Energy Systems

1. Energy Systems The ability to move, work or play sports is dependant on supplying sufficient energy at the required rate for the duration of the activity. All energy in the human body comes from the breakdown of complex nutrients like carbohydrates, fats and proteins.

2. ATP • The end result of the breakdown of nutrients is the production of various amounts of adenosine triphosphate (ATP). • ATP is the immediate energy source for muscular contraction. • An ATP molecule consists of an adenosine molecule bonded to three phosphate groups. • ATP molecules are supplied by chemical reactions that take place in the mitochondria found in muscle cells.

3. To release the energy, a phosphate molecule breaks away from the phosphate group through hydrolysis to form adenosine diphosphate (ADP) HEAT ENERGY Hydrolysis P P P P P P Adenosine Adenosine

4. Breaking ATP into ADP releases energy and allows cross bridge formation to occur between the myosin and actin filaments inside the muscle.

5. ATP is a renewable resource that can be regenerated by the recombination of ADP with a free phosphate. The following reaction describes the regeneration process. + + • To accomplish this synthesis, energy must be available; • Energy is supplied through the breakdown of complex food molecules, such as fats and carbohydrates. ENERGY P P P P P P Adenosine Adenosine

6. Two Energy Systems • Aerobic • An energy system which is used in prolonged continuous activity in the presence of oxygen and does not produce lactic acid. • Anaerobic • Energy systems that do not rely on the immediate use of oxygen. There are two types of anaerobic energy systems.

7. 3 Metabolic Pathways Anaerobic Alactic (ATP-CP) or (ATP-PC) • A short term energy of both fast and slow twitch muscle fibres that does not require oxygen and does not produce lactic acid. Anaerobic Lactic (glycolysis) • A fast twitch muscle energy system which does not require the immediate use of oxygen but does produce lactic acid. Aerobic(cellular respiration) • A slow twitch muscle energy system which is used in prolonged continuous activity in the presence of oxygen and does not produce lactic acid.

8. Anaerobic Alactic - ATP-CP System An immediate - high energy phosphate system Involves high power output activities that require an immediate high rate of energy production for a short period of time. HEAT P P P Adenosine ENERGY Involves activities such as weight lifting, high jump, long jump, shot put, discus 50 metre sprint, 25 metre swim.

9. As muscle contraction begins, the body’s metabolism may not be able to supply ATP to the contracting muscle cells as rapidly as required…The body must then make use of creatine phosphate. Creatine phosphate serves as a quick available energy reserve for muscles as it is broken down into creatine and phosphate. + The free phosphate ions bonds with ADP to produce ATP and leave behind creatine. The new ATP molecule is stored as potential Energy. CP CP CP CP CP CP P P P Creatine Adenosine ENERGY ATP

10. Anaerobic Alactic Characteristics • Only a small amount of ATP and CP is stored in muscle fibres; • Uses very large amounts of energy in a short period of time; • The rate of recovery is relatively rapid. After a brief rest, the system is recharged and ready for the next sprint; • Oxygen is not required; • Lactic acid is not produced; • The system can only provide energy for muscles for the first 10-15 seconds of high intense activity; • Uses both fast and slow twitch muscles; • Work output is relatively high.

11. Anaerobic Lactic - Glycolysis If an athlete must continue vigorous work a second energy system uses a complex biochemical process which breaks down carbohydrates to release energy. Lactic Acid Carbs Glucose/glycogen ENERGY ADP + P ATP

12. Glycolysis 2ADP 2ATP Energy is produced with a buildup of lactic acid

13. Characteristics of the Lactic Acid System • The energy source is entirely carbohydrate; • Oxygen is not required • Energy is provided for 15 seconds to 3 minutes depending on conditioning • Uses predominately fast twitch muscle fibres • Work output is moderate • Used in sports such as football, basketball and hockey.

14. The Effects of Lactic Acid During intense exercise, lactic acid builds up in the blood faster than it can be removed. • As lactic acid builds up an athlete will reach their anaerobic threshold (AT). • This is the point where a person begins to feel discomfort and a burning sensation in their muscles (there is some debate as to whether lactic acid directly causes it). • the muscle loses it ability to contract resulting in muscle fatigue.

15. As work increases, the body reaches the: Anaerobic Threshold (AT) • At this point the anaerobic system can no longer keep pace with the increasing requirements of the muscles. Low Slow twitch fibres dominate Exercise Intensity Moderate Fast-twitch type A fibres are recruited The anaerobic threshold is the highest intensity of workload at which lactate clearance still keeps pace with lactate production. Once this level is reached the intensity level must decrease to reduce the amount of lactic acid buildup High Fast-twitch Type B fibres dominate

16. The Effects of Lactic Acid The Effects of Lactic Acid • Lactic acid causes pH changes in the muscle fibres and they can no longer respond to stimulation. • Lactic acid interferes with cross- bridge bonding by limiting the strength of the fibre contraction. • A high production of lactic acid ultimately limits continued performance in intense activities • When lactic acid accumulates, extreme fatigue sets in and oxygen debt develops. • Oxygen debt is the reason you must breathe rapidly and deeply for a few minutes after strenuous exercise.

17. Oxygen Debt • Oxygen debt refers to post exercise oxygen consumption where the body needs to pay back its debt incurred after the exercise is over • You will notice that even after you are done racing you will continue to breath hard. • At this point your body is still trying to repay the oxygen debt that was created when you were working hard. • After you stop anaerobic exercise, your body needs extra oxygen to burn up the excess lactic acid and return your energy reserves to normal. • Lactic acid cannot be removed until extra oxygen is supplied to convert it to harmless, re-usable products.

18. Cori Cyle • the process by which lactic acid is converted to pyruvate for future conversion to glucose and glycogen • lactate is transported by the blood to liver where most of it is converted back to glucose, from which glycogen is formed in a process of gluconeogenesis • about one-sixth of the lactate is oxidized to carbon dioxide

20. Raising Your Anaerobic Threshold Since it is not possible to convert fast twitch fibres to slow twitch fibres, raising your anaerobic threshold depends on improving the condition of the fast twitch muscle fibres. This occurs when effort intensifies.

21. How do you know if your workouts are pushing your Anaerobic Threshold? • Pay attention to how your running feels. • After several workouts, you'll notice the feeling when you are in the anaerobic zone. • Elite athletes use the Conconi test which requires a hand-held device that directly measures blood lactate concentration. The corresponding heart rate at the AT gives you a convenient way of monitoring your workouts.

22. The Effect of Training on the Lactic Acid System At any level of work, the rate of lactic acid build-up is decreased through training. • The anaerobic threshold rises. • The individual can work out at a higher rate of activity before lactic acid build-up begins. • The individual is able to “handle” a higher level of lactic acid. • Trained individuals are able to remove lactic acid faster from exercising muscles. • Improvements in the cardiovascular system deliver an increased blood flow to the working muscle

23. The Aerobic System: Long-Term Energy • Exercise performed at a lower intensity level relies almost exclusively on the aerobic system for energy production and requires the athlete to use oxygen as its source of energy. • Most daily activities use energy provided by the aerobic energy system • The oxygen energy system is the most important energy system in the body. • While this pathway cannot generate the speed of the anaerobic, it does provide a great deal more efficiency and endurance.

24. The Aerobic System (Cellular Respiration) • The aerobic system energy requires the metabolism of Proteins Glucose (Glycogen) Fats Oxygen Combine to produce ADP + P ATP ENERGY CO2 Water Using energy produces

25. Sub-Pathways – Cellular Respiration Glycolysis • first stage • in the presence of oxygen, pyruvic acid is converted to acetyl-CoA (co-enzyme) (rather than lactic acid) • acetyl CoA then enters a more complicated pathway known as the KREB’S CYCLE

27. Kreb’s Cycle • Central pathway for the metabolism of fats and proteins • series of 8 reactions, two ATP molecules are produced at this stage, along with new compounds • capable of storing “high energy” electrons • high energy electrons are sent to a process within the mitochondria, known as, the electron transport chain

28. Electron Transport Chain • During the final stage of aerobic respiration, large amounts of ATP are produced, with carbon dioxide and water as the only by-products • Electrons pass down the chain, highly reactive molecules (known as free radicals) are by-products and these molecules may be a contributor to long-term muscle fatigue

30. Aerobic Power Oxygen uptake • The power of the aerobic system is generally evaluated by measuring the maximum volume of oxygen that can be consumed in a given amount of time. • This can be measured by determining the amount of oxygen exhaled as compared to the amount inhaled. • As the intensity of work increases the capacity of aerobic system reaches a maximum. • The greatest rate at which oxygen (volume) can be taken in and used during exercise is referred to maximal oxygen consumption or (VO2max)

31. Aerobic Power –VO2Max Each person has his or her own maximal rate of oxygen consumption (VO2 max). • The maximal rate at which oxygen can be used is genetically determined. • A normal VO2 max for most high school athletes would fall somewhere between 45 and 60 range. • The VO2 max values of trained athletes will reach 80-90 for males and 75-85 for females The more active we are the higher the VO2 max will be in that range.

32. The Effect of Training on the Aerobic System A person’s ability to perform an activity is limited by their maximal rate of oxygen consumption. The most efficient method for improving the aerobic energy system is endurance training/exercise. Long, slow distance training or exercise at the low end of your target heart rate tends to use slow twitch fibres. ST fibres are slower to fatigue and are well suited for endurance activities. Endurance exercise consists of repeated, sustained effort of long duration several times per week. Generally, the higher the intensity, the greater the oxygen consumption. When exercising the target heart rate (THR) should be raised to 70% of max.

33. The Effect of Training on the Aerobic System Con’t Examples include: running, swimming or biking for 40 minutes or more at a heart rate of 130-140 bpm Note: A highly trained or elite athlete should be able to sustain a heart rate of 85% of their VO2 max. This type of training does not raise your anaerobic threshold. Endurance training has four major effects on the aerobic system: • Improved delivery of oxygen and nutrients to the muscles • Increase the size and number of mitochondria in muscle fibres • Increased activity of enzymes involved in the aerobic pathway • Preferential use of fats over glucose during exercise which saves the muscles limited store of glycogen

34. Characteristics of the Aerobic System The oxygen system is highly efficient. When oxygen is used in muscle cells: • it prevents the build-up of lactic acid • an individual can work out longer before lactic acid build-up begins • it is able to remove lactic acid from muscles allowing the muscle to continue to contract allowing exercise to continue • it promotes the re-synthesis of ATP for energy when work output is low.

35. Characteristics of the Aerobic System con’t As the duration of activity increases, the contribution of the aerobic system to the total energy requirement increases. Due to this, there are two limitations to the aerobic system: • The system requires a continuous supply of oxygen and fuel sources necessary for the aerobic metabolism. • The use of ATP must be relatively slow to allow the process to meet the energy demands

36. Using The Systems Together While running at a comfortable pace you use both systems, but the anaerobic: aerobic ratio is low enough that the lactate generated is easily removed, and doesn't build up. As the pace is increased, eventually a point is reached where the production of lactate, by the anaerobic system, is greater than its removal (anaerobic threshold). Note: Depending upon the distance, and effort, the body can use different proportions of both of these systems. For example, the 800m race is too long to be a sprint, but too short to be a distance race. Therefore, it is run at the cross-over between the aerobic and anaerobic systems.

37. Training The Systems Together The best method to train all of the systems together is interval training. Interval work consists of repeating a series of short, high intensity, runs alternating with rest (recovery) periods. Whichever method is used, the athlete must continually pushing themselves into a lactate burdened state which makes their body adapt. Regardless of the race distance you are training for, 5k or marathon, interval work will help you run faster.

38. Training The Systems Together Pushing the body past the 'comfortable' speed of running increases aerobic capacity, trains the fast twitch muscles to operate at a higher /faster level and makes the athlete more tolerant of lactic acid build up. The result of interval training is that a runner who can comfortably run at eight-minute/mile pace and runs their intervals at a seven-minute/mile pace will be able to increase their steady comfortable pace under an eight-minute/mile pace.

39. Summary - The Energy Systems • Energy for muscular activity depends on a supply of ATP that can be broken down into ADP and phosphate • All of the body’s biochemical processes and the three energy systems require ATP • Trained individuals are able to use ATP and remove lactic acid more efficiently than untrained individuals • Endurance training can significantly improve the aerobic system

40. A Comparison of the Three Energy Systems

41. Roles of the Three EnergySystems in Competitive Sport

42. ATP - CP System When the systems are used Glycolytic System Aerobic System Feel the burn! Page 103 Figure 5.7

43. Picture all 3 systems

44. Questions: • Describe the role of Carbohydrates, Fats and Proteins in energy production. • Describe the characteristics of the three fibre types. • What is the importance of Myoglobin? • What features of the Kenyan runners/athletes allow for such results at world-class levels? • body characteristics • muscle fibre type • social factors