Latissimus Dorsi: The latissimus dorsi is the broadest & largest muscle of the back. Latissimus Dorsi actions mainly are Extension, Adduction and Internal Rotation of the upper limb.
Attachment of the Latissimus Dorsi
Origin:
Ilium-Posterior iliac Crest
Sacrum -Posterior
Vertebral Column -Laterally
Thoracic Vertebrae (T7-12) & Lumbar Vertebrae (L1-5)
(thoracolumbar fascia )
Ribs (Posterior) inferior three or four ribs
Insertion: The fibers converge into a tendon that attaches to the intertubercular sulcus of the humerus.
Nerve supply of the Latissimus Dorsi:
Innervation: Thoracodorsal nerve.
Actions of the Latissimus Dorsi
Extension
Adduction
Depression
Internal Rotation of the upper limb
Latissimus Dorsi Primary Actions
Adduction of the arm at the shoulder joint
Agonists: Teres Major, Pectoralis Major, Triceps Brachii (long head)
Antagonists: Supraspinatus, Deltoid (middle)
Extension of the arm at the shoulder joint
Agonists: Deltoid (posterior) Triceps
Antagonists: Deltoid (anterior), Coracobrachialis, Biceps brachii, Pectorial Major (clavicular head)
Rotate internally of the arm at the shoulder joint
Agonists: Deltoid (anterior), Subscapularis, Pectoralis Major, Teres Major
Antagonists: Infraspinatus, Teres minor, Deltoid (posterior)
Secondary Actions of the Latissimus Dorsi
Assists with the extension of the trunk
Agonists: Iliocostalis lumborum, Longissimus thoracis, Iliocostalis thoracis
Antagonists: Rectus abdominis
Assists with flexion of the trunk
Agonist: Rectus abdominis
Antagonists: Iliocostalis lumborum, Longissimus thoracis, Iliocostalis thoracis
Assists with lateral flexion of the trunk
Agonist: Rectus abdominis, Quadratus lumborum
Antagonists: Iliocostalis lumborum,Longissimus thoracis, Iliocostalis thoracis
Assists with anterior and lateral pelvic tilt
Agonist: Rectus abdominis
Antagonists: Semitendinosus, Biceps femoris, Semimembranosus
Assists with depression of the scapula
Agonists: Serratus Anterior (lower fibres), Pectoralis minor, Trapezius (lower fibres)
Antagonists: Trapezius (upper fibres), Levator Scapulae
Assist with protraction of the scapula
Assists with deep inspiration and forced expiration