Carbohydrates are the most important fuel food for athletes. Regardless of the sport, carbohydrates are the body’s preferred source of energy. They are broken down into simple sugars, absorbed, and converted into energy to fuel muscle contractions.

Glucose that is not needed immediately is stored in muscle tissue and the liver in the form of glycogen. Most exercise relies on stored glycogen for energy, especially when short bursts of energy are needed, as in weight lifting or in the stop-and-go sprinting of racket sports.

During longer endurance sports, the body uses fat as energy, but it relies on glycogen to convert the fat into something the muscles can use.

Depletion of glycogen stores, through prolonged exercise, or an inadequate diet, results in the dreaded “bonk,” also known as “hitting the wall.” The body runs out of fuel for immediate exercise. This typically occurs after 60 to 90 minutes of vigorous activity, depending on the conditioning of the athlete. To avoid this, athletes try to increase glycogen stores before exercising, replenish during the activity, and refill afterward to prepare for the next workout.

Simple sugars are the easiest form of carbohydrates for the body to absorb. Because they convert quickly to energy, they are an essential element of sports drinks. (The speed with which they are converted can be experienced in the dreaded “sugar high.”) Complex carbohydrates take longer to absorb, and therefore fuel the body at a slower rate.

To increase glycogen stores, complex carbohydrates from starch are preferred. Foods like potatoes, pasta, whole grains, and cereals are an important element in the athlete’s diet.