Expert Insights: Is Cardio Aerobic or Anaerobic?

Your body needs both aerobic and anaerobic exercise to stay healthy, prevent disease, and maintain your quality of life.

Cardio Overview

To understand the role of cardio, we first have to understand the difference between aerobic and anaerobic exercise. The short story is that they vary in three different ways.

1. The muscle fiber types used
2. The primary energy sources utilized
3. The intensity used to perform them

Every major muscle group in your body is made up of a collection of different types of fibers. The composition of these fibers varies throughout your life, and different kinds of exercise can increase or decrease the proportion of these different muscle fibers.

Slow twitch fibers (also called type 1) are packed with blood vessels and mitochondria, which carry the oxygen needed for long bouts of activity. They’re also most resistant to fatigue.

Fast twitch fibers (aka type 2B) have very little mitochondria or blood-carrying capacity, so they produce significant power but fatigue very quickly.

There’s also a third fiber type called fast oxidative or type 2A that has features of both fast and slow twitch fibers.

Our body creates the energy used in those fibers for muscle contraction that fuels our movements using three different energy systems.

1. Phosphagen
2. Glycolytic
3. Mitochondrial respiration

So because of their makeup, different muscle fiber types excel at different types of movements, like maintaining your endurance for hours or a lightning-fast sprint.

Those different intensity levels also call upon different aspects of our energy supply system, with the long, steady tasks using oxygen for fuel and the speedy, quick ones using our Phosphagen system (the mitochondria is the powerhouse of the cell–ringing a bell?).

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Aerobic/Cardio Exercise

• Utilizes large, slow-twitch muscle fibers
• Includes continuous, repetitive movement
• Sustains a higher heart and breathing rate
• Uses oxygen as fuel

Anaerobic Exercise

• Uses fast-twitch muscle fibers
• Is intense
• Short in duration
• Uses the ATP system within the muscle

Think about aerobic and anaerobic exercise as two ends of the same activity spectrum. The more you slide in one direction, the proportion of muscle fibers used and intensity changes, but all fibers are being used, and each of the three energy systems is at play simultaneously.

Types of Aerobic/Cardio Exercise

Aerobic exercise primarily uses type I muscle fibers called slow-twitch. These fibers are chock full of blood vessels that help to ferry oxygen in and out of the muscle cells. This readily available supply of oxygen allows for slow and sustained muscle contraction over a long period without fatiguing the muscle.

Activities like running, biking, swimming, and rowing are all aerobic when done at a steady pace for an extended period. The more aerobic exercise you do, the greater the proportion of type 1 muscle fibers in your body and the more endurance you will build over time.

Examples of Aerobic/Cardio Exercise

• Running
• Jogging
• Walking
• Cycling
• Rowing
• Swimming
• Dancing
• Hiking
• Kickboxing
• Jumping rope
• Mountain climbers
• Jumping jacks
• Running in place

Types of Anaerobic Exercise

Anaerobic activity relies on fast-twitch fibers, which are built for power and speed. Instead of a steady stream of oxygen for energy, anaerobic exercises rely on stores of energy already in the muscle to contract rapidly.

The downside is that muscle cells have very little energy available at any time, meaning these fibers are quickly exhausted after only seconds of activity.

Thus, less energy in total is produced this way than with aerobic oxidation-the process that powers aerobic activities. Anaerobic activities include sprinting, weight lifting, and plyometrics, to name a few.

Examples of Anaerobic Exercise

• Free weights
• Powerlifting
• Olympic weight lifting
• CrossFit
• HIIT
• Insanity
• Body weight exercises like push-ups, pull-ups, sit-ups, etc.
• Kettlebell exercises like swings, squats, halos, etc.
• TRX
• Burpees
• Sprinting
• Squats
• Deadlifts

Why Cardio Matters

The word ‘cardio’ comes from the Greek word kardia, which means heart and is used interchangeably colloquially with aerobic exercise.

The importance of regular cardio exercise cannot be overstated, as it prevents conditions like heart disease, diabetes, stroke, dementia,  and more. Cardio also has tremendous mental health benefits.

Traditional cardio that is slow and steady technically burns fewer calories than highly intense anaerobic exercise, but it’s an essential component of any fat loss regimen.

The CDC recommends a minimum of 150 minutes weekly of moderate-intensity aerobic movement and at least two days of strength training to see health benefits. Moderate intensity means you should be working hard enough to break a sweat and breathe hard.

Benefits of Cardio Exercise

Regular cardio exercise is one of the best ways we have to prevent disease, slow down aging, improve our mood, increase our energy levels, and improve our quality of life.

Improved Cardiovascular Health

Numerous studies have shown that regular participation in aerobic exercise significantly decreases your risk of developing coronary artery disease (CAD) and dying.

Cardio also increases your good cholesterol, called high-density lipoprotein (HDL), and high HDL levels are associated with a decreased risk of heart disease.

While you want a high HDL, you want a low, low-density lipoprotein (LDL) and triglycerides. Aerobic exercise also helps lower these unhealthy cholesterol components, further reducing heart attack and stroke risk.

Cardiac remodeling is a process that occurs after the heart has been damaged and results in structural changes to the tissue.

These changes often lead to a thickening of the heart muscle, causing it to become stiff and reducing its ability to pump blood effectively. Regular aerobic exercise can slow this process.

Regular cardio also reduces blood pressure, which can help prevent strokes and heart attacks.

Increased Endurance

A synonym for cardio is endurance exercise, and for good reason. Endurance activities like running, swimming, cycling, and hiking all require equal measures of cardiovascular capacity and muscular endurance to keep your muscles firing and your body moving.

Weight Loss and Weight Management

Weight loss is primarily driven by your diet, but that doesn’t mean exercise is not important. How you train and how often you train can play a big role in your ability to lose weight and keep it off, as well as your quality of life and your health in general.

Cardio also certainly contributes to the caloric deficit needed to lose weight or maintain weight loss.

Increased Energy Levels & Reduced Stress

Studies have shown that aerobic exercise can boost your mood and lower your stress levels, both of which contribute to better mental health.

Reduced Risk of Chronic Diseases

Ample research has demonstrated that regular aerobic exercise dramatically reduces your risk of experiencing a stroke, heart attack, or developing diabetes and many types of cancers.Benefits of Anaerobic Exercise

Anaerobic exercise shares many of the same benefits of cardio, with a few unique benefits.

Increased Muscle Strength and Power

Anaerobic exercise is the best way to build and maintain muscle, which is essential for multiple reasons. Without it, we lose muscle and bone mass each year, and then our metabolism slows down due to that loss.

By maintaining a muscular, strong frame, we prevent age-related disability, keep our metabolism fires burning, and stay coordinated and balanced.

More muscle mass combined with proper training means more strength and power. Maintaining strength is especially important as you age, as it is strongly correlated with decreasing fall risk, fracture risk, and hospital stay length in the event you are injured.

Better Bone Health

Age-related bone and muscle loss, called osteoporosis and sarcopenia, cause significant issues for aging people, including falls, fractures, disability, and a loss of independence. Anaerobic exercise like weight lifting combats these losses effectively.

Increased Metabolism & Fat Loss

Research has shown that anaerobic exercise, such as weight lifting increases your muscle mass, which increases your resting metabolism by 7% on average.

Studies have shown that those who partake in anaerobic exercise regularly have a lower body fat percentage than those that don’t.

Increased Energy Levels

Just like aerobic exercise, anaerobic activity releases those happy neurotransmitters, which increase mood and energy levels.

Fights Chronic Conditions

Strength training increases insulin sensitivity, reduces abdominal fat, and improves glycemic control—critical aspects of health affecting those at risk for or who have diabetes and other chronic metabolic conditions.

Common Cardio Injuries & Drawbacks

Now that you know what cardio is and the benefits of aerobic and anaerobic exercise, let’s talk about common injuries at pitfalls to avoid if you’re trying to be more active.

Overuse Injuries

One of the downsides for athletes who love endurance sports is the prevalence of overuse injuries.

For example, a staggering 70% of runners each year will experience an overuse injury. While the mechanisms of these injuries are debated within the research community, their impact is not.

Because nothing will knock you out of a rhythm more than a painful injury.

Performance Plateaus

A very common and frustrating experience in the aerobic exercise world is hitting a performance plateau.

You could have been making progress for months, and then all of a sudden your body hits the brakes, and you cannot progress.

Plateaus are often an indicator of overtraining, so be mindful not to over-train,  accordingly.

Boredom

Let’s face it, while die-hard cardio fans are out there, most of us don’t look forward to long, steady-state cardio sessions. Even cardio enthusiasts will admit to hitting a slump.

When that happens, don’t be afraid to shake things up and try something new. Exercise should be fun!

Common Anaerobic Injuries & Drawbacks

While anaerobic training styles are phenomenal for building muscle and blasting calories, they can be intense.

Recovery Time

Because you’re working at a much higher intensity for most anaerobic workouts (think heavy weight lifting, HIIT, sprinting), you must be more intentional with your recovery strategy.

Anaerobic workouts are unforgiving if you don’t perform a proper warm-up and cool-down or if you’re not carefully minding your form.

Not for Beginner Exercisers

It’s hard to mess up an elliptical workout or jogging session, but anaerobic workouts are often highly technical, and the stakes are higher.

Whether it’s a technical barbell complex or a high-octane sprinting session, these workouts require careful execution and serious attention to detail, which does not suit most beginners.

Easy to Overdo

Anaerobic workouts are easy to overdo and cumulatively overtrain, both of which can lead to injuries and exercise burnout. These are not workouts you can casually hit on the fly but require some planning around workouts and recovery.

Choosing the Right Type of Cardio

You now know that you need both cardio and anaerobic exercise, such as weight lifting, to be healthy and live longer, but which do you choose?

You’ll want to consider multiple factors i when choosing which exercises, including your:

• Fitness level
• Form knowledge
• Injury history
• Preferences
• Time Constraints
• Available Equipment

If you're a beginner, start with some aerobic exercises to build endurance and aerobic capacity. Then add strength training or another anaerobic option two to three times weekly.

Remember that exercises exist on a continuum of aerobic to anaerobic involvement, and most workouts have both components in some capacity.

Aerobic Centered Exercise

Low-intensity steady-state cardio (LISS)

Moderate-intensity steady-state cardio (MISS)

Tabata

Anaerobic Centered Exercise

Metabolic resistance training (MRT)

Every minute on the minute (EMOM)

High-intensity interval training cardio (HIIT)

As Many Reps as Possible (AMRAP)

Sample Cardio Workouts

*Make sure you warm-up for 5-10 minutes before every workout*

Bodyweight Workout

Interval Workout

Metabolic resistance training (MRT) Workout

Bottom Line

Cardio is just another way of describing aerobic exercise, and it’s essential to get regular cardio and anaerobic training to stay healthy and strong.

Cardio exercise has tremendous benefits, including heart health, endurance, aiding in weight management, and the prevention of chronic health conditions like diabetes, heart disease, and stroke.

Anaerobic exercises like weight lifting, sprinting, circuits, and complexes build better muscle size, strength, and power, as well as bone density and metabolism, better energy levels, and fight chronic disease.

When choosing a cardio workout, you need to consider your time constraints, your form experience, injury history, and equipment availability.

Want to learn more about cardio workouts you can do at home? Check out our guide here.

Interested in learning more about circuit training for cardio?  Want to learn more about HIIT training?

No matter what workout you’re interested in, GymBird has the content to educate and empower you.

More Cardio Advice from GymBird Experts

• What is Cardio?
• Cardio for Beginners
• Best Cardio Workouts
• 5 Cardio Workouts at Home
• Cardio Workouts for Runners
• Cardio with Weights
• Cardio vs HIIT
• Cardio vs. Walking
• Top Cardio Benefits

Resources

International Journal of Exercise Science. EPOC Comparison Between Resistance Training and High-Intensity Interval Training in Aerobically Fit Women.

Sports Medicine. The Effect of Resistance Training in Healthy Adults on Body Fat Percentage, Fat Mass and Visceral Fat: A Systematic Review and Meta-Analysis.

HHS Public Access. The Role of Exercise and Physical Activity in Weight Loss and Maintenance.

Frontiers in Psychology. Neuromodulation of Aerobic Exercise—A Review.

Current Sports Medicine Reports. Consortium for Health and Military Performance and American College of Sports Medicine consensus paper on extreme conditioning programs in military personnel.

Current Sports Medicine Reports. Resistance Training is Medicine. Effects of Strength Training on Health.