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The CAROL Bike - Get fit in less than 9 minutes


CAROL is an AI-powered exercise bike that helps people achieve their maximum fitness gains with minimum time requirements. 

Carol Exercise Bike

The CAROL bike uses REHIT, or Reduced Exertion High-intensity Interval Training. REHIT was developed as a time-efficient alternative to traditional HIIT (High-Intensity Interval Training) and moderate-intensity exercise. It's a scientifically validated workout that makes it possible to achieve optimal fitness with 26 minutes of exercise a week — three 8-minute and 40-second workouts.   

The CAROL bike uses AI to personalise your workouts, which helps you reach your fitness goals more quickly. CAROL's AI can calculate the precise resistance that will push you to your limits but never going over. Over time, CAROL's AI continues to adapt as your fitness improves, so you're always working to your maximum potential.  


Three main things make CAROL special: REHIT, CAROL's AI, and the bike itself. 


Carol Bike High Intensity Interval Training

REHIT (Reduced Exertion High-intensity Interval Training) is an optimised form of HIIT (High-Intensity Interval Training) that's more effective than conventional exercise — with a much shorter time commitment. This helps you achieve maximum fitness in the minimum time.  

The CAROL bike is the only at-home, consumer-friendly exercise equipment offering REHIT workouts. The only other way you can do a proper REHIT training is in a lab. 


Carol AI Smart Bike

CAROL's AI is designed to optimise each workout so that you're always reaching your full potential. CAROL's AI measures your performance at each ride and adapts every ride to match your ability. As you get fitter, it will keep pushing you to reach your full potential. It's like having a personal trainer and fitness coach right in your bike — and they're always available when you need them.  


Carol Bike AI-Powered Exercise Bike


The CAROL bike is a certified commercial-grade exercise bike, with built-in AI that is able to control and guide your rides. An on-screen guide tells you exactly when to pedal, and the brakes are automatically controlled so that you achieve exactly the right level of resistance and intensity for the best results. REHIT workouts require you to hit exactly the right level of resistance, at precisely the right moment — just when you've built up enough speed to fatigue your muscles. The CAROL bike is able to automatically, precisely and almost instantly change your level of resistance, which means it can apply the correct resistance for you, at precisely the right time, in a fraction of a second.  



One of the things riders love most about CAROL is that it “gives them their time back.”   

CAROL’s workouts are far more time-efficient than traditional exercise, and make it easy to make exercise a habit.  Doing REHIT workouts with CAROL takes 26 minutes a week, and provides double the health and fitness gains vs. 150 minutes a week of traditional moderate-intensity exercise. That’s double the gains, in 20% of the time.   


Doing a CAROL workout 3 times a week for 8 weeks improves cardiorespiratory fitness by 12%.   This is measured by VO2max — also known as maximal oxygen uptake. This is the maximum oxygen your body is able to use during exercise. The greater your VO2max, the more oxygen your body can take in and the more effectively your body can use that oxygen.   

In the general population, VO2max tends to decline by about 10% per decade after the age of 30 — since CAROL increases VO2max by 12% in 8 weeks, it effectively turns back the clock on your fitness by a decade.   


Working out with CAROL 3 times a week for 8 weeks will:   

  • Reduce the risk of type 2 diabetes by 62% (the same reduction as taking Metformin, a common drug), measured by MetS z-score  
  • Reduce blood pressure by 5%  
  • Reduce triglycerides (the fat found in your blood) by 10%   
  • Increase good cholesterol by 6%  
  • Reduce blood sugar by 2%  

Studies have proven that REHIT workouts lead to double the health and fitness benefits compared to moderate intensity exercise. Three 8-minute and 40-second REHIT workouts a week will give you twice the health gains as five 30-minute moderate intensity workouts a week.


CAROL burns over twice as many calories, minute-per-minute vs. traditional exercise. This is thanks to the afterburn effect, which kicks in with a REHIT workout. This causes a boost in your metabolism that keeps your body burning calories for up to 3 hours after a CAROL workout.   

66% of the calories riders burn are burned after a CAROL workout. This is compared to only 10-20% of calories burned following traditional exercise. The afterburn effect applies to both CAROL’s REHIT workout (the Intense ride) and HIIT workouts (the Fat Burn rides).   


Working out with CAROL for 8 weeks adds 2 years of healthy life expectancy to your lifespan, thanks to improved cardiorespiratory fitness; a 10% improvement in VO2max adds 2 years of healthy life expectancy.  

CAROL also supports healthy aging. In the general population, VO2max tends to decline by about 10% per decade after the age of 30. Since CAROL increases VO2max by 12% in 8 weeks, it effectively turns back the clock on your fitness by a decade.   


CAROL's workouts are guided by the bike's AI, which creates a personal ride to keep the rider working at your own optimal intensity and achieving their personal maximum fitness gains as quickly as possible.  

The AI is able to control the bike's brakes automatically, applying the personalised sprint resistance at exactly the right time in a fraction of a second, which is key to achieving a REHIT workout.  During a REHIT sprint, you will reach your peak power for a split second and then fatigue — which means your power and pedal speed will drop off. If you fatigue too quickly, the resistance is too high. If you fatigue too slowly, the resistance is too low.  

CAROL's AI algorithms analyse your ride and combine your data with that from hundreds of thousands of other rides. This enables the AI to determine the optimal rate of fatigue and calculate your optimal, personalised resistance. That optimised resistance is applied to your next ride.  

Think of the CAROL bike as a really great personal trainer — it knows you and your body, and it knows exactly how hard to push you to get results. Yes, it's probably going to make you work harder than you would on your own, but always at the right intensity for you.  

Every ride is personalised according to your own data, your own current level of fitness, so it can match where you're at and adapt your workout as your fitness improves.  


  • Ramp Up — a series of 6 workouts every new rider completes to help them get used to CAROL, and help the CAROL AI learn about the rider to start creating personalised workouts 
  • Intense — our signature REHIT workout, 8 minutes and 40 seconds total including a gentle warm up, recovery and cool down, with two 20-second sprints 
  • Energizer — A gentler version of REHIT with two shorter 10-second sprints, ideal for a light, energising workout 
  • Fat Burn — get ready to sweat with a HIIT workout; choose either a 15 minute or 25 minute ride alternating 8 second sprints and 12 seconds of recovery 
  • Free Ride — this gives you control over the length and intensity of your ride, or you can set a target power and the bike will automatically adjust the resistance to match 
  • Endurance — this ride is a special fitness test for your maximum aerobic ability/capacity/power, and can be used to test VO2max with a separate breathing analyser 

You can also use the CAROL bike to ride along with other fitness apps and cycling programs. 

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