Sit on the floor with your knees bent and lean your torso back until you feel your abs switch on, keeping your back straight and your guard up. From this position throw alternating punches straight out in front of you, extending each arm fully and pulling it back to guard. Your abs hold the lean for the entire set - the punches are just there to make sure they never get a moment's rest.

Works: abs, obliques, shoulders, hip flexors

Breathing: Exhale sharply with each punch, like a boxer working the bag.

Common Mistakes: Rounding the back into a slump instead of leaning with a straight spine, dropping the non-punching hand instead of keeping it at guard, and rocking the torso back and forth to add power.

Make Easier: Sit up taller to reduce the lean, or build up the position with Sitting Twists first.

Make Harder: Lift your feet off the floor and balance on your sit bones while you punch, or move on to Elbow Strike Sit-Ups to add a full sit-up to every strike.