Sources of Energy Affecting Physical Performance

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1 The Sources of Energy Affecting Physical Performance TOPIC TOPIC The TOPICS. Sources of Nutrients: s, s and Protein.2 Food Breakdown into Nutrients: Glucose, Glycogen, Triglycerides, Free fatty acids.3 Aerobic and Anaerobic Energy: ATP-CP System, Lactic Acid System, Oxygen System.4 Contribution of Energy Systems in Specific Activities.5 Acute Responses to Exercise: Responses in the Circulatory, Respiratory and Muscular Systems Sources of Energy Affecting Physical Performance KEY IDEAS Characteristics of each nutrient Available sources of fats (lipids), carbohydrates, and protein Breakdown process (digestion) and link of Sources of macro nutrients to Food breakdown into nutrients (e.g. protein into amino acids, carbohydrates into glucose) Function in the body (fuel use) of each nutrient during rest, sub-maximal activity, and maximal activity (e.g. carbohydrate fat relationship, glycogen sparing) Storage and availability of nutrients in the body Key features of aerobic and anaerobic systems (e.g. fuel use at different intensities) Advantages and disadvantages of systems Recovery and restoration of energy supplies Understanding of the different energy system contributions based on the intensity and duration of activities Interpretation using a range of techniques (e.g. games, performance, graphs, tables) to explain how and why the different energy systems contribute to performance Understanding of the key processes involved during energy system use at different intensities (e.g. oxygen deficit, steady state, OBLA, lactate threshold) Exploration of activities where each system is the major (dominant) supplier of energy Exploration of how energy systems work together the concept of interplay Understanding of the energy systems during recovery (EPOC) Understanding of the acute responses in the body Examining/exploring key examples in: the circulatory system the respiratory system the muscular system Effect of the acute responses and systems to exercise (e.g. increased oxygen delivery to the muscles) (Copyright SACE Stage 2 Physical Education Subject Outline 205. Teachers and students are advised to check the current curriculum statement on the SACE website, < for any changes). Essentials Workbook Adelaide Tuition 205. All rights reserved, copying of any pages is strictly prohibited by law. 5

2 SACE 2 ESSENTIALS PHYSICAL EDUCATION WORKBOOK. Sources of Macro Nutrients: s, s and Protein All energy in the biological world originates from the sun in the form of light energy. It is the chemical process of photosynthesis in plants that converts this energy into stored chemical energy in the form of three main nutrients: carbohydrates, fats and proteins. These nutrients are referred to as energy nutrients because they can be broken down in our cells to provide energy for the body. We obtain this energy directly by eating the plants that photosynthesise, or indirectly by eating the animals that feed on the plants. When food is eaten, it travels through the mouth to the stomach and intestines where it is digested. The digestive system breaks down the nutrients contained in the food we eat and they are transported to various sites around the body. s s are found in food sources such as fatty meat (e.g. bacon), fast foods, butter, full cream dairy products and nuts. They are the secondary source of energy within the body. Once consumed, fats are converted into fatty acids for transport in the bloodstream and stored in the body as triglycerides in either skeletal muscle or adipose tissue. s s are found in food sources such as pasta, fruit, breads and cereals. They are the primary energy source within the body. Once consumed, carbohydrate is broken down into glucose (the immediately usable form of carbohydrate) and transported via the blood to the muscles for energy release. If not required for immediate use, this glucose will be stored in the muscle as glycogen. Glycogen stored within skeletal muscle is muscle specific meaning it is locked in for use by that muscle only. If muscle glycogen stores are full, excess glucose is transported to the liver where it can be stored as liver glycogen. Glycogen stored in the liver can be converted back into glucose to maintain blood glucose levels, or it may be transported (via the blood) to various muscles as required. If muscle and liver glycogen stores are full, excess glucose is converted to triglyceride (fat) and stored in the body as adipose tissue (fat cells). Proteins Proteins (amino acids) are found in food sources such as meat, fish, eggs and milk. They are the building blocks of the human body and used primarily for growth and repair. They are only used as a nutrient fuel in extreme circumstances (i.e. starvation when the body is depleted of all carbohydrate and fat stores). Energy Stored The amount of energy stored in the two main energy nutrient fuels is as follows: s (g) s (g) 37Kj (9Kcal) 7Kj (4Kcal) As can be seen from table., the total stores of carbohydrate in the body are limited to approximately 6375Kj of energy this would be equivalent to the energy needed for 90 minutes of running (at an approximate speed of 6km/h). Compared to carbohydrates, the amount of energy in total fat stores around the body is large and practically unlimited. Even on a lean individual with 5% Body, fat stores can exceed Kj of energy which could fuel over 238 hours of slow walking! However, because it takes substantially more O 2 to metabolise fat than carbohydrate, the energy release from fat is usually too slow to meet all of the energy demands in intense muscular activity. 6 Essentials Workbook Adelaide Tuition 205. All rights reserved, copying of any pages is strictly prohibited by law.

3 The Sources of Energy Affecting Physical Performance TOPIC Table.: Approximate fuel and energy stores in the body (assuming the subject mass is 65kg with 5% Body ). Nutrient Amount stored (g) Energy Stored (Kj) Blood glucose 5g 7Kj 5g = 255Kj Muscle Glycogen 250g 7Kj 250g = 4250Kj Liver Glycogen 0g 7Kj 0g = 870Kj Total 375g 6375Kj Adipose tissue 7800g 37Kj 7800g = Kj Intramuscular fat 60g 37Kj 60g = 5920Kj Total 7960g Kj Focus Question. a. Explain the role of the following within the human body: Energy nutrients s s Protein Essentials Workbook Adelaide Tuition 205. All rights reserved, copying of any pages is strictly prohibited by law. 7

4 SACE 2 ESSENTIALS PHYSICAL EDUCATION WORKBOOK b. Complete the table below, showing the location and type of fuel stores in the body. Fuel Protein Stored as Site a) Blood Glycogen b) Excess stored as fat c) d) Blood Triglycerides e) Adipose Tissue f) g) Around body c. Explain why protein is generally not used as a nutrient fuel by the body? 8 Physical Education.indb 8 Essentials Workbook Adelaide Tuition 205. All rights reserved, copying of any pages is strictly prohibited by law. 3/08/205 9:2 pm

5 The Sources of Energy Affecting Physical Performance TOPIC.2 Food Breakdown into Nutrients: Glucose, Glycogen, Triglycerides, Free fatty acids The energy stored in foods is not used directly by the body for biological work. Instead this energy is released to rebuild a chemical compound called adenosine triphosphate (ATP). ATP is the energy currency of the human body. ATP is an energy rich molecule that consists of an adenosine molecule and three phosphate molecules chemically joined together. The breaking away of one of the high energy phosphate bonds forms adenosine diphosphate (ADP) and releases the energy required for all forms of biological work. This is a reversible reaction, meaning ADP + P can be resynthesised to reform ATP (but it requires energy). Adenosine triphosphate Adenosine triphosphate A P P P Adenosine diphosphate Phosphate phosphate A P P + P Food Energy s CARBOHYDRATES s FATS PROTEIN ENERGY RE EASED Energy Released Muscular Contraction M S L N RACTION I E I N Digestion NERV R N MISSION Nerve Transmission Diagram.: ATP broken down to ADP releasing energy. Food energy is used to resynthesise ATP. s and fats are the main nutrient fuels used to supply the energy needed for the resynthesis of ATP, but the relative contribution of carbohydrate and fat as a fuel will depend to a large degree on the exercise duration and intensity. s can only be broken down to resynthesise ATP in a process requiring oxygen called aerobic lipolysis. s can be broken down aerobically in a process called aerobic glycolysis, but they may also be broken down without oxygen (anaerobic) in a process called anaerobic glycolysis. Essentials Workbook Adelaide Tuition 205. All rights reserved, copying of any pages is strictly prohibited by law. 9

6 SACE 2 ESSENTIALS PHYSICAL EDUCATION WORKBOOK 00 The Crossover Concept % Energy from and % VO 2 max 80 Diagram.2: As exercise intensity increases, there is a progressive increase in carbohydrate as a fuel. Source: Adapted from Howley & Powers (date unknown), Exercise Metabolism. Diagram.2 and.3 represent the crossover concept, which is a theoretical means by which we can describe the effects of exercise intensity and exercise duration on the contribution of carbohydrate and fat metabolism during exercise. Diagram.2 illustrates that at rest, up to 75% of energy may come from fat and only 25% from carbohydrate; but as exercise intensity increases (measured as %VO 2 max), the reliance on glycogen as a fuel source increases. This is because fats are larger molecules and require more oxygen to break down. Therefore fats tend to be more dominant at low intensity exercise when oxygen delivery is not a limiting factor. Because carbohydrates require considerably less oxygen to break down, glycogen usage tends to dominate with more intense exercise. For this reason, carbohydrate energy is more accessible during exercise than fat, and therefore carbohydrates are considered the body s principal exercise fuel. 70 The Crossover Concept % Energy from and Exercise time (min) 90 Diagram.3: As exercise duration increases, there is a progressive increase in fat as a fuel. Source: Adapted from Howley & Powers (date unknown), Exercise Metabolism. Diagram.3 illustrates that there is shift in fuel use from carbohydrate to fat as the duration of exercise increases. Although the preferred fuel for high level performance in a marathon or other long duration events would generally be carbohydrates, the body has a limited supply of glycogen stores (refer table.). As a result, when an athlete continues to exercise for an extended period of time, their muscle and liver glycogen stores will slowly become depleted. After approximately 90 minutes of intense exercise, glycogen stores will be depleted and the body must begin to rely on more fat as the major fuel source. However, because fat requires more oxygen to break down than carbohydrate, the body cannot cope with the increasing oxygen demands of fat breakdown and the oxygen demands of exercise, so the exercising muscles must significantly reduce their work output (exercise intensity) to cope. 0 Essentials Workbook Adelaide Tuition 205. All rights reserved, copying of any pages is strictly prohibited by law.