Lie back with your knees bent, feet flat on the floor, and your hands up in guard by your head. Sit up and, at the top of the movement, drive one elbow horizontally across your body in a strike, rotating through your torso - then lower yourself back down with control and sit up into a strike with the other elbow. The sit-up powers the strike: come up fast, rotate hard, go down slow.

Works: abs, obliques, hip flexors, shoulders

Breathing: Sharp exhale as you sit up and strike, inhale on the way back down.

Common Mistakes: Throwing the strike with the arm only instead of rotating the torso behind it, yanking up with the neck, and collapsing back to the floor instead of lowering with control.

Make Easier: Drop the strike and build your base with Sit-Ups, or keep the strike but anchor your feet under something solid.

Make Harder: Pause at the top and throw both elbows before lowering, or move on to Sit-Up Punches.