Hatha Yoga teaches us to use the body as the bow, asana as the arrow, and the soul the target.
B.K.S. IyengarI also say with backbends, you have to be cautiously bold. Not carelessly bold. You have to descend to the dictation of the spine. You cannot command from the brain to do the poses. As you play with a child, guarding the child from injuries, similarly you have to play in backbends, guarding your spine.
B.K.S. IyengarThe practice of yogasana for the sake of health, to keep fit, or to maintain flexibility is the external practice of yoga. While this is a legitimate place to begin, it is not the end. Even in simple asanas, one is experiencing the three levels of quest: the external quest, which brings firmness of the body; the internal quest, which brings steadiness of intelligence; and the innermost quest, which brings benevolence of spirit.
B.K.S. Iyengar