Does Running Build Muscle?

For many people, their exercise routine has a clear separation between strength training and cardio exercise. However, the two aren't mutually exclusive.

So, does running build muscle? Newsweek spoke to experts in order to find out how regular cardio exercise can also contribute to muscle gain.

Andy Griffiths, a personal trainer and certified nutritionist, told Newsweek: "Running can build muscle, specifically the quads, hip flexors, glutes, hamstrings, calves and even the muscles in your core.

"Though, that's not to say that signing up for a half marathon is the first step towards being a seven-time Mr Olympia, starring in The Terminator franchise and becoming governor of California. When I say running can build muscle, it depends on the person, the intensity of the run and the duration."

How Does Running Build Muscle?

Muscle building occurs when stress is applied to a muscle while it contracts. This breaks down tissues within your muscles, which then rebuild and progressively grow back stronger than before.

"Someone who is brand new to training, with muscle mass far from their genetic potential, might well see some muscle gain from throwing on their old running shoes," Griffiths stated.

This physical stress imposed on muscles takes place whenever you exert more work on your body or particular muscle group than normal - whether that's lifting weights, or running.

Andy Reay, the Head of Strength and Conditioning at Pure Sports Medicine, explained how the process works.

"Your body and muscles will adapt to any stimulus that is placed upon it, which in this case is running. If the run is challenging enough, your body will try to adapt and improve in order to complete the task more efficiently next time.

"If the muscles in the legs are not big or strong enough, this could be the adaptation that is needed for you to improve. This will, however, depend on getting adequate rest and nutrition, as your body needs both of these things to rebuild," Reay told Newsweek.

Running allows for muscle growth by inhibiting proteins that obstruct muscle growth, therefore hindering a process known as muscle protein breakdown.

The results of muscle growth from running will vary per individual, depending on the size of the stimulus each person requires.

Reay added: "If you are just starting out, you should start to adapt from much shorter or slower runs. If this is the case, just try and increase the distance and/or speed with every run to challenge your body. If you are a high-level athlete the stimulus would need to be much larger, and the training much harder to elicit any changes."

Which Running Exercises Build Muscle?

Shorter training methods, such as High intensity interval training (HIIT), have been found to help muscle growth.

A 2017 study performing HIIT found that after 10 weeks of regular training, participants saw a 10.6% increase in the muscle fiber in their quadricep muscles.

"We can appreciate that sprint work and especially resistance training are much more effective ways to build muscle compared to longer, steadier runs exceeding 20 minutes," Griffiths said.

Reay also told Newsweek about how different running speeds and inclines can target different muscle groups.

"Your body will use different muscles more depending on speed and incline. At a jogging pace you will get lots of input from your quads and calves. As you increase your speed you get a gradual increase in work from your glutes and hamstrings.

"You may therefore want to bias some higher speed work if you want to build your glute muscles. At an incline you will get much more work from your quads and calves, so this could be a strategy to build these muscles," he said.

Long-distance running can actually be detrimental to muscle growth, as it has been found to increase muscle protein breakdown.

One study found that the longer the distance of your runs, the higher muscle damage is sustained - therefore inhibiting your body's ability to grow muscle.

Griffiths stressed the importance of proper nutrition to avoid muscle loss that may come as a result of long-distance running.

"Due to the energy demanding nature of long-distance running, you have a fair chance of breaking down muscle as well as fat. To avoid muscle loss during longer runs, it's important to consume a decent amount of protein. Aim for at least 1.6 grams of protein per kg of your body weight each day, as well as consuming an adequate amount of calories," he said.