In addition to being a cyclist, I'm also a personal trainer and indoor cycling instructor, and I often tell the people in my cycling classes that if they're using cycling as their main aerobic exercise, to add weight training....if they don't do enough of that, there are some studies that suggest jumping up and down 50 times daily (landing lightly) is enough to increase bone density, particularly in the hip region.
However, if there is any chance that you have osteoperosis, osteopenia or any other issues affecting the knees, hips or lower back...check with your physician before doing this.
Vertically challenged, but expanding my horizons.