Interactive Summaries

Chapter 11: Sports Nutrition: Eating for Peak Performance

Energy for Optimal 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. 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 .

Nutrition Supplements and Ergogenic Aids

For most athletes who select a variety of foods and meet their energy needs, nutritional supplements are not necessary. However, iron and supplements may be recommended for athletes if their diets are low in these nutrients. Liquid supplements and sports bars that contain carbohydrates, proteins, and fats can provide an easy way to increase intake. One way athletes try to increase muscle mass is to add extra calories from to their diet. Protein powders are a relatively easy way to add extra calories. Studies show that only about of weight gain on high-calorie diets is muscle, while the remaining amount of weight gained is . Caution should be used when weight-gain powders are used because the extra calories ingested may increase body fat rather than .

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