Is Cardio Bad for Your Strength Training?

Key Points:

A recent meta-analysis investigated if cardio training affected strength gains in the squat and leg press.
Based on 27 studies, combining cardio and strength training did not negatively affect strength gains in untrained participants.
In trained participants, combining cardio and strength training resulted in slightly smaller strength gains.
However, this effect was only present when participants did cardio and strength training in the same session (<20 mins). When split into two sessions (>2 hours), the effect vanished.

Do Cardio Affect Your Strength Gains?

In 1980, Dr. Robert Hickson published his infamous study on combining cardio with strength training.¹

He had participants do either:

Strength training only
Endurance training only
or strength and endurance training combined

The results?

Combining strength training with endurance training (S+E) was worse for strength development than strength training only (S).

cardio and strength training — Strength training only (S) lead to greater strength gains than combined strength and endurance training (S+E), over 10 weeks of training.

It was the first study of its kind and the results have been cited in hundreds of scientific articles since then.

What’s less known is how intense the program that Hickson put the participants on was:

For endurance training, the participants trained six days per week: three days of 6 x 5 minutes cycling intervals, alternated with three days of continuous running “as fast as possible” for 30–40 minutes.
For strength training, the participants trained legs for five days per week: three workouts consisting of squats, leg extensions, and leg curls; two workouts consisting of leg presses, deadlifts, and calf raises.
The combined strength and endurance training groups did both. That’s eleven workouts per week.

If you think that sounds like a program that could kill someone, that makes two of us. Frankly, I’m surprised they could gain strength for as long as they did before things went south.

But, no matter what you think about Hickson’s zealous training program, the idea that cardio is bad for strength gains has stuck around.

And been studied. And been found correct.

At least at times.

Cardio and Strength Training: What, When, and How Much?

Despite 40 years of research and at least as many studies on the subject, we still don’t really know exactly when and how there is an interference effect between anaerobic and aerobic training – or strength training and cardio. Some studies find that there is such an effect, some don’t, and yet others find that cardio training improves your strength and hypertrophy gains from strength training.

Clearly, we’re still some way from figuring out exactly what kind of cardio, done when that hampers strength gains for whom.

A recent meta-analysis, just published last week, does however take us one step closer to understanding exactly how cardio interferes with strength training.

Cardio for Trained vs Untrained Lifters

A Swedish team of researchers sought to investigate if there was a difference in interference effect between cardio training and strength gains in the squat and leg press in untrained vs. trained individuals.²

They found 27 studies in which a total of 750 participants trained either:

Strength training only (including either the squat or leg press)
Combined cardio and strength training

Furthermore, they classified the participants into three categories:

Untrained individuals that were not recreationally active and did no regular training.
Moderately trained individuals that were recreationally active, but did no regular training.
Trained individuals that had been training regularly for at least three months.

Seven of the 27 studies were with untrained participants, ten with moderately trained, and ten with trained.

Here’s the average training frequency per week across all included studies:

Untrained: 2.9 strength workouts + 2.9 cardio workouts for the combined group
Moderately trained: 2.7 strength workouts + 2.8 cardio workouts for the combined group
Trained: 2.5 strength workouts + 2.6 cardio workouts for the combined group

Results

The analysis showed that for untrained and moderately trained individuals, adding cardio to your strength training program did not affect squat or leg press 1RM negatively.

In trained individuals, however, it did.

Trained individuals that combined cardio and strength training did get stronger from their training programs, but the individuals that strength-trained only gained slightly more strength. Not by a landslide by any means, but still a small negative effect.

However, a subgroup analysis revealed that when trained participants split their cardio and strength training into different sessions, the negative effect disappeared.

The Better Trained You Are, The More You Need to Specialize

Getting stronger as a beginner is easy. Almost any training will make you bigger and stronger, and, judging by the results of this new meta-analysis, you will still improve your strength even if you do cardio in the same session.

As you get more advanced, you must specialize further if you still want to improve your performance. While it is certainly possible to reach a high level of endurance and strength simultaneously (look at Crossfit athletes), you could still probably reach an even higher level of performance if you would specialize 100% in one thing.

However, for most of us, doing both endurance and strength training is about the best thing we can do for our health. But if you still want to lift a massive weight in the squat or deadlift, how do you minimize the interference effect?

strength training combined with cardio — Endurance training does not have to get in the way of increasing your squat 1RM.

Practical Recommendations for Combining Cardio and Strength Training

Here are my recommendations for combining endurance and strength training:

Split strength training and cardio into different sessions. Even better, do them on separate days. If possible, this will help you stay fresh for your strength training and perform at your best.
If you’re doing both in the same session, do strength training before cardio. This has been shown to decrease the interference effect.
Periodize your training. Training both strength and endurance hard at the same time can challenge your recovery. By periodizing and focusing on one quality at a time, you can maintain one while progressing in the other.

Cardio and strength training offer different positive health effects and enhance your general athleticism. Most of us would probably be wise in trying to include a little bit of both in our training, and hopefully, this post have helped you figure out how to do that.

In case you still don’t feel that you have gotten all the answers, I’ll wrap this post up with a few frequently asked questions on combining the two.

Frequently Asked Questions

Can You Do Cardio and Strength Training the Same Day?

Yes, but unless you are a beginner, this might have a small negative effect on your strength gains.

For the trained athlete, separating cardio and strength training by a few hours (two or more) minimizes this interference effect.

Should You Do Cardio Before or After Lifting Weights?

Ideally, you should do the form of training that is your main priority first. That way, you are fresh and can perform at your best, thus stimulating new training adaptations the most.

So, if strength and power is your priority, you should lift weights before doing cardio.

If you prioritize both equally, doing cardio before strength training seems to harm strength gains more than leading with strength training harms your cardiovascular improvement.

How Much Cardio Can You Do Without Negatively Affecting Strength Gains?

The more cardio you do, the more resources in terms of recovery and energy it will demand.

An earlier meta-analysis on concurrent training from 2012 found a dose-response relationship between strength gains and the number of endurance workouts per week.³ The more endurance training the participants did in combination with their strength training, the more their strength gains were affected.

Where does the limit lie for you personally? You will probably have to find out for yourself. But as a starting point, the trained individuals in the aforementioned meta-analysis from 2021 trained 2.6 endurance workouts per week. As long as they didn’t train strength and cardio in the same session (>2 hours apart), it didn’t negatively affect their strength.

Thanks for reading, and good luck with your training!