Can Riding Up Hills Be Considered Strength Training?

[OakLeaf]

Begging to differ, I don't see where weight lifting, pilates, yoga differ from cycling in terms of building bone strength, as they equally do not have "impact".

When you do exercises like leg presses, step-ups and squats (that stress the legs, pelvis and spine), you're lifting more than your body weight, so the bones get slightly compressed. When you do upper body work with free weights in a standing position, then your spine and legs are again supporting significantly more than your body weight. Just like muscle, the way you build bone is by slightly breaking down what you already have, so your body builds it back stronger.

With yoga, you're doing body weight only, and with Pilates if you use resistance it's not a lot, plus it generally isn't along the length of the spine or legs. Same thing with upper body work in a weight machine (that is, it can be a lot, but you're not using legs or spine). So your bones don't get stressed beyond what they do in "real life." That's the difference.