Day 12 is Ab Work with a flip built in. Four 15-second stations alternate between face-down and face-up: climbers, knee to-elbow crunches, climbers again, knee to-elbow crunches again - with a turn over between each, at 3, 4 or 5 rounds. The transitions are printed right on the card, because they are part of the workout.
Climbers are a moving plank: shoulders stacked over wrists while the legs sprint, which trains the core to stay rigid under fast, uneven loading. The crunches answer from the other side - knee and elbow drawn together over the midline, adding rotation to flexion. And the flips between them do quiet work of their own: changing position every 15 seconds under a running clock keeps the transitions athletic and denies the abs any moment where nothing is happening.
In the climbers, keep the hips low and level - the legs sprint, the torso does not bounce - and drive the knees all the way toward the chest. On the crunches, bring knee and elbow to meet in the middle rather than hauling the neck forward, and alternate sides evenly. Flip over briskly but land organised: the next interval starts whether you are ready or not.
Face down, face up, face down again - your core works every angle it has today.
Make it Harder: Sprint the climbers - as fast as your feet can cycle while the hips stay quiet.
Make it Easier: Take an extra breath at every turn over - the flip can wait two seconds, the work cannot.
