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Exercise Energy Systems – Powering The Body Using ATPExercise energy systems are the types of energy that the body possesses that can be used to fuel exercise at different stages of exercise. There are three systems which are used to help you start exercising, to speed up exercise and to sustain exercise and these are: the ATP (adenosine triphosphate)/CP (creatine phosphate) system, lactic acid system, and the oxygen system.
ATP/CP Energy System As exercise begins and the muscles begin to contract, the body has a reserve of energy in cells that is used immediately. This energy is the body’s immediate energy source, ATP which is adenosine triphosphate. Once the energy reserve of ATP is used up, then the body calls on its small reservoir of creatine phosphate in the muscles which it converts to ATP. In order to continue exercise the body must then call on its carbohydrate reserves stored as glycogen in the muscles and liver, which it then converts to glucose from which ATP is then extracted to provide additional energy. If an all out effort is being made, then this system can power the body’s efforts for only 3-15 seconds. The ATP/CP system does not require oxygen and is considered an anaerobic process meaning without oxygen. Lactic Acid Energy System As the pace begins to pick up during the acceleration stage of exercise which lasts about 1-2 minutes, the body then uses the lactic acid system to produce ATP from glucose. Lactic acid is actually a byproduct of the breakdown of glucose into ATP and was previously thought to be what causes muscle fatigue, but it is now known that it is the rise of acidity in the cells as a result of lactic acid accumulation that causes muscles to fatigue. To get the body over the hump of fatigued muscles the body moves on to the next energy system to remove this lactic acid and convert it into useable energy (more ATP) that will keep the body’s exercise efforts going. Oxygen Energy System This system is the reason that proper breathing is necessary during exercise, properly inhaling and exhaling. Taking in oxygen helps the power generating plants of the cell, the mitochondria to convert food and oxygen to energy ATP to fuel the body’s continued efforts, this is called an aerobic or oxygen using process. When the muscles are able to contract, the blood vessels dilate and deliver oxygen rich blood to muscle cells, which then allows ATP to be produced, and although the process is slower than the other two systems because oxygen must travel from lungs to blood to muscle cells to the mitochondria, the amount of energy produced is more abundant allowing the exercising body to get over the hump and complete the exercise routine. Depending on the type of exercise being performed and the level of intensity, one one of the exercise energy systems may at times predominate over the others, but it should be noted that all three systems are always active because we are active to some degree every waking hour of the day. The issue is to make these exercise energy systems work more efficiently in order to achieve a healthy body and a healthy weight, and to increase the body’s tolerance for exercise which will result in a healthy body that burns calories efficiently. Next:
For other information on nutrition some great references are: • Nutrition – Fourth Edition by Paul Insel, Don Ross, Kimberley McMahon, and Melissa Bernstein
Nutrition and Exercise
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