Hi - from what I understand, the body is always building new bone and breaking down old bone. When the rate of breakdown exceeds the rate of bone formation, osteopenia and then osteoporosis sets in. Bone breakdown rate is measured quarterly for me, and if your bone breakdown rate is high, like mine was at 27, an antiresorptive is used to slow down that rate. The bone breakdown rate is measured by a simple blood test and the goal is to get that rate under 10. So in my case, Reclast has slowed that breakdown rate from 27 to 12.5 over the course of four annual Reclast infusions. My body is still building bone and I am helping it build bone by doing weight training 3x weekly with barbells for an hour in a class at Loyola Fitness Club at Loyola Medical Center in Chicago area. The teacher is extremely well informed about proper form, which helps me avoid injuries at the age of 68, when our tendons and ligaments are more susceptible to injury from bad form and moves that are sometimes called “dynamic.” Slow and steady with progressively heavier weight (but don’t go up too fast) has worked for me. Also having a teacher and classmates inspires me to push myself harder than I would if working out alone. I’ve also made friends. Thanks for writing — this is new territory for all of us as we age and we need each other!