Do your legs feel heavy when running? You may be doing something wrong.

In this guide, we’ll show you how to build stronger legs running according to science. We also tackle questions that new runners often ask, like “Does running build leg muscle?” and “Does running help your legs?”

Let’s jump right in!                                   

Why Do Legs Feel Heavy When Running?

Your legs can feel heavy when running for many different reasons, from insufficient recovery to wearing the wrong running shoes. Let’s take a closer look at these reasons.

Not enough post-run stretches and recovery time

Overtraining is often the most common reason why legs feel heavy when running. Running, strength training, and cross-training all stress the muscles in your legs.

Are you at the beginning of your journey as a runner? Or preparing for a demanding race? You may be pushing yourself too hard.

Add at least 1–2 rest days to your training plan. Runner’s legs need rest.

Also, pay attention if you get heavy legs after a specific workout. If you do, give yourself a rest day after to allow your body to recover.

Low-carbohydrate diet

Carbohydrates are a key source of energy for your body. Your muscles store carbs as glycogen. Glycogen is the fuel that powers you during runs. As a runner, you need to eat more carbs than a less active person.

Following a low-carb diet such as the keto diet may not give your body enough fuel. One side effect of this is heavy legs. Other side effects include reduced capacity for effort, lower sprinting power, and slower recovery.

Eat a meal rich in carbs before a demanding long run and a carb-rich recovery snack after the run. And make sure to refuel on carbs during runs that last longer than an hour.

Don’t forget about electrolytes, which are essential minerals you lose through sweat. If you exercise for more than an hour, choose a drink with sodium and other electrolytes for effective fluid replacement.

Not enough protein

Protein is the building block of muscles. If you don’t eat enough protein, your muscles will not be able to repair themselves.

More than having heavy runner’s legs, you’ll not be able to develop strong and toned legs. Over time, not enough protein can also lead to muscle waste, particularly if you try to lose weight.

Good to know: While the average adult needs 0.8 grams of protein per kilogram, runners need 1.4 to 1.7 grams of protein per kilogram.

Too little or too much strength training and cross-training

When you run over long distances, your body may use some of your muscle mass as fuel. Strength training compensates for this. More than helping you preserve your muscles, it can help you grow them. Cross-training can also support your muscle-building goals.

Another reason to do strength training is to develop more balanced muscle groups and improve your running form. Muscle imbalances, including weak hip abductors, can increase your risk of injury.

But don’t train your muscles every day, or you may end up with the very problem you’re trying to avoid – sore legs.

Two strength-training sessions a week should be enough to help you boost your running economy and maximum sprint speed.

Poor running form

Inexperience and lack of strength training are two major factors leading to poor running form. According to a 2015 study, novice runners become injured more often than experienced recreational runners.

Avoid injuries by working on improving your running form. Run tall, engaging your core. Don’t run with your head looking down but keep your neck in a neutral position. Make sure your arm swing is natural and relaxed, and don’t hunch forward as you run.

Pay attention to your stride too. Run with a comfortable stride, using quick feet.

Iron deficiency

Iron deficiency impairs muscle function. If your body doesn’t get enough iron, it will struggle to transport oxygen to your running muscles. You may then feel fatigued.

What’s more, low iron levels can reduce the amount of oxygen your body can use during exercise, limiting your running capacity.

Iron deficiency can be especially a problem for female runners and runners who are vegans or vegetarians. If you’re in either of these categories, consider eating more iron-rich foods like tofu, lentils, and white beans. You could also take an iron supplement.

Not wearing proper shoes

When changing your running shoes, pay attention to their weight. A heavier pair than the one you’re used to can add a bit of extra weight to your runs. You may feel it especially during long runs.

Weight gain

It may sound funny, but running for weight loss can actually lead to weight gain if you’re not counting calories. As a runner, you may take in more protein to sustain muscle mass. And with it, more calories.

Weight gain can slow you down as a runner and give you heavy legs. So, keep an eye on your weight and adjust your diet accordingly.

Medical conditions like poor circulation

Certain medical conditions can also give you the sensation of heavy legs. They can include peripheral arterial disease and superficial venous insufficiency. These conditions affect blood flow or lead to blood pooling in the legs.

Does Running Tone Your Legs?

Running can tone your legs, provided you’re getting enough calories and protein and don’t overdo it.

But if you run long distances for weight loss, all that effort may reduce your muscle mass, leading to lean rather than toned legs.

Does running strengthen legs then? Running is a form of cardiovascular exercise that builds muscle endurance rather than strength.

Resistance training, such as sprinting and high-intensity interval training (HIIT), may help you build more muscle mass than long-distance running. These forms of training put stress on your muscles, making them grow bigger and stronger.

The key benefits of toned legs, apart from the looks, are a lower risk of injury and better endurance.

Exercises to Tone Your Legs While Running

Some exercises will help you tone your muscles when running better than others. Add them to your training plan for stronger, more defined legs.


Skipping looks fun, but it’s challenging. To get the most out of every skip, bounce high after landing with an explosive movement. Do a few minutes of skipping regularly as part of your training plan.

Squat jumps

Next, how about an exercise that makes your quads stronger while also burning fat? Squat jumps are another form of exercise that can tone your legs.

To do a squat jump, start with feet at shoulder width. Then bend your knees to a full squat.

Engage your upper leg muscles and push your body off the floor with an explosive movement. Lower your body into a squat as you land.

You can start with two sets of ten reps each.

HIIT running

The short bursts of hard running in high-intensity intervals train your muscles to adapt to different levels of movement. This form of training helps you build stronger running legs.

HIIT running combines slow pace running with hard running and can last anywhere from a few minutes to an hour.

Keep in mind that HIIT running is demanding. Don’t do it every day, or you will risk injury.


Sprinting can help you speed up your muscle metabolism and burn fat faster. At the same time, it gives your running workout that oomph that makes your legs stronger.

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During a beginner sprinting exercise, combine sprinting at full speed for 15 seconds with a rest period of 45 seconds. Repeat this six times and then progressively increase repetitions every week.

For an even tougher workout, try hill sprinting.

Bodyweight exercises

Bodyweight exercises like lunges, single-leg squats, or box jumps are easy to do at home. They strengthen your leg muscles, making it easier for you to do other leg toning exercises such as HIIT running or sprinting.

Weight training

Want to build large running muscles? Add weights to your lunges and squats. It will force your muscles to contract at a faster rate and squeeze more effort out of them.

But don’t add too much weight too soon expecting faster results. Add more weight gradually to avoid injury.

What Running Does to Your Body

It may be your legs pounding the pavement, but running has a big impact on your whole body.

A runner’s body is leaner, has stronger bones, and is healthier than that of a person with a sedentary lifestyle.

Let’s take a closer look at what running does to your body.

Build stamina

By stressing your heart and lungs, running boosts your cardiovascular strength and endurance. This is true for both long runs and sprinting.

Running is the go-to exercise for boosting endurance for athletes across sports.

Decreased risk of disease

Running regularly as a form of exercise decreases mortality risk from any cause by around 27%.

At the same time, it reduces the risk of dying from cardiovascular disease, the leading cause of mortality worldwide.

Bone strength

A high-impact activity, running stresses your bones, therefore improving bone density. But to reap this benefit of running, you have to give your body time to recover.

Running too much or too hard will increase your risk of shin splints, stress fractures, and other running injuries.

Lose weight

When you run, you burn more calories than when you walk. Running regularly can help you shed extra pounds and become leaner, provided you keep an eye on your calorie intake.

Improve sleep quality

Trouble falling asleep? Running can improve sleep quality. According to a 2018 study, running at a moderate intensity is better for sleep than running vigorously.

Improved mental health

The benefits of running regularly extend to the mind as well. A 2020 review article found a strong association between running and better mental health and mood.


As a recap, here are the key things to keep in mind.

  • Running intervals and sprints and doing strength training tones your legs better than long-distance running.
  • You have to eat enough calories and protein so that long runs won’t chip away at your leg muscles.
  • You can tone your legs with skipping, squat jumps, bodyweight exercises, and weight training.
  • Add enough rest days, and don’t overtrain to avoid injuries.
  • Avoid heavy legs by watching your weight and iron intake and doing strength work.

Now that you know how to get toned legs when running and avoid heavy legs, what are you waiting for? Start working those legs!

Frequently Asked Questions

What is the difference between runners legs and dancers legs?

Runners’ legs typically exhibit well-defined muscles, enhanced flexibility, and stronger tendons due to the continuous strengthening and toning of these muscles during running. Dancers, on the other hand, tend to have lean and elongated muscles, well-developed core muscles, and increased joint mobility due to the specific demands of dance movements.

Can you get toned legs from running?

Yes, running can help you sculpt toned and defined leg muscles, particularly in the quads, hamstrings, and calves. The repetitive nature of running engages these muscles, promoting muscle growth and definition. However, it’s important to combine running with strength training exercises for optimal leg toning.

Does running make your legs stronger?

Yes, running strengthens the leg muscles, tendons, and bones, improving overall leg strength and power. The repetitive impact forces during running stimulate muscle growth and development, while the continuous use of the leg muscles enhances their strength and endurance.

Does running make you have nice legs?

Running can contribute to having nice-looking legs by toning and strengthening the muscles, enhancing flexibility, and improving overall leg shape. However, it’s essential to maintain proper running form and incorporate strength training exercises to maximize these benefits.

How do runners’ legs differ from non-runners’ legs?

Runners’ legs typically have well-defined muscles, enhanced flexibility, stronger tendons, and slightly higher bone density compared to non-runners. Additionally, runners may exhibit slightly thicker calves, more leg hair, and slightly calloused skin on the feet. These differences are considered normal and reflect the adaptation of the body to the demands of running.


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Written by

Chris Zibutis

Chris Zibutis is the Head Running Coach and founder of Joggo – that one person on earth who loves interval runs.  He holds a degree from Copenhagen Business School and is an avid runner – having participated in numerous marathons and triathlons, Chris brings substantial fitness and running experience to the Joggo team.