Challenge requirements:
Have limbs crippled 50 times.
Repeatedly breaking bones has led them to become stronger (somehow).
This perk is based on Wolff's law, the practice of increasing the strain on a bone to make it stronger.
Nicks' notes:Only, in Wolff's Law it's based on strain, not the actual breaking of bones.
List of Challenges/Perks that are based off of science:
http://fallout.wikia.com/wiki/Free_Radical
http://fallout.wikia.com/wiki/Tough_Guy
http://fallout.wikia.com/wiki/Set_Lasers_for_Fun (star trek reference!)