Day 13 rebuilds the opening crunch circuit out of entirely new parts. Five exercises at 10 reps each, run 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 survive from Day 1, and the four arrivals push the session lower and longer. Long arm crunches keep both arms extended overhead through the whole rep, lengthening the lever and making an ordinary crunch noticeably heavier. Knee crunches bring the knees in and the shoulders up at the same time so both ends fold toward the middle. Scissors and flutter kicks then end the round with the legs low and moving - scissors crossing them over each other, flutter kicks alternating them up and down, both keeping the heels off the ground for all ten reps. Where the first crunch day worked mostly above the waist, this one runs the whole length of the midsection.
In long arm crunches, keep the arms beside your ears rather than letting them swing forward to drag you up. Knee crunches want both halves arriving at the same time. In scissors and flutter kicks the height of the legs sets the difficulty: the lower they travel, the harder the lower abs work and the more the lower back needs pressing into the floor. If the back lifts, raise the legs.
Twelve days ago your abs met five exercises; today they meet five more, and not one of them is easier.
Make it Harder: Run the scissors and flutter kicks with the legs a hand's width lower to the floor.
Make it Easier: Do long arm crunches with the arms crossed over your chest instead of overhead.
