Does Gaining Muscle Make You Run Slower?

The common misconception I always hear from new runners is that they want to avoid building muscle as much as possible because it might slow them down. I know for a fact that it isn’t true but I went ahead and did further research on the topic.

In general, gaining muscle does not necessarily make you run slower. In fact, gaining lean muscle mass is linked to a faster running speed because muscles allow your body to generate more power to your stride.

But that’s not all, the type of strength training that you do to build that muscle also plays a part in whether or not it will slow you down. Ahead, we will discuss in more detail why gaining muscle doesn’t necessarily make you slower and how to build muscles that don’t slow you down. We will also find out where this misconception may have originated. Let’s get started!

Why Gaining Muscle Does Not Necessarily Make You Slower

The common misconception is that by having large muscles, you’re sacrificing your speed because you’re carrying “extra weight”. But in fact, it’s quite the opposite.

The more developed your muscles are, the more efficient it is at generating power. That said, having large and efficient muscles is actually a benefit for faster running.

Another argument is that gaining muscles will destroy your running economy. It’s largely false. In fact, it’s the opposite once again.

According to a study published by the Journal of Sports Medicine, heavy strength training resulted in an 8% improvement in the athlete’s running economy.

Think about how great it can impact your marathon time!

According to the book Running Well, the improvements resulting from strength training are not only because of stronger muscles. It also has something to do with a more efficient neuromuscular pathway or the brain-body connection.

In that same book, the authors explained it through this analogy: Increasing your strength (and therefore building muscle mass) is a lot like adding another cylinder to your car’s engine.

It means that although gaining muscle will add to your weight, it will also make you more powerful and efficient.

And by the way, not having a strength portion in your running program is one of the 10 reasons why you’re not improving as a runner.

But there’s a catch. The kind of strength training you do and the kind of muscle you build may affect the results that we’ve discussed.

In general, you should focus more on strength and muscle endurance exercises rather than hypertrophy and explosiveness if you want muscle mass that is efficient for running.

Muscle building through hypertrophy training builds large muscles FAST but adds little value for the overall strength and it increases the overall oxygen uptake of the muscle (bad for long-distance runners).

On the other hand, explosive strength training gives powerful muscles, but no endurance (good for sprinters but bad for long-distance runners).

The muscles you need for running are one that is strong and one that can endure (I’ll explain how to do this later in this article).

Related post: Does Trail Running Regularly Help Build Muscle?

Where Did The Misconception Come From?

To know more about the topic of discussion, let’s first find out where this misconception often comes from and find compelling arguments as to why they’re often untrue.

Bodybuilders Are Often Slow

Well, there’s some truth to that. If you let a bodybuilder run, more often than not they’re slow. But that’s not because they have a lot of muscles, rather, that’s because their muscles are not trained for efficiency and strength.

Bodybuilders are lifting for aesthetic purposes, so they focus on hypertrophy (muscle growth) rather than strength training which is more beneficial for running.

Hypertrophy training focuses on prolonged muscle contraction to force it to adapt. Whereas strength training focuses on the amount of weight your muscles can carry.

Take a look at football and rugby players. They’re obviously muscular and strong but I doubt they run slow. In fact, some of them can even make a career on track.

Fast Runners Are Almost Always Less Muscular

Perhaps you’ve heard people say that fast runners are less muscular. But that’s not true at all. In fact, most of the fastest runners in the world are very muscular.

Don’t believe me? Take a look at Justin Gatlin, one of the fastest runners in the world.

He’s undoubtedly very muscular, in fact, more muscular than we could probably be and yet he’s one of the faster runners on the planet.

Or perhaps they’re referring to marathon runners who are often skinny. Sure, they are often skinny but that could be due to the fact that they spend less time lifting and more time running. Them finishing a marathon in sub 3 hours has nothing to do with having smaller muscles.

In fact, Nick Bare (on the left) finished a marathon in sub 3 hours despite the fact that he has the physique of a bodybuilder and he weighs somewhere around 200 lbs.

The More Muscle You Have, The Less Flexible You Get

Maybe it’s because of flexibility? Running requires flexibility and building more muscle limits that.


Flexibility has nothing to do with muscle size. In fact, you can be incredibly flexible even if you’re built like a tank. Not surprisingly, you can be extremely tight despite being skinny.

The key is to do flexibility exercises often to maintain the flexibility of your muscles. I recommend spending at least 10 mins every day stretching out different groups of muscles, most especially those that are involved with running (hip flexors, hamstrings, calves).

What People Really Mean By “Muscular People Are Slow Runners”

When people refer to “muscular people”, it often means people involved in competitive bodybuilding, powerlifting, and strongman.

But it doesn’t mean that because they’re muscular, they’re slower. it just means that because they spend less time running, they don’t excel at it.

Being competitive in those sports takes a lot of time and hard work. The training they do for their sport is hard enough that inserting a decent amount of running in their program can risk fatigue.

In exercise physiology, there is something called Specific Adaptation to Imposed Demands (SAID) Principle which asserts that our body adapts to the specific demands we impose on it.

And because those athletes don’t spend enough time running, they often run slow.

How To Build Muscle That Does Not Slow Your Runs

As mentioned earlier, the way that you build your muscles plays a part in whether or not those muscles will slow you down.

In general, you should build muscles by strength training or muscular endurance training to build muscles that don’t slow you down.

But what are those, exactly?

To give you an idea of what they are, I’ll give you the protocols for the types of exercises that you should do as well as examples to build upon.

Strength Training Protocol

For strength building, the lift speed doesn’t matter. Just do the rep not thinking about how fast or slow the lift is. Rest for 2-6 mins in between sets.

Preferably, do compound exercises such as squats and deadlifts.

To maintain strength: 5 sets/week; 30-80% of max; close to failure

To improve strength: 10-15 sets/week; 30-80% of max; close to failure

To apply this specific to running, apply this protocol to compound exercises that target the muscles involved in running

Strength Training Example

Squats 6 sets of 10 reps at 70% of max squats
Lunges 6 sets of 10 Reps

*Rest 2 mins in between sets
*Repeat twice a week

Endurance Training Protocol

3 to 5 sets of 12-100 reps with 30s to 3 mins rest in between sets.

The thing that differentiates this from hypertrophy training is that it has no major eccentric loading. In other words, don’t descend the weight slowly. Just pump the weight and get on with it.

The main idea is to increase the duration you can perform repeated work in the muscles involved in running. Feel free to turn it into a circuit as long as it applies the protocols stated above.

Endurance Training Example

5 Rounds

30 Db lunges
30 Calf raises

30 Db Deadlifts

*30 seconds rest in between movement

Key Takeaways

To get the most out of this discussion, I put everything that we’ve discussed in an easy-to-digest bulleted list.

  • Building muscle through strength training showed 8% improvement in running economy
  • Strength training not only increases physical strength, but also makes the neuromuscular pathway more efficient
  • Build muscle through strength and muscular endurance training instead of explosiveness and hypertrophy training
  • The fastest runners in the world are muscular
  • Some strength athletes are slow runners not because they have big muscles but because they spend less time running – Specificity principle

Nicho Mauricio

Running wasn't always my favorite sport. I was a CrossFit athlete and I loved every bit of it. But since the pandemic began, I was forced to stay away from the gym and train at home instead. Things got boring. That's when I decided to trail run with my friends. I instantly got hooked. So I started training and researching all things running. As a beginner, I want to buy only the best running gear and do only the best practices. This blog is where I share what I've learned in my journey and my experiences as a runner.

Recent Posts