Helix is a plank workout that spirals around one exercise the way its namesake winds around an axis. Climbers appear four times - forty reps in total - threaded between shoulder taps, two 10-count all-fours holds and never once letting you off the floor. One movement, returned to again and again, each pass one turn deeper.

The repeating climber is the strand everything else wraps around. Each block of ten loads the hip flexors, shoulders and heart rate a little further into deficit, and the exercises between blocks are chosen to deny recovery in specific ways. Shoulder taps keep the shoulders under bodyweight load while adding an anti-rotation problem. The two 10-count holds - performed on all fours with knees hovering just off the floor - look like a break and are quietly the meanest part of the workout: the bent-knee hover keeps the quads, hip flexors and core under continuous tension precisely when they were hoping for slack. By the final climber block, the spiral has done its work.

Drive your knees fully forward on every climber and keep your hips low - bouncing hips are wasted effort. During the hovers, knees stay one inch off the floor, back flat, no sagging into the wrists. On shoulder taps, make the touch deliberate and keep your weight centered rather than rocking side to side with each lift.

Around and down, one turn per block. The helix only goes one direction - through.

Make it Harder: Extend both hovers to a 20-count.

Make it Easier: Slow the climbers down and rest your knees during the holds.