Building and Preserving Muscle Mass as a Runner

Scroll this

The topic surrounding building and preserving muscle mass as runner is a hotly debated one. I’m often asked how I’m able to build and preserve muscle mass with the extensive amounts of running that I do. There’s a wide held belief in the fitness community that too much cardio can impede muscle growth and even cause muscle loss. The phrase used commonly in the world of bodybuilding is, cardio kills gains. Another popular question that runs parallel to this saying is: does muscle mass stymie running performance? Or in other words, does our muscle mass make us slower or faster? 

I’ve also been told that my current body composition will make me a slower runner. Some have said that I have too much muscle for a cis woman, and that my body type is not “suited” for endurance sports. While initially I got angry and defensive at these comments, I sat with it a bit, and to my surprise, it actually just peaked my curiosity. I’m sure I’m not the only one who’s been on the receiving end of these sort of comments, so I wanted to further investigate the topic, dispel some myths, and hopefully enlighten myself and others in the process by doing a deep dive into the literature surrounding the subject. Don’t worry, I won’t make this a lit review.

I remember a few years ago, I was out for dinner and conversing with my server (who also happened to have a muscular physique). He noticed we had matching Garmin watches, so naturally we fell down the conversation rabbit hole about running and endurance races. He mentioned his aspirations of running a marathon one day, but felt discouraged because of his build. He said verbatim, “I want to run marathons, but I just don’t have the body type.” That comment really stuck with me…I wondered how many other people think that their body type is a self-imposed limitation—preventing them from signing up for races, dipping their toes in long distance running or even discouraging them from engaging in running at all?

I personally don’t fit the typical superficial “mold” of a long-distance runner, or at least what’s depicted in the media. I have a bigger build, wider shoulders, a stubbier torso, and a larger chest. However, I’ve never let my body type hold me back from signing up for races, training to improve performance or from even adopting a running routine back in 2008. Neither should you. 

In this post, we’ll go through how to gain and preserve muscle mass as a long distance runner, extrapolate on if cardio really does “kill your gains” and lastly, we’ll uncover if muscle mass really does make you a “slower” runner. Let’s dive in:

How to Build Muscle as a Runner

Is it possible to put on muscle and be a runner? Of course it is! If you’re following a strength training regimen and you get your nutrition right, there is no reason you won’t be able to put on lean muscle mass; it just requires some planning and a bit of simple math. I’m terrible at math so if I can do it, you can too. 

1. Energy Balance
The laws of thermodynamics are the basis for gaining and losing weight at a fundamental level. If you’re eating in energy balance (maintenance), then you’re maintaining your existing weight. If you’re eating in a positive energy balance (surplus), you’re going to gain weight and if you’re eating in a negative energy balance (deficit), you’re going to lose weight. It’s that simple (kind of).

The most prevalent misconception being circulated is the proposed “fact” that you simply cannot build muscle while in a caloric deficit, unless you’re new to training or among the genetically gifted. While it is much harder (especially as you become leaner and build more lean body mass), it is possible to build muscle in a deficit…it’s just harder and slower.

If you’re going to regularly mix in some long runs in your training, it’s important to pay attention to how much you’re burning. I use myfitnesspal to “roughly guesstimate” how many calories I burn based on the number of minutes and my average pace. This method isn’t perfect, but nothing is. Let’s go through a step-by-step process on how to do this:

  1. Calculate your maintenance calories – you can roughly guess this from a calorie calculator. Some calculators can either severely overshoot or under represent the amount of calories you need, but it’s a decent starting point. The best way to figure out your maintenance calories is to track everything you put in your body and your weight daily for at least a week without changing anything significantly to your current diet or workout plan. You then take your weekly averages—if you lose weight, you’re eating below maintenance. If you gain weight, you’re eating above maintenance, and if you stay the same weight, well then voila! You’ve found your maintenance calories. This process is a bit complex, but Dr. Eric Helms put together a fabulous video on the subject, so I encourage you to check it out.


Adjust your calories to eat in a surplus – when you figure out your maintenance calories, don’t forget to factor in the calories you burn from your runs since this will increase your caloric needs for the day. To “lean bulk” or in other words, put on muscle without accumulating too much fat, you’ll want to increase your caloric intake by 10-20% of your maintenance calories. Take maintenance calories + calories burned from your run + 10-20% more calories than your maintenance. Confused yet? Have I totally lost you? Let’s slow it down with an example:

I’m 139 lbs and my maintenance calories are ~2,000 per day. I burn roughly 500 calories per day from my 5-mile runs. With this in mind, to figure out my surplus I’m going to take 2,000 x 10-20%:

Calories (2,000) x 10% = 200
Calories (2,000) x 20% = 400

I’m going to want to eat in a surplus of 200-400 calories/day to progressively gain weight (hopefully from muscle). So, my energy intake should be:  maintenance + calories burned from exercise + caloric surplus

I’m going to go on the lower end so I don’t accumulate too much fat in the process. This is what it would look like:

2,000 maintenance + 500 calories burned from my run + 200 extra calories = 2,700 calories per day.

2. Macros
Once you figure out the calorie portion, then it’s onto step two: ensuring you’re hitting your protein targets. Again, this is a complex issue, but if you aim to get in at least 2 grams of protein per kg of body weight, you should be good. The carb and fat splits don’t really matter as much—this is highly individualized so it’s important to experiment and see what works best for you. Some operate better with high fat and others with a higher carb count. Again, the real macro you need to pay attention to in order to build muscle is protein.

3. Progressive Training Plan
The last component to building muscle is of course to include a resistance training plan—applying the principles of progressive overload. As a general rule of thumb, to gain muscle hypertrophy (growth), you want to aim for a rep range of 8-12 until muscle failure, but there are exceptions. I wrote about this more extensively in another post which you can refer to for a deep dive. In short, progressive overload is lifting more weight, taking less rest, and/or doing more reps/training volume on a week-over-week basis to achieve muscle growth. 

4. Rest
Your muscles don’t actually grow in the gym. It’s during the period of rest when your body is repairing the torn muscle fibers. The process is called muscular adaptation. So all of you checking how “swole” you are in the mirror after your workout, you can pump the breaks a bit.

Rest is a vital ingredient in the mix. While I don’t necessarily follow this advice (I’ve been running every day for almost 4 years now), I do give my muscles a break from strength training and the type of recovery I do is called active recovery. For many of my runs (especially the days following either a long run, hard high intensity interval training or tempo/threshold run), I bring down my pace and intensity significantly. In fact, active recovery can be a great way to reduce lactic acid build up, reduce soreness, increase blood flow, and can even help with flexibility. While passive rest is keeping your body in a restful state (think sitting still, not moving), it’s not entirely necessary. Even on passive rest days, you can still go for a walk or a bike ride, keeping your muscles loose and limber. 

Preserving Muscle Mass as a Runner

What typically follows after eating in a caloric surplus for a prolonged period—what is colloquially known as a bulk phase—is cutting down the body fat that’s been accumulated with your muscle gain. If you’re going to be chopping your calories, you’re going to want to retain as much of that newly gained muscle as possible, especially if you incorporate long runs on the regular. Even if you’re not intentionally cutting the fat, you’ll still want to keep an eye on how many calories you’re burning vs. eating. If you’re in too much of a caloric deficit, this is where you risk muscle loss.

Whether you’re purposely cutting calories or not, try not to exceed 20% off your maintenance calories each day. 10-20% off maintenance is recommended for gradual fat loss. If you go over this not only do you risk losing muscle, but you can mess with your metabolism, deal with hormone imbalances, bad moods, and low energy. No thanks. Since I’m throwing so many calculations at you and giving you elementary school math flashbacks, let’s just quickly calculate a safe deficit to stay within that healthy range. To figure out my deficit, I’m going to take 2,000 x 10-20%:

Calories (2,000) x 10% = 200
Calories (2,000) x 20% = 400

I’m going to want to eat in a deficit of 200-400 calories/day to progressively lose fat. The calculations as follows:

2,000 maintenance + 500 calories burned from my run – 400 extra calories = 2,100 calories per day.

So in short, if you’re an endurance athlete and enjoy longer runs, keep an eye on your energy balance. If you’re running longer mileage on a particular day, make sure to adjust your calories based on how much you’re burning. Also, keep track of your protein intake. If you have this type of awareness, running shouldn’t eat away at your muscle and you can also benefit from a leaner looking physique from the additional cardio (resulting in fat loss). 

The Cardio “Kills Your Gains” Debate

There’s a long-held belief that cardio can stymie muscle growth. There is some merit in this statement which we’ll address shortly, but to the extent to which it actually impedes your progress can’t be boiled down in a one-word answer. 

The long held belief that combining endurance and strength together can limit muscle hypertrophy (growth) was popularized in a 1980 study. Over a 10-week period, researchers traced four male respondents: the first group incorporated resistance training only, the second included cardio only (a combination of biking and running on the treadmill), and the third group incorporated both resistance training and cardio. The study concluded that training for strength and endurance simultaneously “reduced the capacity to develop strength.” However, this study is over 20 years old and the groups doing cardio we’re doing it for 6 days a week. There has been much more research that has emerged since then…

More recent studies have shown that a moderate amount of cardio can actually enhance muscle growth in the gym. Quite the opposite of our eighties study, but note the keyword being moderate.

A 21-week 2012 study observed the same three groups (strength only, endurance only, and strength and endurance) with untrained men, evaluating the impact each of these training programs had on their ability to grow muscle mass. The group that incorporated 2 days of endurance exercise and strength saw increases in muscle hypertrophy (growth), however it’s worth noting that the SE group’s endurance efforts interfered with “explosive strength development, compared with strength and endurance training alone.” Simply put, some power or explosive movements in the gym might be hindered with cardio, but our body’s ability to gain muscle isn’t impacted by including some cardio in our weekly rotation. 

Important Factors to Consider

We can’t just make a blanket statement about strength and endurance without diving deeper into the details. The type of cardio we do, the frequency, our training splits, the intensity, the duration of our runs, and things like our genetics, etc. all play a role in how running will affect our ability to build muscle. I think for the sake of simplicity it’s better to separate out our training goals into two categories: bodybuilders (or those looking to maximize muscle gain and put on serious size) and 2. everyone else (those who want to build some muscle, but don’t care to look like Arnie).

This article isn’t really written for the former group, more so for the latter. If you are looking to maximize muscle size in the lower body, the general consensus is to try to limit the amount of running or cycling you’re doing, as it could impede gains in muscle growth. BUT, and this is a big but, incorporating cardio doesn’t seem to have much of an effect on our body’s ability to gain or maintain upper body muscle mass and strength at all. 

Running Can Actually Build Muscle

Some scientific literature has emerged proving that running alone can build muscle, depending on both the intensity and duration. Sprinting vs. long runs, for example, can have different effects on our bodies. 

One study put university students on a 10-week HIIT program and at the end of the program, the students saw increased muscle mass in the quads. Sprinting can actually enhance muscle protein synthesis: a key ingredient for our bodies to build muscle.

On the other hand, long distance running (>10 kilometers / 6.25 miles) can actually have the opposite effect—it can hinder our ability to increase protein breakdown in our muscles and cause damage—thus impeding muscle growth.

Personally, my 5-mile runs or HIIT workout haven’t interfered with my ability to build and preserve muscle mass on my lower or upper body. When I was running 21.1 kilometers every day for 74 days, I did see some loss in muscle, but mostly because I was struggling to eat enough during the day. Here’s a 2017 photo at the end of the #RUN70 challenge vs. now (where I only include a longer run once a month and average out at 5 miles per day).

Here’s the takeaway: running shouldn’t inhibit muscle growth on the upper body at all, so long as you’re following a progressive training program, paying attention to energy balance, and eating adequate protein. Running long distances can often inhibit both muscle growth and power in the lower body, but to the extent depends on the frequency and duration.

If you want to reap the rewards that running (or other types of cardio) can bring to your strength training sessions and limit the “gain-ruining” (lol), the sweet spot is within the 2-3 day range per week. However, if you’re like me and don’t care about the aesthetics/ maximizing muscle growth on your lower body then you can incorporate as much cardio as your little heart desires.

This leads into the next big question….

Does muscle mass make you a slower runner?

The last point I want to tackle is whether more lean body mass will slow you down or make you faster. I can kind of understand where this idea comes from…I mean, when you think of a marathon runner, what image immediately comes to mind? Someone super lean and toned, right? However, once again, this is just another preconceived notion in the fitness community – there’s more than meets the eye here.

Having muscle on your body will not make you a slower runner. In fact, it will probably do the opposite. 

One study investigated the association between skeletal muscle mass, different types of training (speed vs. weekly hours trained), and body fat on running times in athletes over 35 years old in half marathon, marathon, and ultra marathon distances. The interesting conclusions were that the level of body fat affected race times in all three distances (lower body fat = faster race times). The study concluded that while fat mass and speed training does have an effect on all three race times, the amount of muscle mass doesn’t. Whether skeletal muscle mass affects performance warranted further investigation. 

Gaining strength in our lower body will 100% help make us faster and can also help prevent injury. Lower body resistance training can also improve our VO2 max and running economy.

Resistance training and gaining strength on the upper body doesn’t provide as many benefits to our running as the lower, but it’s still important regardless. Gaining strength in our arms, back, and core helps improve our running form and maintenance of good posture. In other words, it has a stabilizing effect. Upper body strength can help improve the density of your bones and prevent injury. Strength in the back and core can also help protect your spine from the hard impact running has on our bodies. An article in Runner’s World titled, Why Runners Need Strong Arms, points out that, “improved upper-body strength [reduces] oxygen requirement, meaning you’ll run faster while using the same amount of energy.” The truth is that upper body strength can only add value to your running performance—not detract from it.

For the last few years, I’ve incorporated 4 days of upper body strength training with the push/pull split and usually combine core and legs on the same days (1-2x per week). If I do more than 2 days of legs, I feel the dreaded delayed onset muscle soreness (DOMS) and it really affects my workouts. However, I have a unique goal of consistently running every day, so I might not be a prime nor a relevant example to highlight.

The main takeaway is that skeletal muscle mass has no effect on running performance, but incorporating both upper body and lower body resistance training can make us faster, help prevent injury, and improve running economy.


This is a hefty post and if you’ve made it this far, I congratulate you! I said it wasn’t going to be a lit review, so apologies for playing you. To summarize, here are the main takeaways:

How much running you want to incorporate into your training should be based on your own individualized fitness goals—both aesthetically and performance-wise. 

Too much running and long distances can cause more muscle protein breakdown and thus inhibit muscle growth in the lower body. However, if this isn’t a real concern then you can do more running and not really worry much about it affecting building muscle in the upper body. 

Full body resistance training can improve our running and muscle mass does not make us slower. It does the opposite—it makes us faster.

Running can also expedite our fat loss efforts by burning more calories, but we want to make sure we’re not in too much of a calorie deficit or else we put ourselves at risk of losing lean muscle mass. 

Resistance exercise should be a vital component of our training—it will really move the needle in our body recomposition, increase our metabolism, and make us stronger runners.

Lastly, no matter what your body shape or size is, how genetically “gifted you are”, if you can run, you’re a runner. You can deploy training strategies to improve performance and if you train properly you can run any distance you want.

Leave a Reply

%d bloggers like this: