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.
Coming soon to the Agen appYou 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.
Soon, every ride sharpens your Agen picture.
The CAROL Bike is complete on its own today. Next, it joins the Agen app — so your rides and Fitness Score sit beside your biomarkers, sleep and supplement protocol, in one clear view of the fitness that adds years.
- Rides sync automaticallyYour REHIT sessions and Fitness Score flow into Agen — nothing to log.
- VO₂max in contextSee your cardio fitness right next to the rest of your longevity markers.
- Smarter next stepsAgen turns the trend into simple, personalized guidance across training, supplements and recovery.
CAROL integration is on the Agen roadmap. The bike's own app and Fitness Score are available today.
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 |
Rated 4.6 out of 5 on Trustpilot
“In just 4 months, my VO₂max increased by about 12 points.”
“Transformative — and as a sports-medicine physician, I highly recommend it.”
“It's easy to fit a quick five-minute workout in.”
Reviews and results sourced from CAROL riders and Trustpilot. Individual results vary.
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?
Does it work with the Agen app?
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