A fundamental distinction in joint locks - linear and twisting locks
Joint locks can be divided into two broad families. The first are linear or straight locks. Common examples are juji gatame (armbar), ude gatame (straight arm lock) and hiza gatame (knee bar). These locks are probably the clearest and simplest examples of lever and fulcrum in the entire skill set of jiu jitsu. The second family are the twisting or rotational locks. Common examples are Kimura, Americana and heel hook. In general these locks tend to be more complex in nature. Often the relationship between lever and fulcrum is not so obvious and the forces involved are rotational. Athletes can have favorite moves, but I have always believed ALL athletes most excel in several linear and several rotational locks (you can’t only excel in linear or only in rotational). This is because very often the main escapes from a linear lock lead very naturally into a twisting lock and vice versa. Being able to switch mindset from linear to twisting and vice versa in the blink of an eye is thus very important. In addition, linear locks tend to work best on straightened limbs, whilst twisting locks generally work best on bent limbs - when you excel in both, you will be able to attack regardless of the extension, or lack of, in your opponent’s limb. Once students are made aware of the different nature and demands of these two families of joint locks, I find they usually have no difficulty working with both - but they should always be aware of the important mechanical differences between them in order to maximize their use of them. Here, I teach one of my favorite twisting locks - Kimura - to the students of Columbia University and run them through the various factors that enhance performance with this incredibly versatile hold.