The full Yogasync.tv instruction is here.
This movement stretches the muscles in the front of the chest and all the muscles between each rib, enhancing lung capacity. The more you bring the sacrum underneath you in this movement, the more you increase flexibility in the inner groin and thigh, while the right angle of the knee builds strength in the legs and buttocks. The abdominal organs are being pressed and squeezed, helping to aid digestion and elimination.
If you have a heart condition practise this movement with your top arm on your hip. If you have a groin injury take care not to overstrain by not going in to the movement to far.