Open wedges and closed wedges
Many of you will be aware that a big part of my teaching is bound up with the study of using our body to create IMMOBILIZING WEDGES around important parts of our opponents body to hold them in place while we perform a given move. A BIG part of what we call Jiu Jitsu is the action of setting these wedges around an opponent in a mechanically advantageous fashion - this one of the main basis of mechanical efficiency in our sport. The best wedges are generally CLOSED wedges, where our limbs lock into each other to securely hold the wedges in place. A triangle is a set of wedges around our opponents head and arm and it is CLOSED insofar as the locking of your legs mechanically locks the wedges in place. Closed wedges are not always possible however. More often we have to work with OPEN WEDGES and now we need a substitute method of holding them in place. Sometimes its body weight, sometimes it is simple muscular exertion. Here I am working with the arm bar (juji gatame) - standard variations of this are examples of open wedges. You can see I have to make up for the open wedges through good body positioning and muscular tightness around the head and shoulders. Directionality of force becomes extremely important now if the lock is to be effective against stout resistance. If you are a shorter limbed athlete like me, learning to work effectively with open wedges is extremely important. Every time you practice your application of them, have your partner try to pull out - that will immediately tell you how effective your wedge placement really is.