While it is common to hear about the potential weight loss benefits of running, it less common to hear about muscle growth.
However, there are a lot of runners who would like to know, does running build muscle? And if so, what muscles does running build?
In this article, we will answer the question, “Does running build leg muscle?” and will provide tips for how to build muscle by running.
We will cover:
- How Exercise Builds Muscle
- Does Running Build Muscle?
- How to Build Muscle By Running
Let’s get started!
How Exercise Builds Muscle
Before we delve specifically into whether running can build muscle, it is helpful to understand the process of muscle growth.
Exercising to increase the size of your muscles, termed hypertrophy training, is a two-step process.
Your workouts create the stimulus that ultimately triggers the muscle-building process known as myofibrillar protein synthesis or muscle protein synthesis for short.
When you perform exercise that overloads your muscles, you create microscopic structural damage to the muscle fibers in the form of tiny little tears along the length of the muscle fiber.
This microscopic damage to the muscle fibers occurs because whatever type of load you are using or force you are requiring your muscles to generate in order to contract and produce movement during your workout exceeds the current functional strength capacity of the tissue.
It sounds counterintuitive that you would want to damage your muscle fibers if you’re trying to become a stronger athlete and build muscle mass, but the little tears in your muscle fibers are what actually trigger your muscles to adapt to your workouts by becoming stronger and thicker, thus increasing muscle size and functional ability.
Without inflicting any type of structural damage to your muscle fibers, there is little to no stimulus to begin the muscle-reparative process, which is ultimately required for muscle growth.
After your workout is over, muscle protein synthesis begins to take place, provided your body has the resources it needs to carry out this process.
In order to repair the structural damage in your muscle fibers, your body needs amino acids, which come from the proteins that you consume through your diet, as well as energy, which comes in the form of calories that you have taken in.
This is the primary reason why it is critical to stay on top of your post-run refueling strategy, aiming to consume at least 20-30 grams of protein and about 300 calories within the first 30 minutes after finishing your workout.
Your body can start breaking down the protein into its constituent amino acids, shuttling these building blocks to the muscles worked by running, and then assembling new reparative proteins to reinforce the areas of structural damage in your muscle fibers.
As these new proteins are manufactured, they are inserted into the weakened areas of your muscles, reinforcing, strengthening, and thickening your muscle fibers. This results in stronger and larger muscles after the recovery process is complete.
Does Running Build Muscle?
So, now onto the important question at hand: does running build leg muscle?
Running has the potential to build leg muscle in the glutes, hamstrings, quads, calves, and hip flexors, which are the primary muscles used during running.
With that said, whether or not running builds muscle depends on your overall diet, your post-run nutrition strategy, and the type of workouts that you are doing.
If you do not have these three factors dialed in to support hypertrophy, running will not increase muscle mass and may actually cause you to lose muscle mass.
Your overall diet, mainly in terms of your caloric intake as well as your intake of protein specifically, will have an enormous effect on whether you are able to build muscle while running.
Running burns calories because your heart and skeletal muscles need energy to contract as you run.
In accordance with the Third Law of Thermodynamics from physics, energy cannot be created or destroyed, meaning that it can only be transformed from one form to another.
What this means in terms of your running is that the energy (calories) you need to run must come from stored fuel, which can be oxidized during exercise to create ATP (cellular energy) for your muscles.
The majority of the energy your muscles will need during exercise comes from burning stored carbohydrates (glycogen) and fat (stored triglycerides in fat cells), with a lesser contribution from protein.
However, the relative percentages of overall energy that each of these three macronutrients provides during your run depend on the intensity of the workout, the duration of the run, and your overall diet and energy balance.
Typically, at lower intensities like slow runs and recovery runs, a higher percentage of the calories your body needs come from burning stored fat.
As the intensity of your workout increases and you run faster, the substrate ratio shifts such that most of the energy comes from stored glycogen instead.
However, although protein typically contributes about 10% of the energy needed when running at moderate to high intensities, this relative percentage increases significantly if you are in a caloric deficit or perform a long, vigorous workout and run out of ample glycogen.
Because protein is only stored in the body in the form of muscle tissue, running initially burns muscle rather than builds muscle, especially if you are in a caloric deficit or following a low-carb diet and doing glycogen-depleted runs.
Moreover, studies suggest that muscle protein breakdown escalates rapidly after exercise is over.
With that said, if you’re in a well-fed state, eating a well-rounded diet, not in a significant energy deficit, and running less than 90 minutes or so, the amount of protein—and thus muscle tissue—burned on a run is minimal.
For example, if you are meeting your daily energy needs and running for 45 minutes and burn 600 calories, you might burn about 60-65 calories from protein.
On the other hand, if you are dieting and in a caloric deficit, do a faster run or do a vigorous, long run; you might burn quite a bit of protein.
As long as you refuel immediately after your run with protein, carbohydrates, and enough calories, you shouldn’t experience a significant loss in muscle mass from any given workout, but if you habitually undereat and refuel poorly, muscle loss from running is certainly possible.
How to Build Muscle By Running
Here are some tips for building muscle while running:
As mentioned, the muscle protein synthesis process requires protein and energy in the form of calories.
#1: Eat Enough Protein
According to The International Society of Sports Nutrition (ISSN) position on protein needs for athletes, athletes looking to build muscle should consume at least 1.4–2.0 grams of protein per kilogram of body weight per day, and protein needs to be spread out throughout the day, in doses of 20-40 grams of 0.25 g/kg of body weight per meal and snack.
#2: Eat Enough Calories
In terms of the caloric needs to support muscle building from running, most health and fitness experts say that you need to be in a slight caloric surplus (consuming 10-20% more calories per day than you’re burning) to effectively support significant hypertrophy or muscle growth.
#3: Focus on Your Post-Workout Nutrition Strategy
Refueling with a nutritious post-run snack or meal as soon as possible after your workout will help your body begin muscle protein synthesis so that you can build muscle from running.
Most sports dietitians and research on protein fueling for athletes suggest that the ideal post-workout nutrition involves ingesting a 3:1 or 4:1 ratio of carbohydrates to protein, with at least 20-30 grams of protein consumed in this post-run snack within 30 minutes after exercise.
The protein yields the amino acids necessary to manufacture new proteins to repair, rebuild, and strengthen muscle fibers; carbohydrates help replenish depleted muscle and liver glycogen stores, and adequate calories are required to support the muscle protein synthesis process.
If you strive for a minimum of 20 grams of protein with a 3:1 ratio of carbohydrates to protein, these guidelines mean that you should eat 60 grams of carbs for a total of 320 calories (protein and carbohydrates each provide 4 kcal/gram).
Since these guidelines constitute the minimum, if you are looking to maximize your ability to build muscle from running, you should increase the protein, carbs, and calories in your post-run snack.
#4: Add Hill Workouts
Hill workouts can build leg muscle in the glutes, hamstrings, and calves.
#5: Do Not Run In a Fasted State
Fasted running will increase the percentage of energy supplied by protein.
#6: Add Strength Training to Your Workout Routine
Hypertrophy can be supported by strength training workouts that involve lifting loads that are 65-85% of your 1RM for three sets of 8-12 reps.
It’s certainly possible to build muscle by running but focus on your nutrition to maximize your gains.
To get that nutrition dialed in to be able to build muscle while still running, check out our 7-day meal plan for muscle gain.