From a standing posture, make the spine straight. Keep the spine straight and begin folding forward from the hips. Do not allow the spine to curl/bend until you fold your upper body until the point where the torso is parallel to the floor. This is important for protecting the back.
If you cannot fold far enough to go past being parallel with the floor, it may be useful to bend the knees slightly and bring the chest as far towards the thighs as much as possible. From here, extend as far as you can without taking the chest off the thighs.
If you can fold past parallel with the floor, then continue folding allowing the spine to curl until you reach as far down as you are comfortable. The hands can rest on the floor or they can pull on the calves to help extend the stretch.
Effects and Benefits
Physical – This posture is the best for stretching the hamstrings on the backs of the legs. Tight hamstrings can contribute to lower back problems as well as making folding forward and other daily life activities difficult. This posture also inverts the torso by putting the head below the region of the heart, and that is beneficial to all the organs of the body.
Spiritual – Uttanasana is a very inward going pose. The head is pressed toward the legs and the torso is upside down, since we are folding forward. It can be a posture of great intensity for many people who have tight hamstrings. The pose teaches us to overcome external unpleasantness and centers ourselves within.