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Why Is It So Hard for Endurance Athletes to Gain Muscle?

There’s a lot that goes into building muscle - your diet & nutrition, training & recovery, physiology, physique and genetics.

Now, not everyone can be a body builder, but just about every one of us is more than capable of putting on some decent muscle given the right circumstances.

I’m talking to you, endurance athletes.

Yes, I know you do some off-season strength training. Key word here is ‘some’, which means probably not a lot if you’re like all the other athletes I know. We all need to work at maintaining a decent amount of muscle mass - Mother Nature plays a cruel trick on us as time goes by; we lose muscle with time (aging) and when we do, it’s an uphill battle to get it back.

Now, there’s some nuance with this, as there is with all things health. But, I would argue that it’s a lot tougher for endurance types to gain muscle compared to non-endurance athletes. Sure, we don’t do as much strength training as the gym-athlete. Or, when we do strength training we’re not working as hard (cause we’ve been running, swimming and cycling, too). Or, we’re just not genetically wired to put on muscle.

Each of these certainly play a role, however I do believe there’s a major underlying physiological conflict between strength and endurance training adaptations that limits endurance athlete’s ability to put on some appreciable muscle.

Cortisol Connection

And it has to do with cortisol…

Now, before you role your eyes about another article on cortisol, this is really important and will help explain why endurance athletes don’t/won’t/can’t gain muscle readily…

And to understand that we need to understand what cortisol’s main job is.

We all know it’s a ‘stress’ hormone. It’s released in response to stressors whether they be emotional or physical. Its main job is to make energy readily available to us, in times of stress/emergencies. It does this by freeing up amino acids, which are then sent to the liver whereby they undergo gluconeogenesis, or the creation of sugar. We need that sugar for our muscles to work so we can fight or run, and for our brains to work so we can think our way out of problems.

Now, while this may not be how things are today, this is how things were set up so we could survive as a species. Where else were we supposed to get some very quick energy if we hadn’t had a meal in days or weeks (as was probably often the case with our ancestors at times)?

So, back to the part where cortisol frees up amino acids to be used for sugar production. Where do those aminos come from? Our skeletal muscles, that’s where.

Cortisol is a catabolic hormone, meaning it breaks things down, generally. This is opposed to something that is anabolic, which builds things up.

Chronic Stress, Chronic Cortisol

It’s thought that our ancestor’s stresses was short-lived. They got chased, they fought. They starved, but they survived. That’s why we’re here today.

But it’s different for us. Our stress is long term. Our work stress is never gone. Relationships are much more complicated. And, we train. And train and train. For months at time - for far longer than a chase or hunt did for our ancestors.

So, the thinking is that because our stress is chronic, our cortisol levels are probably higher for us than for our ancestors.

And it’s this physiological patten that makes it tough for endurance athletes to gain muscle - we’ve always got some stressor going, and when you add in the long-term stresses of endurance training, this leads to what’s essentially a ‘push’ in terms of the balance between muscle building and muscle degradation.

But wait there’s more - in order to try and calm things down, your body releases insulin (an anabolic storage hormone) to save that energy. This, coupled with the fact that cortisol also makes fat more available to use - you wind up getting that annoying extra belly fat despite eating really well and exercising all the time.

As I said earlier - there’s some nuance with this. It doesn’t happen to everyone - some of us can put on muscle really easily while others struggle despite doing it all right.

But, if you’re an endurance athlete and you’re struggling to get muscle on (or maybe your arms and legs are skinnier than ever) and you’re getting some belly fat, more than likely the aforementioned scenario is to blame.


Now then, of course there are ways to help your body put on a bit of extra muscle.

These are some things I’ve used with the athletes I’ve seen in clinic, and we’ve had some good success with them.

1. Shift your training focus.

I’m talking about the off-season here. Well…and a bit during race season, too.

Most of us have been taught to do our strength training with a focus on high rep, low weight to build strength. Sure that works. But, if you want to put some muscle on (that will withstand the rigors of racing season) you need to lift like you’re a body builder in the gym during the off season.

This means: Low rep, high weight, and lift to failure. Like, 3-4 sets of 4-8 reps, tops until you can’t squeeze another one out. Of course, you need a spotter. And, you need a trainer or a coach who can give you more detail than I can.

But that’s the gist of it - go heavier in the off season. This maximizes metabolic signals for muscle growth and possibly minimizes metabolic stress. You’ll put on some muscle (and no, you’re not going to get so huge that it’ll throw your power-to-weight ratio off) that you can hang onto easier into race season (and please do some more strength training to maintain it through race season).

2. Protein, more protein.

I’ve seen a lot of endurance types in clinic. And, my estimation is that most of us have ‘cleaner’ diets which usually translates into a more restrictive diets. Adequate protein is often one of the first casualties it seems (meaning there isn’t enough being eaten to promote more muscle mass).

So, I’ll offer you this: The Academy of Nutrition and Dietetics and the American College of Sports Medicine recommend 1.2 to 2.0 grams of protein per kilogram of body weight per day for athletes. Another way of putting this is 0.5 to 0.9 grams of protein per pound of body weight.

As an example, I weigh 165 lbs. Following this suggestion I need anywhere from 90 to 150 grams of protein per day. 150 grams is a lot! I think the sweet spot is somewhere in the middle; but you need to try what feels best for your body.

  • Make sure that protein is spread throughout the day (all at once in a morning smoothie isn’t as advantageous…and, yuck).

  • Make sure that protein is rich in leucine, one of the branched chain amino acids. Leucine is increasingly touted as the primary muscle synthesis activating amino acids. There’s a lot of leucine in animal protein, and plenty in soy (organic please!), legumes, nuts and seeds.

3. Supplement.

  1. Branched chain amino acids - I just got done telling you that you can find them in food. But, if you want to cover all your bases (like me), then supplementing with a bit in the AM and PM is a good idea. All they’re comprised of are the amino acids leucine, isoleucine and valine. Put some in your smoothie, or even take with water.

  2. Cortisol Recovery - This is one we use a lot, because so many people are pumping out too much cortisol for their own good. It works by essentially short-circuiting the production of excess cortisol. Don’t worry, you’ll have plenty left! Take it at bedtime, when we want cortisol at levels much lower than they are at daytime. It’ll also improve your sleep.

  3. Creatine - not just for bodybuilders anymore! Creatine is being touted more and more as a supplement for endurance athletes. It’s great at building muscle during your strength training season. Basically, it helps you re-sythesize your ATP giving you just a bit more muscular energy, allowing you to squeeze off one more rep - vital for muscle growth!

4. Stress Management.

We can’t talk about cortisol excess without this being part of the conversation. It really is important that you have some sort of stress management program. I know, exercise is your stress management.

But I’m talking about what you do more directly in the mental emotional arena - meditation, mindfulness, counseling, etc. We’ve got to manage our stress by learning how our mind interprets it in the first place - and these practices are how we learn to do that.

So please, consider taking a more active role in your own stress management, outside the physical realm. It takes time, effort and practice - it’s just like training, you have to do a bit each day to get better and better.

Adding up all of these suggestions will put your body (and mind) in a physiological environment wherein muscle is more easily attained for you. It won't happen overnight, but you will see some changes with dedication to the above.

Questions about this blog?

Send me an email.


Feel free to schedule a complimentary 30 minute consultation if you’d like to learn more about how we can optimize your health and performance!

In Health, Fitness and Endurance,

Dr. Jason Barker

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