The arm bar is an extremely versatile submission in general. There are variations of it that can be performed from a host of different positions. In general the arm bar gains its notoriety from really just how simple it is. In a fight, especially mixed martial arts, you are constantly using your arms to try and attack your opponent. This means that there is a lot of time when a fighter is focused on using his arms to attack and not deffending them, the perfect time to sneak in for an arm bar.
This particular arm bar setup was used by Carlos Newton in a fight against Kazuhiro Kusayanagi. He finds himself on top in a side control position and is immediately being hit with a Kimura attempt. Instead of letting the opponent finish what he started Newton, looking completely calm and under control, quickly made his opponent pay for this.
The setup for this specific arm bar is very unique and pointed towards a specific situation. First though is that you are in side control position on your opponent. Once in this side control we are going to assume that the opponent is a Kimura lover and goes in for his submission attempt.
The Kimura is a shoulder lock submission that can be equally as quick as an arm bar if you get sloppy with your appendages. From the side control position your opponent will need to bring your arm up and over your back though which is not always very easy to do. This small gap of time in between when he isolates your arm and when he completes the submission is your time to strike, don’t be late though.
The beginning is the do or die situation in the technique. submit or be submitted. To reverse this kimura and bring the hurt to your opponent is technically not very hard but practically not nearly as easy to finish as Carlos Newton makes it look.
First DO NOT let yourself get submitted. Next, your free hand is planted on the opponent’s hip and used as a pivot point as well as a means to separate yourself from your opponent’s body. From here speed and precision of movement are key to switching your position successfully for the finish.
To complete the arm bar you need to be on the other side of your opponent. To do this you walk your hips around on the head side of your opponent. The center of your hips should end up right behind the shoulder of the opponent. One leg is placed over the opponent’s head/neck to keep in pinned down against the mat. The other leg is left bent with the foot/shin pressing into the opponent’s side and up under his armpit.
From here all that is left to do is hold the arm to the body and raise the hips up to finish the submission.
There is certainly an intangibility factor to completing this submission. You could look at it and drill it until the cows come home. During a real match anything is possible and this move has a lot of variables and moving around. Also this is a counter move so by nature there is risk involved, for example if you mess up and the opponent simply finished his submission. If you are going to attempt this move it needs to be done quickly, powerfully, precisely, and with confidence to finish successfully.
Here is a video with a technical explanation of this techique