Extreme HIIT opens by showing you exactly how it works. Six exercises, 20 seconds each, performed back to back with no rest in between: burpees, squats, burpees, plank jump-ins, a plank hold and plank jump-ins again. That two-minute run is one circuit - one set - and depending on your level you will do it 3, 5 or 7 times, with one minute of rest between sets. There is no counting anywhere in this program: the clock decides when an exercise ends, and your job is to fit as much honest work into each 20 seconds as you can.
The circuit splits into two neighborhoods. The first half stays on its feet: burpees bracket a block of squats, so your legs never get a slot where they are not the main engine. The second half drops to the floor, where plank jump-ins - jumping both feet up to your hands and back out to plank - bracket a straight-arm plank hold: body in one line from head to heels, hands under shoulders, hips level. The hold is where the transition rule of this program first bites: you arrive in it straight out of jump-ins, already loaded, and you leave it straight into more jump-ins without ever letting the tension drop.
Go flat out, but let form set the speed limit. Burpees run their full sequence every rep - down, back, in, up. Squats reach at least parallel with the weight in your heels. On jump-ins, both feet travel together and land close to your hands; in the hold, the hips neither pike up nor sag toward the floor. A slow rep done fully beats two fast ones done halfway, even against a clock.
Two minutes is the whole contract - Day 1 is where you find out how long two minutes can be.
Make it Harder: Finish every burpee with a full vertical jump and an overhead clap at the top.
Make it Easier: Step your feet in and out one at a time on the plank jump-ins instead of jumping them.
