Think about how you feel doing your 12-3-30 routine on the treadmill versus during a high-intensity interval (HIIT) class. You probably feel like you could maintain that first one for a pretty solid amount of time without wheezing, while just one round of HIIT leaves you gasping for breath.
Turns out there’s a reason behind this, and it lies in a key difference between the workouts: one is aerobic, while the other is anaerobic. While you might be able to tell if something is aerobic vs. anaerobic based solely on how heavy your breathing is, there’s a little bit more to the story than that.
Your body creates energy in two basic ways: aerobically—with oxygen—and anaerobically—without oxygen—and each of those methods will affect your body differently. Understanding the difference can help you burn calories and fat, plus increase your overall strength, power, and endurance.
Ahead, experts break down how to use aerobic and anaerobic workouts to your advantage.
Meet the experts: Lesley Bell, CPT, is a personal trainer and brain health coach at Pacific Neuroscience Institute at Providence Saint John’s Health Center in Santa Monica, California. Andy Coggan is the director of fitness at Gold’s Gym.
What is an aerobic workout?
If the word “aerobics” makes you think of women dancing in Spandex, you’re on the right track—this is an example of an activity where the body is able to get the energy it needs from oxygen intake.
Oxygen plays a very important role in making sure your muscles have energy during exercise. That’s because oxygen helps generate adenosine triphosphate (ATP), which is the energy molecule in the body. It’s why you start to breathe heavier as you increase the intensity of an exercise; you need more oxygen to make more ATP.
If you’re doing aerobic exercise, you’re taking in sufficient oxygen to sustain your workout, says Andy Coggan, the director of fitness at Gold’s Gym. These workouts primarily utilize slow twitch muscle fibers which can sustain activity for extended periods of time, adds Lesley Bell, CPT, is a personal trainer and brain health coach at Pacific Neuroscience Institute at Providence Saint John’s Health Center in Santa Monica, California.
Any lower- to moderate-intensity exercise is considered aerobic, and they can generally be sustained for longer periods of time. Think about steady-state exercise like walking, jogging, cycling, or even dancing. You’re not going to be gasping for breath during these workouts, because your body is continuously consuming enough oxygen for you to power through.
What is an anaerobic workout?
And then, of course, there are the activities that *can’t* be sustained by your oxygen intake alone. Without oxygen, the body uses glucose in the muscle cells for energy. That process can’t be sustained for more than 90 to 120 seconds of high-intensity exercise because your muscles produce a significant amount of lactic acid in that time. After that, your body must begin to utilize oxygen again in order to break down glucose and fatty acids to continue to produce energy, says Bell. Cue the heavy breathing.
Anaerobic activities are done at a high intensity and usually using multiple intervals, says Coggan. They primarily utilize fast twitch muscle fibers, adds Bell. If you’ve ever done a HIIT workout, that’s anaerobic exercise. Plyometrics, sprinting, and weight lifting are all considered anaerobic—you’re going all out with 100 percent effort, but you can only sustain that effort for a short period of time. “Most sports involve anaerobic bursts followed by periods of rest,” he adds.
Why are aerobic and anaerobic workouts important?
Obviously, these styles of training are pretty different, but they’re both equally important in a well-rounded fitness regimen. Here’s why.
Aerobic exercise boosts endurance.
Working out in a sustainable, steady state heart rate zone for longer periods of time can improve your endurance. Aerobic exercise improves the cardiovascular system by strengthening the heart and potentially increasing the maximal amount of oxygen the body can utilize (a.k.a. your VO2 max), says Bell. This not only lowers the threshold for what your body can handle in the future because it’s getting more efficient as using oxygen, but it also boosts your endurance and can help you workout or run for longer.
Anaerobic exercise helps build strength and burns more calories in a shorter amount of time.
On the other hand, if you’re looking for a more efficient workout, anaerobic exercise—like HIIT—has been shown to burn more total calories in a shorter amount of time. “Science shows that this method of training can be extremely beneficial for power development, building muscle mass, and fat burning,” says Coggan. You’ll also build stronger joints and bones due to the increased impact on your body.
But, you don’t want to sleep on either.
You can’t just do cardio or just do weights if you want to get fitter or stronger—even if you have a specific goal in one of those areas.
“Both styles of training will burn calories and improve the function of the heart and lungs, and the best bet for maximum adaptation and body transformation is to combine these training styles over the course of a week,” says Coggan. “In doing so, you’re getting the power- and muscle-building benefits of anaerobic work while adding the increased stamina and endurance associated with aerobic workouts.”
Here’s How Often You Should Be Doing Aerobic and Anaerobic Exercises Per Week
As Coggan said, you want to make time for both anaerobic and aerobic workouts throughout your week. The most important thing to remember is that there’s an inverse relationship between intensity and duration, says Bell. That means you want to do less of the higher intensity workouts (anaerobic) and more of the low- to moderate-intensity workouts (aerobic).
“Research has shown that a maximum of three to four days of high-intensity exercise with proper rest periods in between is optimal to see results,” says Bell. “Anything more may yield the same or similar health benefits, but can put you at risk for overtraining or overuse injuries.”
Aerobic exercise, though, could theoretically be done as many as seven days a week. The U.S. Department of Health and Human Services recommends adults have at least 150 minutes of moderate intensity cardio per week, and you can slice that into as many days as you see fit.
The average person should start with one to two aerobic sessions with one anaerobic session per week, says Coggan. “Over time, you can work up to three to four aerobic sessions intermixed with two higher intensity anaerobic workouts spaced a few days apart from each other,” he says.
Ashley Mateo is a writer, editor, and UESCA- and RRCA-certified running coach who has contributed to Runner’s World, Bicycling, Women’s Health, Health, Shape, Self, and more. She’ll go anywhere in the world once—even if it’s just for a good story. Also into: good pizza, good beer, and good photos.
Olivia Luppino is an editorial assistant at Women’s Health. She spends most of her time interviewing expert sources about the latest fitness trends, nutrition tips, and practical advice for living a healthier life. Olivia previously wrote for New York Magazine’s The Cut, PS (formerly POPSUGAR), and Salon, where she also did on-camera interviews with celebrity guests. She’s currently training for the New York City marathon.
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