Glycogen Depletion in Training

Considering adding glycogen depleted runs to your marathon training?

Never even heard of these?

Listen in as Coach Michael discusses the benefits of glycogen depleted runs, whether they’re right for you and your training, and how to implement them if so.


Audio Transcript

Michael: Hey Runners Connect fans. Welcome to another episode of the Run to the Top Xtra Kick podcast.

Today, I’m answering a question regarding glycogen depleted runs from Ryan.

“What are the physiological benefits of glycogen depleted runs? When, in your training cycle should you do them, and is it a good idea to do them every day or just long run days? Thank you.”

That’s a great question Ryan and it’s something that we deal with a lot and we’re very passionate about.

It’s very helpful in marathon training to use this, but we need to talk about the science a little bit about it, because you did ask about the physiological benefits.

We’ll talk about the science before we really talk about implementation.

First, let’s talk about bonking. I think everybody knows that people usually refer to it as “the wall” and it’s typically around 20 miles.

A lot of people know about this and a lot of people have experienced it, but not necessarily everyone knows the cause.

The cause is that your body literally runs out of energy, and it’s not just that you’re tired or your heart’s beating too fast or you’re out of breath. It’s literally your body cannot keep going.

It’s like a battery runs out of fuel, your car runs out of gas and it can’t run anymore. That’s what happens when you hit the wall; that’s what happens when you bonk.

Your body literally doesn’t have energy,and that’s why a lot of people end upbarely moving for the last 10 K of a marathon. Your body literally doesn’t have any energy.

What it runs out of is glycogen and it prefers glycogen.

Glycogen is essentially stored sugar in your liver; in your muscles. Your body strongly prefers glycogen because it’s much easier, is more accessible,and it’s a lot easier to burn than fat for your body.

Once it’s gone, you’re not going to have any energy, so what we’re trying to figure out is how do we mitigate that issue?

The obvious solution is, of course, by burning fat, but you know this definitely requires some effort; some careful planning and definitely some time to adapt.

This is glycogen depletion; this is what we’re talking about here.

Basically, the essential way to describe glycogen depleted runs is, you just run without carbs; you totally rely on fat.

You don’t eat any carbs before the run and you don’t allow your body to use that glycogen.

Most of the science on this comes from a 2011 study on cyclists. We have this listed out in one of our articles, but basically they took two groups.

One would consume glycogen; consume carbs before their workouts and one would not, so it was kind of a controlled group versus experimental group.

They did it over a six-week period and both groups did show improvement, but the glycogen depleted group showed a couple of very interesting things.

One was increased enzymes that are correlated with fat metabolism. But what does that mean?

That means you can metabolize fat easier and faster, and then they increased their fat utilization through a range of intensities.

That’s super important because typically, fat utilization for most people is only good at a very low intensity; very slow run. We’re talking about walking.

What that did, when they trained in that glycogen depleted state, they actually improved their utilization at various intensities and not just the slow ones.

That definitely indicated the benefits of glycogen depletion, but nonetheless, it does come with some costs and we’ll talk about those in a minute.

One quick disclaimer I want to make is that, we are not talking about low carb, high fat. Low carb high fat isa total diet.

That’s where you eat very low carbs and very high fat throughout your entire diet, not just before your runs.

This is very different than what we’re talking about and we are absolutely not advocates of low carb high fat for runners.

For normal people, it’s a very different story, but for people training for a marathon, we’re definitely not advocates of it.

Glycogen depletion it’s very different and it should only be used sparingly in training.

Now, in terms of implementing the glycogen depleted, basically, the best time to start is going to be early on in your training.

The reason being it can be a bit like playing with fire.

It’s definitely a little risky as with anything with a big reward, but ideally, what you’re doing is starting it early on in your training, because your long runs aren’t really long.

Typically, you’re kind of slowly building up your long runs, so it’s a great opportunity to get used to it, see what you think and over time, get yourself used to it and improve your fat utilization, without the risk that you have in the later long runs.

Essentially, you want to run completely fasted, with no carbs in the hours before the run, and ideally not a ton the night before either.

For most real advocates of this, you don’t want to have any carbs the night before either or like a very, very low carb meal. You can have water.

Some high level elite Kenyan marathoners usually just consume water and vegetables before the run.

They’re essentially fasting vegetables, especially low carbs. I mean they’re extraordinarily low in carbohydrates and they’re very slow burning, so it’s not going to provide you that glycogen boost anyway.

It’s basically a way to fill your stomach with something just so you’re not starving, but at the same time, you’re still going to get that glycogen depletion. That’s one idea to try, but typically you just do it fasted.

Now this definitely takes some time to adapt to.

The last thing I want to talk about is how this can be a little bit dangerous and how it really shouldn’t be taken lightly.

Not just anybody is prepared to implement glycogen depletion and not everybody necessarily needs to.

I mentioned playing with fire earlier, and I do mean that.

I’m not just using hyperbole; it could be very dangerous because when you do a long run glycogen depleted, it’s very, very tough on your body for a good reason.

Your body is kind of in panic mode. You’re out of glycogen, and that’s why your body shuts down.

That’s why you hit that wall because your body is telling you, “I can’t do this anymore. We need to survive. We need to preserve the vital organs. We need to do whatever we need to do to survive. We’re not worried about running fast anymore. We’re just worried about surviving.” You don’t want to do this.

First of all, you don’t want to do this too often. You don’t want do it every day and part of the question was about doing it.

Do you want to do it every day?

Ideally, you just want to do it and especially if you’re a beginner, I would definitely advocate doing it on your long runs and ideally early on in training.

At RunnersConnect, when we write our training plans, we include them on some of the final long runs, but typically, there’s a huge build up going into that, and we are more confident that we’re able to prepare people for the glycogen depletion, and that they’re going to know exactly what to do.

If you’re just starting,and you’re kind of a low mileage runner,just implement them earlier on in your training and just on long run days.

When people get a little bit more advanced and they’ve trained for marathons with glycogen depletion, they’ve proven that they’re not bonking anymore on marathons, so they kind of have some experience built up, those are the type of people where you can start to experiment, with a little bit more glycogen depletion.

Maybe on some of your mid-week workouts, one or two of those and then your long run as well.

Yet again though, that’s for people who are very experienced, and even then, we would caution anyone doing that to really pay attention to your body.

Pay close attention to your recovery because that’s what’s going to be impacted.

You’re going to recover slower and you’re going to be more tired from glycogen depleted run, because your muscles are going without glycogen.

We’ve talked on several other podcasts about the ideal post workout recovery drink and what it always includes.

It always includes carbs and the reason it includes carbs is because that replenishes the muscle glycogen and allows them to recover much, much faster than they can without.

When you’re depriving your body of that glycogen, it’s going to be a little harder on your body and you’re going to have to take some rest.

What I advocate is, if you’re going to do those glycogen depleted long runs,especially once they start getting a little longer, a little closer to like 16, 18 miles, you’ll want to make sure that you have plenty of rest planned.

Don’t just say,“Okay, I’ve got to work out.”

Let’s say you do your long run on Sunday and you have a workout plan for Tuesday. Some people can make that work, especially if the Tuesday session isn’t that tough.

If you’re doing that long run in a glycogen depleted state, you might very well not be ready for that Tuesday workout.

What I would do is recommend pushing that workout back to Wednesday, maybe even to Thursday, to make sure that you’re recovered.

In addition, I would say, especially if you’re doing those16, 18 maybe even 20 mile long runs glycogen depleted, the next week needs should be a down week.

In our training plans, we typically alternate weeks, so we’ll do a high week, low week, high week, low week and what we do there with glycogen depletion is, you only do glycogen depleted long runs on the high weeks.

Then the very next weekend, you have a lower long run usually like, for most of our beginners, the higher long runs are 16 or 18 and the lower ones are like 12.

That way, you get to absorb the benefits of that glycogen depleted run and help you recover, so you’re making sure that you’re not lining up a hard session right after that glycogen depleted long run, because it’s going to take your body quite a while to recover.

The number one thing to do is to make sure that you’re still very focused on recovery.

The benefits of this are certainly big but in general, you’re going to train better and recover faster when you’re doing glycogen loaded.

When you’re using carbs before the run, or when you’re replenishing carbs right after the run, typically that is going to lead to better performance and better recovery over the long run, but implementing a little bit of glycogen depleted here and there mostly for beginners.

As you get more experienced, implementing it a little bit more can definitely have some really positive impacts.

RunnersConnect fans, that’s it for today. Enjoy your run and don’t forget to submit your questions and we’ll feature you on the show.

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