If you’re an endurance athlete, you already know glycogen is your best friend. If you’re just getting into the arena, understanding what glycogen can do for your physical performance will help take you a long way. Let’s break it down!
What is Glycogen?
Glycogen is the body’s way of storing individual glucose by branching them together to make a larger molecule that can later be broken down for energy.
Where does it come from?
When we eat food, carbohydrates in our food get broken down into individual glucose molecules and released into the blood stream. If there is an immediate need for energy, this glucose will get used, otherwise the body can store it as glycogen for use later.
Where is it stored?
Our bodies store glycogen in the liver from up to 400 calories and skeletal muscle up to 1600 calories worth. The liver breaks down glycogen to help regulate blood sugar. For example, if we haven’t eaten in a while and our blood sugar is getting low, the liver says, “I have some energy over here I can break down and share with the blood.” Glycogen works in the muscles a little differently by providing energy directly for the muscle itself to contract during exercise.
How does it get used? 
During exercise, your body will utilize all energy sources including fat and glycogen, but at varying levels. To begin with, the body will use muscle and liver glycogen more predominantly because it is easier to break down than fat in adipose tissue. In addition, during cardiovascular exercise, the body wants “easy” energy.
After two hours of intense activity, the body has typically burned through its muscle and liver glycogen and is now primarily using free fatty acids and blood glucose for energy. At this time, in order to generate glucose, the body will begin gluconeogenesis, the process of converting non-glucose substrates (such as fat and protein) to glucose to be used for energy. This process is not ideal as it does not produce as much energy as aerobic glycolysis and is not an efficient pathway. In addition, diets low in carbohydrates will deplete liver and muscle glycogen stores faster.
When athletes compete at high VO2 percentages and may become somewhat anaerobic they are no longer able to utilize fat as efficiently and will predominantly rely on glycogen and glucose as energy sources so consuming a diet sufficient in carbohydrates is beneficial. VO2 max, or maximal oxygen consumption, is the maximum amount of oxygen that someone can use during intense or maximal exercise. This measurement is used to describe cardiovascular fitness and aerobic endurance. The most oxygen someone can use during exercise, the more energy they can produce.
To ensure adequate glycogen stores, athletes should consume at least 300-400 grams of carbohydrates per day during training and leading up to an event. On event day, they should consume a meal of 150-300 grams of carbohydrates around 3-4 hours before competition as well as consuming a 60-120 gram carbohydrate snack an hour before competition, and around 50 grams of carbohydrate immediately before competition. During exercise, athletes should consume at least 30-60 grams of carbohydrate per hour, ideally consumed in smaller amounts every 10-15 minutes throughout competition as well as training to avoid depletion and to maximize performance.
How do I replenish glycogen after a workout?
After intense activity, replenishing glycogen stores is crucial to tissue repair, initial recovery, and also helps you bounce back for the next workout. Glycogen synthesis is a somewhat slow process so in order to maximize this, a carbohydrate supplement immediately after exercise with protein is a good practice. A good rule of thumb is to consume 4 grams of carbohydrate to 1 gram of protein. Try chocolate milk or a banana and peanut butter, there’s a reason you always see these snacks at the end of races.
Sources
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