A summary of the energy systems and how they relate to sport and training – Year 10 HPE © Cengage Learning Australia 2011

Predominant Energy Pathways ATP-CP Energy System (0-10 seconds) Anaerobic Energy System (up to 2-3 minutes) Aerobic Energy System (2 minutes +)

Carbohydrates, fats and proteins are the only food fuels that produce energy Phosphocreatine (PC) is a chemical fuel source Food Fuels Carbohydrates are our preferred exercise fuel either as blood glucose or muscle glycogen (2/3) and liver glycogen (1/3). They are: easy to access quick to breakdown (either with or without oxygen) plentiful (stored in large amounts) © Cengage Learning Australia 2011

ATP = energy, and we only have a small amount stored at muscles (only enough for a few movements) The three energy systems all work together (known as INTERPLAY) to rebuild ATP and keep us going. A-P-P-P ↔ A-P-P & P We have two anaerobic energy systems: ATP-PC – also known as the phosphogen or phosphocreatine or creatine phosphate system anaerobic glycolysis – also known as the lactic acid or lactacid system as well as one aerobic energy system: Aerobic – also known as aerobic glycolysis or oxygen system © Cengage Learning Australia 2011

Systems and fitness components © Cengage Learning Australia 2011

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). 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 ATP–PC energy system © Cengage Learning Australia 2011

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 supplies energy from the start of intense exercise and peak power from this system is usually reached between five and fifteen seconds, it 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 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. Summary of the anaerobic glycolysis energy system © Cengage Learning Australia 2011

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 preferentially breaks down carbohydrates rather than fats to release energy. 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 activated at the start of intense exercise, 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. Summary of the aerobic energy system © Cengage Learning Australia 2011