Odd exercises good for osteoporosis

DEAR DR. DONOHUE: A bone density test showed that I have osteopenia. When I looked on the Internet, I found information that said walking would have no effect on osteoporosis or osteopenia. It said odd-impact exercises would be beneficial. What in the world are odd-impact exercises? I go to the gym three days a week, doing some cardio, light weightlifting and using the ball and strengthening bands. - L.H.