Day 21 is the jumping-jack grid one more time, and the floor work is now a hold and a burpee. The circuit is 20 jumping jacks, a 10-count plank hold, 20 jumping jacks, 10 basic burpees, 20 jumping jacks, 10 basic burpees, 20 jumping jacks, a 10-count plank hold, 20 jumping jacks - one pass per set, 2 minutes rest, 3, 5 or 7 sets. A hundred jacks a set, as on Days 1 and 13.
Three versions of one card, three different interruptions. Day 1 put jumps between the jacks, Day 13 put plank movements there, and today puts a still plank at the corners and basic burpees - plank, feet in, stand, no push-up or jump - in the middle row. The plank hold is a full plank on the hands, held for a 10-count, and it arrives twice: once fresh, once at the end of the set after 80 jacks and 20 burpees. Basic burpees are 20 per set, which is lighter than the Day 7 count but they are surrounded by cardio here rather than holds.
Jumping jacks stay full - arms overhead, feet wide, soft landings. In the plank hold, stack the shoulders over the wrists, squeeze the glutes and keep the head in line; ten honest counts. Basic burpees: flat plank on the jump back, feet together on the jump in, full stand. Getting down to the floor and back up between jacks and plank should be quick but never sloppy.
The jumping-jack grid has now been interrupted by jumps, by plank movements and by a plank that does not move - and it is the still one that burns the longest.
Make it Harder: Hold each plank for a 20-count and make the burpees full, with a push-up and a jump.
Make it Easier: Step the burpees and take the plank holds from the knees.
