Proper nutrition is critical to optimizing athletic performance. The term bioenergetics describes how cells possess chemical pathways that are capable of converting food into biologically usable forms of energy. For athletes' muscles to be able to continue to contract and perform, their muscle cells must have a continuous supply of energy. In addition to needing additional calories, athletes need more fluids and an adequate supply of vitamins and minerals that play indirect, supporting roles in the use of energy.
Carbohydrates
Carbohydrates are the body's primary source of fuel and can be stored in the form of glycogen in the muscle and liver for future energy use. Athletes training on a daily basis or competing frequently should obtain 65 to 70 percent of their calories from a variety of carbohydrates, including fruit, vegetables, whole grains and beans.
According to "Exercise Physiology," an athlete's initial levels of carbohydrate stores determine his capacity to sustain prolonged exercise; ample glycogen reserves must be achieved prior to performance.
Fat
Fat is the body's most concentrated source of fuel, providing nine calories per gram, compared with four per gram for carbohydrates and protein. Fat is utilized as a fuel source during prolonged moderate exercise. Athletes should avoid a high-fat diet, particularly one high in saturated fat. Fat sources should be healthy monounsaturated or omega-3 fatty acids, including nuts and salmon, and should make up 20 to 25 percent of the diet.
Protein
While protein is critical for rebuilding muscle, protein is not a significant source of energy during exercise. The amount of protein required by an athlete depends on the type and intensity of exercise performed. For low-intensity exercise, the Recommended Daily Allowance, or RDA, is 0.8 grams per kilogram, or g/kg, of body weight. For high-intensity endurance exercise, the requirement is 1.2 to 1.4 g/kg of body weight. For strength training athletes, requirements may be up to 1.7 g/kg of body weight.
Vitamins and Iron
The RDA for certain vitamins is related to energy expenditure and nutritional status. Vitamins that support the metabolism of athletes include the B-complex vitamins thiamine, riboflavin and niacin.
Vitamin supplementation is unnecessary for an athlete on a well-balanced diet. However, for those with a clear deficiency, supplementation may be necessary.
Iron is an essential mineral for athletes, and inadequate intake is the primary cause of iron deficiency in female athletes. Exercise has been associated with increased hemoglobin loss in feces, sweat and urine, increasing an athlete's risk for iron deficiency anemia. According to Colorado State University, "female athletes and athletes between 13 and 19 years old may have inadequate supplies of iron."
Electrolytes
The elements sodium, potassium, magnesium and chloride are collectively termed electrolytes, which play an immense role in muscle contraction, maintaining proper levels of fluid in the body and regulating acid-base balance of fluids. Because electrolytes are lost in sweat during exercise, they must be replaced by fluids. One glass of orange juice can replace the amount of potassium excreted in two to three quarts of perspiration.
References
- "Total Nutrition: The Only Guide You'll Ever Need"; Victor Herbert and Gesell Subak-Sharpe; 1995
- "Exercise Physiology"; Scott Powers and Edward Howley; 2007
- Colorado State University: Nutrition for the Athlete
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