Perform Virasana. Exhale and lower your back torso toward the floor. First lean onto your hands, then your forearms and elbows. Once you are on your elbows, place your hands on the back of the pelvis and release your lower back and upper buttocks by spreading the flesh down toward the tailbone. Then finish reclining, either onto the floor or a support. Stay their for some time 15 to 20 seconds and then come back to virasana.
If you have any serious back, knee, or ankle problems, avoid this pose unless you have the assistance of an experienced instructor.