Let's say you're mid-roll with some juiced up purple belt who has it out for you because he's jealous of your fabulous kimono collection and amazingly effective, yet flamboyant, De La Riva-bolo guard. He's got you in side control and, of course, goes for the dreaded kimura shoulder sub. His key lock is cinched in and the cranking of your shoulder commences. BUT wait. Because of your insane dedication to Jiu JItsu, you've conditioned your shoulder to withstand the pressure of his kimura attempt. You power through it against all odds, and turn the tables on him to claim an inverted submission of your choosing.
But, that can only happen if your shoulder flexibility and raw power is honed to perfection. And, that's why you need this sweet video tutorial on shoulder flexibility from Jits Mag. I must admit this is an approach I haven't considered seriously in all my years of training. But, it does make sense - the more flexible and strong your joints are in stressed positions, the more time you'll have to defend against submission attempts on such joints. So, do it. Just don't complain to us if your shoulder ends up breaking off in the process (that won't happen).