ENERGY SOURCES FOR PHYSICAL PERFORMANCE

1. ENERGY SOURCES FOR PHYSICAL PERFORMANCE Topic 1

2. ENERGY SOURCES FOR PHYSICAL PERFORMANCE 1.1 Sources of Nutrients: Fats, Carbohydrates and Proteins • Your body needs energy for basic body functions and activity during your whole life for such things as: • breathing, • sleeping, • digestion, • sitting in a chair, • sprinting for a bus etc.

3. ENERGY SOURCES FOR PHYSICAL PERFORMANCE • 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 and are transported to various sites around the body. • The components of a healthy diet are • Carbohydrates, Fat, Protein, Vitamins, Minerals and Water.

4. Carbohydrates • 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 (immediately usable form of carbohydrate). • It is transported via the blood to the muscles for energy release.

5. Carbohydrates • If not required for immediate use, this glucose will be stored in the MUSCLE as GLYCOGEN. • If muscle glycogen stores are full, excess glucose is transported to the liver to be stored as LIVER GLYCOGEN. • Glycogen stored in liver can be converted back into glucose to maintain blood glucose levels, or transported via the blood to muscles as required. • If muscle and liver glycogen stores are full, excess stored as adipose tissue (fat cells).

6. Fats • Found in food sources such as fatty meat, fast foods, butter, full cream dairy products and nuts. • 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. • They are the secondary source of energy within the body.

7. Excess fats will be stored as adipose tissue!

8. Your turn Complete Focus Questions 1.1 Page 9 & 10

9. ENERGY SOURCES FOR PHYSICAL PERFORMANCE Chemical Breakdown of Nutrients: Glucose, Glycogen and Free Fatty acids. • Energy stored in foods is not used directly by the body for biological work. • Instead it is released to build a chemical compound called adenosine triphosphate (ATP). • ATP is the “chemical currency” of the human body and provides the energy for all muscular effort.

10. ENERGY SOURCES FOR PHYSICAL PERFORMANCE • 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. • As a result of this phosphate breaking away energy is released for all forms of biological work. • This is a reversible reaction, meaning ADP+P can be resynthesised to reform ATP.

11. ENERGY SOURCES FOR PHYSICAL PERFORMANCE • Diagram 1.1 page 11

12. ENERGY SOURCES FOR PHYSICAL PERFORMANCE • Carbohydrates and fats are the main nutrient fuels to supply the energy for the resynthesis of ATP. • The contribution of carbs. and fats will depend on the exercise duration and intensity. • Fats can only be broken down to resynthesise ATP using oxygen (AEROBIC LIPOLYSIS). • Carbohydrates can be broken down aerobically (AEROBIC GLYCOLYSIS), or without oxygen in a process called ANAEROBIC GLYCOLYSIS.

13. ENERGY SOURCES FOR PHYSICAL PERFORMANCE • The ‘Crossover’ Concept • At rest, up to 75% of energy may come from fat and 25% from carbohydrate. (See diagram 1.2) • But as exercise intensity increases there is a greater reliance on glycogen as a fuel source. • Why? Because fats are larger molecules requiring more ‘work’ (oxygen) to breakdown. Therefore fats tend to be more dominant at low intensity when oxygen delivery is not limited.

14. ENERGY SOURCES FOR PHYSICAL PERFORMANCE • Because carbs. require less oxygen to break down, glycogen tends to dominate with intense exercise. This is why carbs are considered the body’s primary fuel. Insert diagram 1.2 page 12

15. ENERGY SOURCES FOR PHYSICAL PERFORMANCE • Diagram 1.3 below illustrates the shift from carbohydrate to fat as the duration of exercise increases. Insert diagram 1.3 page 12

16. ENERGY SOURCES FOR PHYSICAL PERFORMANCE • The preferred fuel for a marathon or long distance event is still glycogen, but carbohydrate stores are limited. • If the athlete runs out of glycogen in both the liver and skeletal muscles, then the body must utilise fatty acids as the major fuel source. • Fat needs more oxygen to breakdown, so it is harder work for the athlete (a drop in performance level). They will find it harder to concentrate and may appear disorientated. This is termed “Hitting the Wall”.

17. ENERGY SOURCES FOR PHYSICAL PERFORMANCE Your turn Complete Focus Questions 1.2 Page 13 & 14

18. Exam Example Question • 14. Refer to the following graphs that show the contribution of fat and glycogen as fuels for Aerobic Energy production when exercise is Low Intensity, Moderate Intensity and Relatively High Intensity. The size of the circle represents the total energy requirement at each level of intensity. (1-10T) • a At which intensity is fat the main fuel used? (1 mark) • b At which intensity will the most fat be used?(1 mark) • c Refer to the graph for 84% Exercise intensity specifically. Explain how this graph helps to show the need for ‘carbohydrate loading’ prior to an event requiring relatively high intensity for 90 minutes or more?(2 marks) • d Elite Marathon runners, who race for over 2 hours in their event, train toward ‘glycogen sparing’. • i What is ‘glycogen sparing’?(2 marks) • ii Explain two different ways glycogen sparing will help the Marathon runner’s performance(3 marks) • e What dietary strategy should a marathon athlete use after the race to make glycogen replenishment more efficient? • (3 marks)

19. Example Exam Answer • 14 • a)At 20% Exercise intensity • b) at 84% intensity • c) At 84% intensity, glycogen is clearly the most needed fuel for aerobic energy production. As the intensity increases, glycogen will be in even more demand the Anaeobic Glycolisis system which uses only glycogen, becomes more involved. The body only generally stores enough glycogen for approximately 90 minutes of continuous activity. The extra glycogen gained by carbohydrate loading reduces the risk of running out of glycogen. (hitting the wall) during an event of 90 minutes or more. • d) (i) Glycogen sparing occurs when the athlete is able to use fat, more than normal, as a fuel source for aerobic energy production. In an endurance event, this leads to a situation where glycogen stores are not so depleted and there is more available for high intensity efforts which rely predominantly on Anaerobic Glycolysis. .(ii) Two appropriate benefits required. • Greatest sustainable running speed will be achieved when the runner is as near as possible to their lactate threshold, but still work predominantly from their aerobic system. The nearer the exercise intensity it to the lactate threshold, the more significant the need for glycogen as a fuel for aerobic production. With more glycogen available, the runner will be able to maintain an intensity near their lactate threshold for longer. • The athlete will have more glycogen available for extended high intensity efforts, which rely predominantly n anaerobic glycolysis, such as the start and finish of races and the mid race surges. • e) The marathon runner should ingest HIGH GI CARBOHYDRATES, such as lollies or a honey sandwich in regular small amounts immediately after the the race for 2 – 4 hours. (1 gram for every kg of weight in the first 30 mins then repeat every 2 hours) Avoid ingesting fat as this inhibits glycogen replenishment. • Sports drinks are particularly good post race because they contain HIGH GI Carbs, rehydrate the athlete and replace electrolytes and minerals lost during the race.

20. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • ATP found ‘onsite’ in skeletal muscle is the first choice for energy used in muscular contractions. • ATP is easily exhausted so the body must be able to resynthesise it to maintain an energy supply. • The body can do this by using three energy systems each with their own advantages.

21. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The three energy systems are: • The ATP-CP (Adenosine Triphosphate – Creatine Phosphate) system. • The Lactic Acid (Anaerobic Glycolysis) system. • The Aerobic(Oxygen or Aerobic Glycolysis) system.

22. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The ATP-CP System • Supplies immediate energy for any sprint or maximal intensity, short duration work up to 10 seconds. • A molecule called Creatine Phosphate (CP) splits to release energy, which is used to resynthesise ATP. • Stores of CP are very limited. On average 10 seconds as the dominant energy source.

23. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The ATP-CP System Note: • Once depleted, CP can be resynthesised very quickly with 50% restored after 30 seconds and 100% restored after approximately 3 minutes.

24. The ATP-CP System

25. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • Insert Diagram 1.4 page 15 Your turn Focus Question 1.3 Page 16

26. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The Anaerobic Glycolysis (Lactic Acid) System • Provides short-term energy and is dominant in activities ranging from 20-90 seconds of maximal intensity. • Involves a series of chemical reactions that break down glycogen into pyruvic acid, producing enough energy to resynthesise 2 ATP molecules. • Without sufficient oxygen, pyruvic acid converts to the by-product called lactic acid which causes muscle fatigue as it accumulates.

27. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems Insert diagram 1.5 page 18

28. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems Your turn Complete Focus Question 1.4 Page 19

29. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The Oxygen (Aerobic) System • Also known as aerobic glycolysis. • It is relevant to all of the fitness components as it provides either the basis for recovery between strength and power efforts, or the bulk of energy for sub-maximal efforts which go beyond 2 minutes. • This system can create 38 molecules of ATP from one molecule of glucose, whereas anaerobic glycolysis can only create two.

30. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The Oxygen (Aerobic) System • This extra amount is possible because the abundance of oxygen allows a more complete breakdown of glucose than occurs in anaerobic glycolysis. • Pyruvic acid, rather than becoming lactic acid, is further broken down in the citric acid cycle and the electron transport chain within the mitochondria.

31. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The Oxygen (Aerobic) System • The oxygen system can also use fat as a fuel source (called aerobic lipolysis) but requires a lot more oxygen to break fat down than carbohydrates. • Therefore, carbohydrates are considered the body’s principal fuel. • The aerobic system requires O2. When the energy demands of an activity increase, so must the volume of O2 to be delivered.

32. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The Oxygen (Aerobic) System • Providing sufficient oxygen takes time because of the need to increase the ventilation and heart rate. • From the start of sub-maximal exercise, it may take between 3 and 5 minutes before the person reaches a ‘steady state’. Where oxygen consumption is matching oxygen requirements for a given workload.

33. Aerobic and Anaerobic Energy: ATP-CP, Lactic Acid, Oxygen Systems • The Oxygen (Aerobic) System • The aerobic system produces no fatiguing by products, but after continuous exercise of 1-2 hours or more, there is likely to be a depletion of muscle and liver glycogen stores. • It may take 24-48 hours for the body to replenish these stores, even with a high carbohydrate diet.

34. Energy Systems video (You Tube)

35. Maximum Oxygen Consumption (VO2 Max) • Larger people tend to consume more oxygen than smaller people. • VO2 max is therefore usually expressed as a Relative VO2 max in millilitres of oxygen consumed per kilogram of body weight per minute (ml/kg/min). • This allows for the comparison of different sized individuals • The VO2 max is an important indicator in determining a person’s capacity for the aerobic resynthesis of ATP. • Elite endurance athletes will have higher values than others.

36. Maximum Oxygen Consumption (VO2 Max) Insert diagram 1.8 page 22

37. Onset of Blood Lactic Acid Accumulation (OBLA)(Anaerobic Threshold) • Exercise intensities approaching VO2 max can only be achieved through the dominant use of anaerobic glycolysis (lactic acid system). • As a result lactic acid will accumulate. • The maximum intensity of steady state exercise that a person can sustain without a rapid increase in the accumulation of lactic acid is termed anaerobic threshold. (Approximately 4mmol per lire of blood.)

38. Anaerobic Threshold (OBLA) Insert table 1.9 page 23

39. Anaerobic Threshold (OBLA) • Because there is no actual threshold point where aerobic processes stop and anaerobic processes begin, anaerobic threshold is more correctly known as OBLA (onset of blood lactic acid accumulation). • A person’s anaerobic threshold, or OBLA, has a large impact on their athletic performance. • Training can improve an individuals VO2 max.

40. Anaerobic Threshold (OBLA) Your turn Complete Focus Questions 1.6 Page 24 & 25

41. Exam Example Question • 22. Refer to the graph below showing the heart rate response, taken per minute, of a weekend jogger during a training run. (1-09T) a IWhat does the period between 8 minutes and 11 minutes indicate?(1 mark) • ii Explain which energy system will be dominant during this period.(2 marks) • b What has caused in heart rate from 11 minutes to 13 minutes?(1 mark) • c The jogger finished the main part of the run at 15 minutes but gradually slowed speed until she started walking after 18 minutes. Explain two advantage of an active recovery after an exercise session

42. Answer to Example Exam Question

43. Oxygen Deficit • When exercise begins the need for O2 increases due to the energy demands of the body. • The body then desperately tries to catch up to the oxygen demands on the body. • This is known as Oxygen Deficit. “The difference between the oxygen required for a task and the amount being supplied or consumed by the body.” • A Steady State is reached when the body is meeting the oxygen demands i.e. O2 supply matches O2 demands. • A steady state can be achieved during light to moderate exercise, but not ‘heavy’ exercise.

44. Oxygen Deficit

45. Excess Post-Exercise Oxygen Consumption (EPOC) • Once the exercise session has finished, recovery can begin. • Oxygen consumption will remain elevated for some time following exercise to allow the body to slowly return to pre-exercise levels • The volume of oxygen consumed after exercise (above that normally required at rest) is termed ‘the excess post-exercise oxygen consumption’ (EPOC). • It has traditionally been termed ‘oxygen debt’.

46. Excess Post-Exercise Oxygen Consumption (EPOC) • The EPOC is a result of the following: • Replenishing ATP-CP stores • Removal of lactic acid • Increased activity of the heart and respiratory muscles • Restoration of myoglobin and haemoglobin oxygen supplies. • Other factors: the release of adrenaline during exercise. A hormone that needs to be broken down. • The increase in core temperature raising the metabolic rate.

47. Excess Post-Exercise Oxygen Consumption (EPOC) • The intensity of the exercise affects the oxygen deficit and therefore the extent of the EPOC. • The lighter the exercise intensity the smaller the oxygen deficit, as the cardio-respiratory system is better able to respond to a rise in oxygen demand. • There is a corresponding decrease in the time required for complete recovery post exercise. • EPOC has two parts. Traditionally known as the alactacid and lactacid components.

48. Excess Post-Exercise Oxygen Consumption (EPOC) • EPOC (Alactacid Component) • Also known as the fast component involving the restoration of ATP and CP stores and the replenishment of O2 for myoglobin and the surrounding tissues. • Takes approximately 2-3 minutes, with 50% of ATP-CP replenished in 30 seconds and 100% in approximately 3 minutes.

49. Maximum Oxygen Consumption (VO2 Max) • The volume of oxygen consumed by the body for energy production is called the VO2. • It is measured in litres of oxygen consumed per minute (L/min). • There is a corresponding increase in oxygen consumption with an increase in exercise intensity. • This would continue until the athlete reaches maximum oxygen consumption (VO2 max) – the region where oxygen uptake peaks despite further increases in exercise intensity.

50. Excess Post-Exercise Oxygen Consumption (EPOC) • EPOC (Lactacid Component) • Also known as the slow component involving the removal of lactic acid and some slight glycogen replenishment. • Lactic Acid removal may require up to 90 minutes for full recovery, and 15 minutes for 50% removal.