Day 21 merges the program's two upper-body threads into one Power session: 20-second intervals of squats, shoulder taps, scissor chops, squats again, push-ups and arm scissors, with a jump squat owed between every exercise - 3, 5 or 7 sets, 2 minutes between.
The card is a deliberate hybrid: Day 4's strength grid supplies the squats, the plank shoulder taps and the push-ups, while Day 11's endurance work supplies the scissor chops and arm scissors that park the arms at shoulder height and leave them there. Alternating between the two threads means the shoulders never get a clean break - they stabilise a plank one interval and hold a level sweep the next - while the twin squat intervals and the connective jump squats keep the legs paying their share throughout.
Squat depth stays constant across both intervals. Plank taps: hips square, no rocking. Chops sweep wide and cross with intent; scissors stay straight-armed and level - both live or die on the arms refusing to sink. Push-ups run full range, and every connective jump squat gets a real crouch and a real jump.
Strength work and shoulder endurance take turns all session - Day 21 is two earlier workouts agreeing to split the bill.
Make it Harder: Replace both 20-second squat intervals with jump squats.
Make it Easier: Squat to a chair and stand back up - full reps at a guaranteed, friendlier depth.
