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Next-level HIIT

CAROL’s the only bike with REHIT, the next-level HIIT workout that gives you superior health benefits, in 90% less time.

Reduced Exertion HIIT (REHIT) was developed by scientists looking for the shortest, most effective and accessible way to exercise.


REHIT creates the most potent training stimulus with just 2×20-second sprints. It’s scientifically proven to deliver superior health and fitness benefits compared to normal exercise—in 90% less time.


CAROL’s AI-personalization and Instant Resistance help you push to your limits during the sprints. Like in a ‘fight or flight’ situation, your muscles are forced to mobilize about 25-30% of muscular glycogen—your emergency energy reserve—which releases key signaling molecules (AMPK and PGC-1a), telling your body to get fitter and stronger.


You develop more mitochondria, your blood plasma volume increases, and your heart gets stronger. Resulting in increased aerobic capacity.


Previously REHIT was only possible in a lab setting. But we teamed up with the world’s leading exercise researchers to get REHIT into the real world. And 40 prototypes later, CAROL Bike—the world’s only home REHIT exercise bike—was launched.

“CAROL is the only bike that accurately replicates REHIT outside of the labs. This scientific exercise cannot be done on a regular bike because it requires the supra-maximal resistance tailored to each person’s physiology.”
Dr. Niels Vollaard

PhD, Exercise Physiology Researcher, University of Stirling


Read the full study here.

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%.

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.

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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.

What is a REHIT workout?

Explore REHIT, the game-changing workout that redefines time-efficient training with just 2x20-second sprints.

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