If you can isolate a limb, then you can control the limb, and if you can control that limb you can break that limb: Isolate – control – break. This is the pattern of submission grappling. You need to keep your opponents limbs apart from each other – remember that most of an opponents initial defense to a joint lock is to use his other limb to defend the one that is under attack – so isolation is important here. Get used to the idea of taking opponents limb away from the other limb and away from his center of mass and you'll get the isolation needed to get to your victory
