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Demo: How to do REHIT on CAROL Bike

This article offers a comprehensive walkthrough of REHIT on CAROL Bike, from the basics of what REHIT is to a practical demonstration on the bike, post-ride analysis, and the unique benefits of less being more.

Discover how to maximize your fitness with Reduced Exertion HIIT, or REHIT, on CAROL Bike. This guide answers “What is a REHIT workout?” and “How long does a REHIT workout take?”, as well as exploring the transformative impact it has on your health and fitness. Learn how to effectively perform REHIT workouts on CAROL Bike, understand the science behind the workouts, and embrace the efficiency of getting fitter with minimal time commitment.

REHIT overview: Efficiency meets fitness

What is a REHIT workout? It’s a revolutionary concept in fitness, offering maximum results in minimal time. Developed by exercise scientists, REHIT focuses on brief, intense bursts of exercise, making it a perfect fit for busy lifestyles. This approach, emphasizing time-efficiency and adaptability, delivers significant health gains without the need for prolonged workout sessions.


Key features of REHIT: 

  • Time-efficiency: A standard REHIT session is completed in about 5 minutes, challenging traditional fitness norms and making it ideal for busy lifestyles. 
  • Adaptability: Tailored for both beginners and athletes, REHIT offers accessible yet challenging fitness routines. 
  • Maximum results: REHIT’s efficacy matches or surpasses longer workouts, delivering noticeable benefits without excessive exertion.

Introduction to REHIT on CAROL Bike

CAROL Bike’s signature REHIT Intense workout epitomizes efficient cardio. How long does a REHIT workout take on CAROL Bike? Just 5 minutes, consisting of 2×20-second max-intensity sprints, with low-intensity warm-up and cooldown phases. Scientific validation confirms its effectiveness: a 12% improvement in cardio and a 62% reduced risk of type 2 diabetes in just 8 weeks.

Demonstrating the REHIT Ride

Discover the essentials of a REHIT ride with Ulrich, CAROL co-founder, in this insightful demo clip, and scroll down for an in-depth written summary of the key points covered in the video.



Position yourself comfortably on your CAROL Bike, using either cycling shoes or standard trainers. Cycling shoes offer a slight advantage, as you can eke out slightly more power, but you can also use the bike with normal trainers or gym shoes with the toe cage on the other side of the pedal. Log in and choose a REHIT ride, complemented by your preferred soundtrack. 




Begin with a casual 2-minute warm-up, focusing on loosening joints and mindful breathing. This is not part of the workout that gets you fit. If you are in a rush or warmed up already, you can cut down the warm-up time to just 20 seconds by simply accelerating sharply, taking your cadence beyond the checkered flag on the RPM dial.

CAROL Bike screen explaining how to do REHIT in just 5 minutes.


Once the countdown goes down to 3 seconds, the screen will turn red and that’s your signal to accelerate to the fastest pedal speed possible. Pick up speed at a very low resistance, and then CAROL will apply your personalized, optimal resistance, automatically, in a fraction of a second. This is comparable to cycling up a steep hill as fast as possible.  You wouldn’t want to start in a big gear standing in the steep section. Instead, you’d want to pick up pace in the flat before you enter the steep part.

Sprint demonstration from the Ultimate CAROL Bike resource video.

But what’s happening in your body as you perform these sprints?

The sprints create a sudden spike in energy demand that’s about 100-fold greater compared to rest. While muscles are usually able to burn fat or sugar from the bloodstream, through your aerobic energy system, the sudden increase in energy demand forces your muscles to use local, more immediately available energy sources. You start with burning phosphocreatine, which lasts for about 10 seconds, and after that you will need to anaerobically burn muscular glycogen, which is sugar stored locally in the muscle—basically your body’s “emergency energy reserve”.


The really clever part about REHIT is that your muscles mobilize a lot more glycogen than is actually needed for those short sprints. Because of the extremely rapid increase in energy demand, your body anticipates and prepares for a “fight or flight” situation. And your body doesn’t know that it will only be for 20-seconds.  The body only notices that there is a very severe increase in energy demand and so it mobilizes lots of its emergency energy reserve even though you then use only quite little of it during the sprints. 

Glycogen is a large molecule of branched polysaccharides. Instead of mobilizing just a few molecules and metabolizing those entirely, the body mobilizes a lot of them, about 25-30% in your thighs, and metabolizes just the very outer branches.


This over-preparation of glycogen, triggered by the sudden energy demand, is the crux of REHIT’s effectiveness. Your body really doesn’t like to tap into its emergency reserve, and when it is forced to do so, it sends a signal that it has to adapt and get fitter and stronger. The body releases AMPk, which in turn increases PGC-1a activation. PGC-1a is the master regulator for mitochondrial biogenesis, so your body develops more and larger mitochondria, which means you are getting better at utilizing oxygen in your muscles. Your body will also get better at delivering oxygen to your muscles, with a stronger heart and increased blood plasma volume


This process underscores the efficiency of REHIT, where shorter, maximum-intensity sprints lead to substantial fitness gains.

Recovery and cool down


The recovery after the first sprint takes up to 3 minutes, but if you recover quickly, feel ready for the next sprint, and want to minimize the time needed for the workout, you could keep the recovery as short as 1 minute.


The cooldown, however, takes 3 minutes, and it is important to give your body this entire short period to recover. Metabolic waste products from the sprints create a temporary osmotic imbalance and water shoots into your muscles, so your legs feel pumped, and your blood pressure might drop a little temporarily. The 3-minute cooldown is enough time for blood pressure, heart rate and breathing to go back to more normal levels.

Cool down demonstration from the Ultimate CAROL Bike resource video.

Post-ride analysis: The impact of REHIT 

Compared to the 150 minutes per week suggested by government guidelines for moderate exercise, REHIT offers superior results in just 15 minutes. This remarkable time efficiency doesn’t compromise the workout’s effectiveness. CAROL Bike’s AI algorithms ensure that each session remains challenging and personalized, suitable for any age and fitness level.

Why less is more in REHIT 

The uniqueness of REHIT lies in its paradox: more or longer sprints don’t necessarily equate to better results. In fact, they may be less beneficial. This phenomenon might be due to psychological factors—knowing the sprints are short and manageable, riders are likely to exert maximum effort without holding back. This all-out approach is crucial in REHIT, as it pushes the body to its limits, making these brief workouts incredibly effective. 


REHIT on CAROL Bike blends scientific innovation with practical application, providing a workout that’s as effective as it is efficient. Whether you’re an avid fitness enthusiast or someone struggling to find time for exercise, REHIT on CAROL Bike is your solution for peak health and fitness, achievable in minimal time.


Why CAROL is the only bike suitable for REHIT: Discover our detailed exploration of why CAROL stands alone as the optimal bike for REHIT workouts, featuring exclusive video insights from our brand video, including demonstrations with conventional bikes and the unmatched suitability of CAROL for REHIT.


Explore the ultimate CAROL Bike resource: Uncover everything from REHIT insights and workout comparisons, to exclusive revelations about the unique CAROL Bike design and its fitness-transforming capabilities.

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