Bones strengthen in response to mechanical signals from muscle contraction, converted to chemical signals via estrogen.

“bones effectively have strain gauges in them and they respond to tensile stress so when a muscle is Contracting the muscle via the tendon is attached to the Bone and as the muscle contracts the bone is compressing so imagine a strain gauge inside the bone that senses that well that's a that's a mechanical signal that gets converted into an into a chemical signal so mechanical to chemical via estrogen”