Day 13 rebuilds the crunch circuit out of different parts. Five exercises at 10 reps each, at your level's set count with two minutes of rest: long arm crunches, sitting twists, knee crunches, scissors and flutter kicks.
Only sitting twists carry over from Day 1, and the four newcomers all push the work lower down the body. Long arm crunches keep both arms extended overhead for the entire rep, which lengthens the lever and makes a standard crunch substantially heavier without changing anything else about it. Knee crunches fold both ends of the body toward the middle at once. Scissors and flutter kicks then finish the round with the legs low and continuously moving - crossing over one another in the first, alternating up and down in the second - and neither lets the heels touch the ground until the set is over. It is a floor session that borrows the logic of the bar days: keep the legs in the air and the lower abs never get a break.
Keep the arms beside your ears in long arm crunches; letting them swing forward turns them into a pulley. Knee crunches want the shoulders and knees arriving together rather than one waiting for the other. In scissors and flutter kicks the height of the legs is the difficulty dial - lower is harder, and the moment your lower back lifts off the floor you have gone too low. Raise them an inch and carry on.
No bar today, and your lower abs will have stopped noticing the difference by rep eight.
Make it Harder: Keep your shoulders lifted off the floor throughout both scissors and flutter kicks.
Make it Easier: Take scissors and flutter kicks to 6 reps and keep the legs higher off the floor.
