Interactive Summaries

Chapter 14: Sports Nutrition: Eating for Peak Performance

Energy Systems, Muscles, and Physical Performance

Our muscles process fuel in the form of chemical energy to produce power for physical performance. Although your body contains hundreds of muscles, there are only three types of muscles. The muscles are bundles of parallel, striated fibers attached to your skeleton and are under conscious control. Your body contains more than muscle cells. There are two types of muscle fibers that make up muscle cells – fast twitch and slow twitch. Slow twitch fibers . During shorter, higher-intensity endurance events like a mile run or a 400-meter swim the body utilizes . determine an individual's percentage of slow twitch fibers and fast twitch fibers.

ATP supplies the energy for muscle fiber contraction and relaxation. To produce ATP your muscles use the ATP-CP energy system, lactic acid energy system, and the oxygen energy system. Muscles store enough ATP to sustain muscle movements for . The body also stores creatine phosphate to . After 3 to 15 seconds your body has used up its entire ATP and CP stores. Using the anaerobic glycolysis system, also known as , muscle cells can break down thousands of glucose molecules from stored muscle glycogen to form ATP. This process causes the muscle cell to become more acidic which . In comparison to the ATP-CP and the lactic acid energy system, the oxygen energy system .

Optimal Nutrition for Athletic Performance

Athletes need to fill their glycogen stores prior to training or competition to ensure adequate stores of muscle glycogen and blood glucose concentrations. In the 1 to 4 hours before exercise, the rule of thumb is to consume of carbohydrate per kilogram of body weight. Since protein and fat take longer to digest and absorb, pre-exercise meals should contain no more than of the calories as protein and less than of calories from fat. The best way to replenish glycogen stores after intense exercise is to consume 1 to 1.5 grams of carbohydrate per kilogram of body weight within after a workout. Consuming a high-glycemic-index food during the first few hours after exercise can improve glycogen synthesis. An example of a high-glycemic-index food is . Fat is the main source of energy during low-to-moderate intensity exercise. Some athletes believe that protein intake in excess of recommended amounts will enhance lean muscle mass. A problem with high-protein diets is that .

Nutrition Supplements and Ergogenic Aids

For most athletes who select a variety of foods and meet their energy needs, supplements are not necessary. supplements are sometimes recommended for female athletes who may not get enough in their diets. Because of the documented widespread contamination of nutritional supplements, high performance athletes are generally advised to stay away from supplements as their are not guaranteed. supplements are meal replacement powders, ready to drink supplements, energy bars, and energy gels. Taking large doses of as been shown to cause less use of muscle glycogen during exercise and increased endurance. Its benefits are outweighed by the fact that the substance promotes water loss.

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