How to Transition from Reverse Armbar to S-Mount - a Goatfury BJJ Tutorial
S-Mount and the Reverse Armbar
S-mount is easily one of the worst positions in BJJ to find yourself in if you're on the bottom, and if you have the proper control, you can finish nearly anyone from the top. Here, let's take a look at a particular transition based on the reverse armbar setup from mount (a high percentage move in its own right). Along the way we'll talk about some specific tweaks unique to S-mount itself, and improving the reverse armbar and straight armbar finish. Get ready to unleash terrible weight on your partner's solar plexus and sternum!
The Set Up
Recall first the basic setup for the reverse armbar. Start by smashing your partner's face with your left shoulder, then underhook their left arm with your right arm. Remember: you might not be able to get a clean underhook, but you can do a sort of "heel hook" set up and then cause your partner to react. If your partner has longer arms, or is extremely flexible in either the shoulder or elbow, this might not be enough to get the submission. Fortunately, the following transition is relatively easy. Once you're in the reverse armbar finish position, shift your weight to your left side, and then swing your right leg forward, finishing underneath your partner's armpit, with your foot facing up toward their head. If you put your foot on the ground below their arm or near their waist, this is called technical mount. S-mount differentiates itself by following up with a swoop underneath the shoulder, creating far worse pressure (and taking all of your body's weight off the ground, and concentrating it on your partner).
When you set up the classic reverse armbar from mount, your partner might be able to wiggle their thumb and escape the hyper-extending pressure, ultimately wiggling free. When you make the switch to S-mount, you have an extra anchor of sorts reinforcing your right arm. As you go to apply pressure as normal by pulling your right forearm inward and pushing your neck outward, you can augment this by resting your right forearm against your knee. Instead of pulling your forearm inward, try just using the brace of your inner thigh while pushing your neck outward, maintaining a tight "ear to shoulder" pressure to keep the arm isolated.
Simplest Combo Ever: Switch to the Other Arm
One of the easiest combinations you're ever going to be able to hit in jiu jitsu is when your partner reaches across to try and stop the initial reverse armbar attack. Simply switch to the "juji gatame" style armbar. Keeping your weight shifted forward and on your partner's guts, lean heavily to your right, and then hook your partner's near side arm with your left arm. This keeps your right hand free in order to grab their pants (or hook their near leg, if it's no-gi) and then keep fantastic control during the finish. Swing your left leg over their head, but imagine scraping their face as you do this, finishing with both of your knees together, and with your hips ultimately facing your partner's hips.
A Different Way to Get There
One nice alternative to waiting for your partner to reach across to defend the reverse armbar in order to set up the same side armbar is to start with a nice arm drag sweep. Start with the usual cross sleeve grip from closed guard, and make a shelf as previously described. From here, control your partner's far armpit with your left hand, and then sweep them to your left. Once you establish the mount position, you're going to find yourself in a fantastic "double attack" opportunity. Just go for the underhook with your right arm, and you should be able to set up the reverse armbar, just like earlier. In addition, their right arm is pinned across their body by your chest weight. Making the transition to S-mount and finishing either armlock from here should be pretty straightforward and easy (just stay tight!).
S-mount or regular mount?
This transition to S-mount isn't strictly necessary in order to finish the reverse armbar, and I wouldn't even recommend it as a primary means to do so, but if you're there and just can't get the finish, go for it. S-mount will serve you extremely well in this regard. The transition to the same-side armbar should be something ingrained in you from white belt on (if it's not, go drill it now!). Have fun, stay safe, and let me know how these are working out for you!