Day 4 puts two of the jack family side by side. The circuit is 20 march jacks, 20 step jacks, 20 march jacks and 20 step seal jacks - four exercises straight through, then 2 minutes of rest, for the 3, 5 or 7 sets of your level. Every one of these variations belongs to the same family: legs move, arms move, feet never leave the ground.
March jacks are new. From standing, lift one knee toward hip height as both arms rise overhead together, then lower and switch legs - a step jack where the foot goes up instead of out. Step jacks return in the middle exactly as they were on Day 1: step out wide, arms up to meet overhead, step back. Step seal jacks are the day's second newcomer, and they move the arms into the horizontal plane: with your palms clapped together in front of your chest, step out to the side as both arms open wide, then step back as the palms meet again, alternating the stepping foot each rep. Same footwork as a step jack, but the arms swing open like a seal's flippers rather than up like a jack's, so the chest and rear shoulders take over from the deltoids.
In march jacks, keep the standing leg tall and get the knee to hip height - the higher the knee, the harder the balance works. In seal jacks, open the arms all the way out to a straight line at shoulder height and let the palms actually meet on the way back; a lazy half-open swing gives your chest nothing to do. Keep the stepping foot landing wide and flat throughout.
Three flavours of jack, one flat floor - variety is how this program keeps your heart guessing.
Make it Harder: Take a wider step on every step jack and seal jack, wide enough that you feel it in the inner thigh, and keep the arms moving at full range.
Make it Easier: Do the march jacks with the arms lifting to shoulder height instead of overhead and step out a little narrower on the seal jacks.
