Siddhasana stimulates both the muladhara (root) and svadisthana (spleen or sacral) chakras. It is one of the primary poses used for meditation and pranayama. Practicing siddhasana is said to regulate the flow of prana and calm the nervous system.
Siddhasana stretches the hips, knees and ankles. It also strengthens the posture and the back. The pose promotes a sense of groundedness, reduces stress and purifies the nadis (energy channels) of the body.
It is important to keep the spine straight and lengthened during siddhasana, especially during long meditation sessions or breathing exercises.