Yoga postures are poses or movements which strengthen and make supple limbs, spine and muscles of the back and stomach;they also tone the glands and keep the nerves in condition.Pranayama, which accompanies the postures,strengthens and enlarges the diaphragm,gives the lungs capacity to take more oxygen,strengthens heart and improves circulation.they are not meant to devolop thick knotted muscular limps.Postures fall into two groups; static and dynamic.the first produce circulatory,respiratory,glandular and nervous changes,increase vitality and resistance to disease,help to devolop powers of concentration and are based on observation of humans,animals ,fish and reptiles.