CAR.O.L HIIT Bike Review

Last Updated: Jul 27, 2021

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CAR.O.L is a stationary bike for high-intensity interval training (HIIT) that can improve your fitness and health using artificial intelligence. What makes CAR.O.L unique is that every workout is only 40 seconds long — short enough that you won’t even sweat.

For this review, I tested CAR.O.L to find out how effectively it improves my cardiovascular performance, and to determine whether I could use the bike to complement my CrossFit training.

To see what exercising with CAR.O.L looks like in action, check out a video (below) of one of my training sessions.


Michael Kummer

CAR.O.L - Stationary HIIT Bike
Build Quality
Training Programs


CAR.O.L is a stationary bike for high-intensity interval training (HIIT) that can improve your fitness and health using artificial intelligence.

What makes CAR.O.L unique is that every workout is only 40 seconds long — short enough that you won’t even sweat.


Benefits of High-Intensity Interval Training

HIIT workouts have become so popular in recent years because they’re an incredibly effective way to improve your cardiovascular fitness with relatively little time investment.

Most HIIT workouts take less than 30 minutes, and some are much shorter than that. One of the most popular HIIT workouts is the 7-Minute Workout, which, as the name implies, takes only seven minutes to complete.

Another popular type of HIIT workout is called Tabata, which only takes four minutes per round.

While you can do high-intensity workouts with all different kinds of equipment or with no equipment at all — think bodyweight exercises (mountain climbers or jumping jacks) — some people prefer HIIT bike workouts to get the heart rate up and the blood flowing.

HIIT workouts on stationary bikes have the benefit that you can do them pretty much any time and from the comfort of your home — without requiring a lot of (storage) space for exercise equipment.

Intensity is what makes a HIIT session so effective, but it’s also the reason why many people don’t stick to this type of exercise routine. It’s no secret that HIIT requires a degree of willpower and mental toughness that not everyone brings to the table.

In our labs, we see insulin sensitivity improve by 25-28% and fitness by 15% within 6 weeks. The CAR.O.L stationary bike reproduces these results in the real world. The research programmed into CAR.O.L is benefiting the public, and that’s ultimately what this science is about. 

Dr. Niels Vollaard

That’s one of the reasons why I like CAR.O.L — each workout session lasts only 40 seconds (plus warmup, recovery and cool down).

CAR.O.L – a Stationary Bike for High Intensity Interval Training


  • Minimal time investment
  • Scientifically-proven benefits
  • ISO certified for the most accurate commercial-grade ergometer
  • CAR.O.L dynamically adapts to your progress, so you never plateau


  • Initial investment
  • Internet connection required

So what is CAR.O.L?

CAR.O.L has been around for a while, but it used to be called High Octane Ride. The idea behind CAR.O.L is to take high-intensity interval training to the next level.

CAR.O.L stands for Cardiovascular Optimization Logic. It’s an AI-powered bike ergometer that the company says gets you 132% healthier in 98% less time.

CAR.O.L - Stationary HIIT Bike
CAR.O.L AI Bike – a stationary indoor bike for HIIT.

That first figure is based on a METS Z-score, which is a combined score of various health markers that is often used in medical studies. In one study, CAR.O.L users’ METS Z-score was 132% better than non-users at similar fitness levels.

The “98% less time” claim is based on the reduced time it takes to complete a workout on the bike: just 40 seconds per day three days per week, as opposed to jogging for 30 minutes five times per week.

What’s more intense than HIIT, you might ask? It’s supra-maximal interval training. The goal of supra-maximal interval training is to rapidly empty the glycogen stores in your thigh muscles through two 20-second sprints at super-high intensity.

Scientists call this method reduced-exertion high-intensity interval training, or REHIT, because your perceived exertion is lower than what you experience during traditional HIIT workouts. That makes sticking with REHIT easier than with other types of exercises.

How Does the CAR.O.L AI Bike Work?

CAR.O.L HIIT bike review
YouTube video: CAR.O.L HIIT bike review

CAR.O.L uses artificial intelligence to personalize your workouts based on your physiology and ability. Think of the bike as your personal trainer, or as an exclusive indoor cycling studio that gives you a challenging cardio workout.

During the initial setup of your workout profile, the bike asks you for personal information, including your age, weight and height. Based on those biometrics, 50 years of empirical evidence around the REHIT method, and biometric data from on-board sensors, CAR.O.L constantly assesses your performance and makes continuous adjustments using 1,000 resistance settings.

In other words, every time you mount the bike, you get a personalized workout that improves your health and fitness.

What sets CAR.O.L apart from other ergometers is that the bike can replicate exact lab protocols in the real world — such as the ones used in a recently published study on the benefits of REHIT.

Dr. Niels Vollaard, a lecturer in health and exercise science at the Faculty of Health Sciences and Sport, said:

CAR.O.L is the only system that accurately replicates my research outside of the labs. This scientific exercise cannot be done on a regular bike because of the supra-maximal resistance required that also needs to be tailored to each person’s physiology.

Dr. Niels Vollaard

As a result, exercising on this bike for 40 seconds a day, three times per week is more effective than going for a 30-minute run five times per week.

CAR.O.L vs. Jogging

To give you an idea of how effective cycling on CAR.O.L is compared to jogging, below are some numbers from a study that was published in February 2019, in the International Journal of Environmental Research and Public Health. The figures shown indicate how much better CAR.O.L users’ scores and improvements were when compared to those of the joggers in the study:

  • Risk of developing a metabolic disease ⁠— 62% better
  • Cardiovascular fitness — 78% better
  • HDL cholesterol — 71% better
  • Triglycerides — 78% better
  • Blood pressure — 196% better
  • Blood sugar — 48% better

In another study from 2011 scientists concluded that REHIT increased insulin-sensitivity in male study participants by 28%, which lowers the risk of developing Type 2 diabetes.

I’ve been following a ketogenic paleo diet for a while, and I do CrossFit four or five times per week. As a result, my bloodwork is already in the ideal range and I have no fear of developing Type 2 diabetes or other lifestyle-related diseases.

However, my measurable goal with CAR.O.L is to improve my maximum power — expressed in watts — and my octane score. The octane score is a measure of power output on the bike in relation to your heartbeat, and you can correlate that to your VO2max.

VO₂ max is the maximum rate of oxygen consumption measured during incremental exercise; that is, exercise of increasing intensity. The name is derived from three abbreviations: “V” for volume, “O₂” for oxygen, and “max” for maximum.


While octane score and VO2max aren’t exactly the same, they improve in a similar fashion. That means that as my octane score improves, so does my VO2max.

Workouts/Training Modes

New CAROL.AI dashboard
The new CAROL app makes it easy to see your progress.

CAR.O.L offers the following seven workout modes you can choose from, including a free ride mode.

  • Intense
  • Energizer
  • Fat Burn 30
  • Fat Burn 60
  • Constant Power
  • Continuous Ramp Up
  • Free Ride

Intense is the primary program and the one I use most often. It consists of two 20-second sprints, plus a two-minute warmup, a three-minute recovery, and a three-minute cool down. So, my total time investment is eight minutes and 40 seconds for each indoor cycling workout.

CAR.O.L recommends that you work out three times per week if you want to improve your performance, health and fitness. To maintain your fitness level, you can reduce your workouts to two per week.

Given how often I do CrossFit, I don’t always get to work out three times a week on CAR.O.L. It’s not an issue of finding the time, but it’s a matter of giving my legs enough rest to recover. We’ll see how that approach impacts my octane score in the long run. For now, I think that my CrossFit training more than compensates for the missed biking sessions.

Energizer is a shortened version of Intense that consists of two 10-second sprints. I choose Energizer when I don’t feel like “killing” myself, or on days when I feel sore and I already worked out (CrossFit).

Fat Burn 30 and Fat Burn 60 are both excellent workouts if your fitness goals include burning fat or to lose weight. These two workouts consist of a two-minute warmup, 30 or 60 eight-second sprints with 12 seconds rest in between each, and a three-minute cool down.

CAROL - Fat Burn 30 Workout
Fat Burn 30.

In Constant Power mode, CAR.O.L will adjust the resistance automatically to maintain the chosen power.

CAROL - Constant Power Mode
Constant Power mode.

Continuous Ramp Up is a testing protocol that you can use to measure your VO2max. During the test, CAR.O.L will increase the resistance by three watts every three seconds until you fatigue.

CAROL - Continuous Ramp Up
CAROL – Continuous Ramp Up.

Free Ride, as the name implies, allows you to use the bike like a traditional ergometer. You can freely set the resistance and other parameters and ride for as long as you like.

CAROL - Free Ride
CAROL – Free Ride.

CAR.O.L Hardware and Setup

CAR.O.L - Seat
CAR.O.L AI – adjustable bike seat.

CAR.O.L bikes are shipped from one of two warehouses — depending on whether you live near the east coast or the west coast — via a parcel service. I got my bike wrapped in a large cardboard box.

CAR.O.L features a stainless steel frame and a heavy flywheel. The weight is necessary for stability reasons. The good news is that assembling CAR.O.L usually takes less than 30 minutes. I put my bike together in the garage and then wheeled it into my office.

Once I had found a good spot for my bike, I made sure it was even by manipulating the four adjustment knobs on the underside of the frame.

I have hardwood flooring in my office and was afraid my sweat might damage it; then I remembered that using CAR.O.L doesn’t make you sweat. Unless, of course, you do the fat loss routines or use the bike for free riding to build up endurance.

If so, you might want to cover your floor with a protective plastic sheet — such as the ones you use underneath a rolling office chair — to protect the floor.

Software and App

CAR.O.L Dashboard
CAR.O.L dashboard.

When you first power up the bike, you’ll probably notice that CAR.O.L’s software is just an app running on an Android-powered tablet. That makes using and interacting with the CAR.O.L app straightforward, unless you’ve never used a smartphone or tablet before.

Before you can start your first bike ride, you have to create a rider account with CAR.O.L. You can later access this account via web browser from your computer or via smartphone app.

To ensure that nobody else can access your account, you have to protect it with a password. I usually generate and store unique and complex passwords for each account I have using an app called 1Password*. Unfortunately, every time you ride on CAR.O.L, you have to enter your account username and password via the on-screen keyboard on CAR.O.L’s tablet screen.

This reason for this makes sense: the bike uses your unique rider data in its deep learning process, which is how it ensures that you always have the appropriately challenging cardio workout based on your strength and fitness levels. If other people used your account, that would undermine the program.

Still, this made it so that I couldn’t use a long and automatically-generated password for my CAR.O.L account, because I would have to look it up every time I wanted to work out on the bike.

However, instead of choosing an easy-to-guess password (such as “password” or “Michael”), I chose a password that’s hard to guess but easy to remember. To learn how I did that, check out this article about how to choose a good password.

Competing With Others

CAR.O.L Global Leaderboard
CAR.O.L Global Leaderboard.

Every time you finish a workout on CAR.O.L, you can save the ride and see how you compare to every other CAR.O.L user worldwide on a weekly leaderboard.

Video: Bryan vs. Michael Compete on CAR.O.L
Video: Bryan vs. Michael Compete on CAR.O.L

I enjoy having this community connection and think it makes for a fun workout. Instead of just competing against my personal best performance (which can become tedious for even the most dedicated riders), it’s fun to essentially play an ongoing fitness game against other great athletes.

Riding With CAR.O.L

Me on one of my first rides on CAR.O.L.

Riding with CAR.O.L is pretty straightforward if you follow the on-screen instructions of the workout you choose.

Before starting a workout, you can pick music or spoken instructions (this varies depending on the type of workout).

Once you’ve completed the workout, you see your score and an indication of whether you’ve improved upon your previous scores. CAR.O.L also asks you how you feel after the workout, and if you’d like to save your score or discard it.

How Much Is CAR.O.L?

For consumers, CAR.O.L costs $2,995 plus a $12 monthly subscription fee per household. Corporate users, such as gyms, pay $3,995, but they get a host of additional benefits.

If you want to give CAR.O.L a try, you can use discount code MK150 to get $150 off the purchase price.

Shop Bike*

Tips to Improve Your Score on CAR.O.L

Besides improving your conditioning by working out on CAR.O.L at least three times a week, there are a couple of tricks you can use to get the best possible score.

  1. Make sure the bike seat and handlebar are adjusted properly for your height.
  2. Use biking shoes.
  3. Wait until the end of the three-second countdown before going all-in.

One of the most important factors in biking efficiently is a properly-adjusted seat and handlebar. If you sit too high or too low, you won’t be able to transfer power from your legs to the bike as efficiently. So, make sure to adjust the bike according to the manual and your height.

I’ve also noticed that the pedal straps tend to loosen over time. That’s just because of the force applied when you’re peddling at full speed. For best results, I recommend getting a pair of biking shoes that you can attach firmly to each pedal.

That said, I still bike with my tennis shoes because I don’t care if I lose a few watts.

Last but not least, I recommend holding off on going all-in when the screen turns red and the three-second countdown starts. Why? Because I’ve noticed that I reach peak speed and intensity even before the 20-second workout starts.

In other words, when the actual workout starts, my performance is already declining. So, I usually wait until one second before the workout starts.

CAR.O.L.AI vs. Other HIIT Bike Workouts

CAR.O.L vs. Other Exercises
CAR.O.L vs. other exercises.

So how is CAR.O.L different from other HIIT bike workouts, such as spin classes?

The primary difference between regular HIIT workouts or spin classes and CAR.O.L is the latter’s ability to rapidly empty the glycogen reserves in your thigh muscles. That’s what makes the bike so effective for increasing your aerobic capacity.

CAR.O.L can do that because of how it utilizes science, technology and artificial intelligence. In other words, CAR.O.L can personalize each workout based on your physical abilities at the time of that particular workout.

As a result, CAR.O.L can improve your cardiovascular conditioning with only 40 seconds of work. No other workout, that I know of, can do that.

CAR.O.L. vs. Spinning

CAR.O.L vs. Spinning
CAR.O.L vs. a spin bike.

Before becoming a CrossFitter, I tried various types of exercises, including spinning. From a purely physical perspective, I enjoy training on a stationary bike. Spinning was tough, but I burned a lot of calories doing it and the group setting motivated me to push even harder.

The downside of spinning is that it’s monotonous. After a while, I got bored and stopped doing it.

And another disadvantage of spinning is that it takes at least an hour — and even more if you add the time required to travel to the gym and back. If you plan on using a spin bike at home, you really have to be self-motivated and very disciplined.

Innovations like the Peloton bike have tried to offer solutions to these problems by introducing connected bikes that allow you to work out from the comfort of your home while still interacting with and competing against a community of riders.

While I think that’s a great idea, you still have to commit a significant amount of time for the workouts to be effective.

In contrast, CAR.O.L requires only a few minutes of your time. And while you can’t compete with other riders live (the rides you take with CAR.O.L are simply too short for that), you can compare yourself to others via CAR.O.L’s global leaderboard.

CAR.O.L and Peloton

Near the end of 2020, CAR.O.L. announced new compatibility with the Peloton Digital platform. That means you can use the bike not only for its own high-intensity workouts, but also for the more traditional classes (i.e., longer rides) offered via Peloton.

In order to leverage this compatibility, you’ll need a paid subscription to Peloton Digital.

Who Should Use CAR.O.L?

Kensington Town Hall employee on CAR.O.L
Kensington Town Hall employee on CAR.O.L.

I’d argue that CAR.O.L is a good fit for anyone who wants to improve their fitness and health without having to spend countless hours in the gym. This indoor bike is also an excellent option for those who have had a difficult time sticking to an exercise routine. Moreover, CAR.O.L is particularly useful for those who have a demanding job or family life that leaves little time to work out.

CAR.O.L is also great for serious athletes who seek ways to complement their primary workout routine and improve their cardiovascular strength and capacity.

I do CrossFit multiple times each week, but I also enjoy using CAR.O.L on the days when I don’t have time to go to the gym. Additionally, I use CAR.O.L to improve my octane score and VO2max, which helps me during those WODs that focus on metabolic conditioning (metcon).

Paired with low-heart-rate workouts, I’ve noticed that my workout performance and endurance during metcon exercises has dramatically improved over the past few weeks.

Technical Tidbits

CAR.O.L’s screen is an Acer tablet running the Android operating system. That means CAR.O.L’s software is simply an Android app that communicates with the bike’s sensors.

Considering that we are an all-Apple household, CAR.O.L is the first (and probably last) Android device in our home.

Since I don’t necessarily trust Android (or any of the bloatware that might run on it), I’ll probably quarantine the bike in its own VLAN so that it doesn’t have direct access to any of the other devices that are connected to my home network.

Frequently Asked Questions

What is high-intensity interval training (HIIT)?

If you stumbled across this article, chances are that you already know what HIIT means. For those of you who don’t, let me quote Wikipedia:

“High-intensity interval training (HIIT), also called high-intensity intermittent exercise (HIIE) or sprint interval training (SIT), is a form of interval training, a cardiovascular exercise strategy alternating short periods of intense anaerobic exercise with less intense recovery periods, until too exhausted to continue.”

One of the most famous HIIT workouts you may have heard about is Tabata. During Tabata you perform an exercise, such as pushups, at high intensity for 20 seconds before resting for 10 seconds. Then you repeat that cycle for eight rounds.

If you did the math right, you’ll realize that one round of Tabata takes only four minutes to complete. If you repeated that exercise at the proper intensity — for a total of eight minutes — you should be on the ground trying to catch your breath.

What are the benefits of HIIT?

While high-intensity interval training is relatively new, there are several scientific studies that show the benefits of such cardiovascular exercise strategies, including improved athletic capacity and condition, improved glucose metabolism, lower insulin resistance, a reduction of fat and weight loss, improved brain power and cognitive function, a decreased risk of developing cardiovascular disease, and an increased VO2 max (maximal aerobic capacity).

From a practical perspective, HIIT sessions often have a duration of 30 minutes or less. That makes them attractive alternatives for busy people who don’t have time to go for a long run or spend two hours in the gym.

The combination of short duration and high effectiveness is why the 7-Minute Workout became so popular a few years ago. In fact, before I started CrossFit, I included P90X and the 7-Minute Workout as part of my fitness routine.

What are the drawbacks of HIIT

The downside of HIIT is what makes it so effective — its intensity. It usually requires a high level of motivation to push through those high-intensity intervals, and many people don’t have the willpower for it.

As a result, some people give up early and abandon HIIT, or they perform the exercises with less intensity, which significantly reduces the workout’s effectiveness.

That’s why I was so excited when I stumbled across CAR.O.L — a new bike HIIT platform — which effectively reduces the workout to two 20-second bursts. Everyone can push it for 20 seconds, even if you don’t have the strongest willpower when it comes fitness.

What are other types of traditional HIIT programs?

There are numerous types of HIIT regimens that differ mostly in length, type of exercise and intensity. However, based on a study from 2016, there wasn’t a significant difference in outcome and benefits between them.

Here are a few popular HIIT regimens that you might have heard about — each of them carry the name of their respective inventor: Peter Coe regimen, Tabata regimen, Gibala regimen, Zuniga regimen, and Vollaard regimen.

I won’t go into the details of these HIIT workouts, but if you’d like to learn more, just click on the respective links above.

How difficult is it to assemble CAR.O.L?

I’m not the most gifted handyman, but it took me less than 30 minutes to assemble my CAROL AI Bike. All the instructions are pretty straightforward and easy the follow, with one exception: I didn’t know how to attach the straps to the pedals, because that step wasn’t properly documented and I had never used them before.

The photo below shows how I have them now.
CAR.O.L - Foot straps

Can I use my own seat of pedals with CAR.O.L?

Yes you can! The CAROL AI Bike uses standard bike parts. As a result, you can use your own seat and pedals, if you prefer (and if doing so makes the workout more comfortable).

Where can you try CAR.O.L?

CAR.O.L has a few showrooms in the U.S. and across Europe where you can try out the bike. I tried the bike at the last Paleo f(x) show* in Austin, Texas, and got hooked on the platform.

If you’re a gym or business owner, you might also consider offering CAR.O.L to your customers and employees. CAR.O.L is particularly well-suited for office environments because employees can complete a workout over lunch in business attire without breaking a sweat.

Can I use this stationary exercise bike to lose weight?

You absolutely can! CAR.O.L has two workout routines specifically designed for fat loss. In free ride mode, CAR.O.L even tracks calories burned.

However, if you eat well and exercise regularly, there’s no need to count calories.

Is CAR.O.L better than a recumbent exercise bike?

From a health and fitness perspective, a recumbent exercise bike is basically the same as a traditional bike ergometer. Based on everything I know, I’d say CAR.O.L outperforms recumbent exercise bikes (which focus only on resistance training, and not on intensity training) on every level.

How does such a short workout do anything?

It’s the principle of quality over quantity. CAR.O.L’s workouts do essentially the same thing as a longer workout; they just get your body to the outcomes you’re looking for more efficiently. What you have to realize is that normally, you’re not actually in your target fitness zone over the duration of your workout. If you run for 30 minutes, only a portion of that is truly “productive” from an exercise science standpoint.

More specifically, CAR.O.L uses technology and deep learning to give you just the right levels of resistance at just the right moments based on your particular fitness level, which quickly burns through your glycogen stores (especially in your thighs). This helps you burn fat (spurring weight loss) and build muscle.

Can I use CAR.O.L without an internet connection aka off-line mode?

While CAR.O.L is a cloud-based, networked exercise system and any offline mode will always come with some compromises, the company is working on such a feature. 

Some of the functionality you might lose in offline mode include personalized resistance adjustments, statistics and settings.

What happens to my bike if the company behind CAR.O.L goes bankrupt?

In the unlikely event that the company that makes CAR.O.L goes belly up, you can continue using the bike as a regular spinning bike. Specifically, you can use the “Free Ride” mode and manually adjust the resistance, time and other parameters.

How is CAR.O.L different from an Assault bike?

If you do CrossFit, you’re probably familiar with Assault bikes — the least favorite piece of equipment of many Crossfitters. That’s because riding an Assault bike is tough and exhausting.

So you might be wondering if you couldn’t simply replicate CAR.O.L’s HIIT workouts on such a bike, considering that it costs much less than CAR.O.L.

The thing with Assault and similar bikes is that their resistance goes up in a linear pattern as you increase your energy input.

That’s an entirely different concept to what CAR.O.L offers which constantly adjusts the resistance based on its sensor data and your physical abilities. As a result, you won’t get the same benefits (based on the same time investment) from traditional air bikes as you would from CAR.O.L.

In other words, using an air bike, you have to put more time and energy to get the same benefits as riding a few minutes on CAR.O.L.

What’s CAR.O.L’s Q Factor?

The Q Factor of a bicycle is the distance between the pedal attachment points on the crank arms when measured parallel to the bottom bracket axle.

CAR.O.L’s Q Factor is 165mm or 6.5 inches.

CAR.O.L Review – Closing Words

I used to be a professional sprinter and leveraged HIIT workouts to stay fit after I ended my career and before starting CrossFit.

One of the reasons why I like CrossFit so much is because it offers a variety of exercises that help me improve my physical fitness, including weight training, circuit training, aerobic exercises and more.

That’s why I wouldn’t consider CAR.O.L — or any other piece of cardio equipment — a replacement for strength training of CrossFit. However, I think CAR.O.L perfectly complements my current exercise regimen. More than that, CAR.O.L helps me to be a better CrossFit athlete by improving my VO2max and aerobic capacity.

But you don’t have to be a CrossFitter to benefit from CAR.O.L. In fact, regardless of what sport you do, you can significantly and easily improve your performance with this HIIT bike. If you don’t exercise at all yet, then what are you waiting for? Give CAR.O.L a try and get on your path towards better health!

Have you tried CAR.O.L or other HIIT workouts before? If so, let me know about your experience, and whether it helped you achieve your fitness goals, by leaving a comment below!

Medical Disclaimer

The information shared on this blog is for educational purposes only, is not a substitute for the advice of medical doctors or registered dieticians (which we are not) and should not be used to prevent, diagnose, or treat any condition. Consult with a physician before starting a fitness regimen, adding supplements to your diet, or making other changes that may affect your medications, treatment plan or overall health. MichaelKummer.com and its owner MK Media Group, LLC are not liable for how you use and implement the information shared here, which is based on the opinions of the authors formed after engaging in personal use and research. We recommend products, services, or programs and are sometimes compensated for doing so as affiliates. Please read our Terms and Conditions for further information, including our privacy policy.

27 thoughts on “CAR.O.L HIIT Bike Review”

  1. Have you tried the bike connected to any other bike apps? Their website says it connects to the Peloton app but doesn’t give any more info. Wondering how well/easy it connects and if it would be good for regular spin classes. I’m concerned (like I think many are!) about the usefulness of this expensive bike if this young/relatively unknown company folds and no longer provides a service.

    • Hi Steve,

      I haven’t tried the Peloton app on CAR.O.L yet but considering that CAR.O.L uses Android, I guess the Peloton app is as good on CAR.O.L as it would be on any other Android tablet.

  2. Hi Michael, Great Review! I purchased the CAR.O.L and I ad looking forward to my California shipment to get the Nashville. Thank you for sharing your insights,

  3. Thanks for the thorough review, Michael!

    One thing that I am interested in was the impact this has while using Whoop Strap 3.0. What type of strain does it usually give you for the single “Intense” session or any others that you have tried?

    • Hey Russel,

      WHOOP’s strain is based on the cardiovascular load that you’ll only build when your HR stays up for longer periods. CAR.O.L doesn’t cause your HR to stay up for more than a few seconds. As a result, WHOOP won’t recognize it as (cardiovascular) strain. It’s similar to strength training in that regard. You’ll see the impact on your recovery score but not in your strain score.


  4. Hi Michael,

    I am an extremely unfit grandmother of 6 and need a HIIT option to get fit with minimal time.
    Would this bike be suitable – for the 10 or 20 seconds of sprint am I able to just do my very best – I really am unfit.


    • Hi Denise,

      Yes, I’m convinced that CAR.O.L would be a great option for you. Your level of fitness doesn’t really matter as far as the effectiveness of the bike is concerned. You just do your best you can during those sprints and you’ll see results!


  5. Thorough review, so thank you! You obviously put some effort into this.

    I did have one question about the specification of the bike that I did not see addressed: many purchasers of spin bikes want to know the Q-Factor of the bike. This is basically the side to side spacing between the foot pedals It is considered important both for cycling performance, and for chronic knee injury risk in the case of high mileage riding.

    ( https://en.wikipedia.org/wiki/Q_factor_(bicycles) ).

    A typical road bicycle with have a spacing of about 155mm. A mountain bike or street bike with fatter tires might be 175mm. Many stationary bikes, particularly magnetic resistance ones, tend to be even fatter between the pedals due to the extra machinery that they contain. I’ve seen some bikes with spacings as high as 230mm. The Keiser M3i, comes in at 197mm. I’ve not been able to learn what the Q-factor is for the Car.o.l bike.

    For short sprint sessions (the Intense mode), I doubt that it matters. But if someone wanted to also use the bike for a traditional spin class, or longer free rides, it might be a consideration.

  6. Mike,

    Finally a proper detailed review! Yours is defiantly Still the best out there. Thanks ….

    Given the COVD19 lockdown situation and ARX isn’t an option at this point… What workout would you use (other than CrossFit) to complement Carol’s fat-burning protocol?

    I have been wanting to do weight lifting for strength training but terrified of injuries since I don’t have access to a personal trainer. Do you know any good online programs?


    • Hey Shayme,

      I follow the home workout program of our CrossFit box (which includes dumbbells, kettlebells and sandbags).

      Before starting CrossFit, I used to do P90X. Beyond that, I don’t know of any online programming from the top of my head.

      I’m confident plenty exist, I just haven’t looked into it.


  7. Hi Michael,

    Great through review. I’ve actually tried the bike at a boutique gym when I lived in Nashville along with ARX and it’s fantastic! I’m considering ordering for home use now. The free shipping along with the extra $150 off are enticing. What I would like to know is how often does the bike push updates down? Also, if the company does goes bankrupt does that mean the bike won’t work in any programmed mode? Now that we are living in Covid-19 world that is a major concern for me. Plus, who would work on the bike if technical issues?

    Btw, used to live in ATL for a few years…fun city.


    • Hi Em,

      From what I can see, the bike checks for updates every time you launch the app. Actually updates, I’ve seen a few since I got it last year. I never looked at the changelog, however, so I don’t know what changed.

      If the company goes bankrupt, you can continue to use the bike in “free ride” mode. On other words, you can use it much like a traditional spinning bike.

  8. Hey Michael,

    This was a fantastic review. I’ve actually had the opportunity to use the CAROL bike at a small alternative gym in Napa, CA where I used to live. It was fantastic – especially paired with ARX. I now live in Santa Fe, NM and no CAROL or ARX anywhere to be found. Hence I think I’m going to take the plunge and purchase a CAROL to pair with at-home high-intensity resistance band training.

    I’d love to see other people review this bike as well – yours is the only one I’ve seen.

    • Thanks for the feedback Alex, I really appreciate it! Coincidentally, I just got off the bike 10 minutes ago :)

      Regarding other reviews, I think Ben Greenfield did one but I don’t recall if it was a video or blog post.

  9. Hi Michael,

    great review, just bought the bike using your code :). You seem very fit, can you share what your VO2 Max is? I am trying to figure out how to estimate my VO2 max based on their octane score. I am a bot claustrophobic, do not want to do traditional mask test.

    Thanks for the great review!


    • Thanks, M!

      Frankly, I haven’t kept track of my VO2max because it’s not a crucial metric for what I’m doing (CrossFit).
      Sorry that I don’t have a better answer for you but I hope you’ll enjoy the bike!


  10. Michael, Thank you for this very comprehensive review of the CAROL bike :) Best review I’ve see out there by a long shot!!
    I’ve read up a lot on REHIT lately, the research is solid and I’m seriously considering this bike.
    My only concern is that the company is quite young and I can’t seem to find any actual honest numbers on how many of these AI Software Bikes they’ve sold (500? 1000? 10,000?). If anyone knows an actual number I’d love to find out :)
    I’m a little hesitant to spend so much on a technology that is this heavily dependent on Software Program Updates to function. If the company goes out of business the bike loses all it’s technology and functionality and becomes a very expensive clothing rack!! If anyone knows anything about numbers of bikes out there I’d be super interested and it would put me a bit more at ease for buying one!!

    • Hey Bobby,

      I don’t have official sales numbers either. I’ve only been told that the company was doing well. And if the use of my discount code is any indication, I tend to believe that statement :)


  11. Thanks for your extensive and compelling review, Michael. I’ve been considering the possibility of getting this bike. I’m looking for ways to reduce blood pressure without drugs as mine is starting to creep up there. What does “Blood pressure — 196% better” translate to in real terms for someone whose blood pressure is sometimes reading 143 over 90? Can you point me to a link that indicates the level of improvement I can hope to achieve if I follow the 40-second routine at least three times a week along with a good diet?


  12. Thanks for the in depth and honest review, there aren’t too many out there.
    Like Laine, it sounds too good to be true, but I want to believe it will help.
    I’ve been diswayed from buying because everyone I tell about the bike laughs at me and says its fake news.

    • Hey AJ,

      I got the same reaction when I started paleo…and then keto…and intermittent fasting. Sometimes, people who don’t want to do their own research to confirm if something is legit or not, brush stuff they don’t understand off as fake news. But it’s basic science at the end of the day :)

      If you happen to be in the Atlanta area, feel free to drop by the house and give my bike a try.


  13. I am seriously thinking about getting this bike, but it sounds too good to be true. It’s been 3 months since you posted this blog. How is it going? Are you seeing benefits? I wish there was one of these near me so I could try it but I don’t know of any and I haven’t been able to find a way to search.

    • Hey Laine,

      thanks for stopping by! I still like this bike and I use it as I had planned — on those days where I don’t have time to go CrossFit. I recently wrote an article about the impact of different diets on exercise performance and learned a ton more about how the body uses glycogen.

      Everything I’ve learned backs up the claims CAR.O.L makes regarding its benefits. If you’re in the Atlanta area, you can try my bike anytime :)



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