Why Are My Legs Getting Bigger From Running?

I get a lot of complaints from women who have found their legs getting bigger from running, which isn’t the desired results for most of us. So let me explain why this is happening.

Why Are My Legs Getting Bigger From Running? 

Running uses your glutes, quadriceps, hamstring and calves constantly, meaning that your leg muscles are working and this will cause them to develop and get bigger in size.

Any form of exercise that engages your muscles will cause them to grow in size. However, some exercises cause more muscle growth than others.

Running will not build as much muscle as weightlifting, sprinting and high-intensity interval training.

Let’s Talk About Sprinting

We all know that sprinters have very muscular physiques, especially compared to distance runners. Sprinting engages your muscles more and focuses on muscular power. Therefore, sprinting will build more muscle than just steady state running.

Doing a lot of sprint training and plyometric type exercises will develop a more muscular look, but will also help you get lean. If you don’t mind this look, then this is probably a great style of workout for you. If not, it might be best to avoid these style of workouts.

When I was training for a triathlon, I used fast past interval runs (not a full on sprint) to help me develop my cardio fitness quicker. It definitely did this, but what I found was that it actually helped me lean out my legs quicker too.

If you still want to include some cardio interval training, have a read of this blog post which explains how to do the fast past runs.

It Depends On Your Body Type

Your ability to get bulky muscle from running depends on your body type. If you don’t know your body type, click here to find out.

Ectomorphs find it very difficult to gain muscle and will probably never get bulky even if they do lots of weight lifting. Mesomorphs build muscle easily but can also lose muscle and fat quickly too. Some mesomorphs may get bulky legs whereas others might not.

And finally, endomorphs probably already have naturally muscular legs so find it easy to bulk up.

Running does burn a lot of calories and will help you lose weight all over your body. It may help you lose weight in your legs too. But at the end of the day, it will still build muscle in your legs. I have mentioned this before, but if you are a shorter endomorph build, I would avoid running as it can make your legs bigger.

It Also Depends On Your Muscle Fibers 

There are 2 basic types of muscle fibers. Slow twitch fibers are those used for longer endurance style workouts; and fast twitch fibers are those used for short bursts of energy such as sprinting, HIIT and plyometric workouts.

Everyone has different amounts of these fibers, and the amount and type you have will determine whether or not your legs get bigger from running. Someone with lots of fast twitch fibers might have muscular legs, even though they don’t do any type of weight lifting or sprinting. They may even build muscle just from walking.

On the other end of the scale, someone with lots of slow twitch fibers might do lots of sprinting and HIIT and find it difficult to gain muscle.

As you can see, genetics play a huge factor in whether or not your legs will get bigger from running. Some people will run all their life and their legs will stay slim and toned, while others will get bigger legs from running after just a month or so.

You need to adjust your running (and exercise program) to suit your body type and your goals.

Other Factors That Can Cause Your Legs To Get Bigger From Running 

Running on an incline will also use your muscles more (especially your quads and glutes) and will build them. This is due to the pushdown and jumps motion. If you want a leaner look, always try to run on a flat surface.

Another factor that might cause your legs to get bigger from running is your exercise experience. If you haven’t done much exercise and have very little muscle in your legs, then you start running, you are going to build muscle and this is going to be a significant difference.

But if you already exercise and have muscle in your legs, the change caused by running might not appear as significant. What is considered significantly bigger depends on your preference.

Another thing to keep in mind is that your legs can also swell after a run. This is short-term and the swelling will reduce. So try not to judge your progress based on what your legs look like immediately after a run.

Summary

The takeaway points from this are:

• Running builds muscle in your legs, but doesn’t build as much as sprinting, HIIT and weightlifting;
• Your body type and muscle fibers (i.e. genetics) will determine whether your legs will get significantly bigger from running. But “significantly bigger” is determined by YOU and what you think is too big;
• You need to adjust your running (and exercise program) to suit your body type and your goals; and
• Run on a flat surface and at a steady pace to avoid building more muscle from running.

Lean Legs 1 Program 

If running has made your legs bulkier and you would like to lean them out, I should also mention my Lean Legs Program 1 which is designed to help you get lean legs without the bulkiness :)

There are 3 different versions of my program, one for each body type. Each version includes the right type of resistance training for one particular body type so you can be sure you’re going to get the best possible results. 

The resistance training has FULL-LENGTH videos that you can follow from warm up to cool down.

To find out more about my Lean Legs Program, CLICK HERE!

And as always, if you have any questions, please feel free to ask! 

Love Rachael xx