Day 16 is the program's plank elevator. The circuit: 5 up & down planks, 10 plank crunches, 5 up & down planks, 10 plank rolls, 5 more up & down planks, 10 plank rolls - one pass is one set, and the up & downs have grown since Day 7, three blocks of five where there used to be two blocks of three.
Fifteen up & down planks per set means thirty arm presses, and how you spend them matters: alternate the leading arm rep by rep so neither shoulder does all the lifting. The new arrival is the plank crunch - staying on your forearms, bend your knees and pull them in beneath you, folding at the hips, then press back out to a full line. It is a crunch with the floor taken away: the abs close the distance and the plank keeps them braced while they do it. The rolls you know; they arrive here as the recovery that still charges rent.
On the up & downs, place the forearm where the hand was and the hand where the forearm was - clean exchanges keep the hips level through the transition. In the crunches, pull the knees in with your abs, not by hopping the feet, and re-lengthen fully each rep. By the third up & down block, form is the entire assignment.
Fifteen trips between elbows and hands per set - Day 16 runs the plank elevator all session.
Make it Harder: Push every up & down plank block to 6 reps - 18 trips a set.
Make it Easier: Take the up & down planks at 3 reps per block.
