Take two-they're small. And they perform miracles. Suffering a career-ending, potentially crippling injury to her back and right leg, a young dancer named Elaine Petrone tried everyone from orthopedists to yogis to turn her pain and prognosis around. Nothing worked-until she healed herself through a unique program of therapy and exercise based around the use of two small, squishy balls. From there she turned her passion into a mission that is helping the thousands of people who visit her classes conquer pain, stress, and injury. Now, for relief for sufferers everywhere, comes ''The Miracle Ball Method,'' a healing kit containing two miracle balls and a fully illustrated book, all packaged together in an attention-getting clear plastic cylinder. The work itself is simple. Take a sore back: By resting your aching back on the grapefruit-sized balls and letting your body sink into them, you're unworking the muscles that hurt. Pain and tension drain out of the body. Petrone shows how proper breathing (which she demonstrates) works in conjunction with a range of unexercises that call for placing the balls under the back, head, knees, hip, elbow-wherever there's pain-and then resting, rolling, or rotating on them. She points out that relief can come in surprising ways: Lower back pain may be helped by placing the ball under your neck, or a bad knee might be helped by hip work. It's a revolutionary program of relief, from head to toe.