Does Running Build or Break Down Muscle?

Running can build lower body muscles, but it largely depends on the intensity and duration of your runs.

In one study, 12 recreationally trained college students completed high intensity interval training (HIIT) involving 4 sets of running at near maximum capacity for 4 minutes followed by 3 minutes of active rest (1).

After 10 weeks of HIIT workouts 3 times per week, they showed close to an 11% increase in the muscle fiber area of their quadriceps (located at the front of the thigh), compared with the control group.

As such, workouts like sprinting may benefit muscle growth.

Aerobic exercise like running is thought to build muscle by inhibiting proteins that interfere with muscle growth and decreasing muscle protein breakdown (MPB) (1, 2, 3).

On the other hand, long-distance running can significantly increase MPB and thus hinder muscle growth.

For example, in a study in 30 male amateur runners who ran 6.2, 13, or 26.1 miles (10, 21, or 42 km), all of the groups experienced significant increases in markers of muscle damage (4).

Levels of these markers rose in tandem with the distance and remained elevated even 3 days afterward.

These results suggest that high intensity, short duration running builds leg muscles, while long distance running causes significant muscle damage, inhibiting muscle growth.

Summary

High intensity, short duration running like sprinting may build muscle, while long distance running may inhibit it.

Muscle building occurs when muscle protein synthesis (MPS) exceeds muscle protein breakdown (MPB) (5).

Protein is an important component of muscle that may be added or removed based on factors like diet and exercise (6).

If you think of protein as individual bricks, MPS is the process of adding bricks to a wall, while MPB is the process of taking them away. If you lay more bricks than you take away, the wall grows larger — but if you take more away than you lay, the wall shrinks.

In other words, to build muscle, your body must make more protein than it removes.

Exercise — primarily weight lifting — is a strong stimulus for MPS. Although exercise also causes MPB, the increase in MPS is greater, leading to net muscle gain (5, 7).

Summary

Your muscles grow when your body synthesizes more protein than it breaks down. Exercise helps promote this process.

High intensity, short duration running workouts like HIIT can help you build lower body muscle, especially in your quadriceps and hamstrings (located on the back of the thigh) (8).

Here are a few sample HITT running workouts for building muscle:

• 6 sets of 20-second sprints at maximum intensity separated by 2 minutes of walking or light jogging
• 5 sets of 30-second sprints at maximum intensity separated by 4 minutes of walking or light jogging
• 4 sets of 45-second sprints at moderate intensity separated by 5 minutes of walking or light jogging
• 4 sets of 30-second hill sprints separated by the time it takes you to walk back down the hill

Try to do these workouts 3–4 times per week.

You can also modify them based on your comfort level and training experience.

For example, if you can’t catch your breath between sets, increase your rest time or decrease your total number of sets. Conversely, you can amp up these routines by decreasing your rest time, increasing your number of sets, or both.

In either case, don’t forget to warm up beforehand and cool down afterward to help prevent injuries and boost recovery.

To prime your body for the workout, do light jogging or jumping jacks for a few minutes, followed by dynamic movements like lunges or air squats (9).

After your workout, walk at a normal pace for 5–10 minutes. An active cooldown helps lower your heart rate and prevents waste products from accumulating in your muscles (9).

Summary

HIIT workouts may help you gain lower body muscles. Warming up and cooling down can prevent injuries and enhance recovery.

Good nutrition is just as important for building muscle as running itself. Without adequate nutrients — especially protein — your body can’t support the muscle building process.

Protein

While exercise stimulates MPS, protein enhances it further, promoting greater muscle gains (10, 11).

This is why many people drink a protein shake on either end of their workouts.

To gain muscle, experts recommend consuming 0.64–0.91 grams of protein per pound (1.4–2 grams per kg) of body weight daily. This equals 96–137 grams of protein for a 150-pound (68.2-kg) person (12, 13).

Good sources of protein include meat, poultry, dairy, fish, eggs, soy, beans, and legumes.

Carbs and fats

Carbs are your body’s preferred energy source, especially for anaerobic exercises like sprinting.

Diets low in carbs and high in fats, such as the ketogenic diet, have been shown to impair anaerobic exercise performance (14).

Fat tends to serve as an energy source during lower intensity exercise like long distance running (15).

To fuel your workouts and ensure sufficient vitamin and mineral intake, aim to get 45–65% of your calories from carbs and 20–35% from fat (16).

Healthy sources of carbs include fruit, whole grains, starchy vegetables, dairy products, and beans, while good fat sources include fatty fish, extra virgin olive oil, whole eggs, seeds, avocado, nuts, and nut butters.

Water

Water helps regulate body temperature and other bodily functions.

Your personal water needs depend on several factors, including age, body size, diet, and activity level. All the same, the National Academy of Medicine generally recommends that men and women get 125 ounces (3.7 liters) and 91 ounces (2.7 liters) per day, respectively (17).

These guidelines are for adults ages 19 and older, and include water from both foods and beverages.

Most people can stay hydrated by eating a healthy diet and drinking water when thirsty, as well as during and after exercise (18).

Summary

A robust diet is integral to gaining muscle with running. Be sure to stay hydrated and eat adequate amounts of protein, carbs, and fats.

Although long distance running may inhibit muscle growth, high intensity, short duration running may promote it.

Doing HIIT several times per week can help you build lower body muscle.

Make sure you follow a balanced diet and stay hydrated to support the muscle building process.