ENERGY SYSTEMS
Adenosine Triphosphate (ATP) The molecules responsible for the release of energy in the human body are Adenosine Triphosphate (ATP). ATP is comprised of adenosine and three phosphate groups and when energy is required for muscular work the brain sends nerve impulses to stimulate the required muscles. The chemical reaction takes place in which ATP is split at the third phosphate molecule and energy is released. Once the ATP molecule is split and energy is released, the ATP must be reformed or resynthesised using another source of energy if the muscular work or muscular contraction is to continue. Adenosine diphosphate (ADP) is one of the chemical products of the breakdown of ATP for energy production during muscle contraction. The energy that is required converts the ADP back into ATP to start the process again of remaking ATP again to produce more energy. (education and communties, 2013) The energy systems should not be thought of as working independently of one another, but more so where one system is used predominantly at any given point, depending on the duration and intensity of the activity. For example, sparring in Taekwondo although it’s a short period of time (which is only 5-10 seconds long) use the aerobic system to provide constant energy required to continually kick and punch the opponent – usually at moderate levels of intensity. Occasionally, using a powerful kick such as a roundhouse usually only last a few seconds, and uses the anaerobic energy systems. (Amezdroz G, Dickens S, Hostford G, Stewart T, Davis D, 2012) Creatine Phosphate (CP) The chemical stored in muscle fibres that can donate its phosphate to ADP to rapidly replenish cell stores of ATP is the Creatine Phosphate system (CP). To resynthesize the ADP to ATP the phosphate from CP is needed. The enzyme of creatine kinase speeds up a chemical reaction that results in the separation of the creatine and phosphate and the release of energy. Creatine Phosphate is then used to recombine ADP and creatine phosphate is used to re-form ATP, e.g. For every 1 one molecule of CP, it can resynthesises one molecule of ATP. However there is only a limited store of CP, which means that this process can only be repeated a limited number of times, generally for 10 seconds and at high intensity. (Amezdroz G, Dickens S, Hostford G, Stewart T, Davis D, 2012) After the 10 seconds of high intensity the CP stores are depleted. The CP stores in the muscle can be resynthesised during low-intensity exercise or at rest. It can only take several minutes to fully restore CP in the muscle, which is why athletes training for speed must ensure their recovery times between each effort are adequate. (Amezdroz G, Dickens S, Hostford G, Stewart T, Davis D, 2012) Lactic Acid The lactic acid is the second anaerobic system. The system provides the energy for the resynthesis of ATP during high-intensity, moderate-duration activities lasting 30 seconds to 2 minutes. The lactic acid system, takes over when CP stores become depleted. It supplies the ATP that is in our muscles need to keep exercising, particularly when exercising at a high intensity. It does not require oxygen to produce energy and it uses glycogen or glucose. If the lactic acid is not cleared from the muscle it can make the muscle burn due to an insufficient amount of oxygen. The acidity levels in the muscle build up and result in acidosis. Acidosis is an excessive acid condition which affects the body fluids or tissues. Acidosis affects the cellular processes within the muscle, thus impairing energy production and muscle contraction. Not clearing the lactic acid from the muscles is the limiting factor in this system. (NSW government , 2013) Aerobic System The aerobic system is the most complex of the three energy systems, with many more reactions occurring to provide the energy to resynthesise ATP. This system uses carbohydrates and fats as the primary fuels in the presence of oxygen, which is why it is also known as the aerobic system. The aerobic capacity is virtually unlimited and is active in exercise of more than a few minutes duration. It can take the pyruvic acid produced by the lactic acid system and converts it to energy instead of lactic acid with using oxygen to complete this process. The muscles in your body require a steady supply of ATP during sustained activities like walking, running, swimming, cycling, rowing, and cross-country skiing, which you usually do for longer than two minutes. (Amezdroz G, Dickens S, Hostford G, Stewart T, Davis D, 2012) |