Upavistha means seated and kona means angle. This practice stretches the hamstrings and lower back. It helps the blood to circulate properly in the pelvic region. As this regulates the menstrual flow and stimulates the ovaries. It prevents development of hernia and relieves sciatic pain.
On a subtle level, it stimulates, activates moolandhara ( root ), swadisthana ( base of spine ) and ananhata ( heart ) chakras.