Nine minutes. A different decade.
The Carol Bike is an AI exercise bike built on REHIT science. Two 20-second sprints, three times a week — the cardio of a 45-minute run, in the time it takes to make coffee.
You need a better dose of exercise — not a bigger one.
Most people quit cardio because it takes too long and feels like punishment. REHIT flips that. It's built on a simple finding: a few seconds of true, all-out effort trigger the adaptations that hours of steady jogging chase. So the bike works for the marathoner and the person who hasn't exercised in years — because the workout meets your body exactly where it is, automatically.
A complete workout, start to finish, in about nine minutes.
There's a short warm-up, two very hard sprints, and a cool-down. The hard part totals 40 seconds. That's the whole secret.
Why the AI matters: the resistance is calibrated to your maximum in real time. Beginners can't get it wrong, and the very fit can't coast — everyone gets a true all-out effort.
The single number most tied to a long, healthy life — and how to move it.
Cardiorespiratory fitness, measured as VO₂max, is one of the strongest predictors of how long and how well you live. REHIT is designed to raise it in the least time possible.
Reference: Metcalfe et al., “Extremely short duration interval exercise improves 24-h glycaemia,” and Ruffino et al., Int. J. Environ. Res. Public Health (2019), which found eight weeks of REHIT produced greater gains in cardiorespiratory fitness than time-matched moderate-intensity continuous training. Individual results vary. The Carol Bike is a fitness product and is not intended to diagnose, treat, cure, or prevent any disease.
Smart enough that you just show up.
No programming, no personal-trainer math. The bike measures, adapts, and tracks — you pedal.
- AI-calibrated resistanceReads your power output live and sets the exact resistance for a true all-out sprint — different every ride, personal to you.
- Your Fitness ScoreOne clear number that tracks your progress over time, so you can see the fitness you're building.
- 22 guided programs + entertainmentFrom the signature 9-minute ride to fat-burn and endurance sessions, plus your favourite streaming apps on the 11.5″ screen.
- Up to 8 ridersEach person gets their own profile and personalized workouts — one bike for the whole household.
Carol Bike
The shortest effective workout, engineered.
or about $233/mo, 0% APR for 12 months
- 100-day home trial
- 5-yr frame, 1-yr parts
- Ships US, Canada & UK
- 7-step home setup, supported
Checkout is completed securely on carolbike.com. AI-controlled resistance and progression tracking are enabled through a CAROL membership ($19.99/mo, up to 8 riders). Price shown in USD; taxes and delivery calculated at checkout.
Built for real life — not just athletes.
Founders, parents, shift workers. If you can find nine minutes three times a week, you can stay genuinely fit.
Anyone in their 40s, 50s and beyond who wants to protect their VO₂max — the fitness that keeps you independent for decades.
Coming back from a long break? The AI meets you at your level, so day one is safe and never humiliating.
Athletes use it to add high-intensity stimulus without piling on training hours or extra fatigue.
A 45.5″ × 22″ footprint and a quiet magnetic drive — it fits a spare corner, an apartment, an early morning.
Up to eight rider profiles, each with personalized resistance and progress. One bike, everyone covered.
Commercial-grade, engineered to last.
| Footprint | 45.5″ × 22″ |
|---|---|
| Weight | 120 lb (54 kg) |
| Rider height | 4′7″ – 6′7″ |
| Max rider weight | 330 lb (150 kg) |
| Resistance | Motorized electromagnetic, AI-controlled |
| Drive | Silent friction-free magnetic brake, Poly-V belt |
| Display | 11.5″ IPS touchscreen (2000 × 1200) |
| Audio | Quad speakers with Dolby Atmos |
| Connectivity | Wi-Fi 6E, Bluetooth 5.2 |
| Pedals | Dual-sided (toe cage + SPD clip-in) |
| Power | 100–240V |
| Warranty | 5 years frame · 1 year parts |
In the box
- Carol Bike with 11.5″ touchscreen
- Heart-rate chest belt (with new orders)
- Dual-sided pedals
- Power adapter & cabling
- 7-step guided setup + phone/chat/email support
Less time. More result.
| Carol Bike | Traditional cardio | A standard smart bike | |
|---|---|---|---|
| Time per week | ~27 minutes | 3–5+ hours | 3–5+ hours |
| All-out effort | 40 seconds | Sustained, gruelling | Class-dependent |
| Personalized resistance | Automatic, AI-set | Manual | Manual / instructor-cued |
| Right for beginners & athletes | Both | Intimidating for beginners | Skews toward the fit |
| Objective progress score | Fitness Score | — | Leaderboard, not fitness |
4.8 out of 5 from 600+ riders
“I stopped negotiating with myself about working out. It's nine minutes — I just do it before my shower.”
“At 58 I wanted to protect my heart and my independence. My Fitness Score has climbed every month.”
“Assembly took an afternoon, but the workout is the real deal — my legs and lungs know it was all-out.”
Illustrative rider profiles shown for demonstration. Replace with verified reviews before launch.
Good to know.
Is nine minutes really enough?
Do I need to be fit to start?
How loud is it?
How much space does it need?
What about the membership?
Warranty and returns?
Where do I buy it, and where does it ship?
Add years, not hours.
The most efficient workout ever studied, in your home. Three short rides a week is the whole commitment.
Get the Carol Bike