Day 8 threads high knees through the entire session: six 20-second intervals alternating high knees with floor work - climbers, then plank jacks, then plank jack + jump ins - with one push-up owed at every changeover. Level sets as standard: 3, 5 or 7, with 2 minutes between.
The standing intervals never change; the floor ones climb. Climbers are running turned horizontal, plank jacks add a jump to the plank, and the plank jack + jump in stacks a full crouch on top - a three-step staircase built into a single card. Keeping the high knees identical in every other slot is deliberate: they are your fixed measuring stick, and how much those 20 seconds hurt by interval five tells you exactly what the floor work is costing.
In climbers, drive the knees straight forward and keep the hips low - height is wasted effort. Plank jacks jump small and land soft, feet just past shoulder width. In the jump-in version, snap the feet from the jack straight into a crouch beneath the hips and back out again without settling anywhere.
Day 8 sends you to the floor three different ways and raises the rent on every visit.
Make it Harder: Run the plank jack + jump ins as one continuous chain - no pause in the plank, none in the crouch.
Make it Easier: Step the plank jacks out and in one foot at a time.
