Sports don't necessarily build up strong bones, but they improve them. If you are a lazy person that sits all day long on a couch and inactive, you are more than likely going to have some type of bone problem in the feature. Sports will keep your bones active and healthy and improve their endurance. Here's a good...whatever you call them.
Remember always eat right too so your bones will not become fragile. Also people that are overweight or obese have a higher risk of bone problems if they do not do something about it. It's a lot of weight to be carrying around.
If you keep water just sitting in a freezer, it's going to freeze up eventually.
But if you keep taking that water out, it's not going to freeze, you have to keep it actively moving.
Keep your body healthy and remain active.