Hang from a chin-up bar with both arms extended at arms length in top of you using either a wide grip or a medium grip. The legs should be straight down with the pelvis rolled slightly backwards. This will be your starting position.
Raise your legs until the torso makes a 90-degree angle with the legs. Exhale as you perform this movement and hold the contraction for a second or so.
Go back slowly to the starting position as you breathe in.