagonist muscle named in (1) above in an isotonic concentric contraction with reference to the muscle attachments and direction of fibres.

Answer 1

These are the Shoulder girdle muscles:

Agonist muscles perform contraction and antagonistic muscles perform relaxation.

1.Levator scapula function is to elevate the scapula and tilt the glenoid cavity inferiorly by rotating scapula downward.

Trapezius upper fibers elevate and extend the head.

Levator scapula is originate at the posterior tubercle of transverse process of cervical vertebrae and insert at the scapula between superior angle and root of spine.

Trapezius originate from occiptal Protrubranc and thoracuc vertebrae and insert at spine. It has upper middle and lower fibers. In which upper fiber act as agonist in shoulder girdle movement. And direction of upper fiber is horizontal.

2. Serratus anterior originate from 1 to 9th rib and insert at the medial border of scapula. It draws medial border of scapula away from vertebrae.

Lower fibres of trapezius attached to the spine of scapula

Lower fibers of trapezius depresses the scapula.