How to Identify Aerobic Vs. Anaerobic Exercise (And Why it Matters)

When you go to the gym, it’s to pick up heavy weights, put them back down, and repeat. But when your coach or gym buddy tells you it’s time to “do cardio,” you’ve got to admit that it’d be nice to be able to breathe regularly after a set of six or more reps.

But just like you lift with different goals, you’ll have different goals with your cardio workouts, too. In the world of treadmills, long runs, and sprints, you’ll often hear “aerobic versus anaerobic,” or that one is better for lifters than the other. But what are these types of cardio training? Here’s what the science means for your gains.

What Is Aerobic and Anaerobic Exercise?

The critical distinction between aerobic and anaerobic exercises is the energy system your body is tapping into. By energy system, we’re talking about how your body is producing energy at any given time. During aerobic and anaerobic training, you’re making energy differently.

Aerobic means “with oxygen” or “with air” and anaerobic means “without oxygen” or “without air.” With the former, you’ll be using oxygen to fuel your energy production, while anaerobic exercise means you’ll be producing energy without oxygen.

Primary Energy System	Exercise Duration	Intensity Level	Exercise Examples	Recovery Needed*
Anaerobic (Phosphogen)	0-6 seconds (primary); 6-30 seconds (with anaerobic glycolysis)	Max Effort	Max deadlift	3-5 minutes
Anaerobic (Glycolysis)	6-30 seconds (with phosphogen); 30-120 seconds	Near Max Effort	Heavy clean & jerk double	2-3 minutes
Aerobic (Glycolysis)	2-3 minutes (with anaerobic glycolysis for the first minute)	Moderate to High Intensity	400-meter run	2-3 minutes
Aerobic (Oxidative)	Beyond 3 minutes	Low to Moderate Intensity	5k jog	Energy produced will not deplete as long as you’re still getting enough oxygen.

[Read More: What is Cardio? How to Get Started (+ Best Types of Exercise for Beginners)]

An important clarification before moving forward: your body never “turns off” one energy system to completely rely on another. Saying that an exercise is “aerobic” or “anaerobic” refers to the energy system you’re primarily using or targeting — it doesn’t mean that you’re only getting energy from one source.

Depending on an athlete’s training level and experience, they may require more or less time to recover than those outlined here.

Aerobic Exercise Explained

Aerobic exercise needs a steady stream of oxygen to maintain the activity. (1) According to the American College of Sports Medicine (ACSM), an exercise is primarily an aerobic activity if it meets the following criteria:

• Engages large muscle groups; 
• Can be maintained continuously (without pause);
• Uses oxygen to help provide fuel;
• Is rhythmic by nature. (1)

A prime example of this kind of exercise is low-intensity steady-state cardio — AKA, jogging or low-intensity running. You’re primarily using your legs (a large muscle group); are jogging or running without pause; and running is rhythmic because you are repeating the same movement over and over again.

Anaerobic Exercise Explained

According to the ACSM has laid out the following criteria with which to identify an anaerobic exercise:

• Intense physical activity;
• Performed for a short duration;
• Uses energy sources in the muscles for fuel (independently of inhaled oxygen).

To be clear, all of your energy systems are always at play — some are simply more dominant than others at different times. And there are times when the anaerobic system runs out of energy to give (which is when the aerobic system takes the reins).

[Read More: 3 Reasons Why You Should Perform Cardio After Lifting]

But before that happens, two main types of anaerobic energy systems will kick in in the first three minutes of any activity: 

• Phosphogen System: At maximum intensity, this is the primary system that gives you energy for the first six seconds of activity. This system gives you a big burst of energy but is depleted quickly. (2)
  • It can take upwards of five minutes to replenish the creatine phosphate used in the phosphogen system, which is why many athletes rest between three and five minutes between heavy sets of squats and other big barbell moves. (3)
• Anaerobic Glycolysis: At near-maximal intensity, this system (along with help from the phosphagen system) kicks in primarily between the first six to 30 seconds of an exercise. From about 30 seconds to two minutes, this energy system holds it down. Between the two and three-minute mark of an activity, anaerobic glycolysis still happens but starts to be assisted big time by the aerobic system. (2)
  • In a trained athlete, it can take between two and three minutes to recover the maximum amount of ATP spent during glycolysis, which is why many athletes wait at least two minutes between sprinting bouts. (3)

The anaerobic process requires cells to revert to the formation of adenosine triphosphate — or ATP — via glycolysis and fermentation. This process also leads to the build-up of lactic acid, or lactate, in your muscles. (1) 

Pro Tip: If you’re running what’s supposed to be a slow, steady-state run and feel that lactic acid burn, you’re likely running too hard. That’s because your body produces higher amounts of lactic acid when it doesn’t have a lot of oxygen to work with — when you’re working anaerobically. It’s a cue to tone it down when your active recovery day jog turns anaerobic.

Examples of Aerobic and Anaerobic Training

The core components of aerobic and anaerobic workouts are very different from one another. Once you know the general differences, it becomes relatively simple to separate your workouts into their respective categories. This knowledge also makes it easy to strategize and segment your training so that your body is perfectly prepared for everything it might encounter.

Aerobic Training

Aerobic workouts involve low to moderate-intensity exercises that you sustain for longer than several minutes at a time — think, five to 15 minutes on the short end. (1)

Examples of aerobic exercise include the following types of movement:

Aerobic Exercise	Good For:	Which Exercises?	How Long?
	Providing a slow, sustainable energy source. Improving overall cardiovascular fitness and health. Building bigger work capacity. Supporting activities of daily living.	Treadmill walking (or outdoors) Treadmill running or jogging (or outdoors) Swimming Rowing Machine Exercise Bike Elliptical Stair Climber	Any amount of time you can sustain (low-intensity) that’s continuous and over three minutes. Can be as short as five to 10 minutes or as long as 90+ minutes.

Note: You can use any of the above types of exercise and machines to perform anaerobic exercise, as well. Just majorly crank up the intensity and only perform bursts of work for 10 seconds to three minutes at a time. 

[Read More: Running on a Treadmill Vs. Running Outside — Which Is Best for Your Goals?]

But for the purposes of aerobic training, aim to be able to talk in short sentences while you’re moving, at a pace you can sustain for longer than five, 10, or even 30-plus minutes. That can include brisk walking and even doing cool-down cardio sessions as part of your weightlifting program.

How Long Does Aerobic Exercise Have to Be?

Not a fan of “boring” cardio? No sweat. Workouts don’t have to last for very long before they are considered aerobic training. After three minutes, the maximum end of anaerobic energy reserves tap out, and your aerobic energy systems take over primary responsibility. (4) 

Still, you do likely want to improve your endurance. When you’re just starting out, it’s okay to walk or do other very low-intensity aerobic work for five minutes at a time. As you build your endurance and strength, aim to be able to sustain aerobic exercise for 10 to 15 minutes at a time, and build up steadily from there.

[Read More: Cardio for Lifters? A Conditioning Plan for Strength Athletes]

The Physical Activity Guidelines for Americans by the U.S. Department of Health and Human Services suggest performing a total of 150 minutes of aerobic exercise per week. (5) You might choose to get that from three 50-minute runs, or from a lot of little movement snacks like 15-minute dog walks and 10-minute jogs.

How Intense Does Aerobic Exercise Have to Be?

When you go for a very leisurely stroll, you’re likely at what is considered to be heart rate zone one, or 50 to 60 percent of your maximum potential heart rate. It’s a level of activity that you can sustain without real limits. That’s certainly an excellent starting point for aerobic exercise — but to reap all the benefits of cardio, you’ll want to push it a little further.

[Read More: Demystifying Your Fat-Burning Heart Rate Zone]

The ideal aerobic activity level lies within heart rate zone two, or 60 to 70 percent of your maximum heart rate. You should be able to sustain this effort for a long period. If your fitness is very rusty, “long period” is relative — the same holds true if you’re extremely fit. 

Of course, if you have health conditions that have prevented you from getting in this type of work, consult with a doctor to help craft your exercise routine.

An elite CrossFitter will likely be able to feel like they’re jogging while an athlete who never runs feels like they’re sprinting. Both athletes might be moving at the same pace, but one is able to operate aerobically while the other is struggling to keep up. That’s because — just like in the weight room — your body adapts to what you train it to do.

[Read More: How to Balance Running and Strength Training, No Matter Your Goals]

So meet yourself where you’re at. Aim to be able to breathe mostly through your nose throughout your aerobic training — this will keep you at a sustainable jogging speed. Over time, your aerobic baseline will get better and you’ll be able to accomplish more work with less effort.

Anaerobic Training

Here’s where high-intensity exercise comes in. Anything from performing a single 500-pound deadlift to an intensive CrossFit workout qualifies as anaerobic exercise. That’s because anaerobic training involves anything — including the start of your aerobic workouts — that’s going to take a sudden burst of energy for between one second and three minutes. 

Of course, any heavy strength exercise takes an anaerobic effort to lift, including steady movements like the bench press and squat. But here, we’ll focus on movements that organically involve sudden bursts of energy and power. You can take these examples of anaerobic exercises and combine them into HIIT workouts and other anaerobically-focused sessions. 

Anaerobic Exercise	Good For:	Which Exercises?	How Long?
	Providing fast, immediate energy sources. Improved cardiovascular fitness and overall health. Potential for increased muscle mass. Ability to generate more force more quickly (power).	Clean & Jerk Snatch Box Jump 10-Second Sprint Squat Jumping Lunge Plyo Push-Up Burpee Wall Ball	0-6 seconds for maximal intensity. 6-30 seconds for near maximal intensity. 30 seconds to three minutes for moderate to high intensity.

How Long Does Anaerobic Training Have to Be?

Anaerobic training can include high-intensity cardio — think, sprint and HIIT workouts — but its definition applies to any form of exercise performed in short bursts without the presence of oxygen. As such, a set of squats or a single hang clean rep qualifies as anaerobic activity. 

Although there aren’t exact time specifications for anaerobic training, it physically cannot be maintained beyond two to three consecutive minutes without becoming aerobic. (4)

[Read More: Everything You Need to Know About Endurance Training for Strength Athletes]

In other words, the more intensely you’re training, the less time you should be able to sustain it. The idea here is that if you can sustain it longer, you might be able to run a little faster or lift a little heavier instead.

To build your anaerobic work capacity — so you can lift heavier weights for more sets and reps and over a longer period of time — HIIT and CrossFit-style workouts can go a long way. The premise is to push yourself as hard as possible, make note of your progress, and repeat the same benchmark workout later to test how much better you’ve gotten.

How Intense Does Anaerobic Training Have to Be?

Anaerobic training places a heavy emphasis on developing your power and ability to generate force quickly. When you start off sprinting, you’ve got to be able to generate a lot of oomph very quickly. The same is true when you set up to pull off a power clean or throw up a push press. 

The big, fast, heavy, all-out efforts are the most popular ways to train anaerobically. You’ll get a lot out of sessions featuring hard efforts that last less than 10 seconds, like heavy squat doubles or all-out sprints.

[Read More: The 6 Benefits of HIIT to Inspire You to Go Hard]

That said, not every anaerobic training session needs to be max effort.

Spend some time in anaerobic glycolysis — hard efforts lasting between 30 seconds and three minutes. That might include fast running (but not quite sprinting), intense rowing, or even a two-minute wall ball AMRAP (as many reps as possible).

FAQs

If you still have a few lingering questions about the differences between aerobic and anaerobic exercise, we have some answers for you below.

References

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