A HIIT interval timer exists to stop you from guessing, and the guess beginners get wrong is almost always rest. People shorten rest to feel tough, then spend the whole session at a mediocre intensity, which is just cardio with extra steps.

The ratio is the workout

High-intensity interval training is defined by the intensity, not by the timer. The rest is there to let you reach that intensity again. If you cannot hit roughly the same output on round six as round one, the rest was too short or the work was too long.

Three ratios cover almost everything:

Ratio	Work	Rest	Feels like	Best for
1:3	15s	45s	Sprint, full recovery	True max effort, first month
1:2	30s	60s	Hard, breathing heavy	General conditioning
1:1	40s	40s	Grind, never fully recovered	Circuits, conditioning bases
2:1	20s	10s	Survival	Tabata only, see below

Start at 1:2. Not 1:1. A beginner at 1:1 is doing continuous moderate work with brief pauses, which has its uses but is not what you came for.

A first four weeks that works

Week 1 and 2: six rounds of 30 seconds work, 60 seconds rest. Nine minutes of clock, about six of which you spend standing there breathing. That feels like cheating. Do it anyway.

Week 3: eight rounds, same ratio. Twelve minutes.

Week 4: eight rounds of 40 on, 40 off. Now you are at 1:1 and you have earned it.

Two sessions a week, not more, with at least 48 hours between them. HIIT is expensive. The people who do it five days a week end up doing five days of moderate work because they cannot recover, and then wonder why nothing changes.

Set the whole thing up on the interval timer once and the round count, work, and rest stay put so you are not fiddling between sets.

Picking the movement

The cleanest beginner options are the ones where intensity is self-limiting and form does not collapse:

Bike or rower. Best option. You cannot really do it wrong and the resistance scales with your effort.
Hill sprints or incline walking. Gravity does the intensity control for you.
Kettlebell swings. Good, once the hinge is solid. Not before.
Burpees. Effective and universally hated. Form degrades fast, so cap the work interval at 30 seconds.

Avoid anything technical. Round seven is not the place to practice a snatch.

Intensity, in numbers you can use

Without a lab, use the talk test and RPE. During the work interval you should be at an RPE of 8 or 9 out of 10 and able to say maybe two words. If you can say a sentence, you are jogging. If you cannot say anything and your form is gone, dial it back one notch, because the next five rounds still exist.

Heart rate is a lagging indicator on short intervals. On a 30-second effort your heart rate peaks well after the interval ends, so watching the number mid-round tells you nothing useful. Use it to check your recovery between rounds instead: if it is not dropping meaningfully during rest, extend the rest.

Things beginners get wrong

Skipping the warm-up. Five to eight minutes of easy work plus a couple of build-up efforts. The first interval should not be the first hard thing your body has done.

Treating the rest as optional. Walk during it. Do not do “active recovery burpees.”

Going to failure on round one. The first interval should feel like 90% of what you could do. You have seven more.

Changing the protocol mid-session because it feels easy at round two. It will not feel easy at round six.

Where to go after

Once 8 x 40/40 is comfortable, the natural progressions are longer intervals at slightly lower intensity, or the same intervals with more rounds. Running intervals at 1:1 and 30 second sprints with 90 seconds rest are both preset and worth a look. If you want the four-minute extreme end of the spectrum, read what a tabata timer actually does before you try it.

A HIIT interval timer that beeps at every transition means you never break form to check the screen, which matters more than it sounds like when you are eight rounds in and staring at the floor.

Try it: set up your own work and rest intervals.