Stephen Johnson wrote:
Funny, I thought spinal support and extension was the function of the Erector Spinae
. Latissimus Dorsi
is involved with shoulder and upper back functions.
It's true. But think about this anatomically. The lats cover almost the whole lower back and has fascial connections almost everywhere in the spinal area, except the cervical one. They attach everywhere, including the thoracic spine, ribs, humerus, scapulae. They are one of the most active muscles in the whole back, during all kinds of movements. Holds and carries, presses, squats, pulls, you name it. It has huge importance in core and spinal stability.
I'd consider that the other spinal extensors and stabilizers hold a much smaller, but a necessary role in the back. When talking about erector spinae or multifidus or the spinalis muscles, they are not as big as lats, don't have much coverage, or they don't have much leverage so to speak. They are mainly connected directly on the spine with lots of insertions, and provide more of an isometric and stabilizing role in my mind. But, this is my opinion, and I should point out that none of these muscles should be counted out when talking about important muscles of the back.
EDIT: One great example is the deadlift. Altough lats are important on keeping the bar close to the body, you need strong and big lats to pull big numbers, they have great purpose on spinal extension and spinal stability. And vice versa, Heavy deadlifts usually build lats quite well.