Yoga is intended to develop flexibility and resilience, so that it is possible to maintain a pose for meditation.
Yoga is a spiritual discipline which originated in India more than 3000 years ago. About 2500 years ago, it was formalized into a discipline by Saint Patanjali, who called it Ashtanga Yoga (Ashta- eight, Anga- limbs). What is called Yoga in the Western society is only one of the eight limbs of Yoga, Asanas, meaning poses. And poses are intended to develop flexibility and resilience, so that it is possible to maintain an erect pose, with ease and comfort, for a long enough period of time, so that meditation can be practiced. Instead, it has become a form of exercise, and various techniques are being devised to make it even more of an exercise and the intended purpose is lost.
I developed a crippling back pain several years ago and faced the prospect of surgery. Although i resisted it, I had to undertake surgery since it became unbearable. Surgery did not help. The pain was back within 6 months. It was through a diligent Yoga instructor and modification in my yoga routine that I was able to become pain-free and continue to be today.