Coach approved

CAROL Bike: Kris Gethin’s cardio of choice

Kris Gethin, world-renowned body transformation coach and founder of BiohackedAF, champions CAROL Bike as one of the smartest ways to build cardiovascular health and resilience in minutes a day. For Kris, CAROL isn’t just efficient—every workout is backed by science.

Partner offer Save $400 with code KRIS

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Kris Gethin on a CAROL Bike

Kris Gethinon CAROL Bike

I’ve trained every way imaginable, and CAROL is the most efficient cardio I’ve found — five minutes that genuinely move the needle on my fitness and longevity.

Kris GethinBody transformation coach

Why it works

The most efficient workout there is.

Short and easy to fit into your life, smart enough to meet you exactly where you are, and proven in peer-reviewed research.

Short

The whole ride is done in 5 minutes — warm-up, two sprints, cooldown. Three rides a week is all the habit asks of you.

5:00 ride

Smart

AI-personalized workouts calibrate resistance to you at every moment — simple to perform and suitable for any age and fitness level.

Any fitness level

Scientific

Scientifically proven to deliver superior health and fitness benefits in 90% less time compared to regular cardio.

−90% time

Inside the ride

Two 20-second sprints. That’s the workout.

Developed by leading scientists, Reduced Exertion HIIT (REHIT) creates the most powerful training stimulus from the shortest possible ride. CAROL’s AI applies exactly the right resistance at exactly the right moment — here is every second of it.

CAROL Bike REHIT workout stage

Warm-up

Pedal slowly for up to 2 minutes.

Pedal slowly for up to 2 minutes to prep for your first sprint.

AI applies Instant Resistance. You push to your limits for 20 seconds, forcing 25-30% mobilization of muscular glycogen, releasing key signaling molecules.

Pedal slowly for 3 minutes, clearing lactate and preparing for your second sprint.

Push again to your limits for 20 seconds to activate the signaling molecules released in Sprint 1. This tells your body it must get fitter, stronger.

Light pedalling for 3 minutes, so blood pressure, heart rate, and breathing go back to normal.

CAROL Bike REHIT workout - Warm-up

Warm-up

≤ 2:00

Pedal slowly for up to 2 minutes to prep for your first sprint.
CAROL Bike REHIT workout - Sprint 1

Sprint 1

0:20

AI applies Instant Resistance. You push to your limits for 20 seconds, forcing 25-30% mobilization of muscular glycogen, releasing key signaling molecules.
CAROL Bike REHIT workout - Recovery

Recovery

≤ 3:00

Pedal slowly for 3 minutes, clearing lactate and preparing for your second sprint.
CAROL Bike REHIT workout - Sprint 2

Sprint 2

0:20

Push again to your limits for 20 seconds to activate the signaling molecules released in Sprint 1. This tells your body it must get fitter, stronger.
CAROL Bike REHIT workout - Cooldown

Cooldown

≤ 3:00

Light pedalling for 3 minutes, so blood pressure, heart rate, and breathing go back to normal.

The research

Your results, backed by science.

CAROL Bike is scientifically researched and proven to improve your fitness and health. Just 3x5-minute REHIT rides a week.

+12%cardio fitness (VO2max) in just 8 weeks
10 yrsa 12% VO2max gain is like turning your fitness age back a decade
−62%risk of type 2 diabetes; blood pressure down 5%
2×more calories burned on a 15-minute CAROL ride than a 30-minute run
More on the science

Beyond REHIT, CAROL is a fully customizable indoor bike: Free Ride with control over timing, resistance and target power, plus Zwift, YouTube and Netflix integration.

Rider results

Hear it from our riders.

Our riders are at the heart of everything we do — and their fitness scores do the talking. Join our 35,000+ rider community.

All rider reviews
VO₂max +5% in 2 weeks I’ve been training for a half marathon and since adding CAROL Bike to my daily routine in the past 2 weeks, my VO₂max has gone up 5% already.
Everett MyersCAROL rider for 4 years 3 months
Fitness Score +52% My CAROL Bike has been great to help me achieve greater fitness and power without the time investment but with all the fun!
Dr Gabriela MorenoCAROL rider for 5 years 5 months
VO₂max +12 · heart rate −10 bpm In just 4 months, my VO₂max has increased by about 12 points, and my heart rate has decreased by 10 bpm. For someone with a history of heart issues, these improvements are huge!
Matt NguyenCAROL rider for 4 years 4 months
Bodyfat −2.6% in 8 weeks Dropping 2.6% bodyfat in ~8 weeks for someone who prioritizes a healthy lifestyle is no easy feat. I’d go so far as to label it as a gamechanger.
Peter BaumanCAROL rider for 4 years 9 months
5-minute habit It’s easy to fit a quick 5-minute workout in, especially if you don’t need to shower after your workout!
Phil CoxCAROL rider for 4 years 5 months
The ultimate biohack I get more cardiovascular benefit in 5 minutes than I used to get from 30-minute runs, and my recovery is faster too.
Germany MayfieldCAROL rider for 4 years 3 months
Michael KummerRider for 7 years@mkummer82
Christy LemireRider for 5 years@christylemire
Joel EvanRider for 6 years@joelevancoaching
Amy StantonCAROL rider

The offer

Good habits start here.

Order CAROL Bike now, try it at home for 100 days, and build a habit that lasts.

100-day trial

Feel the benefits risk-free for 100 days. Not for you? Return it, no questions asked.

Delivery from $99

Delivered to your door, ready for your first calibration ride.

0% APR financing

Pay just $232.92/month at 0% APR, with Affirm.

Fitness Advisors

All our experts have MScs in Exercise Science — here to help you reach your goals.

CAROL Bike — $2,795 Save $400 with code KRIS at checkout
Order CAROL Bike

Pay with HSA/FSA. Qualified customers use pre-tax dollars and save 30-40%. Contact us for HSA/FSA payment, or read how it works.