Latissimus Dorsi

The latissimus dorsi (Thompson, 1989) has these functions:

1. Adduction — draws the arm to the side from the side-horizontal position and rotates inward as it adducts; a very strong action. Exercise: lat pulldown (pronated grip, medium and wide).
2. Extension — draws the arm from a front-horizontal position down to the side. Exercises: seated row (neutral grip & narrow width with pronated grip), pullovers, lat pulldown (supinated grip with shoulder width and smaller).

Origin: posterior crest of the ilium, back of the sacrum, and spinous processes of the lumbar and lower six thoracic vertebrae, with slips from the lower three ribs. Insertion: medial side of the intertubercular groove of the humerus.

It is a 2-joint muscle. The 2 most common training movements are shoulder-joint adduction (most effective — perform scapular depression & adduction) and shoulder-joint extension (2nd best — perform scapular adduction). Horizontal abduction (extension) is a weak action of the lat because it primarily emphasizes the trapezius and rhomboids. Because of the pectoral and lat insertion points, the lat pulldown produces eccentric tension in the pectorals. Every time the lats are trained, the teres major is too; secondary muscles are biceps brachii, brachialis, and brachioradialis.

• 2-joint muscle.
• Strongest action: adduction (arm to side from side-horizontal, rotating inward).
• Second action: extension (arm from front-horizontal down to side).
• Origin: posterior iliac crest, back of sacrum, spinous processes of lumbar + lower 6 thoracic vertebrae, slips from lower 3 ribs. Insertion: medial intertubercular groove of humerus.
• Most effective training: shoulder adduction with scapular depression + adduction.

• adduction — strongest action.
• extension — second action.
• scapular-movement — scapular depression/adduction for optimal work.
• trapezius — emphasized instead during lat horizontal abduction.
• lat-pulldown / seated-row / pullover — training exercises.