Transcript Chapter 1
KEY KNOWLEDGE The characteristics of the two anaerobic (without oxygen) and aerobic (with oxygen) energy pathways. The energy pathways used for different movement types and intensities and the dominant muscle fibre type linked to each pathway KEY SKILLS Identify the effects intensity and duration have on the anaerobic and aerobic energy pathways and use of predominant energy source. Participate in, analyse and report on class data linked to the anaerobic and aerobic pathways and associated exercise responses. Food Fuels •Carbohydrates, fats and proteins provide energy for ATP production. •Phosphocreatine (PC) is a chemical fuel source •Carbohydrates are our preferred exercise fuel either as blood glucose or muscle glycogen (2/3rds) & liver glycogen (1/3rd). They are: •Easy to access •Quick to breakdown (either with or without oxygen) •Plentiful (stored in large amounts) Carbohydrates Preferred source of fuel, especially during exercise. Broken down to glucose for almost immediate energy and then stored as glycogen in the muscles and liver. Glucose is absorbed from the intestines into the blood stream, then taken to the relevant muscles. Glucose enters the muscles through the aid of insulin. Insulin controls the levels of glucose in the blood by allowing glucose to be transferred from the bloodstream into the muscle. Excess carbs are stored as adipose tissue (fat). Fats Essential in our diet. Fats are involved in: • protecting body organs • maintaining body temperature • hormone production • energy storage and supply Essential fatty acids • health and wellbeing Free fatty acids • broken down aerobically to provide energy for movement. Fats • preferred source of fuel at rest • require more oxygen to produce energy • produce more ATP than carbohydrates • produce energy slowly Proteins Proteins are mainly consumed for growth and repair of body cells & tissues. Proteins: • are mainly used as a “last resort” fuel • produce energy slowest of all food fuels Energy from ATP When energy is required, one of the phosphate molecules breaks away from the ATP, releasing the stored energy. An ADP (adenosine diphosphate) molecule is now left. During aerobic effort or rest, oxygen assists with the reattachment of loose phosphate molecules to ADP. ADP + P = ATP Limited amounts of ATP are stored in the muscles. Adenosine Triphosphate (ATP) Three Energy Systems The body uses 3 methods of recovery to resynthesize (rebuild) ATP supplies. The three energy systems are: ATP-PC system (or phosphocreatine, alactacid) Anaerobic glycolysis system (or lactic acid, lactacid) Aerobic glycolysis (or oxygen, aerobic) All three energy systems work at the same time, but the contribution of each one depends on the intensity and duration of the activity. This is called INTERPLAY. All 3 systems work together to supply energy / ATP Intensity of Exercise vs. Preferred Food Fuels ATP-PC System (Phosphocreatine system) Provides energy during powerful & explosive efforts. Stored energy lasts approximately 10 seconds. After this, effort must be reduced. Does not require oxygen. Broken down ATP (ADP) combines with a phosphate molecule (from a phosphocreatine molecule) which then replenishes ATP. ATP stores can take 3-5 minutes to fully replenish once depleted. Muscle fibres = ?? Anaerobic Glycolysis System Provides energy during high-intensity, sub-maximal efforts, between 10-75 seconds. Does not require oxygen. Involves the incomplete breakdown of glycogen. Lack of oxygen leads to lactic acid production. Lactate threshold is the level at which lactic acid levels prevent an athlete from continuing to work at the same intensity, and can be increased as a result of training. Muscle fibres = ?? (Aerobic glycolysis) Provides energy in sub-maximal efforts. High levels of O2 allow ATP to be continuously replenished from ADP, and allows fat to be broken down easily and used for energy production. Fuels: During activity = carbohydrates At rest = fats (fats produce more ATP than carbs) Muscle fibres = ?? All 3 systems work together to supply energy / ATP Energy Contributions Activity Thinking things through Page 53 Summary of the ATP-PC energy system •Does not require oxygen to liberate energy (anaerobic) •The ATPPC system provides the most rapidly available source of ATP for energy because it depends on simple and short chemical reactions and ready availability of PC at muscles (PC being broken down to P + C). •A limited amount of PC is stored at the muscles (about 10 seconds’ worth at maximal intensity), with larger muscles capable of storing slightly more PC than this (12 to 14 seconds at maximal intensity). •There is approximately four times as much PC stored at muscles as there is ATP. •Once phosphocreatine has been depleted at the muscle, ATP must be resynthesised from another substance typically glycogen, which is stored at the muscles and the liver via anaerobic glycolysis using the lactic acid system. Summary of the Anaerobic Glycolysis energy system •The lactic-acid system is also anaerobic (doesn’t require oxygen to liberate energy) but involves more complicated and longer chemical reactions than the ATPPC system to release energy. •It also supplies energy from the start of intense exercise, and peak power from this system is usually reached between five and fifteen seconds and will continue to contribute to ATP production until it fatigues (two to three minutes). •It produces lactic acid, which can be broken down to glycogen to provide further energy. •It supplies ATP at a slower rate than the phosphagen system. •It provides energy for longer during submaximal activities when PC is depleted and lactic acid accumulation is slower. This provides a stop-gap until sufficient oxygen is transported to working muscles for the aerobic system to become the major energy contributor. •It provides twice as much energy for ATP resynthesis as the ATPPC system. Summary of the Aerobic energy system •The aerobic system is the slowest system to contribute towards ATP resynthesis due to the complex nature of its chemical reactions. •It is capable of producing the most energy in comparison to the other two energy systems ~ between 30-40 times •It preferentially breaks down carbohydrates rather than fats to release energy. •It provides 50 times as much ATP as the ATPPC and lactic acid systems combined. •It contributes significant amounts of energy during high-intensity/maximal activities lasting one to two minutes. •The aerobic system is also activated at the start of intense exercise, and peak power from this system is usually reached between one and two minutes and will continue to be the major ATP contributor as the lactic acid system decreases its contribution.