Day 17 gives the cardio day a chest exercise. Three exercises, 20 seconds each: step jacks, step chest expansions, step twists - one minute per set, a minute of rest, sets by level. The step chest expansions are the newcomer: the chest expansions from Day 4 stitched onto the side step, so the upper back works while the feet keep the heart rate up.
Step jacks open with the reach overhead. Step chest expansions are drawn from a hands-crossed-in-front start: step out to the side and swing straight arms wide open behind you, then step back in as the arms cross in front again, alternating the stepping foot - the shoulder blades squeeze together on every open. Step twists close: step to the side and rotate the torso and arms toward the stepping leg, then the other way. Reach up, open wide, twist round - three shapes, one footwork.
Keep the step wide on all three. On step chest expansions, open the arms fully - palms turning forward at the widest point helps - and feel the pinch between the shoulder blades before you cross back. Step twists turn from the ribs with the hips mostly still. Move continuously; the third cardio day of the program should feel like one uninterrupted minute of motion.
Chest expansions on the move - the postural muscles a desk switches off just got a cardio interval of their own.
Make it Harder: Take the step twists overhead - arms straight up instead of at chest height, a longer lever and a bigger twist.
Make it Easier: Keep the feet together for the step chest expansions - arms only - and save the stepping for the other two.
