We'll start with the two largest muscles of the back musculature... the lats and traps.

The Latissimus Dorsi muscles (also known as the Lats) are the largest muscles of the back. Being large, fan-shaped muscles, they are able to provide force in a wide range of body positions, e.g. leaning back to straight vertical and all points in between.

The Lats are attached to the upper end of the humerus with fibers running down in a fan down the vertebral column and pelvic girdle.

The Trapezius (trap) muscle is a long, trapezoid-shaped muscle that runs down the upper section of the spinal cord, originating at the base of the skull, down the spine and in the middle back, attaching to the scapulae.

The angles of the Trapezius fibers provide pull in three different directions: up, down and in towards the centerline of the body. These actions are performed by the three different sections of the muscle...upper, middle and lower traps.

The Teres Major muscle originates on the outer (lateral) edge of the scapula and attaches to the humerus.

The Teres Major muscles work with the Rotator Cuff muscles to stabilize the shoulder joint and works with the Latissimus Dorsi muscles to pull the humerus back.

The Rhomboids (Major and Minor) originate on the spinal column and attach to the middle (medial) surface of the scapula.

The Rhomboid muscles get their name from their shape: rhomboid. The Major and Minor designations refer to their relative size to each other.

The Erector Spinae is a group of muscles that support the spinal column. They include the Longissimus, the Spinalis and Iliocostalis. The muscles of the Erector Spinae attach to the vertebrae, the ribs and the pelvis.

The functions of the Erector Spinae group are to extend the spine as well as provide support for it.

Exercises that work the Erector Spinae include hyperextensions, deadlifts and good mornings.

Exercises that work the Erector Spinae include hyperextensions, deadlifts and good mornings.