Day 4 closes the program's first four-day cycle, and it takes the load off your abs completely. The circuit is knee-to-elbow, back arches, a kneeling stretch hold and back extensions - 30 seconds each, all of it on the floor. Three days of flexion have asked the front of your torso to shorten repeatedly; today the back of it gets to extend, and the movements are slow by nature rather than by instruction.
Each panel is aimed at the posterior side of the trunk. Knee-to-elbow starts on all fours with the opposite arm and leg reaching long, then draws that knee and elbow together underneath the body - stability and mobility in the same movement. Back arches round and hollow the spine through its full available range, segment by segment, which is exactly what a spine that has spent three days curling needs. The kneeling stretch hold sits the hips back toward the heels with the arms stretched out along the floor ahead of you, lengthening the whole back and the sides of the ribcage. Back extensions finish face down, hands at the head, lifting the chest against gravity to work the muscles running either side of the spine.
In knee-to-elbow, reach fully long before you fold - the extension matters as much as the contraction. Move slowly through the back arches and let your breath drive the shape: exhale as you round up, inhale as you hollow. Settle into the kneeling hold rather than pushing into it, and let each exhale drop your chest a little closer to the floor. In back extensions, lift only to a comfortable height and keep your neck in line with your spine rather than craning it up.
The cycle's fourth day exists so the other three keep paying out.
Make it Harder: Not the day for it - if you want more from this one, halve the speed of every movement so each repetition takes twice as long to complete.
Make it Easier: Lift only your chest in the back extensions and leave your legs resting on the floor throughout.
