Balls of Steel

I came across this clip quite randomly (I googled Juko Ryu, more about that later). If I am honest, it is pretty amazing stuff, I can't work out how they manage to withstand punches to the throat and kicks to the groin. If we disregard the ambiguous claim of channeling 'chi' energy, I would imagine that this skill takes many many years of repetitive training of those parts of the body to tense at exactly the right moment.
Not easy, but certainly feasible physically (not that I would want to test the idea personally!)
Genki Sudo is a MMA star who rather shockingly knocked out Royler Gracie in an MMA tournament. Us Royler fans don't talk about that one too much. Ahem. BTW Royler is coming back to the UK in October for a seminar, hoorah! I'm getting my gi ironed in anticipation right now!!!!