What do you need for strong bones? Of course, calcium and vitamin D are essential in building and maintaining bone mineral density. But you can’t draw the line there. To really optimize bone strength, you need something you can’t supplement: real muscle. You don’t need a ton of it, either. Being jacked-up and muscle-bound isn’t necessary, but some degree of muscle strength is. Why? There are two main reasons. The first is that muscle offers support for bones. It can help protect them from bumps and breaks and provides some essential resiliency. But perhaps more importantly, the process of building muscle can actually make your bones stronger and boost bone density. Putting stress on your bones through resistance training forces bones to respond to the pressure by becoming stronger and denser. And you don’t necessarily need to start squatting heavy weights or doing shoulder presses, either. You can get the …