Until now, our focus has been on what the bottom player is attempting to do. The top player as been providing resistance, but that resistance has been unskilled. We shall now begin dealing with a skilled opponent.
The first objective of a skilled top player who finds himself in half guard is to gain good posture. Specifically, he will bring his butt close to his heels. This gives him good base without needing his arms to support himself. Good base allows him to easily use his arms and move his torso to begin to attack.
This butt to heels posture is bad for the bottom player. Even if she manages to win the head control battle, it will be difficult for her to gain control of the top player’s centre of mass because the limb orientation makes this awkward.
The objective of the bottom player is for the top player to lift his butt away from his heels. We will look at a leverage based way of achieving this.
To begin, the bottom player will triangle her legs and place the outside foot on the floor. She triangles her legs so that the top player’s inside knee becomes pinned. A joint that is pinned can act as a fulcrum.
With gi jiu-jitsu, the simplest way to force the top player’s butt to lift is to grab the front of his belt and yank forwards.
No-gi needs a more technical approach. The bottom player will apply upwards (towards the sky) pressure with her inside leg. The force generated by the upwards pressure is not enough to lift the top player’s butt, but it has other purposes. Firstly it forces the top player to actively sit down harder to counteract this upwards pressure. Secondly it engages the muscles that the bottom player will use to sit up.
By actively sitting down, the top player is in-effect, trying to rotate his body backwards around his pinned knee. This is not ideal for him, as he wants to prepare for the bottom player fighting for head position. He wants the ability to quickly rotate forwards to use bodyweight to block the top player’s attempt to sit up. By rotating backwards, he has to first stop and then reverse direction before he can fully apply force in a forward direction.
By engaging her muscles, the bottom player will be able to sit up faster as her muscles are primed for use.
So the effect of the upwards pressure is to slow down the top player, and to speed up the bottom player. The bottom player will use this speed differential to sit up and hug the top player’s torso. With a tight hug, she can push off her outside foot (which is flat on the floor) and pull the top player forwards so his butt separates from his heels.
Now the battle for head position can proceed.