HIIT workout: what counts, three sessions to run and where it fits in your week

HIIT is high-intensity interval training: short, hard efforts with easier recovery between them. The sessions are brief, which is the appeal, and hard, which is the catch. This page is the workout itself: what counts as HIIT, how the trials set the work and the rest, three sessions to run, how hard "hard" is, and where one fits in a week.

Whether to do intervals at all instead of steady cardio is on HIIT vs steady-state cardio. The 20-seconds-on, 10-seconds-off format has its own page, the Tabata workout. Another way to run the same shape is a battle rope session.

What counts as HIIT

A 2017 review describes interval exercise as repeated bouts of relatively intense exercise with short periods of recovery between them. It splits the method in two: high-intensity interval training, with "near maximal" efforts, and sprint interval training, with "supramaximal" efforts.¹

The World Health Organization describes vigorous activity as usually a 7 or 8 on a 0-to-10 scale of perceived exertion.² That is a workable picture of "hard" for the efforts below: a pace where you could manage a few words, not a sentence. If you can chat through it, it's a steady session, which is fine, but it isn't HIIT.

How the trials set the work and the rest

There is no single HIIT recipe. These are designs that trials used, not prescriptions:

Read together, the efforts ran from 20 seconds to a minute and the recovery from 10 seconds to four minutes. A 2019 meta-analysis of 53 randomized trials sorted programs by length: even intervals of 30 seconds or less, low-volume sessions (5 minutes or less, in the review's classification) and programs of 4 weeks or less improved maximal oxygen uptake against doing nothing, but only intervals of 2 minutes or more, high-volume sessions (15 minutes or more) and programs of 4 to 12 weeks or longer did better than moderate steady training.⁸ The authors recommend longer intervals, volumes and programs to maximize the gain, and the shorter ones as a time-efficient option.⁸

Three HIIT workouts

These are practical starting points built on the shapes above, not protocols from a trial. The sprint trial used a two-minute warm-up and a three-minute cool-down;⁴ five easy minutes before and three after is a practical default for the sessions below.

The hard work in these sessions adds up to three or four minutes; the rest is warm-up, recovery and cool-down. Progress one thing at a time: add an effort every week or two, then shorten the recovery, then add load or a harder version of the move. The rowing-and-bodyweight trial above used 75 seconds of recovery.⁶

Sprints, once the sessions above feel routine: on a bike, three efforts of 20 seconds all-out with two minutes of easy pedalling between, the shape of the ten-minute cycling trial above;⁴ a rower is a practical swap. Running sprints are a skill of their own, so start on a machine.

How hard is hard

The single-session studies in the table measured it: average heart rate in four all-out 30-second efforts was about 85% to 87% of peak,⁷ and peak heart rate in six one-minute efforts reached 92% to 96% of maximum.⁶ You don't need a monitor to get there. Use effort and the talk test instead:

• During an effort: a few words at most, 7 or 8 out of 10.
• During recovery: breathing slows enough that you could say a sentence by the end of it.
• Across the session: the last effort will usually be a little slower than the first. If the second is already much slower, start the next session with fewer efforts or longer recovery.

Where it fits in your week

The WHO's guideline for adults is 150 to 300 minutes of moderate aerobic activity a week, or 75 to 150 of vigorous, or an equivalent mix, plus muscle-strengthening on two or more days; it counts bouts of any duration.² The short sessions in the trials above ran three or four times a week.^3,4,5

As a practical start, do one session a week for two weeks, then two, on days when you aren't training legs hard. Cardio and lifting covers how far apart to put them.

Common questions

How long should a HIIT workout be?

The three sessions above run 17 to 20 minutes with warm-up and cool-down, with 3 to 4 minutes of hard work in them. The 2019 meta-analysis classed sessions by volume: even low-volume sessions (5 minutes or less) improved maximal oxygen uptake, and high-volume sessions (15 minutes or more) did better than steady training.⁸

Can a beginner do HIIT?

The trials above included sedentary men (average age about 27) and inactive adults (average age about 20); the inactive group chose its own "challenging" pace.^4,5 Start with the first version of a session, rate the efforts 7 or 8 rather than 10, and add one effort at a time. If you're new to exercise altogether, steady sessions twice a week first are a gentler start.

Is Tabata the same as HIIT?

Tabata is one HIIT format: 20 seconds hard, 10 seconds rest, eight times. The Tabata workout covers what the original study measured and how to run one.

Are circuits, EMOMs and AMRAPs HIIT?

Not by themselves. HIIT is defined by hard efforts with recovery between them.¹ A circuit is defined by the order of the exercises, an EMOM and an AMRAP by a clock. Any of them can be run hard enough to count, and none has to be.

What if something hurts?

If you have pain, an injury or a medical condition, a doctor or a physical therapist should set the limits before you train hard; this page is general guidance for healthy adults.

If you'd rather have the week planned

Choosing a HIIT session is a small decision next to fitting it around lifting, work and the rest of your week. Coaching is the version where your workouts live in the Trainerize app, sized to the days you actually have, and a weekly call looks at the week you just had and rebuilds the next one. Fat loss coaching explains how the training and the daily movement fit together, and apply is the first step. Otherwise: pick one session above and run it once this week.