Can You Build Muscle When You Run? The Answer Is More Complicated Than You Might Think.

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CARDIO AND STRENGTH TRAINING workouts are typically thought to be useful for distinct purposes: Running is for moving your body, burning calories, and training your heart, and hitting the iron is for building strength and muscle. That’s the supposed order of the world. That said, you might see a jacked guy on the track or trail and wonder about his routine. Can you build muscle by simply running?

The short answer is no—at least not in the same way that strength training can. You shouldn’t expect to experience the same level of muscle growth by going on runs that you would by lifting weights. But there are some circumstances where you might see some muscle growth from running.

“If you’re untrained and you do some running, you will see additional lean body mass,” says Mike Nelson, Ph.D., C.S.C.S., an associate professor at the Carrick Institute. “But if you are more trained, running probably isn’t going to be a big enough stimulus to directly increase lean body mass.”

If you’re already trained, the type of running workout you do will also make a difference on the potential muscle-building benefits. “Someone that has a good base of endurance running would not receive hypertrophy stimulus from a longer duration, lower intensity run,” says Dr. Pat Davidson, an exercise physiologist. “They would probably need the higher intensity, shorter duration run. It’s very population specific.”

As Davidson notes, there certain types of running workouts can help increase the size of your quads, and sub in for some hard-to-find gym equipment (depending on your level of experience and physiology). And pounding the pavement may also improve the results you see from your lifts in the gym. Nelson, Davidson, and Percell Dugger, a running coach and founder of Fit for Us, explain how.

How Running Does (and Doesn’t) Build Muscle

There aren’t a ton of studies on the topic of running and muscular hypertrophy, but the few that exist back Nelson up: In a small 2017 study of untrained 19- and 20-year olds, running high intensity intervals three days per week for 10 weeks increased the size of the subjects’ quadriceps by 10 percent. A much older study that tested older, untrained men saw guys in their 60s and 70s increase their quad size by nine percent after six months of steady state running.

The reason these types of muscle gains don’t continue, Nelson says, is related to the amount of time your muscles are under tension. When you’re strength training, the muscles you train are under stress for the entirety of a repetition.

“Running creates more of an impulse load or impact load, which is going to be really, really brief,” Nelson says. Even though the impact can be huge—four to six times your body weight—the impacts don’t add up to as much time under tension as you’d get from a few sets of resistance training exercises, he says.

Who you are and the type of running you do is also important in terms of how much muscle growth you might be able to yield from your efforts—but again, you should have very specific expectations for how far those gains will go.

“High intensity sprinting can result in muscle hypertrophy,” Davidson says. “Is it the most direct path towards substantial muscle hypertrophy? No.”

“You can get to the same destination by the highway or the byways, and there are byways that can take you to muscle building, but lifting weights with progressive overload on sets that get close to failure, clearly, is the highway,” Davidson continues. “The best approach is something that brings you close to failure. Is that a good approach during sprints? Probably not. So it’s not checking the perfect series of boxes, but I think that it probably checks enough boxes for the signal for anabolism to come through.”

In other words, you can build muscle using specific types of running workouts—but if your main training objective is to add more mass, there are more direct and effective paths to accomplish your goals.

Exactly what your goals are become important when you’re considering what you’re hoping to get out of your run training (and any other workout, too). Just because the brief impacts of running aren’t building significant muscle size in other parts of the body doesn’t mean they aren’t making the legs stronger, according to Dugger.

“To think that [world champion marathoner] Eliud Kipchoge isn’t strong, you’d have to have a very limited understanding of what strength is and what it means,” he says. A belief that running will make you less strong, he says, holds many men back from doing cardio training that could benefit their health and well-being—and their strength training.

Just because running doesn’t make you bigger, Dugger says, doesn’t mean it will automatically make you smaller. In fact, it could help your resistance training work better.

How Running Can Improve Muscle Building (and Reveal Your Muscle)

While running doesn’t build a ton of muscle mass on its own, it may help with muscle growth in the long term, Nelson says—so long as you’re pairing it with resistance training.

There are two reasons this may be the case: First, running increases your aerobic capacity, or your ability to recover quickly from a bout of work. “If you look at someone who has a horrible VO2 Max or aerobic capacity, they’re probably going to be limited by just how much volume they can do in the gym because they can’t recover,” he says. Running builds this capacity, so you’ll have more gas in the tank to do more sets, more reps, and more volume when you’re lifting. And all that adds up to more muscle.

The second reason is also related to endurance. When you run, “you may have more local capillarization,” Nelson says. When you do aerobic training, your body makes more capillaries in your muscles. This increase in small blood vessels increases the blood flow to your muscles.

Why that matters: “Let’s say you’re doing a set of leg extensions, for example. At some point, you’re not getting enough blood flow there, so you’re not getting enough oxygen to the muscle. Therefore, it becomes painful and you have to stop,” he says. “In theory, if you can get more blood flow to that muscle, you can do more work and build more muscle.”

Don’t be so concerned that supplementing your strength training with running will cut into your potential for gains, as is typically thought to be the case. A 2021 systematic review of 43 studies published in Sports Medicine concluded that “concurrent aerobic and strength training does not interfere with the development of maximal strength and muscle hypertrophy compared with strength training alone.”

Basically, this means that you can still make strength and muscle gains while you train for endurance, too. And if you’re primarily an endurance running-focused athlete, including the types of more intense running protocols could be especially helpful, according to Davidson:

“If we’re talking about an endurance runner, their strength training could very well be hills, stadium stairs, sprints,” he says. “That’s probably more specific to running for them, for the muscles they want for hypertrophy, without hypertrophy in other areas that might be just excess weight that’s not beneficial and potentially harmful.”

What Kind of Running Can Build Muscle

Certain types of running can have an effect and even aid parts of your strength training routine. One of those ways? Taking to the hills.

“For someone who has been doing sled pushes, go find a steep hill, and run up it as fast as you can,” Dugger says. “I promise you: Your heart and your mind will feel like you’re carrying a 500-pound sled or wearing a 50-pound vest.”

For guys who don’t have access to that equipment, or who want to get outside, this kind of hill work can offer the same high-intensity, muscle-building finishers as expensive sleds, he says. Nelson agrees. Compared to sprinting on flat land, which can lead guys to suffer injuries when they’re not used to super speeds, hill work provides similar, intense work while making trainees go slower, he says.

One caveat, he says: Running downhill is a completely different beast. This type of work is focused on different muscles than when you ascend. Your quads are working on the way up, while your lower legs (think calf and shin muscles) will bear more of the burden on the way down. So if you want to swap in hill sprints, choose a steep hill to run up a few times each week. But be smart: Walk back down the hill before sprinting again.

Another potential running-adjacent approach to building more muscle: The drills that you probably use to warm up ahead of an intense workout. “There’s some adjunct stuff that I think almost all runners would be familiar with, like bounding and hops, even squat jumps and things like that, which could also have more of a muscle stimulating effect,” says Davidson.

Overall, just remember that your goals will dictate where you should spend your time and energy—and what you expect out of your workouts. If building muscle is your ultimate aim, you’ll be better off focusing the bulk of your attention on strength training with a progressive overload program. Running can yield some gains, but you’ll have to push hard.

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