Relier Pairs Muscle Actions Part One (D)Version en ligne muscles par Jennifer Jennings 1 rectus abdominis 2 flexor carpi radialis and ulnaris 3 triceps brachii 4 pectoralis major 5 deltoid 6 levator scapulae 7 sternocleidomastoid 8 biceps brachii 9 latissimus dorsi 10 trapezius elbow flexion, forearm supination. adducts and medially rotates humerus, extends the shoulder joint rotates head left and right. bilaterally draws head forward and down. flexes wrist anteriorly flexes, adducts, and medially rotates humerus elevates scapula if cervical vertebrae are fixed., flexes neck laterally when scapula is fixed. ant. fibers flex and medially rotate arm, lat. fibers abduct the arm, post. fibers extend and laterally rotate the arm flexes waist and compresses abdominal viscera extends and laterally flexes the neck. extends elbow