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Does Running Turn You Skinny?

Gerry Asks:

“When you were marathon training, did it cause you to slim down and lose any muscle mass?

There’s so much noise online from trainers who are so anti-running coming out with all sorts of reasons not to do it.

Lost muscle mass is one I see over and over”

This is a great question from Gerry, and just as he says, it’s one that comes around time and again.

Let's think about it.

Why are many runners skinny with little muscle mass?

Because they do little else other than run, plain and simple. If they do other stuff, it’s very often basic callisthenics, like push ups and lunges.

Back in my endurance running days, when I did train for a marathon, yes, I lost mass. But this was acceptable as I was training to try hit a specific time goal.

I missed this goal by 10 minutes, I think I started out too fast which is a rookie error!

Now, training for a specific goal will lead to specific training with specific changes in your body. Know this, understand this and you will be fine.

Once I had completed my marathon, I didn’t like how light I was so I spent several months on a mass building style program, successfully putting on a lot of muscle mass in short order. My running dropped to near zero as I just didn’t want to. Then a new goal came up, a martial arts based goal, so training changed again. Now, I did one strength, 2 conditioning and I reintroduced running. Only this time the running was interval based for conditioning purposes.

Net result, I was strong, yes lighter than when in the bodybuilding phase, but strong and near indefatigable!

What I was is what most martial arts folk aim to be, a term that has gained in popularity of late, a Hybrid Athlete.

The first time I saw this term it was Alex Viada using it, it was a term he used for people who trained to run distance or do triathlons while still being big and strong. It’s now being utilised by the Hyrox people to describe their training  and competition style.

So all that said, is there truth in the story that we shouldn’t run, or that running eats away muscle mass?

Should we run?

As a species, it’s kind of our super power, so why not?

As a species we have unbelievable endurance, we’re built for covering huge distances.

The key is to keep the body healthy enough to run, I hate the idea of running as a starter exercise for fitness. But a considered approach to starting and developing running is something people returning to exercise or starting running should do alongside strength and general fitness work.

If you want a resource for this, you must head over to little buddy Helen Hall’s website ( I highly recommend her work, her book “Even With Your Shoes On” is the best I’ve read on the topic.

So yeah, we should run.

Will it eat away our muscles?

This is one of the most common anti running arguments you get, but look at who makes it, usually meatheads with zero cardio. Thankfully with the resurgence of Zone 2 training (which used to be demonised as “long slow boring cardio”) we’re seeing aerobic fitness make a comeback, which has lead to the rise of things like Hyrox as an example.

Runners in general are slight, they don’t want to be dragging around excess weight, even if it is muscle, so why build a massive set of Traps when it’s not going to help them.

But a well rounded athlete, a so called Hybrid Athlete and martial arts folk, well they train for a range of abilities, not just running.

So to them running is a tool. Just like deadlifting is a tool, pull ups are a tool. If we want to develop our Anaerobic system for strength and power, we lift and throw heavy stuff If we want to develop out aerobic system for health, endurance and also recovery, we need to move continuously for 30+ minutes at a mildly elevated heart rate (such as Zone 2) If we want to build muscle, we need to lift close to failure

The outcome determines the training method Or, if the desired outcome is the function, and the training develops that function, then any training that brings you towards your goal is functional training no matter what it looks like or what any internet guru tells you.

Running isn't the only way to develop your aerobic system, but it’s a good way. Most athletic endeavours happen on your feet, most sports involve locomotion at various speeds, so running is a great tool. Don’t let anyone tell you otherwise.

And if you want to run and build muscle, make sure your weight room training is muscle building focused, and your calorie intake is sufficient. And you should be fine. Last thing, run AFTER lifting, or better still, on a separate day entirely. And put the heavier / more exhausting lower body work early in the week as most long runs happen on the weekend, the further we separate these the better for recovery purposes. If your shoulders are tired, it won’t take too much away from a run, and you could probably do a solid back session the day after a run with little issue.

Be very careful listening to anyone who talks in absolutes, or starts articles and social media posts with “Stop doing” or “Never do this” In my 36 years of training since starting karate at 11 and all the various things I’ve done and helped others do since then, I think I’ve contradicted every rule ever written.

Define the Function you want Design the training to get you there. And if you need help, that’s what I’m here for.

Now, who else has a question?

Hit reply and let me know what you want me to talk about next week

Till then, 



Dave Hedges

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