Day 28 puts knee-to-elbow on the outside of a jumping jack. The circuit is 20 knee-to-elbow, 20 jumping jacks, 20 knee-to-elbow and 20 side jacks - straight through for a set, 2 minutes rest, 3, 5 or 7 sets by level. It reverses the layout of Day 16, where jumping jacks framed the twist; here the twist frames the jump, and there are 40 rotations in every set.
Knee-to-elbow leads: hands behind the head, elbows wide, knee lifting up and across as the opposite elbow twists down to meet it, alternating sides, no jump. Twenty of them, then jumping jacks - feet wide, arms overhead, both feet leaving the floor - to lift the heart rate, then 20 more knee-to-elbow on legs that have already balanced through the first block. Side jacks finish from the wide stance, one arm reaching up and over toward the opposite side, other hand on the hip, alternating. Between the two knee-to-elbow blocks and the side jacks, 60 of the circuit's 80 reps rotate or bend the trunk, which makes this the most waist-focused day in the program.
In knee-to-elbow, keep the standing leg tall, the elbows wide and the rotation coming from the waist - the elbow travels down to the knee, not the chin to the chest. Jumping jacks land soft with the arms overhead. In side jacks, lean from the waist and reach with the whole arm rather than bending the knees to fake the reach.
Two blocks of twists around a single jumping block - the program's most core-heavy day arrived with two days to spare.
Make it Harder: Touch elbow to knee on every single rep of both blocks - if they do not meet, the rep does not count.
Make it Easier: Halve the second knee-to-elbow block to 10 and keep the rest as written.
