The shortest,
most effective

AI-powered workouts proven to give you the benefits of a 45-minute run in as little as 5 minutes.

Shorter, smarter workouts

Effective cardio workouts from just 15 minutes a week

A 5-minute workout 3 times a week. This is cardio without the dread, thanks to the science of reduced exertion high-intensity interval training (REHIT). 

Get in the best shape of your life in 8 weeks

In 8 weeks you’ll increase your cardiorespiratory fitness by 12%, reduce your risk of type 2 diabetes by 62% and give yourself an added 2 years of healthy lifespan.

Personalized workouts push you to your limits

CAROL’s AI calibrates and optimizes each ride for you. It’s like having a personal trainer right in your bike — CAROL knows exactly how hard to push you to get results.

Get double the results

Studies have proven that doing three REHIT workouts a week will give you double the health and fitness gains vs. five 30-minute moderate intensity workouts per week.

Get fitter

In 8 weeks, you’ll increase your cardiorespiratory fitness by 12% (measured by VO2max) — and see the difference in your endurance, especially when you get to the top of the stairs

Stay healthy

You’ll reduce your risk of type 2 diabetes by 62%, lower your blood pressure, triglycerides and blood sugar, and add 2 years of healthy life expectancy to your lifespan

Boost your metabolism

REHIT triggers the afterburn effect, burning twice as many calories, minute-per-minute vs. traditional exercise

Book a FREE fitness consultation

Talk with our fitness experts with Masters in Exercise Science to learn more about the science of REHIT and how CAROL can benefit you. Whatever your fitness level or knowledge, CAROL bike can help you reach your fitness goals.


Join 17,000+ riders

ONLY CAROL uses AI that really helps me – I can feel my body get a max intensity workout every single time. And they tell the truth – not breaking a sweat. Add the impeccable product design and engaged, friendly, always useful product support and CAROL’s a top reason to get up and get on every morning!

John Odden

Let’s be honest, it’s so easy to blow off a 45-minute workout but a 9-minute workout?? No excuses! Thank you for keeping fitness accessible despite the battles of life. With CAROL on my side, I can keep my fitness goals and regain my health!


All I can say is nothing matches the return on investment that this bike provides. Everything from the high quality construction, effectiveness , and the variety of training rides have made this the best investment in my long term health and fitness.

David Desroches

I have lost 41 lbs since starting with CAROL in July of 2020. I am in the best “physical condition” that I’ve been in since my early forties, and I’ve had significant medically demonstrable improvements in my health!

Larry Gipson

How it works

1. Science-backed REHIT

Our scientifically proven REHIT workout can be done in as little as 5 minutes. That’s 2x 20-second maximum intensity sprints plus warm up, recovery and cooldown. 

2. AI-powered personalization

Your ride is completely controlled and personalized for you by CAROL’s AI. The resistance is set and automated for you — so you can hit your maximum intensity and get faster results.

3. Smart fitness tracking

CAROL’s smart metrics will show you both your actual and target heart rate, cadence and power. After every ride, you’ll get a report of your performance and improvements across the board.

Get started with CAROL today

0% financing options available

Pay over 12 months with 0% financing available through Klarna or Affirm financing.
(US and UK only)

Free delivery and 30-day trial

Experience the benefits of CAROL for yourself, risk-free with free delivery.
(US and UK only)

3-month free membership

Benefit from AI-optimized resistance, detailed performance metrics, and new workouts and features with CAROL membership.

Not another exercise bike

No instructor-led classes

CAROL’s REHIT workout can be done in just 5 minutes. Hop on, get a great cardio workout, and then get on with your day!

A fully automated workout

CAROL’s AI guides and controls your workout. You don’t need to push any buttons or worry about finding the right resistance — every ride is calibrated to maximize your performance and results.

Scientifically-validated results

CAROL’s REHIT workouts were developed by scientists — they’ve been tested and proven to provide the most effective, efficient cardio workout available, both in the lab and in the real world.

Backed by science

CAROL’s revolutionary workout is based in the science of REHIT, Reduced Exertion High-intensity Interval Training.

This is HIIT, taken to the next level. Developed by scientists looking for the most effective, efficient workout possible.

It turns out that two 20-second, maximum intensity sprints are all you need for a great cardio workout. Those two sprints are like a switch — triggering a release of glycogen from your muscles that tells your body it needs to get fitter, now.

Read about the science behind REHIT

Trusted by health and fitness pros

Dave Asprey

“This is real. You’re spending 1/5th the amount of time on CAROL bike and you’re getting twice the results.”

Dave Asprey

Founder, Bulletproof and Upgrade Labs

— Hear why Dave loves CAROL on Bulletproof Radio

Dr. Niels Vollaard, PhD

“In our labs, we see insulin sensitivity improve by 25-28% and fitness by 15% within 6 weeks. The CAROL bike reproduces these results in the real world.”

Dr. Niels Vollaard, PhD

REHIT Researcher, University of Stirling

Lance Dalleck, PhD

“REHIT workouts generate a meaningful EPOC (excess post-exercise oxygen consumption, known as afterburn), that can have an important impact on the overweight and obesity epidemic.”

Lance Dalleck, PhD

Professor of Exercise and Sport Science, Western State Colorado University