REHIT: The 10-Minute Workout That Beats 30 Minutes of Cardio

I’ll admit it: I’m lazy.

That’s why I was so excited to hear about about REHIT, and the possibility of building real cardiovascular fitness just by doing 10 or 20 second bursts of activity.

REHIT, short for Reduced-Exertion High-Intensity Interval Training, is the most extreme version of the "less is more" cardio trend. But it’s not something dreamt up by some Instagram influencer with 100K bot followers: there’s 15 years of peer-reviewed research behind the lab that coined the term.

If you like the sound of a workout protocol that could boost several cardio and metabolic markers, as well as improving VO2 max, on just 20 to 30 minutes of work weekly, stick around, and I’ll explain all there is to know about REHIT training.

What Is REHIT?

The original REHIT is a 10-minute cycling workout built around two 20-second all-out sprints, separated by a few minutes of easy pedaling.

The protocol was developed by exercise physiologists Richard Metcalfe and Niels Vollaard at the universities of Swansea and Stirling. Their goal was to find the smallest dose of sprint exercise that still produced meaningful health and fitness adaptations.

The answer was two short sprints, two or three times a week.

REHIT sits in the broader category of sprint interval training (SIT). It’s not the same as traditional HIIT (High-Intensity Interval Training), which usually targets 85 to 95% of your max heart rate for 1 to 4-minute intervals. REHIT asks you to push past that, but for a very short time.

It’s "reduced-exertion" because compared to traditional HIIT, or other sprint protocols (which used four to six 30-second sprints per session), REHIT cuts the volume by more than half. 

It is still high-intensity because those 20 seconds are as hard as it goes; harder than anything you would do in Zone 2, harder than typical HIIT, and harder than your VO2 max workload.

How the REHIT Protocol Works

A standard REHIT session looks like this:

1. 2 to 3 minutes easy pedaling to warm up

2. 20 seconds all-out sprint at high resistance

3. 3 minutes easy pedaling to recover

4. 20 seconds all-out sprint

5. 2 to 3 minutes easy pedaling to cool down

The total session lasts about 10 minutes, with 40 seconds total sprint time. The idea is to do 2 to 3 sessions per week, which equals 20 to 30 minutes’ time commitment per week.

Here are a few more important details about REHIT you need to know about:

The sprint has to be genuinely all-out

The most important part: for the time you’re active, you need to be giving everything.

The resistance has to be high enough that you can't keep pace for the full 20 seconds. Your power output will drop noticeably in the second half of the sprint, and that is the point. You’re trying to deplete the muscles as much as humanly possible in a short window.

If you finish the sprint thinking you could have gone harder, the resistance was too low.

The recovery period is just as important

After an all-out 20-second effort, plasma volume can drop transiently by around 15%, and standing up or stopping abruptly can cause lightheadedness.

That’s why there’s a prescribed period of light pedaling. The active recovery keeps your blood circulating and lets your body clear lactate before the next sprint.

Ramping up

The original research protocols ramp the sprint duration over the first two to three weeks: 10 seconds in week 1, 15 seconds in weeks 2 and 3, then 20 seconds from week 4 onward. 

Twenty seconds of all-out sprinting is harder than it sounds. When you first start out, don’t try to complete the full thing your first time.

Benefits of REHIT (What the Research Shows)

Let’s look at the health and performance benefits gained from doing REHIT, as backed by scientific trials.

VO2 max gains around 10 to 12%

The strongest finding across REHIT studies is improvement in cardiorespiratory fitness. A 2024 review by Metcalfe and Vollaard synthesized data from over 115 REHIT participants and reported an average VO2 max increase of about 10% over 6 weeks.

In a head-to-head randomized trial by Cuddy and colleagues (2019), 8 weeks of REHIT (2 sessions per week, 10 min each) raised VO2 max by 12.3% in previously inactive adults. The comparison group, doing 30 minutes of moderate-intensity continuous training five days per week, improved 6.9%. 

REHIT roughly doubled the VO2 max gain at one-fifth the weekly time commitment.

This is a big deal. VO2 max is one of the strongest single predictors of all-cause mortality, and even small improvements have outsized longevity effects. A 2018 study found each 1 ml/kg/min increase in VO2 max was associated with roughly 45 additional days of expected lifespan.

Better cardiometabolic markers, with caveats

The same Cuddy trial showed REHIT outperformed traditional cardio on several other markers:

• Systolic blood pressure dropped about 5% (roughly 7 mmHg) with REHIT versus 2% with continuous cardio

• Metabolic syndrome z-score improved 62% with REHIT versus 27% with continuous cardio

• Waist circumference shrank slightly more with REHIT

• Body weight didn't change in either group

It’s worth saying that REHIT has not been shown to produce significant weight loss on its own. It’s powerful for fitness and cardiometabolic health, but the low activity time means it’s not as effective for pure weight loss (the calories burned won’t be as much as, say, a 45 minute moderate intensity run).

It may improve insulin sensitivity

Researchers have noted that insulin sensitivity improvements with REHIT happen in some studies and populations, but are not a universal finding.

The early REHIT studies, including the 2012 paper by Metcalfe and colleagues that introduced the protocol, reported improvements in insulin sensitivity in sedentary men but not women.

However, a larger 2016 follow-up couldn't replicate it, and a study in men with type 2 diabetes found REHIT didn't improve fasting insulin sensitivity or 24-hour glucose, though it did reduce plasma fructosamine (another blood glucose marker). 

Same VO2 max gains, in less time

A 2017 meta-analysis by Vollaard, Metcalfe, and Williams covering 34 sprint interval studies and 418 participants found that reducing the number of sprint repetitions in a session did not diminish VO2 max gains. Two sprints worked about as well as six.

A related study found that cutting sprint duration from 20 to 10 seconds, however, did cut VO2 max gains roughly in half. The 20-second window appears to be roughly the minimum effective dose per sprint.

Why It Works at Such a Low Volume

A single 20-second all-out sprint is an extreme physiological event. In the muscle, intramuscular ATP drops about 50%, phosphocreatine is depleted, glycogen falls 20 to 30%, and muscle lactate climbs roughly 50x.

As Metcalfe and Vollaard wrote, "the only physiological event leading to a greater drop in intramuscular ATP levels is death."

That kind of stress triggers a strong cellular response. A single REHIT bout produces about a 15-fold increase in PGC-1 alpha gene expression, the master regulator of mitochondrial biogenesis. The body responds by building more and better mitochondria, which is the main driver of aerobic adaptation.

The implication is that you don't need long-duration work to get aerobic adaptations. You need the right kind of stress, applied often enough for the body to keep responding. REHIT delivers that stress in 40 seconds of actual hard work.

REHIT vs Other Cardio Approaches

So how does REHIT differ from other types of cardio, in terms of the effect on your body, demands, and more?

Let’s take a look now.

REHIT vs HIIT

Standard HIIT, or extended HIIT protocols like the Norwegian 4x4, uses intervals of 1 to 4 minutes at 85 to 95% of max heart rate. REHIT uses 20-second all-out sprints. Different intensity zones, different demands.

For pure VO2 max gains in moderately trained populations, the Norwegian 4x4 still has the most direct evidence, though REHIT appears to deliver a comparable VO2 max boost in a fraction of the weekly minutes.

REHIT vs Zone 2

Zone 2 cardio (and steady-state cardio) sits at the opposite end of the intensity spectrum: 60 to 70% of max heart rate for long durations. It builds aerobic base, mitochondrial density, and fat oxidation, and you can do a lot of it without accumulating fatigue.

REHIT (or regular HIIT) and Zone 2 drive very different adaptations and benefits. You wouldn’t choose one or the other. The smart play, if you have the time, is to do both: Zone 2 for volume and base-building, REHIT or another HIIT protocol for VO2 max and time efficiency.

Do You Need Special Equipment for REHIT?

There’s a commercial REHIT product, called the CAROL bike, designed specifically for this exercise protocol. It uses an algorithm to set resistance based on your body weight and prior sprint performance, and it runs the protocol automatically. 

It works well and most of the published research uses it. But you don’t necessarily need it.

The protocol works on any cycle ergometer with adjustable resistance, including most spin bikes, Peloton-style indoor bikes, and gym air bikes or assault bikes.

The key is resistance. You need it high enough that:

• You can reach near-peak power within the first 3 to 5 seconds of the sprint

• You can't sustain that power for the full 20 seconds (power should fall in the second half)

• You wouldn't be able to do a third sprint at the same intensity

On a magnetic-resistance bike, that usually means cranking the resistance well above your normal Zone 2 setting. On a spin bike with a friction knob, dial it up until standing in the pedals feels heavy. On an air bike, the resistance is self-adjusting (push harder, get more resistance), so the goal is simply to push as hard as possible.

Who Should (and Shouldn't) Try REHIT

Here’s when REHIT may be a good fit for you and your fitness goals - and when you should avoid it.

REHIT could be a good fit for:

• Time-pressed adults who otherwise wouldn't do cardio at all

• People looking to improve VO2 max

• People who already lift and want a small dose of cardio that doesn't interfere with strength work

• Anyone returning from a long layoff who wants to rebuild cardio capacity without long sessions

REHIT is not a good fit for:

• People with uncontrolled hypertension or recent cardiac events. Peak systolic blood pressure during sprints can hit 218 mmHg in the Cuddy data. That is a hypertensive response by definition, and the authors recommend pre-participation screening for inactive adults and anyone with cardiovascular risk factors.

• Anyone with knee, hip, or back injuries that don't tolerate maximal cycling efforts

• Competitive endurance athletes whose training already includes substantial high-intensity work. 

• People who genuinely dislike maximal effort. If you don’t push yourself literally to the limit, the protocol doesn’t work.

Because of the level of output you’re hitting, anyone with little history of activity, health problems, or anyone over 50 should definitely get advice from a physician first - or just go ahead with a less intensive workout protocol first.

Final Thoughts on REHIT: Is It Right For You?

REHIT is one of the most thoroughly studied minimal-dose exercise protocols. The case for it is straightforward: if you have 20 to 30 minutes per week for cardio and you want VO2 max gains, it works as well as or better than 150 minutes of steady-state cardio.

But it’s not magic, and it’s not a complete fitness program. It’s a shortcut, and like most shortcuts, you’re going to miss out on some things.

It may be good for VO2 max, but for an overall aerobic base, as well as muscle-building and overall body composition, there’s a lot more you’ll need to do.

Consider REHIT if you’re really pushed for time and want to get a cardiometabolic boost with just a few minutes of work. Otherwise, regular HIIT, plus some steady-state cardio and resistance training, will work fine.