Day 16 mixes half jacks with full ones. The circuit is 10 half step jacks, 10 step jacks, 10 half step jacks, 10 side jacks and 10 knee-to-elbow. The first three run the same footwork with and without the arms, so you feel the difference the moment it changes.
A half step jack steps the foot out with the arms hanging; a full step jack adds the overhead sweep. Put them side by side and the arms turn out to be more than decoration - they raise the heart rate, they change the breathing, and they make the movement feel bigger even though the legs are doing the same thing. Side jacks then take the arms sideways instead of overhead, adding the lean that brings the waist in, and knee-to-elbow closes the round with the trunk folding to meet a lifted knee. Four patterns, one step, and a circuit that never stops moving.
Keep the same step width for both jack versions so the arms are the only variable. Sweep the hands all the way overhead on the full jacks rather than stopping at head height. In side jacks, let the reaching arm lengthen the whole side of your body. On knee-to-elbow, keep the elbows wide and squeeze at the point where knee and elbow meet before you unfold.
Two versions of one step, running back to back, and the second one always feels bigger.
Make it Harder: Widen every step so each jack covers more ground and the legs travel further.
Make it Easier: Run the circuit with the arms down and let the legs do all the stepping.
