Sometimes, even a quick, efficient HIIT workout isn’t fast enough. Whether you’re juggling work or family responsibilities or just can’t commit to a longer session in the gym, you might be looking for a way to hack your fitness routine to get it done in as little time as possible. That’s where REHIT, or reduced-exertion high-intensity interval training, might come in handy.

The REHIT training protocol involves alternating between short periods of all-out effort and slightly longer periods of rest for a total of just 10–15 minutes, explains Peloton instructor Dr. Charlotte Weidenbach. Even though that amounts to a really quick sweat session, you’re still able to reap the benefits of exercise because the work intervals are maximum intensity.

Intrigued? Here’s everything you need to know about the benefits of REHIT, its limitations, how to do it, and the best way to add it to your fitness routine. 

What, Exactly, Is REHIT Training?

“REHIT is a very specific form of HIIT (high-intensity interval training),” Dr. Charlotte says. It usually involves just two or three maximum-intensity efforts that only last 10 or 20 seconds, followed by recovery periods of two or three minutes. The lengthier recovery periods “make sure you’re well rested in order to execute one or two more all-out efforts,” she says. And those work intervals are short by necessity: You shouldn’t be able to sustain your maximum effort for very long.

Because REHIT is so quick, this structure appeals to a lot of people looking to make their workouts more efficient, according to the American Council on Exercise (ACE). Typically, you’ll alternate between work and rest for no more than 10 to 15 minutes, which means you may only be working hard for a total of one or two minutes of the entire workout. “That’s why it’s called ‘reduced exertion,’” Dr. Charlotte says. “But it’s still maximum intensity!” 

How can you tell if you’re really giving it your all? Check in with your rate of perceived exertion (RPE). Estimate how hard you’re working on a scale of 0 to 10, where 0 is lying down at rest and 10 is all-out intensity. You’re aiming for a 9 to a 10 on every work interval. You can also keep an eye on your heart rate, which should reach 90–100 percent of your maximum heart rate, according to ACE. “The key is to be able to reach and maintain a target heart rate without causing injury,” says James J. Murphy, MD, an orthopedic surgeon with OSF HealthCare.

REHIT vs. HIIT

These two forms of interval training are similar but not exactly the same. Think of HIIT as the umbrella term, Dr. Charlotte says. It encompasses other formats of high-intensity interval training workouts, like Tabata, as well as REHIT. 

Overall, HIIT workouts can vary greatly in terms of overall duration and the length of the work/rest intervals. For example, you might do a HIIT workout that’s 15–45 minutes long, with intervals of 30 seconds on and 30 seconds off, 40 on and 20 off, or 20 on and 10 off. Because the workouts can be somewhat long and the rest intervals are relatively short, the efforts are usually high-intensity (7–9 RPE) but not maximum-intensity (9–10 RPE), Dr. Charlotte says. Otherwise, you wouldn’t be able to sustain your workout for that long.

REHIT, on the other hand, is a very formulaic form of HIIT, Dr. Charlotte says, with less variation and creativity in interval timing. The work usually lasts just 20 seconds, and you typically only do two or three bouts at a 9–10 RPE or 90–100 percent of your maximum heart rate.

The Benefits of REHIT

For many people with busy schedules, the short-and-sweet nature of REHIT is a big perk, Dr. Murphy says. It takes even less time than HIIT. In fact, it’s essentially the least amount of exercise you can do and still experience health benefits, according to 2019 research published in the World Journal of Cardiology. (The catch is that you’re working really hard.)

And because it’s so short, you might be more likely to stick with it and therefore see better long-term success, Dr. Charlotte says. When your workout only takes 10 minutes, it gets harder to accept the excuse that you truly don’t have the time! 

REHIT also gives you an opportunity to shake up your regular routine, Dr. Charlotte adds. If you’re used to long walks at a steady pace and a couple of strength-training sessions each week, you can push yourself to include a few all-out efforts to “present the body with different stimuli” and help you avoid strength and endurance plateaus, she says.

The REHIT protocol has also gained a bit of a reputation for improving your VO2 max, which is the maximum amount of oxygen your body can use during exercise, Dr. Murphy explains. It reflects how efficiently your heart, lungs, and muscles utilize and deliver oxygen during exercise and is generally used as a measure of your cardiovascular fitness. Several small studies show that just a few weeks of REHIT improves VO2 max, including for people with diabetes and those who weren’t previously active.

In one very small 2019 ACE study published in the International Journal of Environmental Research and Public Health, inactive people were assigned an eight-week exercise program consisting of REHIT cycling or moderate-intensity continuous aerobic exercise. At the end of the study period, the people in the REHIT group saw more improvement in VO2 max, blood pressure, and waist circumference than those who did steady-state cardio. Another very small follow-up study suggests REHIT may deliver some of those benefits in as little as three weeks, according to ACE.

Larger and longer studies are needed to fully understand why REHIT has these effects, Dr. Murphy says—but there are some theories. “Each level of workout intensity contributes to different adaptations to a different extent,” Dr. Charlotte says. “With REHIT, one factor is its rapid depletion of glycogen stores. This activates different pathways that contribute to the body improving its aerobic capacity.”

How to Do a REHIT Workout

The tricky thing about REHIT is actually reaching your maximum effort. “I think this is why the trend should be regarded skeptically—most people aren’t able to do a full, all-out effort,” Dr. Charlotte says. For one, this can be quite difficult for someone who hasn’t worked out a lot. It’s likely that only more advanced athletes will have a real sense of what maximum intensity feels like and be able to achieve it without a high risk of injury. 

Second, “the thing with an all-out effort is that it needs a lot of resistance,” Dr. Charlotte says. “For most people, 20 seconds of jump squats or burpees isn’t really going all-out. The best (and potentially only) way to do a proper all-out effort is with a machine where you don’t have to manually increase resistance and can go all-out at once—like a ski ergometer or air bike, where anyone can go to their max and it gets more difficult the harder you push.” You could maybe pull off REHIT while sprinting outside (not on a treadmill), though an all-out sprint is quite difficult to do, Dr. Charlotte adds. 

With all the above in mind, how do you actually do one of these super-short, maximum-intensity workouts? Aside from choosing the right piece of equipment, the crucial first step is warming up. Your body needs to be ready to reach maximum effort. Dr. Charlotte recommends a warm-up of at least 3–5 minutes to increase your heart and breathing rate and warm up your muscles and joints. This is also the time to mentally focus on the work to come, she says.

Here’s how you might structure a REHIT workout on an air bike, for example:

As you can see, the total duration of this workout, including the warm-up and cooldown, is less than 12 minutes, and you could technically complete it in under nine. (We weren’t kidding about REHIT being short.)

Who Should Try the REHIT Training Protocol?

Lots of different athletes can benefit from REHIT. As the research above highlights, it’s even effective for people who haven’t exercised much recently. That’s because the concept of an all-out effort varies based on your starting point. Even beginners can push themselves to their limits and gain health benefits—they just need to do so with a little extra care.

However, if you’re going to try REHIT as a way to get back into exercise, it’s a good idea to talk to your primary care provider to make sure “there are no extra precautions or contraindications,” Dr. Murphy says. That’s especially true for anyone with existing health conditions that affect the heart and cardiovascular system or lungs, Dr. Charlotte says.

Once you have the OK from your doctor, start with lower-intensity workouts and build an aerobic base. “I wouldn’t recommend anyone start their workout journey with REHIT,” Dr. Charlotte says. “I recommend having a good base cardiovascular endurance level first, or else it may feel overwhelming and can increase injury risk.” When you feel ready to give it a shot, it’s a good idea to warm up really well and try REHIT cautiously the first time to see how it feels, she says. Then try this type of interval work first at a lower intensity—say, an RPE of 7 or 8—before working up to a 9 or 10. Ramping up in this way can help you learn what your maximum intensity feels like and get more comfortable spending time there.

Experienced athletes may be more comfortable with the all-out efforts characteristic of REHIT, Dr. Charlotte says, and therefore less likely to injure themselves with such an intense routine.

Should REHIT Replace Your Cardio Workouts?

Even though all of this probably sounds pretty impressive, no one is suggesting you drop everything and only do REHIT workouts from now on. “REHIT should not replace a diverse workout routine, which is optimally a combination of cardio and strength training at least three times per week, complemented by regular low-intensity movement, like taking walks and climbing stairs,” Dr. Charlotte says. 

That’s especially true if you’re training for a race or other event: You won’t be able to build up the mileage necessary to perform your best in a half-marathon or marathon, for example, if you only do REHIT cardio. 

How to Incorporate REHIT Into Your Routine

Dr. Charlotte sees REHIT as a complement to your fitness routine, rather than something you necessarily need to do regularly. To her, REHIT is the solution when you had planned to do a longer workout but didn’t end up having the time. Instead of skipping an entire day of exercise, you can break a quick sweat with REHIT—“but I wouldn’t recommend training only in the REHIT style, and I don’t think it needs to be implemented in a fitness routine,” she says.

If you just want to sprinkle in some harder workouts now and again, you can stick with more traditional HIIT classes. They may not be quite as fast or gnarly as REHIT, but they still offer a lot of benefits in a short time. Check out a Tabata class or a Power Zone Max ride on the Peloton App, Dr. Charlotte suggests.

When you’re traveling or going through a particularly busy time when it’s hard to stick to your regular workout routine, you might lean on REHIT a little more, she says. Just make sure you’re still getting enough rest between REHIT sessions. That means doing REHIT no more than two or three times per week, according to the ACE.

And like with any workout trend, don’t expect dramatic, overnight results. “Getting really fit in a healthy, consistent way still does take time; there’s no shortcut,” Dr. Charlotte says. “REHIT can help you stay on track and diversify your routine, but it isn’t the magical workout to make everyone fit in under 15 minutes twice a week.”

Takeaway

REHIT, or reduced-exertion high-intensity interval training, is a specific type of HIIT training that involves very short 20-second bursts of maximum-intensity work followed by 2–3 minutes of low-intensity work or rest. REHIT workouts total only 10 to 15 minutes, meaning they’re a super-efficient way to break a sweat, get your heart pumping, and feel noticeable results in just a little bit of time. REHIT can help improve VO2 max, add variety to your workout routine, and challenge your body in new ways to avoid plateaus. 

All that said, it’s tricky to do right, isn’t a replacement for a well-rounded workout routine, and doesn’t come without risk. Regular HIIT workouts are more suitable for most exercisers and still offer a host of benefits while being quick and efficient, so if REHIT isn’t a fit for you, don’t sweat it.