Clinical Director of the National Osteoporosis Foundation (NOF), Felicia Cosman, M.D. says, "Time and time again, I'll recommend weight training to patients and they come back expecting to see big changes in bone density in a year or two. That's not realistic. You're helping to prevent bone loss, and the changes may be relatively small per year. But if you persist with your weight training, even a 1% change in bone density every year adds up to a 10% difference after ten years….that's a lot of bone." Read more on WebMD.