Running is so much more than just moving your legs at a fast pace.
When you break down all the muscles that are involved, how each of these individual muscles works, and how they work together in perfect harmony to propel you forward.
It’s an eye-opener, in which one thing becomes clear: Your body is a fascinating, complex machine that’s made for movement.
While you can probably name some of the muscles you use when you run. After you’re done reading this guide, you will have a full understanding of every single muscle you use.
And let me be clear about something: Having this knowledge is more than just “nice to know.” It’s key information for anyone who takes running seriously.
Because it will help you become a better runner.
You see, runners often have specific muscles that are disproportionately strong or weak. This can get in the way of peak performance.
Even worse. It can also cause running injuries, like runner’s knee, Achilles Tendinitis, and Hamstring issues. A problem that can also be caused, or made worse by bad running shoes.
Something l will get into later. But let’s start at the basics.
What are the 3 types of muscle?
Your body has three types of muscles. Each of these muscles is used when you run.
The Cardiac Muscles
Cardiac muscles are the muscles located in the walls of your heart. Your heart pumps blood when they contract.
That’s why they’re in constant motion.
And they don’t fatigue.
When you run, they start contracting faster. And this strengthens them, which is good for your heart.
The Smooth Muscles
Smooth muscles are the muscles located around your hollow organs, like your liver, stomach, and bladder.
Their function is to keep your body functioning properly.
They do this by controlling your blood pressure, breathing, and even changing the size of your iris.
The Skeletal Muscles
Which is about one-third of your entire body mass.
Skeletal muscles make it possible for you to move and change your posture.
While all three of these muscles are used when you run. Your skeletal muscles make the running motion possible.
But which of the 640 Skeletal Muscles are used?
To explain that, let’s first get into the 2 phases of running.
The 2 phases of running
There’s a big difference between walking and running: One of your legs is always on the ground when you walk.
But this is not the case when you run.
When you run, both of your feet will be off the ground at some point. To make this possible, your body has to do a lot more work.
This motion is explained by “The Gait Cycle”: The time it takes for one of your feet to hit the ground 2 times. It consists of 2 phases.
- The Stance Phase: This is when one of your feet is on the ground.
- The Swing Phase: This is when both of your feet are off the ground.
The Stance Phase
The stance phase consists of 4 stages.
1) Initial contact
Initial contact is when your foot is about to land on the ground. Your other foot will be in the swing phase, which I’ll get into.
To allow your foot to land on the ground, your knee flexes, and your feet roll inwards. Your arch also flattens, to absorb the impact of your bodyweight. Your tendons and connective tissues also start storing energy to use in the propulsion phase.
Once you’ve completely landed you’re in midstance: You will have one foot in the air and one on the ground. At this moment, your entire body weight has to be carried by one leg. And this puts pressure on the lower limb of that leg. Your knee and ankle are at a maximum flexion angle.
Propulsion starts when you lift your heels off the ground. A certain amount of force is needed to make this happen. This propulsion comes mostly from your hips.
Your hip, knee, and left ankle all extend to generate force. And push your body forward. Once both your feet are off the ground you’re in the swing phase.
The Swing Phase: Your lower leg lifts off the ground (toe-off). And folds towards your butt.
The swing phase ends just before the foot makes contact again.
What muscles does running work the most?
So, there’s obviously a lot of motion involved in the running gait. But which muscles make all of these motions possible?
The main muscles in your lower body:
- Hip flexors
- Calf muscles
- Feet and toe muscles
1) Glutes: The glutes are the muscles that make up your buttocks. It’s the largest and most powerful muscle group in your entire body. And it consists of three muscles:
- The Gluteus Maximus
- The Medius
- The Minimus
While many people believe most of the power of running comes from their legs, your glutes generate the most power and strength and also provide:
- Provide stability for your hips and legs
- And they make sure your knee stays properly aligned
That’s why strong glutes can be so beneficial, you will be able to generate more power, which can help you run faster, but it can also help you prevent back and knee injuries.
Tips to strengthen your glutes
- Donkey kicks
2) Quadriceps: The quadriceps are the muscles in front of your thighs. They run from your hips to your kneecap. And they consist of 4 muscles:
- The VastusMedialis
- The Intermediate
- The Lateralus,
- The Rectus Femoris
You use your quadriceps the most when you move your legs forward, its functions are to:
- Extend and bend your knees
- Lift your knees upwards
- And to stabilize your knees
3) Hamstrings: The hamstrings are the muscles in the back of your thighs. They consist of 3 muscles:
- The Biceps Femoris
- The Semitendinosus
- And The Semimembranosus
Your hamstrings counterbalance what your quads do. While your quads push you forward, your hamstrings pull your body back over your legs. Its main function is to:
- Extend your hips
- Flex and bend your knees
Runners often have weak hamstrings compared to their quadriceps and this causes a problem: You won’t be able to generate as much power from your knees and hips.
Because they act as a counterbalance, you will be more injury-prone.
That’s why training your hamstrings can pay high dividends.
Tips to strengthen your hamstrings
- Romanian deadlifts
- Glute-Hamstring Raises
4) Hip flexors: The hip flexors are the muscles on the front of your hip. They connect your spine to the Femur. This is the only bone located in your thigh. And the strongest bone in your entire body.
You hip flexor consists of 5 muscle:
- The Iliacus and Psoas: The Iliopsoas
- The Rectus Femoris
- Pectineus Muscle
- Sartorius Muscle
- And the adductors
Its main functions are to:
- Bring your knee towards your chest and bend at the waist
- Provide core stability
- Connect your back and hips
Unfortunately, hip flexors can easily be strained. You can usually immediately tell when you feel a pain in the front of your hip.
That’s why stretching is so crucial.
You can also strengthen them with bodyweight exercises.
Tips to strengthen your hip flexors
- Skating squats
- Crescent lunge knee-up
5) Calf muscles: The calf muscles are located in the back portion of your lower leg. The muscles in your calves are:
- The gastrocnemius (the larger calf muscle)
- And the soleus (the smaller calf muscle underneath the gastrocnemius)
Your calves play a big part in helping you accelerate in speed. But also in helping you slow down. Here are its functions:
- Plantar flexion: The movement in which your foot flexes downwards towards the sole
- Curling your toes
- Bending your knees
- Returning blood to your heart
Your calves muscles are under a lot of pressure when you run. That’s why they’re strained quite easily and that’s also why they’re one of the main causes of Achilles tendonitis. One of the most common running injuries.
You can prevent it by always stretching before you run and by strengthening your calves.
Tips to strengthen your calf muscles:
- Weight-Bearing Lunge Test
- The Double-Leg Calf Raise
- Seated Calf Raise
However, the right running shoes can also make a world of difference by improving your posture. Symptoms of bad running shoes include:
- Toenail loss or bruising
- Heel pain
- Uneven wear
Looking for some good options? See the best running shoes that help prevent Achilles Tendonitis.
6) Your feet muscles: And finally, you also use the following muscles in your feet:
- The Flexor Hallucis Longus
- The Flexor Hallucis Brevis
- The Posterior Tibialis
- The Flexor Digitorum Longus, flexor
- The Peroneus Brevis
- And the Peroneus Longus.
These muscles are crucial to propel you forward. But they have the crucial functions of:
- Absorbing the shock of your body weight landing on the ground
- And stabilizing your sides
Wearing the wrong sized shoes can hinder these functions and therefore be a major risk factor for running injuries.
You can tell if your shoes are the right size by doing a finger test: Stick your finger in between the heel of your foot and the heel of your shoe.
Does your finger have any space?
If it does, you should go down a size. If there is not enough space, then the shoe is too small.
However, some people have a harder time finding the right sized shoes because their feet are shaped differently.
If you have wide toes and a narrow heel read the article on the best shoes.
The upper body muscles used when running
But you don’t only use muscles in the lower part of your body when you run, you also use upper body muscles in:
1) Shoulders: The muscles in your shoulders are the main upper body muscles that get worked:
- The Anterior Deltoid
- The Posterior Deltoid
They allow you to swing your hand forward and backward:
2) Back: One muscle in your back is used:
- The Latissimus Dorsi Muscle.
It’s the largest muscle in your back. And it’s responsible for the extension, adduction, flexion, and the rotation of your shoulder joint.
3) Core: And finally, all of your core muscles are also used:
- The Pectoralis Major
- The External Oblique
- The Internal Oblique
- The Rectus Abdominis
- The Transverse Abdominis
All of these muscles work together to:
- Spare your spine from excessive load
- Keep your torso upright
- Stabilize the hip and shoulders
- Transfer force from the lower body to the upper body
Running doesn’t work these muscles as much as your lower body muscles and that’s why running is not an effective way to train your upper body.
What does running do for your body shape?
You now know all the major muscles that are used when run. This information can also give you an idea of how running changes your body.
But let’s get a bit deeper and learn how running changes your body shape.
1. Become leaner by losing weight and body fat
Running is one of the best ways to lose weight and body fat. Why? It burns more calories than any other type of steady-state cardio.
It’s also way more effective at burning calories per session than weightlifting although lifting weight allows the body to burn more calories in the long term according to Medical News Today.
2. Your abs can become more visible
You might think ab-exercises are the best way to get a six-pack. But here’s the thing, you already have a six-pack. It’s just hidden underneath your body fat.
You need to have a low enough body fat percentage for your abs to show. And that’s something running can help you achieve.
However, it doesn’t strengthen your core as much as some people claim, bodyweight exercises are better for that purpose.
So, if you want visible, rock-hard abs, combine running with ab-exercises.
3. Will shape and tone the butt
A lot of the force from running comes from your glutes: Your buttocks muscles. And that’s a great thing for the shape of your butt.
It builds the muscles in your buttocks, which accentuates its natural shape.
And no: It won’t make your butt flat.
4. Build strong thighs and calves
Ever watched a running competition and looked at the contestant’s body? There’s usually one thing that immediately stands out: Strong thighs and calves muscles.
Now, these are high-level athletes and you won’t achieve that same look unless you train just as much. You can expect your thighs and calves to get significantly more toned.
5. You won’t bulk up a lot
And finally, you won’t bulk up a lot from running, or in other words, the size of your muscles won’t increase that much.
Here’s why: Running mostly helps you build muscular endurance: The ability to sustain repeated contractions over an extended period.
It doesn’t build a lot of muscular strength: The amount of force your muscle can produce in a single effort.
And that’s why less “hypertrophy” happens: The increase in the size of your muscle cells.
While you can expect to build some muscle in your lower body. Especially when you start running.
There’s a limit to how much size you can put on from running.
Sprinting, however, can build more muscular strength.
So, to recap:
- Leaner body by losing weight and body fat
- Can make your abs more visible
- Will shape and tone the butt
- Build stronger thighs and calves
- You won’t bulk up a lot
Your major muscle groups are all used when you run: Cardiac, Smooth & Skeletal. But your skeletal muscles make the motion possible.
The skeletal muscles in your lower body: The quadriceps, hamstrings, glutes, hip flexors, calves, and feet do the most work. The muscles in your upper body: The shoulders, back, and core play a secondary role.
A total of 200 muscles are used when you take a step.
You can prevent these muscles from getting injured by strengthening your glutes, hamstrings, hip flexors, and your calf muscles. But also by wearing running shoes that are the right size. And that improve your posture.
Founder of EWS. Research writer and test performance hacker, avid intermittent faster, and weight loss specialist. Improve your health and torch fat by downloading the 31 Day Fasting Method.