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What is a REHIT workout?

Discover REHIT: The ultimate time-efficient workout with CAROL Bike. Just 2x20-second sprints unlock substantial fitness gains for unmatched cardiorespiratory and metabolic health improvements. A game-changer in fitness, REHIT is the smart solution for the time-conscious.

REHIT, or Reduced Exertion HIIT, represents the cutting edge of time-efficient training, offering substantial fitness benefits with just 2×20-second sprints per session. This blog answers the question “What is a REHIT workout?”, as well as delving into the science and benefits of REHIT, contrasting it with traditional HIIT methods, and highlights how just a few minutes on a REHIT bike can yield significant improvements in cardiorespiratory fitness and metabolic health—ideal for the modern, fast-paced lifestyle.


In a world where time is a luxury, fitness enthusiasts and researchers alike have sought the most efficient ways to exercise. Enter Reduced Exertion HIIT (REHIT)—the next level HIIT workout that promises maximum results in minimal time. But what sets REHIT apart? A REHIT session consists of only 2×20-second sprints, performed at supra maximal intensity, with a very light warm-up, recovery and cool down. This format emphasizes achieving peak intensity in a condensed time frame, distinguishing REHIT as a uniquely efficient workout option.

REHIT: The epitome of time-efficient training

Developed by leading scientists, REHIT is designed to provide the most efficient and accessible exercise regimen. REHIT stands out with its emphasis on peak intensity in short bursts. The approach focuses on time-efficiency, adaptability to various fitness levels, and delivering great gains with less strain. It’s the answer for those seeking substantial health outcomes without dedicating hours to the gym or feeling drained after workouts.


Key features of REHIT: 

  • Time-efficiency: A typical REHIT session can be completed in as little as 5 minutes, redefining what counts as HIIT by maximizing intensity in minimal time. It offers a solution for those struggling to fit workouts into their busy schedules. 
  • Adaptability: REHIT caters to various fitness levels, making it accessible for beginners and challenging for seasoned athletes. 
  • Less strain, more gains: Despite reduced exertion, REHIT matches or exceeds the benefits of longer workout sessions, according to numerous studies.


While HIIT workout benefits are renowned, its challenging nature and time commitment can be daunting. A typical HIIT session lasts about 20 to 30 minutes with multiple high-intensity intervals. REHIT, on the other hand, transforms the HIIT concept into a more accessible format. Its entire workout, including 2×20-second sprints, can be completed in as little as 5 minutes, and you only need to do it 3x per week.


This approach offers maximum intensity training that pushes your body to new fitness levels, efficiently and effectively. So, where HIIT offers high-intensity training, REHIT offers maximum intensity training. You push your body to new limits, making you much fitter and stronger.

CAROL: the only REHIT bike

CAROL Bike is a specialized REHIT bike that has been scientifically proven to give you superior health and fitness benefits in 90% less time compared to regular, moderate intensity cardio. CAROL Bike’s AI learns to push you to your limit and applies your optimal resistance, at exactly the right time, instantly. It’s been designed to offer the shortest and most effective workouts that are easy to fit into your life—so you can build a sustainable habit for a fitter and healthier you. What’s more, the simple and AI-personalized REHIT workouts are suitable for any age and fitness level.


Research backs the remarkable effects of REHIT. When you engage in a REHIT workout on CAROL Bike, your body experiences a ‘fight or flight’ response. This leads to the mobilization of a significant portion of your muscular glycogen stores, triggering the release of key signaling molecules. These molecules signal your body to improve its fitness and strength, leading to increased mitochondrial density, enhanced blood plasma volume, and a stronger heart.

Ulrich talks through the innovative features of CAROL Bike, revealing how it revolutionizes fitness with cutting-edge technology and REHIT workouts.

The benefits of CAROL Bike’s REHIT workout

Proven key benefits include:


Enhanced cardiorespiratory fitness

One of the primary benefits of REHIT on CAROL Bike is improved cardiorespiratory fitness. Cardiorespiratory fitness is measured by your VO2max —which is your maximum capacity or ability to burn oxygen during exercise. VO2max is the most important health marker and the strongest correlate to life expectancy. Scientific studies have shown that with REHIT on CAROL Bike, you can improve your VO2max on average by over 12% in only 8 weeks, a very significant improvement.


To put this significance into further context, as we age past the age of 30, our VO2max declines by about 10% each decade. Scientists have shown that a 10% higher VO2max  adds 2 years of healthy life expectancy. So, in only 8 weeks, you can turn the clock back on your age by over 10 years.


Metabolic health benefits

REHIT can reduce the risk of developing type-2 diabetes by 62% in the same timeframe, a result comparable to pharmaceutical treatments, such as the drug metformin.


Calorie burn

New research by Western University Colorado shows you’ll burn more calories on a 15-minute CAROL Bike ride, than a 30-minute run. This is because the short, maximum intensity sprints on CAROL Bike generate a significantly higher level of afterburn compared to conventional exercise. Scientists refer to this phenomenon as Excess Post-exercise Oxygen Consumption, or EPOC. The increased metabolic rate following a CAROL workout can last for up to three hours and accounts for up to 66% of the total calorie burn.


Muscle development 

The forces applied during the sprints are relevant for developing your muscles and on average leg strength will increase by 13% over 8 weeks.


Mental health advantages

REHIT also contributes significantly to mental health, effectively aiding in the treatment of anxiety and depression. This is because it stimulates the release of BDNF (brain derived neurotrophic factor) which supports neuroplasticity and so helps keep your brain healthy and young. In addition, high intensity exercise is good for your mental health and has been shown to be as effective in treating anxiety and depression as psychotherapy or medication.


Of course you could achieve all the above benefits with other forms of exercise. But you’d need to spend a lot more time on it: with other, moderate intensity cardio you would need at least 2.5 hours per week whereas with CAROL it is as little as 15 minutes per week.

Scientific studies have shown that with REHIT on CAROL Bike, you can improve your VO2max on average by over 12% in only 8 weeks, a very significant improvement.

Is 5-minutes really enough?

The idea of achieving substantial health and fitness benefits from a 5-minute workout might seem too good to be true. Can such a short workout be effective? The key lies in understanding that fitness gains occur during recovery periods, not the workout itself. REHIT workouts deliver the necessary stimulus in record time. While the sprints are intense, requiring you to push your limits, their brevity makes them manageable—the discomfort is fleeting, and before you know it, the workout is complete. Offering a ‘pain-free’ path to significant fitness improvements.


REHIT workouts on CAROL Bike are not just about doing less; they’re about achieving more. This innovative approach to fitness is a perfect blend of science and practicality, offering a workout that is as effective as it is efficient. Whether you’re an exercise enthusiast or someone struggling to find time for the gym, REHIT on CAROL Bike is your answer to reaching peak health and fitness with minimal time commitment.


Discover how to do REHIT on CAROL Bike: Get the lowdown on performing REHIT workouts on CAROL Bike, with step-by-step instructions for maximizing fitness results.


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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All our experts have MSCs in Exercise Science, and they’re here to answer your questions. Whether it’s about the science behind CAROL Bike, or general fitness advice, whatever’s on your mind—we’re here for you.

Get Fitter

Improve your fitness by 12% in just 8 weeks.

Live Younger

Improving your VO2max by 12% is like turning the clock back on your age by 10 years.

Live Healthier

Reduce your risk of type 2 diabetes by 62%—and blood pressure by 5%.

Next-level HIIT

Why Reduced Exertion HIIT (REHIT) is the most effective workout.

Maximum Metabolism

You’ll burn more calories on a 15-minute CAROL ride, than a 30-minute run.

Time to thrive

Make the most of your time with CAROL Bike's short and efficient REHIT workouts.

Demo: How to do REHIT on CAROL Bike

Explore a hands-on guide to doing REHIT on CAROL Bike, showcasing its efficient, effective workouts tailored for every fitness level.

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