Day 7 is the jack family in full: 10 step Ts, 10 step seal jacks, 10 step Ts, 10 side jacks and 10 step half jacks, with the feet stepping out and back rather than jumping. Every variation changes what the arms do while the legs do roughly the same thing, so the legs keep one steady rhythm going while the upper body works through a different pattern each time.
Step Ts open the arms straight out to the sides at shoulder height as the foot steps out, making a T of your whole body. Step seal jacks cross the arms in front of the chest and then fling them wide, a clap and release that opens the chest with every rep. Step Ts come round again, and side jacks shift the work into the waist with a lean and an overhead reach. Step half jacks close the round with the arms staying down at your sides, which sounds like a rest and is not: with no arm swing to ride on, the legs supply all of it.
Step wide enough on every jack that the movement is a real step and not a shuffle. Keep the arms straight on step Ts and stop at shoulder height rather than letting them drift higher. On seal jacks, cross the arms fully and open them fully, because the range is where the chest work lives. Side jacks bend sideways with the hips steady underneath you, and half jacks want relaxed shoulders and quick feet.
Five ways to do the same step, and your shoulders will name a favourite by round four.
Make it Harder: Stay low: keep a soft bend in the knees through all five exercises so the legs never fully straighten.
Make it Easier: Make every step smaller and keep the arms below shoulder height throughout.
