By Dr. Rita Khanna
You are as young or healthy as your spine. ‘Keep the spine erect,’ you will often hear the teacher calling the instruction in a class of Yogasanas. In the entire animal kingdom, the human being has the most erect spine. Let us see the implications of this instruction. In Kundalini Yoga, it has a significance of its own, as far as the Nadis and Chakras are concerned; but in this article, we shall consider only from the anatomical point of view.
Upon entering the world, a newborn baby’s spine is flexed (bent forward) at the beginning. Later, when the infant turns on its tummy, and starts to raise its head, it develops the first backward curve of the spine, in the cervical (neck) region. Still later, when the young child first stands on its own feet in the erect position, it develops another backward curve in the lumbar (lower) region. These curves will continue to develop until growing continues.
BACKWARD LUMBAR CURVATURE OF THE SPINE
While standing in the erect position, the lumbar spine has to bear the weight of the upper half of the body. Due to this, and also due to strides of the legs in erect walking, the spine develops this backward curvature which pre-disposes man alone, amongst all the animals, to a new range of evolutionary spinal diseases, including low back pain, slipped disc, sciatica, scoliosis, and spondylitis.
In addition, various disturbances of digestion, menstruation, and reproduction arise, due to congestion and irritation of emerging spinal nerves in the lumbar region. Another disadvantage of the erect posture is the increased likelihood of developing piles (hemorrhoids) and varicose veins, because the column of venous blood from the legs and rectum, has to travel so much further upwards against gravity to reach the heart.
THE STRUCTURE OF INDIVIDUAL VERTEBRA
• The spine is like the trunk of a tree, supporting the entire body structure. Atop this trunk, sits the bony, enclosed cranium or box of the skull, containing the most important of all human organs – the brain – which not only controls the human body, but gives a real purpose to its existence.
• The top-most vertebra is called the atlas, because it supports the round head like the Greek mythical figure Atlas, who supported the earth upon his shoulders.
• The second vertebra is the peg-like axis, so named because the atlas and skull rotate upon it. Thus, the head moves both independently of the movement of the neck, and with the neck as well. Of the 33 vertebrae of the column, these are the only two which are named. All the others bear only numbers.
• In the thoracic region, the spine supports the expansive rib cage, which is composed of bones (ribs), muscles, and cartilage. The rib cage surrounds the lungs and the heart, which are next in importance to the brain. The lungs purify the blood, while the heart circulates it to the entire body, supplying the cells and tissues with all their nutrient requirements, and taking away their waste products.
• In the lumbar or abdominal region, the spinal column serves as an anchor for the muscles, which hold the gastro-intestinal organs in place: stomach and intestines, liver, spleen, and pancreas, and also, the kidneys and urinary system. These are held suspended, as if in a cloth handbag, with the spine forming the handle.
• At the lower (sacral) end of the spine is the pelvis, which is like a bony basket or cavity cradling the excretory and reproductive organs. Here the fertilized human egg is nurtured in the mother’s womb, like a bird’s egg in its nest.
• Like the main branches of this tree, the upper and the lower limbs shoot out from this central trunk, with the nearer joints (the shoulder and the hip) having a full range of movements in all the three planes, like a ball and socket, while the distal joints (the elbow and the knee) can move in only one plane, like a door on a hinge.
Thus, we find that the spine is not absolutely erect in the true sense of the word, but has four distinct curvatures.
The cervical curvature in the neck has seven vertebrae. The dorsal in the chest has twelve and the lumbar in the lower back has five. Like a stack of coins, these bear the progressively increasing weight of the column above. Thus, each vertebra is slightly larger than the one above, as we descend from the neck to the buttocks. The atlas is only ¼ as large or heavy as the last lumbar vertebra. In Sirshasana, (headstand posture) one should bear the weight of the entire body on the triangle formed by the head and the two elbows. If too much weight falls onto the cervical vertebrae alone, they will suffer damage, as they are meant to carry the weight of the head only, and not that of the whole body.
The sacral vertebrae (five in number) are fused to form a single bone at the back of the pelvis. These are smaller as they have no weight-bearing function and take no part in the movements of the spine described above. The coccyx is the vestige of the tail. The tail is used by lower animals for warding off troubling insects, for holding onto a branch and for balance while jumping. A man can perform these functions with his upper limbs. It is also used for expressing emotions like anger and fright. Human beings have evolved better ways of expressing emotions, and man had lost his tail during evolution.
THE HUMAN SPINE
The human spine is not a single bone, nor is it like a bamboo. It is like a string of beads; but instead of the string holding the beads together, as in a Japa Mala, it is the beads (the vertebrae) that protect the string (the spinal cord) inside. The spine is made this way because it has to perform so many movements. It bends forwards and backwards and sideways and also twists up on itself – hence, the string of beads. There is a degenerative condition called bamboo spine (ankylosing spondylitis), where the spine really becomes like a bamboo (and looks like one on X-ray). Just imagine the miseries of that person – stiff like a bamboo. Between two beads, there is a resilient disc, or pad, to absorb shocks while walking, running, jumping, or even while standing and sitting. Thus, wear and tear on the bones is lessened and the brain and internal organs are cushioned. The delicate string of the spinal cord runs through the central vertebral canal, and numerous nerve branches emerge from it and pass through the gaps between the vertebrae.
THE ROLE OF YOGA
Now, let us see what afflictions the spine can have and the role of Yoga in prevention and cure of some of them. At the outset, it should be clear that where the bone tissue of the vertebrae itself is seriously diseased, or has been destroyed by a disease, like tuberculosis, cancer, or a serious injury, the lost bony structures cannot be restored by Yoga.
• Yoga helps maintain and restore the auxiliary structures, like the ligaments which hold the vertebrae together, the joints, and the shock-absorbers in between, and the para-vertebral muscles on either side of the vertebrae.
• Yoga also helps in aligning the curvatures of the spine, maintaining the full range of spinal movements and flexibility, and relieving pressure on the nerves emerging between two vertebrae.
• All the Yogasanas have some action on the spine, in addition to their other individual actions and applications. The backward bending, forward bending, and sideward bending Asanas have obvious actions on the spine. Even the balancing Asanas, and sitting postures, help to maintain the para-vertebral musculature.
• Matsyendrasana, and its variation Ardha- matsyendrasana, are the only two Asanas which give a complete rotatory movement to the entire vertebral column; the locked position of the leg, and the arm, acts as a fulcrum for the twist.
• The natural curvature of the spine in the neck region is backwards, but most of our time is spent working with our heads bent forwards. Hence we get