KEY KNOWLEDGEKEY SKILLS  The three energy systems (ATP-PC, anaerobic glycolysis, aerobic systems) including how they work together to produce ATP – both the rate and capacity of ATP production each system demonstrates  How food and chemical fuels are used during performance and their contribution to ATP resynthesis  The amount of ATP produced by each system (relative contribution) and the fuels called upon to resynthesise ATP whilst considering activity intensity, duration and type. Demonstrate an understanding of both the energy system interplay and collective contribution during a range of sporting activities  Collect primary data and report on a practical/physical activity designed to highlight the energy system interplay during that activity  Explain how the energy systems work together to supply energy during physical activity as well as energy system contribution to active and passive recoveries. © Cengage Learning Australia 2011

ATP = energy, and we only have a small amount stored in muscles (enough for a few movements) The three energy systems all work together (interplay) to rebuild ATP and keep us going A-P-P-P ↔ A-P-P & P We have two anaerobic energy systems – ATP-PC system and anaerobic glycolysis or lactic acid system as well as one aerobic energy system – the aerobic system © Cengage Learning Australia 2011

All three systems work together to supply energy/ATP © Cengage Learning Australia 2011

The three energy systems rebuild ATP by using – chemical fuels = phosphocreatine (PC) or food fuels = carbohydrates, fats and proteins. © Cengage Learning Australia 2011

The breakdown of glycogen can occur in the absence of oxygen (anaerobic) and primarily calls upon the anaerobic glycolysis energy system, or in the presence of oxygen and primarily call upon the aerobic energy system. Fats and proteins can only be broken down aerobically. Carbohydrates can be broken down both aerobically and anaerobically © Cengage Learning Australia 2011

All three energy systems are activated at the start of exercise (interplay) but one system will contribute more than the other two, depending on – intensity of exercise duration of exercise amount of oxygen able to be used by muscles depletion of chemical and food fuels during exercise © Cengage Learning Australia 2011

Intensity of exercise vs. preferred food fuels © Cengage Learning Australia 2011

Oxygen availability to muscles and fuel availability vs. preferred energy system usage © Cengage Learning Australia 2011

Notice the different fuels used depending on duration and intensity © Cengage Learning Australia 2011

Relative contributions of anaerobic (ATP–PC & LA) and aerobic energy to maximal exercise of varied duration © Cengage Learning Australia 2011

The carbohydrate-fat ‘fuel mixture’ during extended endurance events © Cengage Learning Australia 2011

Fats take a lot of oxygen away from working muscles in order to rebuild ATP, and they require many more chemical reactions than carbohydrates to be broken down in order to ‘recharge/rebuild’ ATP. Even though fats produce more energy than carbohydrates, they are not our preferred exercise fuel – why? © Cengage Learning Australia 2011

Summary of the ATP–PC energy system Does not require oxygen to liberate energy (anaerobic) The ATP  PC system provides the most rapidly available source of ATP for energy because it depends on simple and short chemical reactions and the ready availability of PC at muscles (PC being broken down to P + C). 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 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). ATP and PC are stored at the muscles and available for immediate energy release. This system is limited by the amount of PC stored at the muscles – the more intense the activity, the quicker this is utilised to produce ATP. After approximately five seconds of maximal activity, the PC stores are 40 to 50 per cent depleted and the lactic acid system becomes the major producer of ATP. There is approximately four times as much PC stored at muscles as there is ATP. Once PC has been depleted, it can only be replenished when there is sufficient energy in the body, and this usually occurs through the aerobic pathway or during recovery once the activity has stopped. 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. © Cengage Learning Australia 2011

Summary of the anaerobic glycolysis energy system The lactic acid system produces ATP without oxygen, hence it is referred to as anaerobic glycolysis. The lactic acid system is also anaerobic (doesn’t require oxygen to liberate energy), but involves more complicated and longer chemical reactions than the ATP  PC 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). During maximal exercise, the rate of glycolysis may increase to 100 times the rate at rest. It produces lactic acid, which can be broken down to glycogen to provide further energy. About 12 chemical reactions take place to make ATP under this process, so 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 stopgap 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 ATP  PC system. It increases it’s ATP contribution if performance intensity exceeds the lactate inflection point. © Cengage Learning Australia 2011

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 to 40 times. It requires oxygen, which can be provided (90% of VO 2 max) within 60 seconds. It involves many more complex chemical reactions than the ATP  PC and lactic acid systems to release energy. It preferentially breaks down carbohydrates rather than fats to release energy. 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. It provides 50 times as much ATP as the ATP  PC 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. © Cengage Learning Australia 2011

The ATP–PC and anaerobic glycolysis energy systems produce energy very quickly, but in relatively small amounts and are quickly fatigued (limited fuel sources). The aerobic energy system produces energy slower than the two anaerobic energy systems, but is capable of producing very large amounts of energy (it can call upon all three food fuels). Energy system rate of ATP production vs. capacity (amount of ATP production) © Cengage Learning Australia 2011

Capacity of chemical and food fuels © Cengage Learning Australia 2011

As the running distance is increased, notice the increased contribution from the aerobic energy system and the ‘fixed’ or finite contribution from the anaerobic systems – in particular the anaerobic glycolysis or LA system. © Cengage Learning Australia 2011