Day 10 introduces the plank days: 20 seconds of high knees, 10 seconds of plank hold, alternating four times per set, at 3, 5 or 7 sets with 2 minutes between. Half of this workout is furious motion. The other half is refusing to move at all.
That contrast is the entire design. Sprinting spikes the heart rate; the plank then demands total stillness on top of that spike - a straight-armed hold, drawn high on the hands, where the challenge is not the position but the composure. Breathing hard and holding steady are usually opposite skills. This card trains them as one, ten seconds at a time, and those ten seconds get longer every time the high knees get faster.
Give the high knees everything - they buy their own rest. Then take the plank seriously as a position: hands under the shoulders, arms locked, one clean line from head to heels, no sag and no pike, breathing loud and staying put. The plank is not a break. It is the second exercise.
Twenty seconds of chaos, ten of stillness - Day 10 grades you on how quickly you can find your composure.
Make it Harder: Hold every plank with your feet together.
Make it Easier: Take the planks from your knees.
