Can You Build Muscle While Running? What 43 Studies Say

Short answer: yes.

The long answer covers why so many people think building muscle while running can’t be done, and the handful of rules that make the difference.

Where the fear came from

Before his famous study, a young researcher named Robert Hickson started going on afternoon runs with his new boss, John Holloszy, at Washington University. Hickson was a powerlifter. He kept lifting the same way he always had, but his strength and muscle started slipping.

Holloszy told him that should be the first study he ran in his own lab. It was.

In 1980, Hickson split people into three groups for 10 weeks: strength only, endurance only, and both.

The combined group kept pace with the lifters for about 7 weeks. Then their strength leveled off and started dropping. Their endurance kept improving the whole time.

That result got a name, the interference effect, and it has been scaring lifters off cardio for more than 40 years.

What they did

The strength training was 5 days a week, focused on the legs, with every set done as heavy as possible.

The endurance training was 6 days a week. Three days were bike intervals at maximum aerobic effort. The other three were runs where the instruction was to go as fast as possible, building to 40 minutes a day.

The combined group did all of it. That’s 11 hard sessions a week, with anywhere from 15 minutes to 2 hours between them.

No gym program looks like that. It was a stress test, and the surprising part is that strength held up for 7 weeks of it.

What the modern research says

In 2022, Moritz Schumann’s team at the German Sport University Cologne pooled 43 studies with 1,090 people. They compared lifting alone against lifting plus cardio.

Doing both didn’t compromise muscle growth. It didn’t compromise max strength either. Those results held for trained and untrained people, under and over 40, and people doing more or fewer than 5 concurrent sessions a week.

The one thing that took a hit was explosive strength, the ability to produce force fast. That effect showed up mostly when cardio and lifting were done in the same session. When the two were separated by at least 3 hours, the drop wasn’t significant. If jumping and sprinting matter to you, keep some power training in the week.

Running vs cycling

The same 43-study review found no difference between running and cycling for muscle or max strength. Keep your running shoes.

The running penalty shows up in other research. A 2012 meta-analysis led by Jacob Wilson found that lifting combined with running led to smaller gains in muscle and strength, while lifting combined with cycling didn’t.

In 2022, Tommy Lundberg’s team at Karolinska Institutet looked closer, at the size of individual muscle fibers. They found a small negative effect overall, and in one fiber type it showed up with running but not cycling. The researchers called that evidence preliminary.

The likely reason: every running stride has a braking phase, where your leg muscles lengthen under load. That causes more muscle damage than cycling or rowing, which are mostly pushing. More damage means your legs take longer to be ready for the next lifting session.

So run. Just be smart about when.

4 rules for building muscle while running

1. One session a day beats two stacked. The one real cost in the research, lost explosive strength, showed up mostly when both were crammed into one session. If you have to double up, put at least 3 hours between them and do the one you care about most first.

2. Easy cardio stays easy. Most of your cardio should be at a pace where you can speak in full sentences. Stephen Seiler’s research on elite endurance athletes found roughly 80% of their training is done at low intensity. Easy work is easy to recover from, which leaves you fresh for your lifts. Keep hard cardio to 1 or 2 sessions a week.

3. The day after heavy legs, pick the bike or rower. You still get the cardio, without adding more braking damage to legs that are already recovering. If the rower is new to you, learn the stroke first.

4. Never heavy legs the day before intervals. Both sessions get worse. Give yourself at least 1 day in between. The 3, 4 and 5 day hybrid weeks are laid out so this never happens.

What this doesn’t mean

It doesn’t mean you can do unlimited cardio and keep every gain. Volume still matters. Marathon training and a powerlifting peak don’t mix, and trying to max both at once shortchanges one of them.

It means that if you train 3 to 6 days a week, the fear around building muscle while running is overblown. You can build muscle, get stronger and improve your engine at the same time, as long as the week is laid out properly. For the bigger picture, start with what hybrid training is and what it isn’t.

Want it programmed for you?

OnlineWOD’s new 10-Week Complete Hybrid Program is built for getting stronger while you run 3 times a week. The leg volume is set with the running counted, nothing goes to failure, and week 6 backs off on both sides at once so you recover from both.

It’s 3 full-body lifts and 3 runs a week, one session a day, Sunday off. Every run is set by the talk test, so any of them can move to a bike or rower when your legs need it, and you pick one of three running levels.