You know those workouts that take it all out of you? The ones where you’re left feeling beat. The ones where you want to fall over and nap afterward. The ones where you feel shaky.
These are just some of the feelings you might get from a glycogen depletion workout.
Now, you may be wondering what glycogen is.
Glycogen is carbohydrates that your body stores in your muscles and liver. It's your body’s most readily available form of energy.
When you eat carbs, your body breaks them down into a simple sugar called glucose in the blood. The glucose that your body doesn't use for energy immediately is then stored as glycogen.
During high-intensity exercise and resistance training, your body uses this glycogen. It breaks the glycogen down to glucose that it can use during exercise for energy.
So, when you run out of glycogen during exercise, you can feel like you've hit a wall. Plus, once your workout is over, you can feel absolutely drained. This would be a glycogen depletion workout.
The question is, are there benefits to these glycogen depletion workouts? What do glycogen depletion workouts look like? All of this and more, I'm here to walk you through today!
What Are Glycogen Depletion Workouts?
Glycogen depletion workouts are workouts where you exhaust your body’s glycogen stores. It's really that simple.
However, I'll take it a step further. I would argue that glycogen depletion workouts are workouts you do with the intention of depleting your glycogen stores.
This can be high-intensity workouts, resistance training workouts, long endurance workouts, and more.
Regardless of what the workout is, the goal is to use all of your body's glycogen! Again, once this happens, you can feel extremely fatigued. But, that's not the reason why people do them.
So, why do people do glycogen depletion workouts? What are the benefits?
Why Are Glycogen Depletion Workouts Beneficial?
High-intensity glycogen depletion workouts can offer quite a few different benefits. However, that doesn't mean they're necessarily better than other styles of training.
I would argue there are two main ways that glycogen depletion workouts can be beneficial. I'll walk you through each real quick so you can decide whether these workouts make sense for you or not.
Glycogen Depletion Workouts Can Help Improve Insulin Sensitivity
Exercise in general has been shown to be beneficial for increasing insulin sensitivity (1). Insulin is the hormone your body releases to help manage blood glucose levels.
With greater sensitivity, your body can more effectively use glucose and other nutrients. It can also help keep your blood sugar levels more stable throughout the day for more sustained energy.
In the case of glycogen depletion workouts, this benefit could be even greater.
Glycogen Depletion Workouts Can Be Beneficial For Endurance Athletes
For endurance athletes, glycogen depletion workouts could be particularly beneficial.
I'm talking about their training for competition specifically. It certainly wouldn't be the best idea to run a marathon or do an Ironman without carbohydrates.
So, why would it be beneficial to deplete glycogen for training purposes? Well, with low glycogen, your body can adapt and improve oxidative capacity (3).
Oxidative capacity is a measure of how efficiently your muscles can use oxygen. Basically, the higher the oxidative capacity, the better an endurance athlete can perform.
How To Know When Your Workouts Deplete Glycogen
Our bodies use different things for energy at different times. Our main fuel sources are carbs and fats, but we use them at different times and for different reasons.
Carbs are used for higher-intensity exercise. Fats are used for lower-intensity exercise. So, how do you know when you are depleting glycogen?
When it comes to resistance training, you are depleting glycogen for energy. That's whether it’s at-home workouts, CrossFit, traditional lifting, or anything in between.
When it comes to cardio or aerobic training, it depends. At lower intensities, your body will likely be using fats for fuel. But when does your body deplete glycogen for these workouts?
You deplete glycogen in these workouts when they are high-intensity. The Maximum Aerobic Function Equation is one way that will tell you how you can use heart rate readings to see if you are using glycogen or fats for fuel.
That equation is 180 - AGE. So for example, if you are 30 years old and your heart rate gets up to or above 150 bpm during your cardio workout, then you are likely using glycogen for energy (4).
Examples of Glycogen Depletion Workouts
There are many different ways that you can do glycogen depletion workouts. In my opinion, it's all about finding what you enjoy the most! Part of this could also involve which workouts will be most beneficial for your goals.
Here are two examples of glycogen depletion workouts you can try out now! I wrote one for your lower body, one for your upper body, and one for endurance.
Lower Body Glycogen Depletion Resistance Workout
Complete 3 rounds of the following exercises in rapid succession! Don't worry - You can take 1-2 minutes rest between each round. You can also do these exercises with or without weights. Do what challenges you and is within your physical capabilities!
| Exercise | Reps |
| Sumo Squats | 20 |
| Reverse Lunges | 20 Each Leg |
| Glute Bridge | 20 |
| Romanian Deadlift | 20 |
| High Knees | 30 Each Leg |
| Butt Kicks | 30 Each Leg |
| Jumping Squats | 20 |
Upper Body Glycogen Depletion Resistance Workout
For this workout, you'll complete each exercise for a set number of reps and sets. Make sure you are choosing weights that make the last 2 reps a challenge!
| Exercise | Reps | Sets |
| Incline Dumbbell Press | 6-12 | 4 |
| Close Grip Lat Pulldown | 6-12 | 4 |
| Push-Ups or Machine Chest Press | 12-15 | 3 |
| Seated Cable Row | 12-15 | 3 |
| Incline Dumbbell Fly | 25 | 3 |
| Straight Arm Lat Pulldown | 25 | 3 |
Endurance Glycogen Depletion Workout
Obviously, this can look a lot different for each person depending on their fitness level. For me, running a half marathon would be more than enough! For others, even biking that much could be too much.
Whatever you choose to do, I would aim to do it for 30+ minutes and keep your heart rate above your maximum aerobic threshold. For this, you'll have to refer back to the equation I gave you. 180 - AGE = A good estimate of your maximum threshold.
Reaching Your Goals with Glycogen Depletion Workouts
Glycogen depletion workouts can come with some great benefits, that's for sure. If you want to improve your health, gain muscle, or lose fat, there can be a time and place to use them.
So, how can glycogen depletion workouts help you reach your goals? That depends.
In most cases, glycogen depletion workouts won't be very relevant to helping you reach your goals. Unless you're an athlete who's really trying to maximize their performance, or you want to increase insulin sensitivity ... I would argue it's not necessarily worth keeping on your radar. Truthfully, you'd be splitting hairs at that point.
Now, yes, workouts that deplete glycogen can be very beneficial.
For example, if you want to lose fat or build muscle, resistance training is an excellent option. Even still, it's not an excellent option just because it depletes glycogen.
So, consider what your goals are. Because at the end of the day, glycogen depletion workouts are a very small piece of that equation. A lot of times, I would argue it's not even worth worrying about depleting your glycogen.
Your overall approach to exercise and nutrition is what matters more than anything else. Plus, that's where we can really help you out!
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References:
(1) Borghouts, L B, and H A Keizer. “Exercise and insulin sensitivity: a review.” International journal of sports medicine vol. 21,1 (2000): 1-12. doi:10.1055/s-2000-8847.
(2) Margolis, Lee M et al. “Exercising with low muscle glycogen content increases fat oxidation and decreases endogenous, but not exogenous carbohydrate oxidation.” Metabolism: clinical and experimental vol. 97 (2019): 1-8. doi:10.1016/j.metabol.2019.05.003.
(3) Knuiman, P., Hopman, M.T.E. & Mensink, M. Glycogen availability and skeletal muscle adaptations with endurance and resistance exercise. Nutr Metab (Lond) 12, 59 (2015). https://doi.org/10.1186/s12986-015-0055-9.
(4) Maffetone, Philip, and Paul B Laursen. “Maximum Aerobic Function: Clinical Relevance, Physiological Underpinnings, and Practical Application.” Frontiers in physiology vol. 11 296. 2 Apr. 2020, doi:10.3389/fphys.2020.00296.
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