Day 8 brings a third way of counting: the clock. Part I is 140 butt kicks or 140 march steps. Part II is a full circuit of 5 squats, 10 climbers and 20 high knees, but there are no sets this time - you set a timer and cycle through the three exercises continuously until the time is up. Level I is 60 seconds, Level II is 2 minutes, Level III is 3 minutes. One block, no rest inside it: finish the high knees and start the squats again.
A timed circuit turns the goal from finishing reps into sustaining a pace. The three exercises are short enough that you complete a round in well under a minute, which means you will lose count of rounds and that is fine - the timer is the only number that matters. Squats give the legs a brief strength moment, climbers are the fast version of Day 1's slow ones and push the heart rate up, and high knees keep it there. The level choice here is about how long you can hold the pace, not how strong you are; pick a time you can keep moving through.
Keep the pace even from the first second to the last rather than sprinting the first round and walking the third. Squats stay full depth even when you are tired. In the climbers, keep the hips low and drive the knees quickly toward the chest, alternating. High knees reach hip height every rep, arms pumping. When the timer sounds, stop, walk it off and breathe - the rest comes after the block, not during it.
Day 8 has no rep target to finish - it has a clock to outlast.
Make it Harder: Do the full 3 minutes regardless of level and count how many complete rounds you fit in.
Make it Easier: Take the 60-second option and march the high knees instead of running them.
