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The power of cardio for all-round fitness

Discover the significance of cardio in achieving overall fitness and uncover the incredible benefits it brings. Explore the shortest, most effective cardio workouts, including HIIT and REHIT.
There are 3 pillars of fitness: cardio, strength, and mobility. Contrary to popular belief, cardio doesn’t have to involve long and gruelling sessions of running or cycling. In this article, we will explore the importance of cardio, the incredible benefits it offers, and how shorter, more efficient workouts can transform your fitness journey. By debunking the myth that cardio has to be lengthy and painful, we’ll show you how to make cardio workouts not only effective but also time-saving and enjoyable.

Why cardio matters

Cardiorespiratory fitness is the best indicator of overall fitness. That’s because cardiovascular exercise gets your heart pumping, lungs working, and muscles moving. Like strength training, cardio helps with fat loss, but, as with strength training, its benefits go well beyond appearances.

7 cardio exercise benefits.

  1. Reduces heart disease risk – Improves heart disease risk factors: high blood pressure, obesity, poor aerobic fitness. 
  2. Reduces type 2 diabetes risk – Helps regulate insulin and blood glucose levels. 
  3. Reduces stroke risk – Improves stroke risk factors: high blood pressure, obesity, type 2 diabetes. 
  4. Regulates mood – Improves symptoms of anxiety and depression. 
  5. Reduces cancer risk – Helps reduce the risk of developing certain cancers.
  6. Maintains brain health – Slows the natural cognitive decline associated with aging. 
  7. Improves sleep – Improves both sleep duration and quality

The science of cardio

Here’s what happens to your body when you do cardiovascular exercise:

  1. As your muscles begin to work, they need more oxygen and fuel for energy.
  2. Your heart rate quickens to pump more oxygenated blood and glucose to your muscles.
  3. Your muscles use available glucose from your blood as fuel.
  4. Your muscles begin to break down glycogen (stored glucose) for energy.
  5. Your insulin sensitivity rises, helping your muscles drive glucose into your cells for energy.
  6. Your breathing speeds up from around 15 breaths a minute to 40–60 breaths a minute to draw more oxygen into your body.
  7. Your skin looks flushed as your blood vessels expand to improve blood flow to your muscles.
  8. Waste products are created from breaking down glucose, glycogen, and oxygen for energy.
  9. Your blood vessels carry the waste products away.
  10. Your body starts to break down stored fat for additional energy.
This chain reaction, caused by the need for more fuel in the body, is why cardio has so many health benefits. And because your heart and lungs work hard, cardio improves general lung function as well as your cardiovascular fitness—as measured by VO2max—and aerobic endurance.
VO2max is the main measure of fitness. The higher your VO2max, the fitter and healthier you are.

Short, efficient cardio

The American Heart Association (AHA) recommends at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity a week. However, if your schedule makes that impossible, groups of research show you’ll get more benefits, in less time, from interval training.

Research show you’ll get more fitness benefits, in less time, from interval training.


High-intensity interval training (HIIT) involves brief bursts of intense exercise punctuated by low-intensity recovery periods. Working hard and with varying intensity triggers a host of physiological adaptations that make you fitter and stronger in minimal time.

An elliptical workout not only helps you to burn calories and lose weight, but it is also great for strengthening muscles and improving cardiovascular health. It engages both the lower and upper body muscles, providing a whole body workout.

HIIT benefits

Saves you time

In terms of health and fitness gains, the science is indisputable: it’s more time-efficient to exercise hard for a short amount of time than it is to go easy for a longer period.

Burns more calories

A HIIT workout offers a significant advantage in calorie burning compared to steady-state cardio and even strength training, making it an excellent choice for weight loss. Research demonstrates that this intense workout can yield calorie expenditure similar to traditional cardio and weighted exercises, but in a shorter duration. In just 30 minutes, a HIIT session comprising 20-second exercise cycles followed by 40 seconds of rest can burn up to 30% more calories than a half-hour run or steady-paced cycling. This increased calorie burn makes HIIT bike workouts highly effective for achieving weight loss goals.

Increases metabolic rate

In addition to its ability to shift the body’s metabolism towards burning fat instead of carbs, HIIT has been shown to increase post-workout calorie burn. This phenomenon, known as excess post-exercise oxygen consumption or afterburn, means that you continue to burn fat and calories even after your HIIT session is complete. Compared to steady-state workouts like jogging, HIIT leads to greater fat and calorie burning for up to 24 hours after your workout, maximizing the benefits of your exercise routine.

Stabilizes heart rate and blood pressure

Research indicates that incorporating HIIT into fitness regimens leads to notable enhancements in blood pressure and heart rate. A 2014 study focused on participants aged over 60 who engaged in HIIT sessions consisting of 6-second maximum intensity pedaling followed by 1 minute of rest, repeated for 10 sprint-rest intervals. The findings revealed that as few as 2 sessions per week resulted in a remarkable 9% decrease in blood pressureThis highlights the significant cardiovascular benefits achievable through HIIT training.

Increases endurance

Research indicates that individuals who performed 4×20-minute HIIT workouts per week achieved comparable muscle durability and strength to those who engaged in 40 minutes of continuous cycling daily. This highlights the remarkable efficiency and effectiveness of HIIT in enhancing muscle oxygen consumption and overall fitness.

HIIT workout

You’ll see health and fitness benefits from applying the basic HIIT principle—going hard, recovering, and then going hard again—to any kind of aerobic exercise.
Try this simple HIIT workout that can be done at home or the gym. Remember to listen to your body, modify as needed, and complete each movement with proper form.
Before starting the workout, make sure you complete a 2-minute warm up to get your muscles ready to go.

20-minute HIIT workout

Repeat each move for 30 seconds, resting 15 seconds between moves. After your first circuit, rest 60 seconds. Repeat the circuit 2 more times (3x total):
  1. Jumping Jacks – Start by standing upright with your feet hip width apart and your arms at your sides. Jump your feet out while raising your arms.
  2. Bodyweight Squat – Stand straight with your feet hip-width apart. Lower yourself down (as if sitting in an invisible chair). Straighten your legs and lift back up and repeat.
  3. Mountain Climber – Start in a high plank position, with your wrists directly under your shoulders, core engaged, hips level, and legs extended straight behind you. Draw your right knee to your chest, return to your starting position, and immediately draw your left knee to your chest. Return to your starting position and continue to alternate, moving quickly.
  4. Jump Squat to Twist – Start with your hands behind your head and feet wider than hip-width and do a squat. As you stand, lift your left knee toward your chest and across your body to tap your right elbow. Return elbow and left leg back to starting positions and do a squat. Alternate sides.
  5. Push-Up With Tuck – Start in a high plank position. Bend your elbows and lower your chest to the floor. Drop to your knees if needed. Push through the palms of your hands to straighten your arms. At the top of your push-up, bring your right knee toward your right elbow, then immediately return to a high plank position. Alternate sides.
  6. Bicycle With Punch – Lie faceup with your shins parallel to the floor, knees bent to 90 degrees, and stacked over your hips. Hold your hands in fists at your chest. Use your abs to raise your shoulders off the floor. Bend your left knee in toward your chest, while simultaneously straightening your right leg and punching your right arm toward the ceiling. Then twist to bring your right knee in, simultaneously straightening your left leg and punching your left arm into the air. Continue alternating sides. Go at a slow, steady pace so you can really twist and feel your abs working.
  7. Drop Lunge – Stand with your feet shoulder-width apart, core engaged, and jump your right foot back behind you and bend both knees to 90 degrees to sink into a lunge. Return to your starting position by pushing off your right foot and jumping forward, bringing your feet together. With your feet together, hop up, and jump your left foot behind you so that you land in a staggered stance with your left foot back. Immediately sink into a lunge by bending both feet to 90 degrees. Jump both feet together to return to your starting position. Continue to alternate sides.
  8. Shoulder Tap – Stand in a high plank position, with your palms flat on the floor, shoulders stacked directly above your wrists. Lift your right hand. Place your right hand back down on the floor and immediately lift your left hand to tap your right shoulder. Continue to alternate sides.
  9. Jackknife – Lie faceup with your legs extended and arms overhead so that all of your limbs are resting on the floor. Engage your core and lift both arms and legs a few inches off the floor to come into a hollow hold position. Now bring your knees to your chest, simultaneously bringing your arms toward your legs and wrapping your hands lightly around your shins. Keep your core tight and do not grip your shins or hug your knees in order to achieve the crunch. Extend your arms and legs to return to the hollow hold position.

The shortest, most effective cardio

Traditional HIIT workouts, although effective, can feel overwhelming and challenging, especially for those with busy schedules, health conditions, or a dislike for cardio. Fortunately, there’s another option: Reduced Exertion HIIT (REHIT).

What is REHIT?

REHIT is the next-level HIIT workout proven to deliver double the health and fitness benefits in 90% less time compared to regular cardio. Developed by scientists looking for the shortest, most efficient way to exercise, it involves just 2×20-second sprints, separated by a low-intensity recovery and ending with a low-intensity cooldown.
REHIT workouts can be done in as little as 5 minutes, but that’s not even the best part…

CAROL’s the only bike with REHIT, the next-level HIIT workout that gives you double the health benefits, in just 10% of the time.

REHIT creates the most potent training stimulus with just 2x20-second sprints.

How does REHIT work?

The magic lies in those 2×20-second sprints. In a HIIT session, the goal is to work hard for each interval, but with REHIT, you work at your absolute maximum during each 20-second sprint.
Like in a ‘fight or flight’ situation, your muscles are forced to mobilize about 25-30% of muscular glycogen—your emergency energy reserve—releasing key signaling molecules (AMPK and PGC-1a), telling your body it must get fitter and stronger.
You develop more mitochondria, your blood plasma volume increases, and your heart gets stronger. Resulting in increased aerobic and anaerobic capacity.

What are the health benefits of REHIT?

Doing 3x 5-minute sessions of REHIT for 8 weeks has impressive health benefits including:
  1. Improve VO2max by up to 12%
  2. Lower blood pressure by 5%
  3. Increase good cholesterol by 6%
  4. Lower risk of type 2 diabetes by 62%
  5. Reduce triglycerides (fat found in blood) by 10%
  6. Reduce blood sugar by 2%

How to do REHIT

REHIT works because it requires you to sprint at your personal maximum intensity, switching from zero to max instantly. You may be wondering, though, how to manage this rapid onset of maximum intensity. Well, CAROL Bike is designed to make this transition as easy and as safe as possible.
Of the alternatives, all-out sprinting on a running track would be the next best thing—if your joints can take it and you’re careful not to trip. This would involve doing the following:
  1. Gently jog for 2 minutes to warm up
  2. Sprint as fast as you can for 20 seconds
  3. Gently jog for 3 minutes to recover
  4. Sprint as fast as you can for 20 seconds
  5. Gently jog for 3 minutes to cool down
But while this may work in theory, in practice it’s simply not practical. That’s because REHIT only delivers results if you do both 20-second sprints at maximum intensity.
This precise dilemma is why CAROL partnered with exercise researchers to create the only home (and gym) exercise bike that makes it possible to reap the full benefits of REHIT outside of a lab setting.

How to really do REHIT

CAROL Bike is the only bike fully optimized for REHIT—making it simple, effective, and safe. It provides the shortest, most effective workouts suitable for any age and fitness level.
CAROL’s AI-personalization tailors the workout to you and helps you push to your limits during the sprints. Like in a ‘fight or flight’ situation, your muscles are forced to mobilize about 25-30% of muscular glycogen—your emergency energy reserve—releasing key signaling molecules (AMPK and PGC-1a), telling your body it must get fitter and stronger.
You develop more mitochondria, your blood plasma volume increases, and your heart gets stronger. Resulting in increased aerobic and anaerobic capacity.
Here’s what CAROL Bike’s signature REHIT workout looks like. And why it works.
Just 2×20-second sprints, 3x a week. Scientifically proven to be the most effective cardio workout—a moment of effort you can always master. Shop CAROL Bike.

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All our experts have MSCs in Exercise Science, and they’re here to answer your questions. Whether it’s about these workouts, or the science behind CAROL Bike, whatever’s on your mind—we’re here for you.
Get Fitter

Improve your fitness by 12% in just 8 weeks.

Live Younger

Improving your VO2max by 12% is like turning the clock back on your age by 10 years.

Live Healthier

Reduce your risk of type 2 diabetes by 62%—and blood pressure by 5%.

Next-level HIIT

Why Reduced Exertion HIIT (REHIT) is the most effective workout.

Maximum Metabolism

You’ll burn more calories on a 15-minute CAROL ride, than a 30-minute run.

Time to thrive

Make the most of your time with CAROL Bike's short and efficient REHIT workouts.

What is a REHIT workout?

Explore REHIT, the game-changing workout that redefines time-efficient training with just 2x20-second sprints.

Demo: How to do REHIT on CAROL Bike

Explore a hands-on guide to doing REHIT on CAROL Bike, showcasing its efficient, effective workouts tailored for every fitness level.

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