Food Fuels (Macronutrients)

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1 KEY KNOWLEDGE KEY SKILLS 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 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.

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3 Food Fuels (Macronutrients) Carbohydrates, fats and proteins (macronutrients) are the only food fuels that produce energy EG: can be converted to ATP Phosphocreatine (PC) is a chemical fuel source 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)

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5 Fats are involved in: protecting body organs maintaining body temperature hormone production energy storage and supply. Triglycerides are broken down to free fatty acids (FFAs) which are broken down aerobically to provide energy. Fats are mainly used at rest require more oxygen to produce energy produce more ATP than carbohydrates produce energy slowly. Proteins are mainly consumed for growth and repair of body cells & tissues. All enzymes are made up of proteins. Proteins are mainly used as a 'last resort' fuel have a very high 'oxygen cost' produce energy slowest of all food fuels.

6 ATP = energy, and we only have a small amount stored at muscles (only enough for a few movements) ALL fuels must be converted to ATP (via energy systems) to be used as energy for movement. The three energy systems all work together (known as INTERPLAY) to rebuild ATP and keep us going. We have two anaerobic energy systems: ATP-CP creatine phosphate Anaerobic glycolysis uses CHO s (glucose/glycogen) as well as one aerobic energy system: Aerobic uses O2 to break down CHO s, fats or proteins to ATP

7 Systems and fitness components

8 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). 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.

9 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 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.

10 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 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.