Glycogen is an important energy store for the body.
Skeletal muscle and liver, both of which are essential to normal body function, store this important substance. Liver glycogen, for example, plays a role in regulating blood sugar levels and homeostasis. On the other hand, muscle glycogen helps in the contraction of skeletal muscle and thereby physical activity.
Learning about this substance and its many roles in the body will help an individual better understand sugar regulation, storage, and its significance in both exercise and dieting.
What is Glycogen?
Glycogen is a sugar (or carbohydrate) in its storage form. Sugars, which can go by many names including glucose and carbohydrate, transform and store in the body. These stores are then accessible when needed—such as in exercise and in-between meals. It is significant for maintaining daily energy levels as well as stable moods.
Uses for Glycogen:
This carbohydrate lives primarily in skeletal muscle and liver. The liver is the major site of storage, compared to skeletal muscle (approximately a 5:1 ratio) (1). The distribution in its stores between the muscle and liver are better understood by taking into account the regulatory functions influencing its storage.
Stores in the liver assist in regulating sugar-dependent functions of the entire body. For example, low blood sugar levels due to glycogen depletion can affect cognition (brain function) because sugar is the brain’s primary source of energy.
In periods of carbohydrate starvation, one may experience headaches, mood swings, trouble concentrating, and fatigue. When this happens, the body shifts to other sources of energy to maintain brain and other functions—such as breaking down fats into what are known as ketone bodies. Some diet plans, including ketogenic diets, exploit this response by the body for weight loss purposes.
In skeletal muscle, stores of this substance are accessible to fuel and regulate physical activity. It is especially important to fuel high-intensity exercise and explosive movements.
During exercise, depletion of carbohydrate stores leads to the onset of fatigue. For this reason, many distance athletes practice “carbohydrate loading”. This is a technique in which one consumes large amounts of carbohydrates the night before or the morning of a big event. This is done to maximize glycogen stores before the event to delay the onset of fatigue and supplement athletic performance.
Sports and Exercise:
The roles of carbohydrate and of glycogen stores in athletic performance and skeletal muscle are well documented. For this reason, sports drinks such as Gatorade and other workout drinks include some type of carbohydrate in their formula. The goal is to replenish carbohydrate stores during exercise to delay the onset of fatigue and sustain exercise longer.
Distance athletes have developed many techniques such as carbohydrate loading and training adaptations to influence athletic performance through glycogen availability.
Glycogen and Insulin Sensitivity:
By now most everyone can see that there is a connection between glycogen storage, blood sugar, insulin, and Type-2 Diabetes. In fact, insulin resistance characterizes Type-2 Diabetes, and insulin is an important hormone for storage.
Insulin is most known for its role in regulating blood sugar. In a normal individual, the presence of insulin triggers the transformation of glucose to glycogen and its subsequent storage in the liver and muscle. When insulin resistance occurs, cells become desensitized to insulin and limit its ability to promote carbohydrate storage.
This leads to a build-up of both sugar and insulin in the blood, which has detrimental effects on the body at molecular, tissue, and organ levels.
Exercise and Insulin Sensitivity:
Exercise, which relies heavily on glycogen stores and available carbohydrates, helps combat insulin-resistance and thereby Type-2 Diabetes. Skeletal muscle consumes carbohydrates, or sugar, to fuel muscle contraction during exercise, especially high-intensity exercise. This includes the extraction of free-floating carbohydrates in the blood and glycogen stores in the muscle.
Exercise, therefore, helps normalize circulating blood sugar levels and is therapeutic to Type-2 Diabetes. Additionally, there is an increase in insulin sensitivity immediately after exercise, which stabilizes blood sugar for longer.
Understanding how your body works in conjunction with diet, exercise, and lifestyle can be confusing. Luckily, you don’t have to go it alone! Santa Cruz CORE offers excellent treatments and assessments which can help you to become more adept at recognizing what your body needs and finding better balance in your life.