Dhanurasana roughly duplicates the benefits of bhujangasana and shalabhasana. However, there are notable differences. In shalabhasana, the back muscles are tensed, while in dhanurasana they are passive. In bhujangasana, the back muscles should also be relaxed, but the main influence is on the small of the back in the region of the sacrum. In dhanurasana, the main influence is the intense intra-abdominal pressure. Each of these asanas has its place in an asana program. They complement each other. It is for this reason that they should be done one after the other.
Dhanurasana is very useful for overcoming lethargy and sluggishness in mind and body. It has a direct effect on the solar plexus at the navel, which is a large sympathetic nervous centre so important for healthy functioning of the organs of the body.
These nerves are brought into maximum efficiency, which in turn leads to improved functioning of the whole body, especially the digestive, eliminative and reproductive organs.
It decongests the entire abdominal region and its organs. The liver, the multi-duty organ of digestion is massaged, which leads to an overall improved digestion. The pancreas is toned up so that it secretes the correct amount of glucagon and insulin at the right time. The entire alimentary canal is reconditioned, as well as accessory glands. Blood is encouraged to flush through the whole system and this acts as a cleaning process. The kidneys are rendered more efficient, which leads to better fluid balance within the body. It helps to alleviate constipation, dyspepsia, sluggishness of the liver, diabetes and excess fat.
The spinal column is realigned and rejuvenated. The ligaments, muscles and nerves are given a good stretch, especially on the front (anterior) surface. This relieves stiffness and the spine is made more supple and healthy. The deep muscles of the back are exercised which recirculates stagnant blood.
Dhanurasana massages the heart. This is done via the diaphragm, which is pushed towards the heart by the extra pressure in the abdomen. It is also useful for alleviating various chest ailments. For example, it is suitable for removing the hunching tendency of asthmatics, which aggravates ill health. Dhanurasana realigns the back and thereby improves the breathing processes. This in turn leads to free flow of air through the nasal passages.
Various endocrinal glands are massaged and toned, notably the thyroid and the adrenals. The secretions of the adrenals are regularized. Blood is flushed through the glands. It is this effect that quickly removes tiredness, for cortisone is secreted to give you the required lift; or if you are overactive, the secretion of cortisone is reduced so that the body attains balance. This also helps to alleviate various types of rheumatism.