Back and stomach muscles play an important role in allowing your spine to do its job properly. They give the spine extra support and allow movement to take place.
Many people don't realise how important the muscles in your abdomen and pelvic floor are and how they also play an important role in giving the spine support.
There are many different back muscles attached to and providing support to your back.. Some are designed to add support and stability; others are designed to move the spine. There is a close relationship between these different types of muscles.
The muscles that add support are also often referred to as the core muscles or core stabilisers.
The following diagrams show the main surface abdominal (stomach) muscles:
You can't see all these muscles from the surface.
The transversus abdominis muscle (also known as the transversus abdominus or trans abs for short) has been in the headlines over the last few years because of its role as a core stability abdominal wall muscle in the treatment for lower back pain.
The transversus muscle is a corset-like abdominal wall muscle that is the deepest (or the furthest in) of the abdominal muscles. It is attached to the body in a few places including the spine, the ribs and the pelvis. It runs in a circular, tube like fashion around the whole of the trunk.
The next layer up is the internal oblique and the external oblique sits above that. The rectus abdominus sits in the centre and makes up the 'six pack'.
In addition to transeversus there are other small muscles such as multifidus, and quadratus lumborum which play an important role in stability. The diagram below shows a cross section of a lumbar vertebrae showing where the muscles sit in relation to one another. Notice the psoas major muscle - that is the muscle that bends your hip joint upward. It passes close in front of the lower back vertebrae.
We tend to think of abdominal muscles as being the six pack muscles you get when you do a lot of sit ups. Actually, sit ups mostly focus on the rectus abdominis muscles and also to a lesser degree the internal and external obliques.
You may not realise that some abdominal wall muscles actually attach at the spine and pelvis and create a tube like support structure for your back. This is why they play an important role in giving your back support and why they have come into such prominence in the treatment for lower back pain.
There are two main types of muscle in the human body, those designed for fast short bursts of activity, the sprinters - examples are your leg muscles, and those designed for longer, endurance work, the marathon runners. The transversus muscle is like a marathon runner. It is designed to have long, slow endurance. Exercising this muscle can therefore be a little tricky.
There is a lot of research currently underway looking at the relationship between this muscle and back pain. You may hear transversus abdominus talked about a lot as one of the key 'core stabilising' muscles.Much of the abdominal muscle work we do in physiotherapy concentrates on the core stabilisers. See some core stability exercises here
If you imagine for a moment that your trunk is a cylinder.
If the abdominal muscles and pelvic floor are strong and supportive they stiffen the cylinder and give the spine good support. The image below shows the layers in the walls of the cylinder, as if you are looking at a slice from the head down (just one side is shown here).
The bones, discs and joints are connected together and given excellent flexibility by tough bands of cartilage called ligaments.
There are many ligaments in the spine. The diagram below shows some of them.
I won't name them all but you can see that they pass between all the different parts of the vertebrae including the parts that stick out at the back and sides (the spinous and the transverse processes).
A sleeve of ligamentous tissue, called the capsule, also surrounds each facet joint. This keeps each joint fully enclosed, adding extra support and protection.