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REHIT vs HIIT - High Intensity Interval Training

CAROL Bike AI-Powered Exercise Bike

What's the difference between REHIT and HIIT?

REHIT is a specific form of HIIT; essentially, if HIIT is about "high intensity," REHIT is about "maximum intensity."  

HIIT Training is a combination of brief, high intensity intervals of cardio exercise, followed by equal or longer periods of recovery. REHIT follows the same model, but aiming for the minimum number of sprints, done at maximum intensity but for the shortest required duration, while still delivering the health and fitness benefits people need and want from exercise.   

There are many different forms of HIIT that vary in their overall duration, number of high intensity intervals, and length of the intervals. HIIT Training is also referred to by different names, including Tabata Training and Interval Training. 


If HIIT is high intensity, REHIT is about maximum intensity; the maximum intensity during a REHIT sprint is 2.4X higher than in other popular HIIT cycling intervals. 


Most HIIT sessions last from 20-45 minutes and involve multiple high-intensity intervals that vary in length. Warm-up and recovery periods between those intervals are often performed at a moderate intensity level.

While the benefits of HIIT are well researched and proven, HIIT sessions are commonly perceived as very fatiguing and not much more time-efficient than traditional exercise. Because of this, HIIT may be challenging for inactive and sedentary populations and time-poor people to take up and adhere to.   


  • The duration of the workout in REHIT is significantly shorter (8 minutes and 40 seconds vs. 20-45 minutes)  
  • The duration of the high-intensity effort in REHIT is significantly shorter (20 seconds vs. several minutes)   
  • REHIT sprints are shorter and fewer (2 x 20 seconds vs. a typical HIIT workout which would include many more intervals, of longer duration)  
  • REHIT sprint intensity is at the maximum level possible, whereas HIIT intervals are usually too long to sustain maximum intensity, so they are performed at a lower intensity level  
  • REHIT warm-up and recovery are made at a very low intensity, whereas HIIT warm-up and recovery periods are often done at a moderate intensity  
  • REHIT is maximum intensity training, while HIIT is merely high-intensity training   
  • Even though REHIT's intensity is higher, the overall exertion in REHIT is lower than in HIIT, which makes it easier to perform and keep doing  


The Carol Bike, and how it works, is founded on the principles of REHIT, which stands for Reduced Exertion High Intensity Interval Training.  

Carol Exercise Bike Smart Fitness

Pretty much everyone is familiar with HIIT, so REHIT is a specific form of HIIT, developed by Drs. Niels Vollaard and Richard Metcalfe at the University of Bath (with follow up research done at the University of Sterling and Swansea University). They developed an exercise protocol that is MUCH more time efficient than both conventional exercise and HIIT, while still providing the same or better health and fitness benefits.  

CAROLs core REHIT workout (the "Intense" ride) consists of just two 20-second maximum intensity sprints, combined with a gentle warm up, recovery and cool down. This short workout, done 3 times a week, will give you double the health and fitness benefits as you would get going for a 30-minute run, 5 times a week. 

While many fitness smart programs offer HIIT/Tabata/Interval classes, the intensity reached in those is much lower than the maximum intensity reached in a CAROL Intense (REHIT) workout.  

It's scientifically proven that any interval you can do for longer than 20 seconds, and can repeat more than twice, or that is embedded in a moderate intensity workout cannot be performed at your maximum intensity.  CAROL riders achieve 2.4X higher intensity levels in a CAROL sprint compared to their maximum intensity in other popular HIIT cycling workouts. 

Learn more about getting fit in less than 9 minutes with CAROL 

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