This is what Mr Iyengar say’s about the pose in “Light On Yoga”
Purvottanasana One* (Plate 171)
Purva literally means the East. It means the front of the whole body
from the forehead to the toes. Uttana means an intense stretch. In
this posture, the whole front of the body is stretched intensely.
Technique
Sit on the floor with the legs stretched straight in front. Place
the palms on the floor by the hips, with the fingers pointing in the
direction of the feet.
Bend the knees and place the soles and heels on the floor.
Take the pressure of the body on the hands and feet, exhale and
lift the body off the floor. Straighten the arms and the legs and keep
the knees and elbows tightened. (Plate 171)
The arms will be perpendicular to the floor from the wrists to the
shoulders. From the shoulders to the pelvis, the trunk will be parallel
to the floor.
Stretch the neck and throw the head as far back as possible.
Stay in this posture for one minute breathing normally.
Exhale, bend the elbows and knees, lower the body to sit on the
floor and relax.
Effects
This posture strengthens the wrists and ankles, improves the movement of the shoulder joints and expands the chest fully. It gives
relief from the fatigue caused by doing other strenuous forward
bending asanas.