Lie on your back with your arms reaching straight up and your knees stacked over your hips at right angles. Press your lower back flat into the floor and keep it pinned there for the whole set — that's the entire exercise. Everything else is just testing whether you can hold that shape while your limbs move. Slowly lower one arm behind your head and the opposite leg out straight, just above the floor, while the other arm and leg stay put. The moment your lower back arches off the floor or your ribs flare up, you've gone too far — stop there, even if your arm and leg haven't gone all the way down. Bring them back and switch sides. Move slowly enough that your spine never has to fight to stay still.

PLANS THAT USE IT 5

Upper Body (No Equipment)2× / week · beginner

Full Body (No Equipment)2× / week · beginner

Minimalist Full Body — Essential Moves2× / week · beginner

Core & Mobility — Movement Foundations3× / week · beginner

Squat Specialization — Multi-Stance Progression4× / week · intermediate