ATP and Muscles In order for muscles to contract, there needs to be a significant amount of energy present. So, the question is where does all the energy come from in order to power the muscle? The answer is in adenosine triphosphate, better known as ATP. ATP can be defined as energy that is packaged away in the cell. The energy, through cellular respiration, is released from the cell as adenosine diphosphate. Then a phosphate group is added. This produces adenosine triphosphate or ATP. The process is reversed when energy is needed in the cell. A phosphate group can be extracted from ATP, to give the cell ADP and phosphate, followed by a burst of energy. Just as the cell produces ATP, the muscle fibers also must produce ATP. In fact, there are 3 ways that ATP can be created in muscle. The first is the process known as aerobic respiration. Aerobic respiration involves two main ingredients, glucose and oxygen. After reacting with each other, the result is ADP and phosphate turning into ATP. Aerobic respiration is a very efficient way to produce ATP. For example, if a glucose molecule is burned off, that means that 36 molecules of ATP were produced. When burning glucose, carbon dioxide and water are the only waste products. There are some problems to think about when considering aerobic respiration. First, the process takes a long time. It also requires a power source, which includes a food source, glucose, and oxygen. Another fault with aerobic respiration is that it can’t deliver lots of energy in a short amount of time. The most practical time muscle fibers use this process is used is during rest and sleep. During these times, energy is less demanded. Aerobic respiration is most commonly applicable to exercise warm-ups and long-distance running. Muscle fibers use times of rest to store energy in reserve. The second way muscle fibers produce energy is through creatine phosphate. Creatine phosphate is a chemical that is produced from aerobic respiration. This chemical can be held on reserve in the muscle. Another important fact to know is that creatine phosphate is extremely high energy. Creatine phosphate can react with ADP to get creatine and ATP. This reaction is important because it creates energy efficiently and at high speeds. With this, muscle can easily convert ADP to ATP. When ATP is being used in large quantities, the creatine phosphate can replenish the lost ATP. In