Half jacks meet the compressed ladder: 30 seconds of work with 10 seconds of rest, 30 with 20, and a final 30 with a full minute after - ninety seconds of jumping per set, at 3, 4 or 5 sets by level.
This is Day 13's exercise inside Day 21's rest scheme, and the pairing shows the program's whole method on one card: learn a movement gently, then bring it back with the recovery squeezed out. Ten seconds between the first two blocks never lets the calves and lungs clear the debt, so the third block runs on accumulated fatigue - light-impact hopping that, by the end, does not feel light at all. The fast feet you built two weeks ago get their invoice today.
Guard the rhythm above all: quick, springy contacts, feet flicking just past shoulder width, tempo identical across all three blocks. The short rests are for breathing, not recovering - two deep breaths and you are back. If the ankles stiffen and the hop turns into a stomp in block three, soften the knees and shorten the ground contact rather than slowing down.
Day 13's exercise meets Day 21's rest scheme - the program is quoting itself, at a higher price.
Make it Harder: Hold a shallow half-squat through every rest period instead of standing tall.
Make it Easier: Trim each work block to 20 seconds and keep the shrinking rests as written.
