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Cardio Helps You Build Muscle, but Not in the Way That You Think

Updated: Feb 18, 2022

Fit and lean man using battle rope as cardio to build muscle and lose weight

Does cardio build muscle?

Many people think that cardiovascular exercise is only for weight loss or pure health benefits, and that cardio doesn't actually help you build any muscle.

However, this is simply not true.

You see, while it is a fact that most cardio exercises do not build very much muscle on their own (due to the nature of the exercise), it can help you build muscle in other ways that you may not have thought about.

In this blog post, we'll be going over why most cardio exercises don't build muscle like strength training does, why some do, and how doing cardio is going to affect your muscle building progress.

Cardio and Strength Training

In case you're unsure of the difference between cardio and strength training, we'll briefly explain it here.

If you would like a full, in-depth breakdown of the differences between these two training styles, you can click here to read that after finishing this article.

The main difference between these two training styles is the fact that cardio is mainly done to increase muscular endurance and aerobic capacity or fitness, whereas strength training is done to increase muscular strength and muscle size.

Cardio generally includes exercises such as running, swimming and rowing (all exercises that are very good at raising your heart rate and making your heart and lungs work hard).

On the flip side, strength training includes exercises that have you actively moving against resistance such as the push up or bench press, the squat, the deadlift, pull up and overhead press. These are all exercises that are generally loaded pretty heavily on and used to develop muscular strength and size.

Some exercises such as swimming and rowing are going to see some overlap with both cardio and strength training.

Fit and athletic man running along waterfront doing cardio workout in the morning

Both cardio exercises and strength training exercises have their own benefits, and it's generally a good idea to incorporate both training styles into your workout program for a more well-rounded training week.

So Why Don't Most Cardio Exercises Help You Build Muscle?

In order to answer this question, we first have to understand how muscle building occurs.

In order to build muscle, we have to take our muscles through an active range of motion whilst resisting some weight.

However, when you're doing the majority of the cardio exercises out there, the resistance simply is not high enough for your muscles to get a proper challenge. Especially if you're doing something like a L.I.S.S (low intensity steady-state) workout such as a 5km run or a 10km cycle.

And even when you do get to the point where your muscles are starting to fatigue and quickly lose their ability to produce force (usually towards the end of your workout) you've gone into a rep range that simply isn't very optimal for muscle growth.

A study conducted Thiago Lasevicius found that once you dip down below 20% of your one-rep max, the effectiveness of your training in terms of muscle growth becomes extremely limited.

It might even be the case that the lower you go, the less and less effective your training becomes for muscle growth.

Chart showing difference in effectiveness for muscle growth between various rep ranges

For most people, this would go as high as 100+ reps in a single set before reaching muscular failure.

And while it doesn't really make sense for people to be doing that many reps in a strength training workout, we go far above that quite often in long distance cardio workouts such as a 5km row.

Assuming that we travel 10m in each stroke that we take (which is reasonable for a fit man), we're looking at somewhere around 500 strokes taken throughout the workout.

Can you see why such a workout wouldn't build very much muscle?

You're simply not giving your muscles enough of a challenge to grow. Your cardiovascular system is working hard all the time, but your muscles aren't being taken close enough to failure quick enough.

And sometimes, the range of motion that we go through during cardio exercises simply isn't large enough to be favorable for muscle growth.

For example, when we're running, our quads do not actually go through that much movement.

They don't stretch under the weight of our bodies, nor do they shorten. They contract over and over again, but don't go through much of a range of motion at all.

They sort of just catch the weight and then release it.

You can even get up and try it.

Go for a quick jog just for 15 meters or so.

You'll see that your quads contract, but they don't go through much of an active range of motion like they would during a squat or a leg extension.

It would be the equivalent of doing quarter reps on a bench press and expecting to see massive gains over time.

To back this up, a study conducted by Brad Schoenfeld concluded that: "performing RT through a full ROM confers beneficial effects on hypertrophy of the lower body musculature versus training with a partial ROM."

This is why something like a lunge walk (where your quads are constantly lengthening and shortening under weight) will almost always be more effective for muscle building than running.

And that is also why most of the world class sprinters don't have massively bulky legs. Even some amateur bodybuilders could have legs larger in size.

Due to these two reasons, most cardio exercises are not going to be very effective for muscle growth.

They either don't take your muscles through a very good range of motion, or they simply don't have your muscles working hard enough to receive a proper challenge.

Now you may see that some world class cyclists and rowers do have HUGE muscles.

Remember, these athletes do this for a living and train these movements every day. Even if their training wasn't fully optimal for muscle growth, it's not unexpected that they'd end up with large muscles.

And there's no saying that they're not doing some extra work with strength training in the gym either.

Many long distance cardio athletes still do work in the weight room to develop their peak power and muscle size.

So What Cardio DOES Build Muscle?

So we established that low intensity cardio generally isn't going to build very much muscle.

Nowhere near as much as strength training would.

However if you were to do a more intense cardio workout such as a 10 x 30 seconds of all out cycling dash or 5 x 100m row with intervals in between, then those sessions would be more favorable for muscle growth.

Strong and muscular man doing rowing machine workout to increase cardio and build muscle

You'd be working in slightly lower rep ranges, closer to rep ranges that are the most conducive to muscle growth.

If you've seen pictures of world class 100m freestyle swimmers or the world records of the 500m row on the machine, you'd notice that most of them are very muscular.

This is due to the fact that when you're pushing for max (or very close to your max) intensity, your muscles are going to be producing peak force in shorts bursts.

This more closely resembles a strength training set in the gym, where you work hard for a short period of time before getting a break and going again.

And just due to the nature of the exercise, some cardio exercises such as cycling and rowing are going to count as strength training as well like we mentioned earlier.

You're actively moving against some type of resistance, and taking your muscles through a full range of motion (especially in rowing, which has you basically doing a leg press and barbell row at the same time).

So if you want to choose a cardio exercise that also directly helps you build muscle at a good rate as well, you'll want to pick one of the following exercises and do it at a high intensity with some rest breaks in between (H.I.I.T).

  • Rowing

  • Cycling

  • Boxing

  • Swimming

  • Battle ropes (long range of motion)

  • Ski machine

  • Assault bike

  • Kayaking

These aren't the only ones you can choose from, but they're probably the most common and are a good place to start for most people.

To recap: low intensity cardio is generally not great for building muscle, and higher intensity cardio with breaks in between is going to be slightly more favorable.

However strength training is still going to be the best option for muscle development in terms of strength and size.

How Else Does Cardio Help Us Build Muscle?

Believe it or not, doing your cardio also does have some indirect benefits towards building muscle that are going to help you reach your goals even quicker.

Cardio Can Improve Muscular Endurance and Lifting Capacity

Doing cardio can actually improve your muscular endurance and train your body to work for longer periods of time.

It can train your body to keep working, even when you're under lots of metabolic stress.

And as a result of this, you're able to push harder on your working sets and get more reps with heavier weight.

If you train seriously with endurance sports such as cycling, running or rowing, you'll find that you're able to train hard and push for reps that others around you would've otherwise failed.

It will come from a combination of both mental toughness and muscular endurance, but it will help you get the job done.

Personally, I rowed for two years in high school and I find that I'm able to push and grind through extremely tough and long reps, when the training partners around me otherwise would've failed them.

Especially on exercises such as the barbell bench press, I'll very often get reps that last upwards of 6 or 7 seconds long.

Definitely a great indirect benefit of doing serious cardio training for such a long time.

Doing Cardio Can Help You Sleep Better

Woman sleeping in bed after intense cardio workouts

By expending more energy throughout the day from exercising, you're going force your body to need more sleep to recuperate and restore its energy levels.

Naturally, this is going to cause you to sleep better as you need to regain your energy in order to survive the next day.

This study conducted by Sebastien F. M. Chastin found that moderate-intense cardio could help effectively help to enhance sleep quality.

Sleep has been shown in several studies such as this one to be an important factor in muscle growth, and that not getting enough of it is going to be detrimental to your gains.

Again, an indirect benefit of cardio that helps drastically with building muscle.

Cardio Can Decrease Chances of Injury

Cardio can also be used as a form of active recovery, and a warmup as well.

Whether you're choosing to do 30-45 minutes on a casual bike ride during your rest day, or you're doing 5-10 minutes of jogging on the treadmill to warm up before leg day, cardio can help you reduce your chances of injury.

Male consulting physical therapist after suffering sports injury in the lower body

Especially if you pick a low impact cardio exercise such as walking or cycling.

If you get injured, your ability to build muscle is undoubtedly going to be impacted and you won't be able to see the gains that you were seeing before.

Doing your cardio can help to reduce the chances of this happening, and help you train safely for more long-term muscle growth.


There are a couple more ways that doing cardio can help you build muscle by indirectly benefiting you, and you can read about that in the blog post here if you haven't already.


Cardio is a great option for weight loss and health benefits.

However if you do your research and make smart choices, it can be an effective tool for aiding your muscle building goals in both direct and indirect manners as well!

Why do you do cardio?

Let us know in the comments section down below!

We'd love to hear your thoughts :)


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