How To Deplete Glycogen Stores

Have you ever “hit a wall” during your workout? One minute you’re pushing yourself, and the next you feel like you physically can’t anymore.

You may even notice increased sugar cravings the rest of the day afterward.

This could be your body’s way of signaling that it's running low on a vital fuel source: glycogen.

If you’re wondering what exactly glycogen is, don’t worry. I’m going to get into the fine details in a minute. Here’s a quick explanation before I do that...

When it comes to fueling high-intensity workouts, glycogen is your main fuel source. 

It's our reserve energy stored in muscles and the liver. The moment you need to sprint, lift weights, or do anything physically intense is the moment you start using glycogen.

But what happens when these stores run low? How can you tell if glycogen stores are depleted?

Well, your performance will take a hit. You probably won’t feel very strong and may actually feel weak. Your endurance can plummet, and your overall energy levels will likely drop too. This is all backed up by plenty of research (1).

As far as “how to tell if glycogen is depleted” goes … those are the main signs.

Some other telltale signs include your muscles seeming less responsive, and even changes in your mood during exercise could be one.

Understanding how to spot glycogen depletion symptoms can help you figure out when and how often to refuel.

Let's dive into what glycogen is before we look further into the signs, symptoms, and how to tell if glycogen is depleted.

Glycogen and Glucose

Most people don’t really know how to tell if glycogen is depleted. Really, it’s because most people don’t know what glycogen even is. 

Once you understand what glycogen is, its purpose, and how it works, it becomes pretty easy to see the signs. So, what is it?

Glycogen is an energy reserve that plays a key role in muscle contractions. Without muscle contractions, we wouldn’t be able to move an inch. So, it’s pretty important!

When you eat carbohydrates, your body breaks them down into glucose. Glucose is a simple sugar that provides immediate energy for our cells. 

Once absorbed, glucose molecules enter the bloodstream and raise our blood sugar. In order to bring our blood sugar levels back to baseline, our bodies produce insulin.

Insulin shuttles the excess glucose into our muscles, liver, brain, or fat cells. Where it goes depends on where it’s needed and if there is room for it. Some supplements, like glucose disposal agents, are even designed to support this process.

If energy isn't needed right away, and there’s room in the muscle cells, it gets converted to and stored as muscle glycogen. If your muscle stores are full, it will go into the liver as liver glycogen.

If your muscles and liver are both full, then it may be converted and stored in your fat cells. Those are the main places our bodies will store any excess glucose.

But what do we use these glycogen stores for?

In our muscles, glycogen acts as a readily available energy source during physical activity. It’s great for sustained or high-intensity exercise like running, lifting weights, and cycling. 

If we continue exercising once glycogen levels get low, our muscles may grab some of the glucose in our bloodstream. This will lead to a drop in blood sugar levels, but that’s where liver glycogen comes into play.

The sole purpose of liver glycogen is to help us maintain stable blood sugar levels. All we have to do is break down liver glycogen and release the glucose into the bloodstream.

I like to think of liver glycogen as a backup generator.

Just like when the power goes out, a backup generator provides temporary power. When your blood glucose levels drop, your liver supplies a backup source of energy to keep your blood sugar stable.

Let's bring this full circle. 

Muscle glycogen, a form of stored glucose, is your number 1 fuel source for exercise. When our stores are full, we have plenty of fuel.

It doesn’t last forever, though, and our body has a backup plan for when we do run low. That backup plan is liver glycogen.

Both of these together are designed to ensure we don’t run out of energy. We only have a finite amount, though, so unfortunately, we can run out.

It takes a lot to deplete your whole body of glycogen, though. This isn’t something you’ll do in a typical 60-minute workout.

You can, however, deplete glycogen from specific areas of the body (4). This can lead to the same low glycogen symptoms, but they may be less intense.

If you have longer & harder workouts, though, the symptoms may get more intense. For example, I’ve run 4 marathons. I’ve hit that wall where my muscles all felt like jello. It's not a fun feeling!

How Long Does it Take to Deplete Glycogen?

You might be wondering: how long does it take for glycogen stores to deplete?  It depends on activity, but high-intensity or long workouts can lower glycogen in 1–2 hours.

Even still, it wouldn't be accurate to say everyone will deplete their glycogen fully in 1-2 hours. Too many different variables are at play. Generally, though, that's about how long it should take.

But now that you know what glycogen is, what it does, and how long it takes to deplete glycogen ... you still need to know how to tell if glycogen is depleted. Let’s dive into that next.

How To Tell If Glycogen Is Depleted

Suffering from glycogen depletion is no fun.

You can’t perform well when glycogen is low.

It doesn’t feel good when it happens.

Knowing the signs and symptoms of low glycogen can save you from hitting a wall in your workouts.

Whether it’s running a marathon or doing any other workout, hitting a wall isn’t ideal. No one likes the feeling of wanting to keep going, but not having the energy to do so.

So, here's how to tell if glycogen stores are depleted. Keep an eye out for these signs and symptoms:

Fatigue and Exhaustion

The most obvious indicator is exhaustion. I don't mean the "out of breath" type of exhaustion, though. I’m talking about if you're abnormally tired and lack the energy to put effort into your workouts. 

You may even start to feel weak, dizzy, and shaky. Some people also sweat and get that cold, clammy sensation on their skin. 

When it happened to me, I felt like my legs didn’t have the energy to stand up. I also started seeing spots, and I felt a little nauseous.

The easiest way to describe it was an overwhelming feeling like I just wanted to lie down and take deep breaths. That’s how it was for me, at least.

Excessive fatigue like this can be an indicator of depleted glycogen stores. This is especially true if it’s during a workout that you could normally handle with ease.

Decreased Strength

A noticeable decrease in strength can occur when glycogen levels are low, too. 

This makes perfect sense as your muscles lack the ability to produce force in a meaningful way without glycogen (2). It becomes very difficult to produce ATP fast enough without it.

That can lead to a major loss of muscle strength. Why? Because without enough ATP, our muscles can’t contract properly.

So, if you’re working out and you feel abnormally weak, you could be noticing some low glycogen symptoms. It’s important to recognize this so you know when it’s time to refuel or rest up.

After all, depleted glycogen won't only lead to lower strength, but it could also potentially lead to injury (3). 

More Perceived Effort With Less Performance

This ties into fatigue and decreased strength, but there’s a little more to it.

When glycogen is depleted, you might find it challenging to push as hard as you normally can. That, or you’ll feel like you’re trying really hard with a lot less to show for it.

Depleted glycogen isn’t the only reason this can happen, but it's a plausible explanation. If your muscles have less energy, it’s going to take more effort to do the same amount of work.

Either that or you just flat out won’t have the energy to do it at all. There’s a reason athletes put so much effort into proper fueling before competition.

They want to perform, and they don’t want to struggle or fail along the way.

Consecutive Workouts With Lower Performance

If you feel like you’ve all of a sudden lost progress out of nowhere, it could just be glycogen depletion symptoms.

Here’s an example...

Let’s say you can normally do 15 pull-ups when you’re fresh in your first set. All of a sudden, you can barely do 10 in your first set.

You chalk it up to being an off day, so in your next workout, you try again. This time, you still only get 10 reps.

This could happen if you didn’t start your workout with a lot of glycogen. The second workout could be from the same thing if you don’t eat carbs a whole lot.

Glycogen is a carbohydrate, just a stored form. If you don’t eat a lot of carbs, you probably won’t have a ton of glycogen.

Now, if you are eating tons of carbs and this still happens, then it’s likely from something else. There are many reasons our performance can take a hit.

Low levels of glycogen are just one of those reasons.

But now you'll be able to recognize when your glycogen levels may be low. Next, let's talk about how to restore them when they do get low.

Restoring Muscle Glycogen

The good news is that most people can replenish and maintain their glycogen stores with some simple practices.

If your goal is to perform and see consistent results, you should try to maintain your glycogen stores.

Here are the core principles to keep in mind...

Carbohydrate-Rich Diet

To keep glycogen stores topped off, you need to eat a lot of carbs. Foods like pasta, rice, bread, fruits, and vegetables are all excellent sources.

These carbs provide the glucose that your body needs to store glycogen. Without carbs in your diet, you won’t have a lot of glycogen, just like you’ll be dehydrated if you don’t drink enough water.

Timing of Carbohydrate Consumption

Consuming carbs immediately after exercise can be extremely advantageous. That’s when your body is most sensitive to insulin and wants to store more glycogen.

You can do this with whole foods, but the fastest way is actually with high glycemic carbs (5). They digest quicker, so they can become glycogen quicker.

Consistent Meals

Another thing you can do is simply eat more regularly. You also need to make sure you have a good amount of carbs in each meal. A consistent supply of carbs throughout the day can help you maintain higher glycogen levels.

It’s kind of like stopping at a gas station to fill your tank several times a day. You'd never run out of gas that way.

Allowing Recovery

It typically takes about 24 hours to fully replenish glycogen stores after they've been depleted. However, this time frame will depend on: 

• How intense the workout was
• How much glycogen you lost
• How much and what type of carbs you ate

In order to allow yourself to replenish glycogen, you have to rest. If you're constantly active, you’ll constantly be using up whatever glycogen you have.

Why do athletes carb load? It’s because tapering physical activity allows the body to fully replenish glycogen stores. Allow yourself some rest between workouts, and your body will thank you.

Hydration

Staying hydrated is also crucial for efficient glycogen storage. Hydration supports glycogen synthesis by ensuring that each gram of glycogen can bind with the water it needs to be stored effectively. In fact, every gram of glycogen needs at least 3 grams of water to be stored properly (5).

If that’s not enough, we deplete glycogen faster when we’re dehydrated, too (6). That’s a double whammy! Getting enough water is about more than quenching your thirst. If you want to maintain higher glycogen levels, stay hydrated.

Keeping Glycogen Levels Full

Keeping your glycogen stores full may not seem like a huge deal. At least until you are miserable during and after your workout.

At that point, trust me, you’ll wish you took this seriously.

On the other hand, when your glycogen levels are in a good spot, you're more likely to experience improvements in performance. The more energy you have, the more potential you have to push yourself and make progress. 

It doesn’t mean you will, but you’re in a better position to make progress than if you had less energy to work with. No matter how much glycogen you have, you still have to do the work.

So, what do I do? I follow the principles I laid out in the last section. 

I do struggle to get all my carbs in with only whole foods, though. I know not everyone struggles with this, but a lot of people do, and I’m one of them.

I’m a busy person, like many of you, and it’s not always easy to focus on eating a perfect diet. Especially with how focused I am on my protein intake, my carb intake usually takes a back seat. 

For me, I look for the most convenient option. To be honest, I just like making my life easier in that regard.

So, what I’ve found to be the most helpful for me are 2 things:

• Mixing Ignition into my post-workout shake

• Drinking Ultra-Formance either before or during my workout

These are all carbohydrate supplements that serve different purposes.

Remember when I talked about timing your carbs effectively in the last section? I mentioned that high glycemic carbs can help you replenish glycogen the fastest after training (5).

Well, Ignition is a high glycemic carb source designed specifically to be taken after workouts. It can help support glycogen replenishment and better recovery.

Ultra-Formance is a mixed carb source designed to fuel your body during exercise. There are some faster and slower-digesting carbs in it, along with plenty of electrolytes.

This could help support better energy and performance during your training. It may also help spare your body from breaking down as much glycogen during the workout.

Now, I need to clarify something. I’m not saying you should get all of your carbs from supplements.

I do eat plenty of whole food carbs as well. I’ve just found that I don’t get enough. 

These supplements make it easier to hit my goals, and I know they can do the same for you, too!

At the end of the day, you just have to do what works best for you and your goals. If you want to get all of your carbs from whole foods, be my guest. I'd prefer that you do.

If you’re like me and know you can't eat enough carbs without eating a bunch of junk food, check them out. They could make a big difference!

Otherwise, now you know how to tell if glycogen is depleted. You also know how to go about making sure you always have enough for when you need it!

I know we covered a lot today, so if you have any questions, don't hesitate to reach out. We have a full team of NASM Certified Personal Trainers and Nutrition Coaches right here in St. Louis, Missouri. 

Just give us a call at 1-800-409-9732 or send us an email at CustomerService@1stPhorm.com. We're available Monday through Friday from 6 AM to 8 PM Central and Saturday & Sunday from 9 AM to 7 PM Central. We'll be more than happy to help in any way we can!

References:

(1) Ørtenblad N, et al. Muscle glycogen stores and fatigue. J Physiol. 2013;591(18):4405-13.

(2) Henselmans M, et al. The Effect of Carbohydrate Intake on Strength and Resistance Training Performance: A Systematic Review. Nutrients. 2022;14(4):856.

(3) Schlabach G. Carbohydrate strategies for injury prevention. J Athl Train. 1994;29(3):244-54.

(4) Jensen J, et al. The role of skeletal muscle glycogen breakdown for regulation of insulin sensitivity by exercise. Front Physiol. 2011;2:112.

(5) Murray B, Rosenbloom C. Fundamentals of glycogen metabolism for coaches and athletes. Nutr Rev. 2018;76(4):243-259.

(6) López-Torres O, et al. Hydration, Hyperthermia, Glycogen, and Recovery: Crucial Factors in Exercise Performance-A Systematic Review and Meta-Analysis. Nutrients. 2023;15(20):4442.

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