Can You Benefit From Glycogen Depleted Runs

Audio Transcript

Sinead: Today’s questioner says, “I’ve read that if you generally eat low-carb, you become better at using fat for fuel. If that’s true, do you benefit any more or less from ingesting carbs during a long run?”

This is a great question and there’s been kind of a debate around it in the running community. At Runners Connect we get a lot of questions from users regarding this dietary strategy that seems to enhance the body’s adaptations to training and fuel utilization.

What you are talking about here is the train low theory and what this is, is it’s training with low-carbohydrate availability.

This theory has stemmed from the discovery that the transcription of a number of genes involved in muscular adaptations to training, is actually enhanced when exercising with low muscle glycogen.

Many of you have probably heard of the glycogen depleted long run and this is the theory behind that.

Our particular interest is the body’s increased ability to use fat as fuel and then thus rely on less glycogen.

This theory is of special importance to marathoners, and a lot of marathoners train by this theory, because by adapting the body to rely on less glycogen, you are putting yourself at less risk of hitting the dreaded wall that many of us runners are all too familiar with.

This wall usually occurs somewhere between 17 miles and 22 miles in the marathon. This is when you are completely glycogen depleted.

A lot of runners go by this training and dietary strategy so that they can train their bodies to use fat as fuel rather than their glycogen or carbohydrates.

Training with low-carbohydrate may seem counterintuitive since it’s pretty well documented in the scientific literature around running, that the availability of carbohydrate during intense, prolonged endurance exercise is amajor determinant of overall performance.

Many of us are accustomed to the traditional carbo loading before a race.

This might seem a little bit counterintuitive, however, training with low-carbohydrate doesn’t mean that you are completely denying yourself of carbs.

It means that you are occasionally training with glycogen stores. The theory behind this is that it allows you to optimize your utilization of fat as fuel, and thus make you able to get further into a race without completely depleting your glycogen stores.

There has been a ton of research behind this low-carb strategy. Researchers have been able to identify muscle markers that indicate adaptations to training are enhanced when exercise is performed with low muscle glycogen.

They have shown that training in a fasted state promotes different training adaptations compared to those seen when carbohydrate is taken before and during training.

That said, there are some drawbacks. It is pretty unclear whether or not these enhanced training adaptations actually translate into real performance benefits.

A key highlight of the research is that although training with low glycogen during a hard workout results in enhanced muscle adaptations, these athletes had a lower power output during that workout, compared to athletes with high carbohydrate availability.

The athletes that weren’t fueling with carbs before and during the exercise weren’t able to do as much work as those that were.

In this particular study, they had to determine these enhanced training adaptations actually made up for the decrease in total work done.

By the end of that three-week study done on cyclists, they had all these subjects do a performance test ride during which both groups, the group that trained with carbsand the one that didn’t, showed equal improvements in performance.

This is one study of a lot of different studies. Unfortunately, most of thestudies out there are too short to see any of the real benefits of training with low-carbs.

Of all the research that has been done, it’s been concluded that the availability of carbohydrate during intense, prolonged endurance exercise is actually a key determinant of success.

There is no clear evidence from the studies reviewed, to support a performance advantage from adhering to a low-carb strategy.

That said, there has been a number of elite marathoners who have tried this low-carb strategy and have seen some pretty great success from it.

The majority of these low-carbohydrate training sessions that were done by these elite marathoners consisted of morning runs done in a fasted state.

Usually, a lot of people wake up in the morning and they’ll have some water and some coffee before they run.

That’s called a glycogen depleted run because you are not getting up and eating something before your run and you’ve naturally fasted overnight.
A lot of people do glycogen depleted runs without even intending to.

Something else that elite marathoners typically do is they keep these low-carbohydrate sessions to 10% of their overall training.

They don’t do a ton of glycogen depleted runs. In fact, most elite marathoners on average only do about two and a half low-carbohydrate sessions a week during the general build up in their training.

While in the specific preparation phases, the three weeks before a big race, they would only do it about one and a half times per week.

Again, a lot of elite marathoners have seen success through this. In this particular study that I’m citing, two of the marathoners actually set PRs of 211 and 212 respectively, while the third marathoner in this particular study had a debut of 216.

Obviously, there is a lot of success to be shown from this low-carbohydrate training strategy. What’s funny is that while there is insufficient evidence to provide guidelines to athletes for incorporating this low strategy into their training, a lot of athletes do this without knowing.

Again, a lot of people go for a run in the morning. By doing so, they are running in a glycogen depleted state. You’ll discover that a lot of athletes will do two runs a day without sufficiently replenishing their glycogen between those runs. Often, that second run is glycogen depleted as well.

I will say this low-carb training strategy, as with any other training strategy, serves some individuals very well but doesn’t do the same with others. We are all wired a little bit differently. Unfortunately, there is no concrete universal rule that would suggest everyone would see success through this low-carb training strategy.

If you really want to, you can do a little bit of trial and error and see how it works for you.

If you want to try and do some glycogen depleted runs, I have a few suggestions for you.

First, run your early training segment long runs in a glycogen depleted state. This will teach your body to boost glycogen stores and again increase that as a fuel source early in the training cycle.

Because you are in the early phases of your training cycles, your long runs won’t be too long. You won’t run a high risk of bonking and sacrificing all the benefits of a long run.

Secondly, is to run your last three quality long runs in a glycogen loaded state. In doing so, you will increase the overall quality of these important long runs towards the end of your training phase.

This will also give you good practice for how you’re going to fill yourself on race days.

If you’re running a marathon, you want to practice the nutrition strategy that you’re going to be doing the in the race, so that you can acclimatize your stomach to processing the simple sugars and fluids efficiently.

Lastly, it should be noted that low-carbohydrate training doesn’t mean the same thing as a low-carb diet. All of the athletes in the studies I’ve talked about still maintained a high carbohydrate diet according to their needs.

For an endurance athlete like yourself, you need carbs to perform optimally and also to help you feel good when you are completing the everyday tasks that make up your day.

Athletes that train by the low-carb training theory consume their carbohydrates at different times, depending on the type of training session.

All in all, elite marathoners and our users at Runners Connect have discovered that by implementing both glycogen depleted and glycogen loaded long runs, you can improve the critical fuel efficiency element of the marathon while also maintaining consistency in your training.

You kind of have the best of both worlds there.

That was a fantastic question. Thank you so much for submitting that. I’ve really enjoyed answering that and hope that what I’ve said has helped you and helped our listeners today.

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