If you want to know what whether cardio or weightlifting should come first in your workouts and why, then you want to read this article.

Key Takeaways

  1. Doing too much cardio in general, and doing it right before or after weightlifting workouts can interfere with strength and muscle gain by increasing fatigue and directly interfering with the cellular mechanisms related to muscle growth.
  2. Doing some cardio is still a good idea, however, because it provides a number of health benefits, and can significantly speed up fat loss.
  3. The best way to get the benefits of cardio with few or none of the downsides is to do it more than six hours after you lift weights, or on a different day.

You’ve just stepped into the gym.

Should you hit the weights or do your cardio first?

Some people say that you should start with cardio because it’s a great whole-body warmup, and it’s easier and more enjoyable before an intense lifting session than after.

Others say you should do your weightlifting first because you need all the energy you can muster for it if you want to gain muscle and strength as quickly as possible.

Others still say it doesn’t really matter either way so you should do whatever works best for you.

Who’s right?

Well, here’s the short answer:

If you want to maximize muscle and strength gains, you should do your weightlifting before your cardio.

And in this article, you’re going to learn exactly why.

We’re going to discuss how cardio generally affects strength and muscle gain, the pros and cons of doing cardio before or after weightlifting, when to do your cardio workouts to get all of the benefits of cardio with none of the downsides, and more.

Let’s get started.

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How Cardio Affects Strength and Muscle Gain

For decades now, bodybuilders and weightlifters have harbored an instinctive aversion to cardio.

“I’ll just lift weights faster” they joke.

There’s actually a good reason for this. If you’re trying to gain muscle and strength as quickly as possible, then you want to limit your cardio for two reasons:

  1. In the short-term, cardio can interfere with strength and muscle gain by increasing general fatigue levels, making it harder to progress in your weightlifting workouts.
  2. In the long-term, cardio can interfere with strength and muscle gain by disrupting cell signaling related to muscle growth.

Let’s take a closer look at each of these points.

Cardio, Fatigue, and Muscle Gain

The primary driver of muscle growth is something known as progressive tension overload.

This refers to increasing the amount of tension produced by your muscles over time, and the most effective way to do this is by progressively increasing the amount of weight that you’re lifting.

This is why the biggest guys and gals in the gym are often the strongest, and why your number-one goal as a natural weightlifter should be increasing your whole-body strength over time.

To accomplish this, you have to work hard in the gym. You have do a lot of heavy weightlifting and perform a fairly high number of weekly sets for each major muscle group.

This takes a toll on your body, depleting muscle glycogen stores, damaging muscle cells, and sapping your energy levels, which is why you also need to ensure you’re eating enough food, getting plenty of good sleep, and deloading regularly.

Cardio—even moderate amounts of moderate intensity work—puts more stress on the body, making it even harder to fully recover from your weightlifting workouts. And the harder it is to recover from your lifting, the more likely you are to stall in your muscle and strength gain.

A good example of all this in action is a study conducted by scientists at the University of São Paulo.

To see how doing cardio before heavy strength training affected muscle growth, the researchers split 10 men into 3 groups:

  • The first group did four sets of half squats for as many reps as possible with 80% of their one-rep max (1RM).
  • The second group did 30 minutes of HIIT cycling (one minute of easy pedaling followed by one minute of all-out effort), followed by the same leg workout.
  • The third group did 30 minutes of HIIT running (same protocol), followed by the same lower body workout.

After each resistance training workout, the researchers tallied up the total number of reps and amount of weight lifted (weight x reps x sets), and compared the data of each group.

As you might expect, the first group (no cardio) performed significantly more total reps and lifted significantly more weight than other two groups.

While this study didn’t directly measure muscle growth, based on what we know about the mechanics of muscle hypertrophy, it’s very likely that the subjects in the first group would gain more muscle and strength than the other two groups if the experiment were continued for several months or longer.

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Cardio and Cell Signaling

As you probably know, muscle growth mostly takes place after your workout.

Lifting weights triggers a number of cellular, genetic, and hormonal changes that kickstart physiological processes that repair the damaged muscle fibers and make your muscles bigger, stronger, and better able to deal with future bouts of training (tension).

Cardio, however, triggers a very different set of changes in the body that cause muscle fibers to become smaller and more resistant to fatigue instead of larger and stronger.

The exact mechanisms that drive this adaptation are beyond the scope of this article, but the long story short is this:

Doing too much cardio suppresses the normal rise of anabolic signals triggered by resistance training, which reduces muscle and strength gains over time.

In other words, the more cardio you do, the “less responsive” your muscles become to resistance training, and therefore the harder it becomes to get bigger and stronger.

Furthermore, studies show that the longer your individual cardio sessions are, the more pronounced this “interference effect” is.

That doesn’t mean you should never do cardio if you want to get jacked, though.

There are three good reasons to keep doing cardio even if your main goal is to gain muscle and strength:

  1. Cardio provides some health benefits that you probably can’t get with weightlifting alone.
  2. There’s some evidence that increased cardiovascular fitness can help you recover faster between sets of your weightlifting workouts, which you could turn into more work done per workout.
  3. Doing cardio while cutting helps you burn more calories and lose fat faster, and doing cardio while lean bulking may mitigate fat gain and make it easier to lose fat during your post-bulk cut.

What’s the best way to include cardio in your routine, though? How can you reap these benefits while also avoiding the negative side effects?

Let’s find out.

Should You Do Cardio or Weightlifting First?

cardio or weights first to build muscle

As you learned a moment ago, muscle growth is initiated by a number of anabolic signals that occur after resistance training.

You can think of these signals as bunch of muscle-building switches that training flicks on.

Remember, too, that cardio jams some of these switches and even flicks some of them off.

This fact has given rise to a theory that doing cardio before lifting weights is better because this way, you’re doing it while your body’s anabolic switches are “off” anyway, and then turning them on with weightlifting.

If you do it the other way around—weightlifting followed by cardio—this theory says that you’ll be telling your body to start up its muscle-building machinery, and then telling it to slow it down and even stop some of it, resulting in less muscle gain over time.

This idea sounds reasonable enough, but there are two major problems with it:

  1. While long cardio workouts (>30 minutes) do interfere with these post-workout muscle-building signals, short cardio workouts (<30 minutes) don’t appear to have the same negative effects.
  2. Doing cardio before your weightlifting forces you to lift in a more fatigued state, which is much more likely to hinder progress than the physiological phenomena we’ve discussed.

In other words, a few short (20ish minute) post-weightlifting cardio workouts per week aren’t going to get in the way of your muscle and strength gains, but those same workouts done before your weightlifting most definitely can.

A good example of all of this is the findings of a study conducted by scientists at the University of Jyväskylä and published in 2016.

They divided 42 young men into 4 groups:

  1. Morning cardio followed by weightlifting
  2. Morning weightlifting followed by cardio
  3. Evening cardio followed by weightlifting
  4. Evening weightlifting followed by cardio

For their weightlifting workouts, everyone did full-body workouts, starting with lighter weights and higher reps and progressing to heavier weights and lower reps throughout the study.

For their cardio workouts, everyone did both moderate-intensity steady state (MISS) and high-intensity interval training (HIIT) on an exercise bike.

The MISS workouts involved 30 to 50 minutes of moderately difficult cycling (think ~7 out of 10 rating of perceived exertion), and the HIIT workouts involved 30 minutes of cycling intervals (four minutes of all-out pedaling followed by four minutes easy pedaling, repeated four times).

Everyone increased the duration and frequency of their cardio workouts so that they were doing two steady state and three HIIT workouts every week by the end of the study.

By the end, the main finding of this study was that the group that did weightlifting before cardio gained slightly more strength over the course of the experiment than the group that did cardio before weightlifting.

A number of other studies have found similar results.

One in particular worth mentioning was conducted by a team of scientists from the University of Qatar, who reviewed all of the best research available on this topic.

After their analysis, they found that people who lifted weights before doing cardio added, on average, about 10 pounds more to their one-rep maxes for lower body exercises than people who lifted weights after doing cardio.

In some cases the differences were even greater, but 10 pounds was the norm.

So, the key takeaway here is this: if you do weightlifting before cardio, you can expect to gain slightly more strength and muscle over time than the other way around.

The Best Time to Do Your Cardio Workouts

cardio or weights first to lose fat

For most people, the most convenient time to slot cardio in is after weightlifting, simply because they’re already in the gym.

This isn’t necessarily the best solution, though, because …

  • If these cardio workouts are of the longer-duration, higher-intensity types, they will most definitely hurt muscle and strength gain.
  • If they’re the shorter, lower-intensity variety, they’re not as detrimental, but there will be something of an interference effect.

This is why I recommend that you space your cardio and weightlifting workouts as far apart as you can when doing them on the same days (mornings and evenings, for instance), or even better, that you do them on separate days.

Two studies shed some light here.

First, a study conducted by scientists at the French Federation of Rugby Union found that separating full-body strength workouts and HIIT cardio by at least six hours more or less eliminated the interference effect.

And second study was conducted by scientists at Kyorin University, who divided fourteen 22-year old men into two groups:

  1. One group did their cardio workouts immediately after their weightlifting workouts.
  2. The other group did their cardio workouts at least 24 hours after their weightlifting workouts.

Everyone followed the same workout plan that included two weightlifting and two cardio workouts every week. The weightlifting workouts consisted of three to five sets of biceps curls with 75% of their 1RM (bruhhhh), and the cardio workouts consisted of 30 minutes of cycling at a moderate pace.

After eight weeks, both groups increased their strength by about 20%, but the group that did their cardio 24 hours after weightlifting gained over twice as much muscle.

Specifically, the first group increased their biceps size by 5%, whereas the second group saw a 12% increase. They also improved their aerobic fitness more.

The Bottom Line on Cardio or Weightlifting First

The relationship between cardio and weightlifting can be summarized like this:

The more cardio you do beyond a rather low threshold, the harder it’s going to be to progress in your resistance training workouts and gain muscle and strength.

In other words, if you do too much cardio, it’ll always be harder to get bigger and stronger than it would be if you did less.

That doesn’t mean you should completely shun cardio, though.

If nothing else, it has significant health benefits—some of which you don’t appear to get from resistance training—and it can help you burn more energy, which means faster fat loss and easier weight maintenance.

Fortunately, you can enjoy the best of both worlds by keeping most of your cardio workouts short (30 minutes or less), and by either separating your cardio and weightlifting workouts by at least six hours, or even better, by doing them on separate days.

Personally, I do one to two cardio workouts per week when I’m not focused on fat loss, and I do them on days that I don’t lift weights (weekends).

When I’m cutting, I usually do five strength workouts per week in the mornings, and two or three 25-minute HIIT cardio workouts per week in the evening, after work.

That’s all you really need to know to get most of the benefits of cardio without any of the muscle-building downsides.

If you want to learn more about how to use HIIT to lose fat and stay healthy without interfering with strength and muscle gain, then you want to check out this article:

Why High-Intensity Interval Training Is Best For Weight Loss

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What’s your take on doing cardio or weights first? Have anything else to share? Let me know in the comments below!