Here's the Australian recommendations for exercise for osteoporosis. They recommend high-impact at least 4 days a week (50 jumps) using varying exercises, along with 2 days/week progressive resistance training.
I've also read somewhere else you need high-impact exercise to maintain/improve bone density. I'm going to start doing that more regularly (I've done it off and on but I'll try to add the 50 jumps as they say).
