Carbohydrate Loading

Carbohydrate loading, also called glycogen loading, is a pre-exercise nutrition strategy designed to increase the amount of glycogen stored in skeletal muscle before prolonged endurance exercise. Glycogen is the stored form of glucose in muscle and is an important fuel during sustained or relatively high-intensity exercise. Raising muscle glycogen above usual resting levels is known as glycogen supercompensation .^1,2

The strategy combines increased carbohydrate availability with a reduction in training load before an event. The additional dietary carbohydrate supplies glucose that can be stored as glycogen, while lighter training reduces glycogen use. Together, these conditions allow muscle glycogen stores to accumulate to higher levels before exercise begins .^1,2

Early carbohydrate-loading protocols included several days of glycogen-depleting exercise and carbohydrate restriction before a high-carbohydrate phase. Later research showed that this depletion phase is not necessary for trained athletes. High carbohydrate intake combined with tapered training or rest can produce substantial glycogen supercompensation without first deliberately exhausting glycogen stores .^2,3

Carbohydrate loading is distinct from consuming carbohydrate immediately before or during exercise. Those strategies provide carbohydrate closer to the time it is used, whereas carbohydrate loading specifically aims to increase muscle glycogen stores before exercise begins. Its main relevance is to prolonged endurance events in which declining glycogen availability can contribute to fatigue .^1,3