Developed by yoga guru B.K.S. Iyengar in the 1930s, this method emphasizes proper alignment to strengthen the muscles and support the joints. You often use props, like blocks and straps, to help you get into poses. In the 90-minute to two-hour class, you’ll do standing, seated, and twisting asanas, as well as inversions and backbends. (If your pain is due to an injury, be sure to check with your doctor first before starting a program.)