Concrete Core is a plank workout that never leaves the floor. Climbers return three times - ten reps per visit - separated by plank jump-ins, plank rotations and plank jacks, so your shoulders and midsection hold the same position for the entire set while your legs do increasingly disruptive things underneath.
The recurring climbers are the aggregate that binds the mix. Each block drives your heart rate up and loads the hip flexors, and each return finds your shoulders a little more tired than the last. Between them, the other exercises each attack the plank's stability differently: jump-ins bring both feet forward explosively and send them back, demanding a core that can absorb impact without the hips piking; rotations open the body sideways and dare it to keep the line; plank jacks split the legs wide and snap them back, shaking the base your trunk is trying to hold still. Resisting all of it - the bouncing, the twisting, the splitting - is what pours the concrete.
Hips are everything here. In climbers, keep them low and level; in jump-ins, land with your feet under your hips rather than leaping into a crouch and calling it done; in jacks, keep the bounce in your legs, not your lower back. Shoulders stay stacked over wrists throughout - as fatigue builds, they will try to drift backward, and you should not let them.
Mixed, poured and set over four exercises. Give it a few weeks to cure.
Make it Harder: Add a push-up after every set of climbers.
Make it Easier: Step the jump-ins and jacks instead of jumping them.
