What Muscles Does Running Work? The Surprising Answer You Need To Know!

Muscles are an essential framework for your body. It supports the skeletal system in your locomotion. In rigid activities like running, specific muscles are heavily working and grinding.

Running is one the basic regimen for fitness. It is suitable for beginners and even greater for those who have been maintaining their shapes already.


legs running

It is a good cardio exercise and a recommended workout for strength-training. Therefore, understanding the mechanism of running is essential to maximize its benefits.

Knowing what muscles does running work is beneficial to some aspects. First, it will elucidate you the different types of leg muscles are involved and working together in this activity.

Second, by having a clear grasp of the science of running, you can develop these muscles and further improve your balance and form.

"Slow" And "Fast" Muscles

Many athletes, specifically runners, will tell you that there are specific leg muscles that are working for different kinds of runs.

To elaborate more, a particular kind of run targets specific leg muscle groups than the other. And about that, the type of muscles you have is a big determinant to what kind of running you are going to excel, big time!

For this part, we will tell you about the two general specifications of muscles: the fast-twitch muscle fibers and the slow-twitch muscle fibers. In the fitness world, we call these the Type I (slow-twitch) and Type II (fast-twitch) muscles.

Individuals that have slow-twitch muscles have more durability to long-distance activities such as distance runs. Reversely, those that have fast-twitch muscles are easily fatigued, but they are good at instant, explosive kinetics such as sprint.

Have you assessed your built yet if it is fast-twitch or slow-twitch? Later, we will give you some guide on how to determine your muscles type.

Additionally, fast-twitch muscles have two categories: the moderate-fast-twitch muscles or the TypeIIA and the fast-twitch or the Type IIB or Type IIX (Whatever you prefer to call them).

Moderate-fast-twitch muscles are more flexible and faster to contract compared to the fast-twitch muscles. Type IIA muscles are also thicker. On the other hand, the Type IIB muscles are considered to have the lowest endurance, but indeed, the most powerful.

The science of how these twitchy muscles work is quite simple. Fast-twitch muscle fibers rarely utilize oxygen. In the instance of athletes, they can even not breath for a period, especially when sprinting.

The opposite works for slow-twitch muscle fibers. They use oxygen that's why they can endure and last more.

Muscle Fiber Test !

muscle fiber test

So how can you assess if you are either slow-twitch dominant or fast-twitch dominant? Doing the muscle fiber test can help you on this matter. As of now, this is the only verified test to determine the type of muscles that you have.

We suggest that you should do the muscle fiber test in the gym, because what you are required to undergo are big exercises like bench press and load squats.

In any of these exercises, you have to load the bar to the 80% of your maximum single repetition. For example, if your one-rep is 100 lbs, then set the weight to 60.

After you have set the loads, do as many repetitions as you can until you get tired out or too exhausted to continue anymore.

Here are the classifications

    • Seven repetitions or less - you are fast-twitch dominant
    • Seven to nine repetitions - your muscles are balanced; you are akin to either fast-twitch or slow-twitch type
    • Nine or more - you are slow-twitch dominant

Now, we know that you are wondering if there is a way that you can switch up from being fast-twitch dominant to slow-twitch and vice-versa. We cannot guarantee you that it is possible because there are no studies or methods yet that can modify your muscle fiber type.

Remember, what we are up against here is your genetic makeup. The only thing that we can advise you is to focus on your muscle fiber type and develop it for your advantage.

If you are a slow-twitch type, give more time on engaging in your strength and endurance exercises. Do more repetitions as you can and try to outlast them per weekly or monthly basis. We also recommend that you should use shorter rest periods. For example, 30 seconds.

And oh, let's bust the myth that slow-twitch regimens can make your body skinny. Have you seen those athletes who run for an hour or two a day? Did they get skinny? No.

For a fast-twitch type, power and speed exercises should be included in your workout. For this, heavier lifting regimens like jump squats, power cleans, and push presses are necessary. Complement them with fast training exercises such a kettlebell swings and medicine ball slams.

Running Routines And Muscle Groups

what muscles do you use when running

At this point, what we can suggest you is to practice what kind of run you want to excel. But even with that, it is also necessary that you have to integrate different running styles into your current routine.

As we have mentioned, all leg muscles are working when you are running, but running styles can make one muscle group work more than the other. These actions are the reason why daily practice is necessary to keep every aspect in check.

Here are the types of run and the particular muscles that are involved in them. These will answer the question what muscles do you use when running.

    • For sprints, you are using your calves, hamstrings, and quads
    • For short distances run (3km to 5km), you are using your hip flexors and quads.
    • For medium distances (5km to 10km), you are using your quads and hamstrings.
    • For long distances run (10km or more), you are virtually using everything that your leg muscles has
    • For hill workouts, you utilize your calves, glutes, and hamstrings.

Now, Let Us Break Down What Each Of These Muscles Does !

#1 Hamstrings

what muscles do you use when running

Via Hammernutrition.com

what muscles do you use when running

Via Bodybuilding.com

    • These muscles aids you in propelling your body forward as you run. Hamstrings are assisting in pulling the leg back behind you as you are continuously thrusting.


    • Your quads are also involved in propelling your body forward. But it is mainly responsible for keeping the leg straight so that it can touch the ground


    • This muscle group aids the hamstrings and hips flexor in pulling your leg back behind as you are propelling forward. The primary function of glutes is to give power and stability to your hips and legs.


    • They help you in running by acting as shock absorbers. They also help your body in springing forward.

And for running, never forget that you need a good core (abs) and biceps! Your abs can keep your posture and support. Your biceps will help you have a structured arm and leg swings. Also, keep a good diet!


Understanding the science of your exercise is essential to maximize the benefits that you can get from them.

In running, knowing the muscles involved are necessary so that you can keep track on the proper training that you are should suppose to do. Aside from that, you can easily assess what kind of run fits for you!

Do you have any comments, questions, or suggestions? Tell us! We love to hear from you! Kindly share this article too! Sharing is sexy!

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