How To Maintain Muscle Mass while Marathon Training

It’s not easy to maintain—let alone build— muscle while training for a marathon.

The reason? Simple. Long distance running—which is the bread and butter of marathon training—has the ability to limit muscle growth.

So what should you do when your goal is to run more—let’s say train for a marathon—but also want to keep your hard-earned gains in the gym?

Here’s the truth. As long as you follow the right training and diet guidelines, you should be able to maintain your muscle strength and/or mass going into marathon training.

In this article, I’ll share with you a few tips on how to ensure you don’t lose muscle during endurance training, including tips on training smart and eating properly.

Building Muscles Vs. Maintaining Muscle    

First things first, let me clear up one thing. Building muscle mass isn’t the same as maintaining muscle mass.

The main difference comes down to many factors, the most important one being how hard you train.

When you’re trying to build muscle, you’re working your muscles as hard as possible. This forces the muscle to adapt in order to not only survive the workout but also to better manage the stress.

As for maintenance, all you have to do is work out your muscles to mild exhaustion—complete failure isn’t the way to go.

Why Keeping—let alone Building—Muscle During Marathon Training Is Hard?

Although there’s some truth to the “running can burn muscle” myth, the facts are a little bit more complicated.

Other variables matter—most importantly, fuel availability for exercise.

The more fuel your body has to pull from “protein,” the more muscle mass you burn off. The exact amount of fuel deriving from protein depends on the accessibility of other fuel sources such as blood sugar, glycogen, and fat.

If you already have a lot of muscle mass—think amateur bodybuilder—getting into cardio for the first time can slim you down. But that doesn’t inherently means that logging the miles does eat muscle break it down as fuel.

To enter that level of a catabolic state, you’ll have to log in a lot of miles, follow a diet severely lacking in protein, and have low recovery.

That’s why if you have low fuel stores in other reserves, you’ll rely on muscle protein for energy—and vice versa.

A good example of this running a marathon. Research that studied 30 recreational runners who run 6.2, 13, or 26.2 miles reported that all runners suffered drastic signs of muscle damage after completing the race. In fact, the longer the distance, the more muscle damage.

Overall, muscle mass provides a small portion of the fuel for any exercise—running is no exception—therefore, you do indeed wind up using up a bit of muscle as fuel while training.

The challenge comes to figuring out how much exactly.

Most research suggests that the number is often around 10 percent of the fuel for endurance training coming from protein, but the facts are much more complicated.

So is it all doom and gloom? Not really!

If you’re worried whether or not running will eat away at your muscles while training for a marathon, the following measures will help you preserve your hard gains while making the most out of your marathon plan.


1. Have Enough Fuel

If you’re serious about training for a marathon without losing muscle mass, you’ll need to pay a lot of attention to your diet. Training for a marathon requires a lot of fuel, especially on long run days.

Although there’s some truth to the myth that running eats away muscle, overall, this won’t happen if you’re consuming the right calories.

When you ensure that your body has plenty of fuel in other reserves to pull from, you can lower the risk of what is pulled from muscle protein.

So what should you do?

Eat plenty. That’s the rule. Choose dense carbs such as vegetables, whole grain, rice, pasta, sweet potatoes, oatmeal, and fruits.

Timing also matters, so pay attention to your food choice before and after every run.

Having plenty of carbs before and after training is key for filling and refilling your glycogen stores. I hate to sound like a broken record, but you’ll all have the fuel necessary for all the calories you will burn as you train.

Muscle continues to break down post-exercise. But you can limit this breakdown by eating foods that increase insulin, consisting mainly of moderate to high glycemic items.

Have a quick dose of carbs after your runs to restore muscle glycogen and maintain mass.

At the very least, add 50g of carb per hour of running on your long runs. Shoot for 100g carbs for a 2-hour long run.

2. Eat your Protein

In addition to consuming plenty of carbs, protein is another essential macronutrient for maintaining your muscle.

How come?

Protein is literally the building blocks of muscle.

The macronutrient supplies the needed amino acids to improve muscle synthesis and create muscle tissue. Not only you can’t build muscle without it; you won’t even be able to maintain it.

Of course, don’t take my word for it.

Research out of the International Society of Sports Nutrition (ISSN) reported that boosting protein intake from the daily suggested 0.8 per kilogram of body weight a day to 1.2 to 2 grams while also reducing calories to about 30 40 percent can maximize fat loss while preserving existing muscle.

Let’s assume that you’re a 160-pound runner who consumes about 60 to 80 grams of protein per day.

You might be able, in theory, to maintain your muscle by simply increasing your protein intake to 100 – 140 grams, even while limiting your total caloric intake by 30 to 40 percent.

Further research also suggests that increasing protein intake may help also help you build d muscle while following a calorie-restricted diet—BUT as long as you’re doing resistance training.

So how do you get enough protein?

Add more whole-food, quality-protein sources to your diet first, such as:

  • Eggs
  • Lean meat
  • Fish
  • Nuts and seeds
  • Beans
  • Cottage cheese
  • Lentils
  • Greek yogurt

What’s more?

Spread out your protein consumption evenly throughout the day, aiming to have some every three to four hours.

In case you’ve trouble meeting your protein needs, supplementing should be your next option.

3. Strength Training

Although your main focus during marathon training is obviously running a marathon, strength training is also beneficial. That’s why as well as devoting time and effort to your road work, you should also be consistent with your strength training.

In fact, lifting weights is an important component in maintaining muscle mass.

Hit the weight room three to four times a week. Just make sure to make your schedule work with your marathon plan. Know your priorities.

Schedule your strength session on days when you’re not doing hard runs—that include interval sessions and long runs—as these types of training place a lot of stress on your body. Remember to space out your weightlifting session with at least one rest day.

Here’s what your workout schedule should look like:

  • Monday – Chest and back + optional easy run
  • Tuesday – Tempo run of 45 to 60 minutes
  • Wednesday – Legs and core + optional easy run
  • Thursday – Interval run
  • Friday – shoulders and arms + optional easy run
  • Saturday – Long Run
  • Sunday – Rest

4. Supplement

I hate to sound like a broken record, but when it comes to building muscle, your workout routine and diet should be the first place to start.

However, supplementing can help improve the impact of your training.

Research has shown that taking supplements, when combined with strength training, can help maximize your results. That means allowing you to more effectively maintain or build muscle mass over time.

One of the best options is what’s known as BCAAs, which is short for branched-chain amino acids—the three essential acids required for protein synthesis.

These include leucine, isoleucine, and valine. The most important one is leucine, as it has been shown to trigger muscle growth on its own.

Again, don’t take my word for it. Research has found these three essential amino acids to be key for recovery in many different ways.

Like any other source of protein, you can get BCCA s through your diet, eating quality-protein foods. But supplements can help take your intake to the next level.

Here’s the full guide to BCCA for runners.


Don’t let the fear of burning muscle keep away from logging the miles.

You should be on the right path as long as you balance muscle burning—or muscle breakdown—or muscle building—or protein synthesis. The rest, as the saying goes, is just details.