The bones of the human skeleton that perform a lot of physical work have thickenings

The bones of the human skeleton that perform a lot of physical work have thickenings, bumps and other structural features. How do you explain this?

Bone tissue in people exposed to great stress is heavier. From this, the bones begin to thicken, as the load from the muscles on them begins to increase. The amount of bone mass directly depends on the effect of the body’s gravity on it. Accordingly, when these two forces act on a certain bone, it leads to its mineralization, an increase in its strength and a change in its appearance. In people with a huge physical activity (athletes), the total bone mass can be 0.4 times higher than that of the untrained.