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Anaerobic vs. aerobic workouts: How to pick the right kind of cardio for your workout goals

If your workout plan isn't giving you what you want, you may need to spice up your cardio routine.

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A depiction of me, trudging away on the treadmill, bored as all get-out, before I learned about anaerobic cardio exericse.

Malte Mueller/Getty Images

Once upon a fitness goal, a young girl spent hours upon hours on the treadmill, one 30-minute steady-state workout at a time. She wanted to lean out -- aka lose body fat to improve muscle tone -- and she'd always heard that cardio was the best way to do so. 

So she ran and ran, even though she really, really hated being on the treadmill. But she never did meet that goal. 

The girl was me, who's now spent years studying exercise physiology and understands that 30 minutes a day on the treadmill -- or doing any form of steady-state cardio -- isn't necessarily going to help me reach my long-term fitness goals. 

Fast-forward six years: I now follow a workout routine that includes just one steady-state cardio workout per week (unless I'm training for a race; more on that later). The rest is all high-intensity interval training, weightlifting and CrossFit. And much to the surprise of circa-2014 me, I've met my body composition goals, among many others.

If you, too, have been slogging away on the treadmill, StairMaster or elliptical and you're looking for a way out, this is it. 

Steady-state cardio vs. intervals

Male crossing the finish line at a marathon.

Running a long-distance race is about as aerobic as it gets.

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What most people commonly know as "steady-state cardio" and "intervals" are scientifically aerobic exercise and anaerobic exercise, respectively. Aerobic means "with oxygen" while anaerobic means "without oxygen." 

Your body uses different energy pathways to support different types of exercise. When you exercise aerobically, your body utilizes oxygen to support sustained exercise. This kind of movement is what most people think of when they think of cardio: walking, jogging, biking, hiking, stair-stepping, swimming.

When you do anaerobic exercise, your body produces energy in the absence of oxygen. This happens when your cardiovascular system (heart, lungs and blood vessels) can't distribute enough oxygen to support the demands of the exercise you're doing -- which is why anaerobic exercise is only performed in short bursts, or intervals. 

Examples of anaerobic exercise include sprinting the 100-meter dash, long jumps, high jumps and burpees. Basically any movement that requires a high level of exertion for a short period of time constitutes anaerobic exercise. Even heavy weightlifting (lifting a lot of weight for just one to five reps) uses the anaerobic pathway, but for the purposes of this guide, we'll stick to cardio exercises.

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Anaerobic exercise is typically the super hard stuff, like sprinting up hills. That's why you only do it for seconds at a time. 

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The fun thing about anaerobic exercise is that you can turn any traditionally aerobic exercise into an anaerobic workout. Take cycling as an example: Cycling for 20 minutes at a steady pace is aerobic, but cycling very fast for 30 seconds, resting for 30 seconds and repeating for a total of 10 minutes is anaerobic.  

Your body often switches between aerobic and anaerobic exercise during workouts that require varying levels of effort. In the cycling example above, if you keep moving during your 30 seconds of rest but at a slower pace, your body uses oxygen to support that 30 seconds of easy movement. 

Read more: Fast-twitch vs. slow-twitch muscles: How to train both for speed and endurance

Benefits of aerobic and anaerobic exercise

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Aerobic and anaerobic exercise share many health benefits, including improved heart health.

Khwanchai Phanthong/EyeEm/Getty Images

Steady-state cardio and intervals both offer their own set of benefits -- but they are only beneficial to you if you're doing the correct type of cardio to meet your goals. 

Aerobic exercise primarily improves endurance and stamina, or your ability to exercise for long periods of time. It increases the capacity of your cardiovascular system to supply your working muscles with the oxygen and nutrients they need to keep moving. 

Aerobic exercise has also been linked to improved immunity, decreased risk of many chronic diseases, improved heart health, boosted mood and stronger bones -- several benefits that make aerobic exercise worth more than just the fitness outcomes. 

When it comes to components of fitness, anaerobic exercise mainly improves speed and power. It can help you run fast, jump higher and hike steeper inclines. Anaerobic exercise is also known to increase your VO2 max, promote faster and more significant weight loss, as well as contribute to improved body composition -- this is why HIIT earned its place as a top training option for people focused on losing fat.

Anaerobic exercise has health benefits, too: Like aerobic exercise, interval training can reduce your risk of chronic diseases, improve heart health and strengthen your bones, especially if you incorporate resistance training into your intervals. Anaerobic exercise can also speed up your metabolism, especially during the hours following your workout.

Read more: Getting out of breath while walking up stairs: What's normal, what's not

Should you do aerobic or anaerobic exercise?

To determine which type of cardio you need to do, you must first look at the long-term outcome you desire. It's helpful to play the "if, then" game with this. For example: 

If you want to run a marathon... then you need to do aerobic exercise.

If you want to get faster… then you need to do anaerobic exercise.

If you want to get a personal record on your 5K… then you need to do both.

The reason you need to incorporate both forms of cardio in the last example is because achieving a personal record for a 5K requires speed and endurance. You won't beat your best time if you keep running 3.1 miles at the same pace -- adding one or two speed-based interval workouts each week will improve your anaerobic capacity and allow you to run faster for longer.

Read more: The 7 most important workout moves you should be doing

Steady-state cardio or intervals: Which is better?

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Some workouts, such as group dance classes, switch between aerobic and anaerobic exercise.

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As evidenced by the above examples, there is no "best" form of cardio -- it all depends on your goals. In fitness, there's a saying: "Train for what you do." This typically applies to people who compete in various fitness disciplines, but you needn't compete in anything for the concept to apply to you.

Think of it this way: 

  • Runners run
  • Weightlifters lift weights
  • Bodybuilders build muscle
  • Triathletes swim, run and bike

Seems pretty obvious, right? It all circles back to the "if, then" game -- work out according to your goals.

Read more: Best running shoes for 2020  

Don't feel like you're stuck to one kind of cardio because of your current goal, however. All movement is good movement, even if it doesn't directly correlate to the outcome you want right now. In fact, you can benefit from changing up your routine to avoid exercise boredom and burnout, as well as reduce your risk of repetitive stress injuries. 

When I'm training for a long-distance race, I might swap a long run for an interval-style workout for no reason other than that I feel like it. I'll probably make up the long run at some point, but even if I don't, that one swap won't hurt me in the long run. As long as the majority of your workouts match your goal, you're golden. 

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The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.