The spine is surrounded by many muscles and ligaments on different layers. These muscles relate the spine to the pelvis, the legs, the head, the shoulders, the arms, the chest, the groins, and the abdomen (as you can see, with the whole body). Their proper use will lead to a healthy, fluid and beautiful posture in life (I am not refering to an asana) and will spare you from future suffering. The knowledge of these muscles will take you to flex or extend your pelvis, to arch or bend your spine, to turn your shoulders, yo widen the chest, or to ground your sitting bones and grow up like a tree rooting in the earth.
In between the vertebral bodies, it's possible to find some sort of cushions which pad the contact between them called intervertebral disks. When weight and pressure are too much or the discs, the semisolid content of them spills out pressing the spinal nerves and causing an awful lot of pain.
The most vulnerable parts of the spine are only protected by muscles. The cervical vertebrae which "only" carry around 5 kg are surrounded by fewer and thinner muscles than the lumbar which has the whole weight of the upper body, this is the reason why inverted postures, like head balance and shoulder balance, in which the weight of the body is very much on the head and neck should be approached with lots of care so as not to damage the cervical region permanently. The lumbar portion of the spine is protected at the front by a group of muscles called the "abdominal muscles", which are mainly three: the Rectus abdomini, the Transversus abdomini, and Obliques. The back of the lumbar is protected by the Latissimus dorsi and part of the muscular system called the "Erector spinae" which is in charge of keeping the spine upright. (See picture A)
|Picture A. The many muscles of the back.|
There are very many muscles that work in the spine, but the ones we will focus on for the time being are the abdominal muscles, the Latissimus dorsi, the erector muscles, and the Iliopsoas.
The Iliopsoas is a key postural muscle, it a flexor of the pelvis, that means it tilts your pelvis into the forwardbend position. It is composed by two smaller muscles (Iliacus and Psoas major). The Iliacus starts on the pelvic crest and ends on the outer edge of the femur head (lesser trochanter). The Psoas major starts at the transverse processes, bodies and disks of the lumbar vertebrae and the 12th toracic vertebra, and finishes at the same place of the Iliacus at the outer edge of the femur. (See picture B)
|Picture B. Iliopsoas. Note how the insertion of both muscles is on the outer edge of the femur head (EVEN IF IT APPEARS TO BE ON THE INNER SIDE, THE MUSCLES GO AROUND THE BONE!)|
Strengthening the Iliopsoas could tilt the pelvis into an exaggerated flexion which could cause the disks (rememer the cushions) to spill, while stretching it will take the pelvis into its "backbend paddling".
One way of strengthening the Iliopsoas muscle is through "ab crunches". Paradoxically, excercising the abdominal muscles is meant to stabilize the lower back, however, according to Profesor David MacAmmond of Calgary, Canada , specialized in therapeutic yoga and kineseology, very little people who practice abdominal crunches have a healthy back due to the overstrengthening of the Iliopsoas.
A good way of just excercising the abs without getting the Iliopsoas engaged is the following.
1. Lie on your back and bend your knees if needed.
2. put your hands beneath the head.
3. Try to lift your nose around 1 cm and feel your abdominals getting worked.
4. Repeat 5 times.
5. Now try to mimic that abdominal contraction without lifting your head.
6. Repeat 10 times.
Through this excercise, nobody will ever develop a six pack, but that has never been the point of working the abdominal muscles. You want to protect your back, not to be a Greek sculpture with lower back pain! :)
Another important muscle is the Latissiums dorsi (See picture C), which involves the movements of the arms with the spine. It also connects the sacrum with the back.
|Picture C. Latissimus dorsi|
The Latissimus dorsi is the largest muscle of the whole body. It starts at the sacrum, the spines of the thoracic, lumbar vertebrae, lower 3-4 ribs, and iliac crest, and inserts into the inner edge of the humerus (the upper bone of the arm) as shown in the picture.
The fibers of the Latissimus dorsi are transverse. Transverse muscles are not meant for making small efforts for a long time, but rather for making a big short effort, therefore, the Latissimus dorsi must not engage in carrying the spine. The best way of not getting it involved is by widening it and giving space to the other deeper muscles (Erector spinae) to act. Dona Holleman proposes quite an innovative way to widen the Latissimus dorsi while sitting: she says that through the rooting (not pressing) of the outer wrist on the thighs, the Latissimus dorsi moves out of the way of the erectors of the spine. (This outer wrist point is known in Chinese medicine as the gate of heaven)
The erector muscles of the spine are many and are the ones responsible for lifting the spine and keeping it up throughout your life (See picture D).
|Picture D. Erector spinae muscles.|
One good way of excercising these muscles is to stand up straight keeping the sacrum away from the lumbar, feet at hips distance, shoulders above the hips and ears above the shoulders (Tadasana or mountain's pose), respecting all the natural curves of the spine and placing a 6-8 kg sandbag or book on top of the head. Try to lift the sandbag with your head keeping your ears away of the shoulders as much as possible while rooting the feet without pressing or blocking the knees. Feel the widening of the Latissimus dorsi and the elongation of the Erector spinae. This is the same action that takes place in most of the asanas, particularly on the standing ones. Once you have clear mastering of this concept you will be able to stand on your head which involves among a few other things, rooting the head on the floor, and elongating the feet upwards. Doing this will allow you to stay on your head for more than 10 minutes (otherwise you would be using the Latissimus dorsi!) [Do not go into head balance until you have a steady practice, and most certainly don't do it without supervision]
Note how upright are these Gujarati women carrying water on their heads.
|Gujarati women carrying water on their heads.|
I hope I have given some clear and useful information. Keep tuned for more of other stuff :)