It's not too late to protect your spinal bone density

 In a study from the Mayo Clinic, an exercise that strengthened back muscles helped women in their 60s protect spinal bone density even years after they stopped doing the exercise daily. 

Here's a video with a series of back-strengthening exercises you may want to try. (These are not the same as in the study, but are designed to strengthen different areas of the back. As far as I know, they have not been tested for effectiveness in preventing osteoporosis, they are just examples of back exercises.)