How to Run a Marathon Without Losing Muscle

Running a marathon is no small feat.

It requires an extraordinary amount of muscular endurance, aerobic fitness, time, effort and grit. This is why so many people looking for a way to challenge themselves both mentally and physically set their eyes on the 26.2 mile race. 

However, for those of you like myself who have spent an incredible amount of time in the gym trying to cultivate mass in the form of muscle tissue, the idea of spending multiple hours a week running can be scary and off-putting. It's no secret that long duration aerobic exercise is not the best way to build muscle - or even maintain muscle. In fact, in many situations it can often have the opposite effect. Muscle is not easy to build, and if you have spent any significant amount of time trying to build muscle, you can attest to that. So naturally, the last thing you would want to do is sacrifice any of that hard-earned muscle. 

However, I am here to tell you that you can run a marathon without losing muscle. I know because I did it. In 2019 I ran the Bataan Memorial Death March in just over 4 hours (a marathon through tough desert terrain meant to honor American and Philippine POWs during WWII - read more about it here) AND I squatted 465 pounds, deadlifted 505 pounds (PR), and bench pressed 315 a couple days before the race.

Safe to say I didn't lose much muscle..

I am going to breakdown step by step how I did it, and how you can cross running a marathon off your bucket list without losing any muscle.

Check out my YouTube video on the race if you haven't already, and then let's dive in.

Three Areas of Concern

In my opinion there are three main aspects of your preparation that need to be spot-on if you are wanting to run a marathon without losing muscle.

Training, Nutrition, and Recovery. 

I know, I know...shocking right?

The key to success however is not what needs to be optimal, it is how you optimize these three different areas. Which is exactly what I am going to tell you how to do.

1. Training

Let's start with the fun part - training. 

First let me go ahead and level with you and say that while you are training for a marathon you are likely not going to be building any muscle. It's just unrealistic. Instead, our focus is going to be on preserving muscle mass rather than building it.

And fortunately for us, muscle is much easier to maintain than it is to build. It takes a much lower volume of training to maintain muscle mass and strength. Some research suggests that as little as 3 sets per week taken to failure could be enough to maintain muscle mass and strength. 

Make no mistake, your strength training volume is going to need to be reduced as you begin to add in the additional running miles. By how much is going to be relative and depends on your training age and your typical volume. However, I would recommend a decrease of somewhere around a 60% decrease in total training volume. 

For example, I went from strength training 6 days a week with around 20 working sets per muscle group each week, down to strength training 4 days a week and around 8-10 working sets per muscle each week. 

I followed an upper/lower split, which I think is a good option if you plan on training 4x per week, but I also think that a full body split 3-4x per week would be a solid approach. 

The actual training doesn't need to change much, you just have to be slightly more mindful of your exercise choices. I would recommend avoiding any movements that cause a ton of muscle soreness (movements with a large eccentric component or new movements), especially for your lower body. As for upper body, you can get away with a little more intensity and your exercise selection doesn't need to be quite as mindful. 

Now that we've got our strength training parameters established, let's discuss the actual marathon training.

Running should be approached in a similar manner as strength training - meaning it should be progressive in nature and there should be a slow increase in total volume and intensity overtime with planned de-load periods where volume and intensity are lower. 

Based on your current fitness and running level you are going to have to determine how far out to start training and where your initial volume and intensity should start. Personally, I gave myself about 10 weeks to prepare. Leading up to that point I was maybe running about 5 miles a week and was doing 1-2 crossfit-ish workouts a week. Looking back, I feel that 10 weeks was an appropriate amount of time for me. If you are in decent shape but just getting started running, I think around 20 weeks of training is a safe bet. 

I needed some outside structure for my running training because I knew I was less likely to cut corners or go out too hot if I had a plan to follow. I decided to loosely â€‹follow Nike's Marathon Training Plan. The plan is 18 weeks long, follows progressive overload, has planned de-loads, and is based around 5 days of running each week. I thought the plan was well designed, however I felt that the volume was a little on the higher side considering the amount of strength training I wanted to continue with.

Which brings up an important point...

​By making this commitment to be jacked and run a marathon, you have to accept the fact that you're probably not going to be amazing at either. It's a compromise. You can be pretty jacked and run a pretty good marathon. However, by doing both you have to accept that you're probably not going to be the best marathon runner you could be, or the most muscular/strong you could be.

Jack of all trades, master of none. Which I think is pretty cool, personally..

Anyways, like I said, I decided to drop the volume on the plan a little bit. While 5x per week might be optimal for someone solely focusing on running, it's likely going to be too much for us with goals in the gym as well. I ended up dropping the running down to 3-4x per week depending on how I was feeling. I did the both of the speed days each week, the long endurance run, and I made the recovery run an optional day. 

Now comes the tricky part; combining the running and strength training.

There is evidence that shows that long distance aerobic exercise can have an interference effect with strength training, however, it has been shown that this can largely be mitigated if the they are performed at different times. On completely different days is the best case scenario, and in separate sessions on the same day with as much time in between is the next best scenario. Considering your legs are the major muscles of concern when it comes to running, you need to make sure that you are doing your best to keep the running sessions and lower body sessions separate.

Here was my weekly training schedule:
Monday: Morning - Upper body, Evening - Speed Work
Tuesday: Lower Body
Wednesday: Speed Work
Thursday: Upper Body
Friday:  Lower Body
Saturday: Long Endurance Run
Sunday: Rest or Moderate Recovery Run

This isn't to say that this is the only way, or that you have to divide up your training this way, but this is what worked well for me.

An example week from the Nike marathon training plan.

2. Nutrition

Your nutrition is arguably going to be the most important piece of the puzzle.

First and foremost, you need to be eating enough calories to support the high demand you are placing on your body. You should be eating to perform. This is not the time to be trying to diet down and get shredded. You'll just end up feeling terrible and putting yourself at a higher risk for injury. I recommend eating at maintenance or even slightly above maintenance. Not sure how many calories you should be eating? Here is an easy way to estimate your calorie needs.

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Once you've got your calories established, you need to dial in your protein intake. Adequate protein intake is going to be essential to make sure you aren't losing muscle and you are recovering properly. I recommend 1g/pound. You could probably get away with a little less than that, and more isn't going to hurt you, but 1g/ pound is simple. I like simple. 

Once your protein is set you can stop there and just track calories and protein, or if you want to get more in depth you can track your carbs and fats as well. For this kind of training I recommend slightly higher carbohydrate intake so you can properly fuel your training. I would set your fats somewhere around 25-30% of your total calories, and fill the rest of your calories up with carbohydrates. Not sure how to do that? Check out our FREE macro guide here. 

Now that you've figured out what you should be eating, now it's time to talk about when you should be eating. For the most part it's going to be largely up to you but I always recommend trying to consume a large portion of your carbohydrates before and after training. However, there is going to be a big difference with marathon training, and that's going to be the need for intra-workout carbohydrates. Early on it's not going to be very important, but as you get closer to race day and your long endurance runs start to get longer, you are going to want some type of intra-workout carbohydrate. This is going to help replace your body's glycogen stores which will help you perform better and prevent the breakdown of other tissues (such as muscle). 

I recommend starting to incorporate intra-workout carbohydrates once your runs start to last longer than 60 minutes. 30-60 grams of carbohydrates every 45 minutes is a good place to start. This can be in the form of a sports drink, energy gels, gummy worms, whatever you want. I used the GU energy gels and they worked well for me. They don't taste all that great, but you get over it. Plus I liked the fact that they had some product options that contained electrolytes and caffeine. I carried them in my running belt or pocket, and would down 2 of them (~50g carbs) every 45 minutes or so on my longer runs. 

3. Recovery

While proper training and nutrition are going to be crucial for adequate recovery, there is one other thing that you are going to need to manage.

Your sleep.

​You should be aiming for 7-9 hours of sleep each night if possible. 4 hours of sleep is nothing to brag about. If you are serious about running a marathon without losing muscle then you need to prioritize your sleep.

Other than that, you are just going to have to listen to your body and manage your training volume appropriately. If you're feeling extremely beat up then take a day off. Remember, outside of training is where the positive adaptations occur. It's not about how much you can do, it's about how much you can recover from. It's hard to give specific recommendations here because it's going to be different from person to person. But if you are feeling exhausted and beat-up for more than a couple days in a row, then thats probably a good sign you need a day off.

Now it's time to get to work.

There you have it. Everything you need to train for, and run, a marathon without losing any muscle. It's not going to be easy, but it can done. 

As always, I'm here to help in anyway that I can. Have questions? Shoot me an email at [email protected] and let's chat.

​-Clayton