While glycogen is indispensable to athletes, we have a very limited capacity to store it. Despite its limited storage capacity, glycogen is crucial for energy production at all levels of effort. Research has shown that aerobic endurance is directly related to the initial muscle glycogen stores, that strenuous exercise cannot be maintained once these stores are depleted, and that perception of fatigue during prolonged intense exercise parallels the decline in muscle glycogen 3.
Ensure you are optimizing glycogen stores before exercise, maintaining it during exercise, and replenishing it after exercise.
What is Glycogen? You burn about one gram per minute just riding along; about two grams per minute at endurance pace, and three grams per minute at race pace. So most people will start to tap out their glycogen supply after 90 to minutes. Repeated high-intensity efforts can drain your stores more rapidly. You bonk. That means slowing way down. You may feel weak; your legs seem heavy; and sometimes your brain can get foggy.
That amount, of course, is based on your body composition and how active you are. Use these recommendations on exercise level and daily carb intake and as your guide.
Each gram of carbohydrate provides four calories of energy. Aim for a minimum of 30 to 60 grams an hour on long rides. Include some protein, which helps speed glycogen storage and muscle fiber repair. Finally, building a strong endurance base will help you be a better fat burner at higher intensities.
When this happens, an enzyme called glycogen phosphorylase starts breaking glycogen down to supply the body with glucose. For the next eight to 12 hours, glucose derived from liver glycogen becomes the body's primary energy source. Your brain consumes more than half of the body's blood glucose during periods of inactivity.
What you eat and how much you move around also influence glycogen production. The effects are especially acute if you're following a low-carb diet , where the primary source of glucose synthesis—carbohydrate—is suddenly restricted.
When first starting a low-carb diet, your body's glycogen stores can be severely depleted and you may experience symptoms like fatigue and mental dullness. Additionally, any amount of weight loss can have the same effect on glycogen stores. Initially, you may experience a rapid drop in weight.
After a period of time, your weight may plateau and possibly even increase. The phenomenon is partly due to the composition of glycogen, which is primarily water. In fact, the water in these molecules accounts for three to four times the weight of the glucose itself. As such, rapid depletion of glycogen at the onset of the diet triggers the loss of water weight. Over time, glycogen stores are renewed and the water weight begins to return.
When this happens, weight loss may stall or plateau. Gains experienced in the beginning come from water loss, not fat loss, and are only temporary. Fat loss can continue despite the short-term plateau effect. The body can store around 2, calories of glucose as glycogen. For endurance athletes who burn that many calories in a couple of hours, the amount of stored glucose can be an impediment.
When these athletes run out of glycogen, their performance almost immediately begins to suffer—a state commonly described as "hitting the wall. If you're undertaking a strenuous exercise routine, there are several strategies endurance athletes use to avoid decreased performance you may find helpful:. Get exercise tips to make your workouts less work and more fun.
Low-carbohydrate weight-loss diets. Effects on cognition and mood. Glycogen metabolism in humans.
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