Another way to get the benefit of weight bearing exercise is to practice yoga. Moderate postures with longer holding, including standing poses, balancing poses, lying down backbends with pelvic stabalization, and postures lying on the back. In the latter two especially, the weight of your own body rests on the bones. I had a 50 year old female student, who practiced daily for 20 years. A bone density test revealed she had the density of a 30 year old. She attributed this to yoga.