Rafael “Formiga” Barbosa shows how to achieve an Armbar from the knee on belly position, this is accomplished when your opponent pushes the knee to try and relieve the pressure off his belly. Brazilian Jiu-Jitsu technique.
Any time you play knee on belly it is very likely the guy on bottom is going to try and pushing away from your knee in order to escape. When he pushes your knee he creates some space between his bicep and his hips. Use your hand to swim inside his arm, palm facing down and your thumb cutting up into the back of his arm. From here take a step over your training partner’s head and grab your collar. Place your left knee on the floor but make sure to keep your right knee up. After this you may need to slightly adjust your collar grip. Next, grab your training partner’s wrist and then grab your forearm with the hand you previously held your collar grip with. Pull your opponent’s elbow up at the same time you push his head down to create pressure so he can’t free his arm. This will allow you to stand up and switch to the arm bar position. Pay attention to how Formiga switches his hand position on his training partner’s wrist while pulling his arm into his body. Finally, lay back to extend the arm with both your hands grabbing at his wrist. Squeeze your knees, pull and lift your hips. This will cause your opponent to tap.