The best defense against an armbar from closed guard is one of the basic moves that all practitioners need to be aware of; the position of your arms and your head.
Armbar: A joint lock where the elbow is hyperextended in order to cause pain and/or injury.
Things that you need to be aware of:
- Posture, you can play the safes way, which is a straight posture having your head away from your opponent guard, or the last resource is when the posture is broken, then your head needs to be against the chest/side of your opponent.
- Arms, your arms should be on your partner’s belly or holding your opponent’s arms. Try to avoid placing your hands on the mat; this can cause your opponent to look for other submissions.
Defend the Armbar
- Don’t allow your opponent to cross your elbow to his waist or even worst to the middle or pass his belly line.
- When your elbow gets compromised, and your opponent throws his leg over your head, you can quickly with the free arm ‘hug’ under your arm, holding his leg to prevent the exposed arm from being hyperextended. You can also avoid this by stopping his leg above your head by catching that leg with the freehand. Then the stacking strategy comes up; after you prevent the trapped arm’s hyperextension, you need to stack your opponent’s legs against with upper body in the direction of your free hand avoid moving too close to his centerline to avoid any sweeping.
- Once you are applying pressure, you can start jerking your arm trapped, pulling it out, and needing to be patient here. You are almost out; keep pulling that arm until it is free; after you free your arm, then you can work on your pass to secure a safe position.
There are many variations, but all rely on the same principles, giving away positions can generate problems where you need to know how to escape. Still, sometimes giving away positions lure your opponent into attacking so you can counter-attack, but this level of awareness is developed by years in the mat.
You also can view this useful video from Great Grappling for more details