Carbohydrates are perhaps the most important component of an athlete's diet. These high-energy molecules, composed of carbon, hydrogen and oxygen, are the primary source of energy for the body's cells and should account for the majority of your caloric intake. Sufficient carbohydrate intake can also prevent protein breakdown and promote muscle growth, "prime" fat metabolism and fuel the brain and central nervous system. Both complex and simple carbohydrates have important roles in athletic training.
Complex Carbohydrates
Complex carbohydrates refer to either starch or fiber -- plant polysaccharides composed of hundreds of attached sugar molecules. Complex carbohydrates are generally better for athletes because they are digested slowly, contributing a lasting source of energy to the diet and a prolonged feeling of satiety. Complex carbohydrates are ultimately broken down into units of glucose, which the body uses for immediate energy, stores in the muscles and liver for later use, stores as fat for later energy use, or uses to synthesize protein.
The best sources of complex carbohydrates, according to the Harvard School of Public Health, include whole grains, vegetables, fruits and beans. Nuts can also be a rich source of complex carbohydrates.
Simple Carbohydrates
Simple carbohydrates refer to either monosaccharides or disaccharides -- simple sugars containing either one or two attached saccharide molecules. Due to their simpler chemical structure, these carbohydrates are digested quickly and converted to glucose, causing an instant rise in blood glucose levels. Simple carbohydrates are ideal for pre-competition and pre-workout meals in which the body is in need of instant energy. They also are good following workouts or competitions to help replenish depleted muscle glycogen.
You can find simple carbohydrates in any product that contains a lot of sugar, such as chocolate candies and grain-based desserts, as well as fruit and fruit juice.
Carbohydrate Loading
Carbohydrate loading is a strategy athletes use to enhance glycogen storage in the muscles. Normal muscle glycogen storage is about 1.7 g per 100 g of muscle, but it can be elevated to 5 g per 100 g after a well-designed carbohydrate loading program. Non-athlete populations generally need to consume about 45 to 65 percent of their calories from carbohydrates. Athletes can enhance glycogen storage by consuming between 60 and 70 percent of their total calories from carbohydrates, according to "Essentials of Exercise Physiology." Both complex and simple carbohydrates can help you achieve increased muscle glycogen levels, although complex carbohydrates are generally better because of their less-undulating effect on blood sugar.
Specific Training Recommendations
"Essentials of Exercise Physiology" recommends consuming glucose at least 60 minutes before exercise to help increase endurance during physical activity. Fructose is generally not recommended because of its adverse gastrointestinal effects and possible limited availability for energy. During exercise, consuming about 60 g of either liquid or solid, and either simple or complex carbohydrates, can improve exercise performance and delay fatigue. Consuming 50 to 75 g of carbohydrate-rich, high-glycemic foods following exercise can help to restore muscle glycogen.
References
- "Essentials of Exercise Physiology"; William D. McArdle et al.; 2006
- "Essentials of Strength Training and Conditioning"; Thomas Baechle and Roger Earle (Editors); 2008
- Institute of Medicine; Dietary Reference Intakes; Macronutrients; 2005
- Harvard School of Public Health: Carbohydrates -- What Should You Eat?
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