CAROL is an innovative stationary REHIT bike that utilizes artificial intelligence to enhance cardiovascular and cardiorespiratory fitness. What sets CAROL apart is its ability to deliver highly effective workouts in under 10 minutes. In fact, CAROL's signature REHIT workouts can be completed in just five minutes.

Despite the brevity of these workouts, CAROL offers the same benefits as much longer exercise sessions. A study conducted on CAROL users revealed that engaging with the bike three times a week, totaling just 26 minutes of exercise, resulted in significant health improvements. These included a 12% increase in cardiorespiratory fitness as measured by VO2max, a 6% rise in HDL cholesterol, a 10% reduction in triglycerides, a 5% decrease in blood pressure, and a 2% decrease in blood sugar levels.

Personally, I have been a proud owner of the original CAROL bike since 2019 and recently upgraded to the CAROL Bike 2.0 in late 2022. In this comprehensive review, I will delve into the effectiveness of the bike in improving my cardiovascular fitness and related metrics. Additionally, I will highlight the notable differences between the original CAROL and the new CAROL Bike 2.0.

Pros

• Minimal time investment.
• Scientifically-proven benefits.
• ISO certified for the most accurate commercial-grade ergometer.
• CAROL dynamically adapts to your progress, so you never plateau.

Cons

• Initial investment.
• Internet connection required.

The CAROL Bike, formerly known as High Octane Ride, has been a well-established product for quite some time. Its main objective is to elevate high-intensity interval training to new heights.

CAROL, an acronym for Cardiovascular Optimization Logic, is an AI-powered bike ergometer that claims to deliver twice the health and fitness benefits compared to traditional moderate intensity exercises, all within a mere 20% of the time.

According to a study conducted on CAROL, scientists have determined that the bike can enhance your fitness level by an astounding 132%, requiring significantly less time investment.

This 132% improvement is measured using a METS Z-score, which combines various health indicators commonly utilized in medical research. In a specific study, CAROL users exhibited a 132% higher METS Z-score compared to non-users with similar fitness levels.

The claim of "less time" is based on the reduced duration required to complete CAROL's signature workout, the REHIT Intense: 2×20-second sprints. This workout only demands eight minutes and 40 seconds per day, three days a week, as opposed to the 30-45 minutes of jogging five times a week.

CAROL's REHIT protocol aims to activate your nervous system's "fight or flight" response and rapidly deplete the glycogen stores in your thigh muscles through two intense sprints. This method is referred to as reduced-exertion high-intensity interval training, or REHIT, as it offers a lower perceived exertion compared to traditional HIIT workouts. Consequently, sticking with REHIT becomes more manageable than other forms of exercise.

How Does the CAROL Work?

CAROL's workout program incorporates two brief but intense 20-second sprints that elicit a fight-or-flight response in your body, significantly elevating your energy demands by an astonishing 10,000% compared to your resting state.

This heightened demand for energy prompts your muscle tissue to release glycogen, which serves as the storage mechanism for glucose (sugar), in order to meet the anticipated energy requirements of your body. Consequently, approximately 25-30% of your muscle glycogen reserves are rapidly depleted, triggering various metabolic pathways such as AMP-activated protein kinase (AMPk) and Pparg coactivator 1 alpha (PGC-1a). These pathways play a crucial role in signaling your body to become fitter and stronger.

At a cellular level, these pathways stimulate mitochondrial biogenesis, resulting in an increase in the mass of your mitochondria. This enhancement in mitochondrial mass enhances your body's capacity to generate energy, ultimately contributing to your overall strength and fitness.

In addition to these physiological benefits, CAROL offers distinct advantages over conventional workout methods in terms of calorie burn. This is primarily due to the second sprint on CAROL, which cleverly tricks your nervous system into anticipating another sprint. Consequently, your sympathetic nervous system and the associated metabolic pathways remain elevated for several hours, leading to what is commonly referred to as an "afterburn effect." In simpler terms, you continue to burn additional calories even after completing the bike workout.

It is important to highlight that CAROL leverages artificial intelligence to personalize your workouts based on your unique physiology and abilities. Think of the bike as your very own personal trainer or an exclusive indoor cycling studio that provides you with a challenging cardiovascular workout.

During the initial setup of your workout profile, the bike requests personal information, including age, weight, and height. Utilizing these biometrics, along with 50 years of empirical evidence surrounding the REHIT method and biometric data from onboard sensors, CAROL continuously evaluates your performance and makes ongoing adjustments using a comprehensive range of 1,000 resistance settings.

Consequently, each time you engage with the bike, you receive a tailored workout experience that enhances your overall health and fitness. Notably, CAROL dynamically adapts the resistance level of the flywheel throughout the ride, taking into account your power input and data from previous sessions, to optimize the effectiveness of your sprints. This level of customization is unparalleled in comparison to traditional exercise or spinning bikes.

Furthermore, CAROL distinguishes itself from other ergometers by its ability to accurately replicate laboratory protocols in real-world scenarios, including those employed in a recently published study on the advantages of REHIT.

Dr. Niels Vollaard, a lecturer in health and exercise scientist at the Faculty of Health Sciences and Sport, said:

CAROL is the only system that accurately replicates my research outside of the labs. This scientific exercise cannot be done on a regular bike because of the supra-maximal resistance required that also needs to be tailored to each person’s physiology.

Exercising on this bike for less than nine minutes a day, three times per week, yields greater effectiveness compared to engaging in a 30-minute run five times per week.

Pricing: Is CAROL Worth It?

CAROL is available for consumers at a price of $2,595 along with a monthly subscription fee of $15 per household. Corporate users are also required to pay the same amount, but they need to purchase additional licenses for their end-users. Although the cost may seem high compared to other exercise bikes, it is important to understand that CAROL's protocol and associated benefits cannot be replicated without spending more time on the bike. 

The investment in CAROL Bike enables you to achieve maximum benefits in the shortest amount of time. You can use the discount code MICHAEL to get $100 off the purchase price (or up to $250 during promotional periods). CAROL also offers 0% APR financing for 12 months, with a monthly payment of $216.25. The company provides a 100-day in-home trial period, and if you are not satisfied, you can return the bike, and the company will pay for the return shipping if you live in the continental U.S., the UK or Canada. 

Additionally, CAROL offers an extended warranty for two years for $150, and an assembly service for $199 is also available for those who cannot assemble the bike themselves.