Chapter 6 PE
Hypoglycaemia
A condition created when blood glucose levels are significantly reduced, often during extended endurance activities calling upon glycogen reserves in the liver.
Glycogen sparing
A long term adaptation (resulting from aerobic training) that allows fats to be used more readily and earlier during performances; this results in less use of lactic acid system and allow glycogen to be used much later in performances.
Summary of anaerobic glycolysis
This system produces lactic acid, which can be broken down (without oxygen) to glycogen to provide energy (ATP) Like the ATP-PC system, the anaerobic Glycolysis system supplies energy from the start of intense exercise. Peak power is usually reached between 5 and 15 seconds and the system continues to contribute to ATP production until it fatigues, after 2 to 3 minutes. An active recovery is the best way to recover this system. It keeps oxygen levels elevated, meaning there is more oxygen in the system to break down lactic acid faster.
Training the anaerobic glycolysis system
Training sessions occurring about the anaerobic threshold (85% max HR) for 45-60 seconds will improve the anaerobic Glycolysis system. This system has also been proved to have the greatest capacity to improve with training. Any work performed at or above the anaerobic threshold will promote increase lactic acid tolerance and delayed lactate inflexion point.
Steady state
When the body is able to supply sufficient oxygen to meet the oxygen demands
Types of aerobic systems
*Aerobic Glycolysis: The breakdown of glycogen when oxygen is present *Aerobic Lipolysis: The breakdown of fats when oxygen is present
Energy systems are dependant on..
-The duration of the exercise -The intensity of the exercise -Whether or not oxygen is present -The depletion of chemical and food fuels during exercise.
Fats as a fuel source
A problem occurs when liver glycogen is depleted and an athlete is unable to sustain blood glucose levels. Hypoglycaemia sets in and the athlete depends heavily on fat to supply energy. This is quickly resolved by ingesting sugary drinks. Endurance athletes tend to increase their ability to use fatty acids for ATP resynthesises by increasing the number of mitochondria they develop, and by glycogen sparing.
Interplay
A situation in which all three energy systems contribute to ATP production, with one system being the major ATP producer at any time.
Rates and yield of ATP
ATP-PC: High Rate, Low Yield Anaerobic Glycolysis: High Rate, Low Yield Aerobic System: Low Rate, High Yield
Food as energy sources
Adenosine Triphosphate: ATP is the major source of energy that keeps every cell in the body going, including muscles. ATP is a chemical fuel source, and consists of an adenosine molecule with three phosphates joined together in a row. Energy is released when one of the phosphates spills off, changing ATP into adenosine diphosphate (ADP) and an inorganic phosphate (Pi). The chemical reactions that turn the energy contained in ATP into energy for use in muscular contractions can be summarised as follows. Chemically ATP is bound to three phosphates When a cell needs energy, it breaks the bond between the second and third phosphate groups, which releases a large amount of energy, forming ADP and Pi.
The aerobic glycolysis system
Aerobic Glycolysis system uses oxygen to break down glycogen and fats in order to resynthesise ATP. ATP is produced at the slowest rate of the three systems, but can continue to supply energy for many hours, as long as sufficient fuel supplies exist. When sufficient oxygen is supplied to meet demand, the body is said to have reached steady state, which is when the body is able to supply sufficient oxygen to meet the oxygen demands. As a result of the increased oxygen cost associated with the transition from carbohydrates to fats as the main fuel source, less oxygen becomes available to working muscles which explains why athletes usually 'slow down' when fats are used during high-intensity activities. This system tends to dominate ATP resynthesis after 30 seconds when an athlete's oxygen uptake can be as high as 90%. The three by-products of the aerobic system are water, heat and carbon dioxide.
Training the Aerobic system
An aerobic performer who can significantly increase their anaerobic threshold can perform at a higher intensity more efficiently. Training the aerobic system can be divided into high or low intensity bouts and can use continuous or long-interval training sessions.
Anaerobic glycolysis system
Anaerobic Glycolysis refers to energy provided by the incomplete breakdown of glucose when oxygen isn't available. Maximal efforts can only be sustained for 20 seconds. Glycogen is broken down with oxygen and all of the pyruvic acid produced during anaerobic Glycolysis is converted into lactic acid. A by-product of this process is the production of hydrogen ions (H+), which cause muscles to become more acidity therefore restraining Glycolysis. Hydrogen ions are responsible for the inability of muscles to contract maximally due to a decrease in the activity of certain enzymes caused by the increase acidity in muscles. This is a safety mechanism to prevent the cells being destroyed under extremely acidic conditions. Hydrogen ions cause fatigue by accumulating in muscle tissue making contractions painful and causing fatigue.
Glycogen
Energy for muscular contraction stems first from muscle glycogen and then liver glycogen. Glycogen is the bodies preferred fuel source in high-intensity exercises and in comparison to fat, as less they require less oxygen to break down to produce the same amount of energy. It can be broken down with and without oxygen, this is known as aerobic Glycolysis (with oxygen) and one glucose molecule yields 36 to 38 ATP molecules whilst only 2 to 3 ATP molecules are produced without oxygen (anaerobic Glycolysis). High-intensity aerobic exercise predominantly uses carbohydrates as its preferred fuel source.
Fats (triglycerides)
Fats in the form of triglycerides are stored through the body in adipose tissue, under the skin and in the muscles. Triglycerides are broken down into free fatty acids, which in turn are broken down aerobically to provide energy for movement. Fats can only be broken down in the presence of oxygen (aerobically) however they are not the preferred fuel source as it puts added stress of the oxygen and transport and delivery system. During sub-maximal prolonged exercise, fat becomes predominant as glycogen depletes. 1 triglyceride produces 450 ATP molecules, whilst 1 FFA (free fatty acid) produces 147 ATP molecules.
Training the energy systems
It is imperative that once activity or performance demands have been determined from a games analysis, these are replicat4d in training. The best training program will also focus on frequency, intensity, duration, and progressive overload.
Summary of aerobic system
It requires oxygen which can be provided (90% VO2 max) within 60 seconds The system provides 30 to 50 times as much ATP as the ATP and aerobic Glycolysis systems combined It prefers the breakdown of carbohydrates rather than fats to release energy as less oxygen is needed to break down carbohydrates The aerobic system does not release toxic or fatiguing by-products and can be used indefinitely Fats can produce more ATP than carbohydrates, but they require more oxygen to produce an equivalent amount of ATP It releases no toxic/fatiguing by-products and can be used indefinitely The first stage involves fats and carbohydrates being broken down to release energy. Fats are stored as triglycerides, which are made up of glycerol and three free fatty acid (FFA) molecules The second stage involves the pyruvic acid being broken down into carbon dioxide with further energy being released to resynthesise ATP The third and final stage is the electron transport system, which involves water (sweating), heat and large amounts of ATP being released
Training the ATP-PC system
Short-interval, sprint training or plyometrics are favoured training methods to develop the capacity of the ATP-PC system. It is recommended that high or maximal- intensity efforts lasting up to 10 seconds are followed by adequate time to allow full replenishment of PC, usually 3 minutes of passive recovery is enough to restore PC levels. Alternatively, resistance or weight training can be used, where maximal effort occurs up to 5 seconds. This would involve several repetitions of heavy weights, performed explosively, and mindful of using muscle groups specific to actions observed during games analysis.
ATP- PC
The ATP-PC energy system produces energy by breaking down phosphocreatine (PC) to resynthesise adenosine Triphosphate (ATP). ATP is resynthesised through chemical reactions that do not require oxygen (anaerobic). It is worth noting that all activities that are carried out about 100% VO2 max depend on an anaerobic energy supply, and if PC has had time to replenish, this will by 'powered' by the anaerobic Glycolysis system. PC, like ATP, is stored in muscle cells and contains phosphate bonds which, when broken, provide large amounts of energy. PC 'splits' into Creatine (C) and inorganic phosphate (Pi). The energy that results from the splitting of the phosphate is linked to the resynthesis of ATP. As rapidly as ATP is broken down by muscular contractions, it is continuously reformed from ADP and Pi by energy released by the breakdown of PC stored in muscle, this is catalysed by the enzyme kinase.
summary of ATP PC system
The ATP-PC system does not require oxygen to release energy (anaerobic) The ATP-PC system provides the fastest rate of ATP release for energy because it depends on simple and short chemical reactions and ready availability of PC in muscles The ATP-PC system is anaerobic and so does not depend on oxygen being transported to working muscles to release energy. A limited amount of PC is stored in the muscles (about 10 seconds worth at maximal intensity), with larger muscles capable of storing slightly more PC than this (12-14 seconds at maximal intensity) ATP and PC are stored in the muscles and available for immediate energy release. This system is limited by the amount of PC stored in the muscles - the more intense the activity, the quicker this is utilised to produce ATP. After 5 seconds of maximal activity the anaerobic Glycolysis system becomes the major producer of ATP Once PC has been depleted in the muscle, ATP must be resynthesised from another substance - typically glycogen, which is stored in the muscles and liver - via anaerobic Glycolysis using the anaerobic Glycolysis system. The individual must rest for 3-10 minutes, for this system to replenish This system supports maximal intensity activity (95%) + maximum heart rate). Max heart rate = 220 - age.