Learning Asanas with the help of a book sometimes can be dangerous. You are benefited by Asanas only when the “asan” or your sitting posture is correct while doing it. This is why it is always safer to learn Asanas from a good teacher. I do not recommend shrishasana (Head stand). People who can benefit from Shirshasana are only those who have good health. The weak will benefit the same by doing sarvang asana (Shoulder stand). If you spend 20 minutes a day doing the below mentioned Asanas you can remain disease free.
Sarvangasana (Shoulder stand)
Matsyasana (Fish pose)
Halasana (Plough pose)
Bhujangasana (Cobra pose)
Shalabhasana (Locust pose)
Dhanurasana (Bow pose)
Pashchimottanasana (The forward bend)
Ardha Matsyendrasana (The twist)
Savasana (Corpse pose)
You need to exercise your:
Shoulders and arms
Abdomen and the back
Legs
Heart
Lungs; and
Blood vessels
When we exercise, the respiration deepens and the heart rate increases. The circulation of blood increases due to increased heart rate. More oxygen is supplied to blood due to increased respiration. More blood, carrying more oxygen, reaches all parts of the body. Thus all the organs receive more oxygen, more nutrition from the circulating blood and more waste products are also carried away by this blood released by different organs of the body. Thus through exercises the general health of the body starts improving.
During exercises, the muscles go on contracting and relaxing. The muscles constitute almost half of the total body. When they contract all the blood contained in them is expelled out. When they expand all the blood gushes in. The repetition of this process strengthens the muscles. The blood circulation is increased not only by muscular activity but other parts like the nerves system, the blood vessels, heart, lungs also play a role. The nerves supply to the wall of the heart and the blood vessels stimulates them to empty out more completely.
Thus the heart vigorously pumps out more blood and the pulsating blood vessels carry it to different parts of the body, the minute branches of the blood vessels called capillaries which normally remain closed, open up. The blood reaches the most remote areas of the body also. A great deal of carbon dioxide is eliminated in this circulating blood by different organs. When this carbon dioxide reaches the lungs, it stimulates the lungs. The rate and depth of respiration increases. This increase in respiration helps increase the rate of exchanges between carbon dioxide and oxygen in the lungs. So increased demand by the body for oxygen is met and more waste carbon dioxide produced by the more active body is eliminated through the lungs.
The lymph flow increases. The lymph which is a carrier for digested food works for the elimination of the body’s waste products. All the organs of elimination like the skin, kidney, bowels start functioning with a better capacity to cope with extra amount of work load. The skin becomes more active, the pores open up and more perspiration takes place. This, apart from eliminating urea, works as a cooling tower. The body which is getting hotter by doing exercises is cooled down by perspiration.
The kidney gears itself up during exercises. The demand for water increases, you feel thirsty and more amount of urea and waste is eliminated in the urine. Thus the kidney becomes more active during exercises. The bowels are cleared more efficiently. If constipated, you get a clear motion. This happens due to the massaging effect on small and large bowels by the contracting abdominal wall. Diaphragm does a similar job from the top. The intestine has better peristaltic movements thus pushing the content of the bowels forward.
So all the four great channels of elimination – skin, kidney, lungs and bowels work more efficiently and cleans the body from inside. It is better cleaning work than the one done from outside by taking a bath. The digestion and assimilation of food improves by exercise. Increased circulation helps in a better distribution of digested food. During exercise more nutrition is required. Old cells break down and new cells are formed. So in a way body is renewing itself all the time.
For building up new muscles, material for building up cells is required. The body demands more food. Appetite increases. The liver and the pancreas are massaged by the diaphragm. The diaphragm is vigorously depressed and elevated by expanding and contracting lungs. The secretion of liver and pancreas increases and so more amount of digestive juices are available to digest the food. Thus by exercises the appetite increases and food is digested and assimilated better.
The old muscle cell break during exercise, they are eliminated, new muscle cell are formed. These new cells are larger and stronger. The new muscle cells produce less fatigue poison called lactic acid. These cell are efficient and put less load on the eliminative organs of the body. The connective tissue tendons which connect muscles to bones get renewed. They help in improved muscle action.
Through better circulation and more pull by contracting muscles, the bones become firmer, joints stronger and flexible. Stronger bones and flexible joints help in the smooth functioning of joints.The heart benefits by exercise. As the contraction and relaxation of the heart muscles are vigorous during exercise, these muscles are exercised and become stronger. The pumping capacity of the heart increases for two reasons:
due to stronger heart muscles; and
better nerve control
The heart keeps on beating from birth till death. It does an enormous amount of work. The work done by the heart of a young man of twenty five in twenty four hour is enough to fit six tons of weight to the height of one foot. The heart does this job without tiring itself out. The beats are controlled by nerves which are not controlled consciously. There are yogis who can control their heart system through concentration. They can reduce their heart rate at will and even stop it for a few moments.
The lungs receive more blood from the exercised heart. As more blood comes to lungs it has to purify faster and return it to the heart. For this purpose the breath comes faster and deeper. The lungs get adjusted to exercises. They expand more. The chest expansion becomes greater and new lung cells are formed. Lungs become bigger, more elastic so the capacity of the lung to take in more air improves. The intercostal muscles get developed, the ribs are raised higher during inhalation. Thus the capacity of the lungs increases. This can be noted by measuring the chest after breathing in and out. After doing exercises the girth of the chest gradually increases following inspiration (breathing in).