A2 Physical Education Energy Systems

A2 Physical Education Define ‘energy’, ‘work’, and ‘power’. Identify examples of potential, chemical and kinetic energy within the body. The role of ATP within the body and explain how energy is made available for muscular contraction. Describe the three energy systems for ATP re-sythesis Identify the thresholds of each of these systems. Explain the term ‘OBLA’ Explain the factors that determine how these systems combine to provide energy for different sporting activities.

Energy Energy is the ability to perform work. Energy is measured in Joules (J) It is also measured in calories 1 calorie = 4.18 joules

Energy Metabolism total intake of food sufficient to supply enough energy to : keep cells alive keep systems working meet demands of life

Energy Balance Neutral energy balance: Energy input = Energy output Negative Energy balance: Energy output > Energy input Balanced diet and regular aerobic exercise is the most effective means of weight control. Basal Metabolic Rate = the rate at which energy is used by basic bodily functions (@ rest or sleeping) Total Metabolic Rate = the rate at which energy is used by all bodily functions including exercise

Energy FOOD 37 9 29 7 17 4 16 KILOJOULES PER GRAM   FOOD KILOJOULES PER GRAM KILOCALORIES PER GRAM FAT 37 9 ALCOHOL 29 7 PROTEIN 17 4 CARBOHYDRATES 16

Energy   Calories in: a 100g bar of Cadbury's Dairy Milk: 530kcal a pack of Maltesers: 183kcal a Mars Bars (65g): 294kcal A 30g bowl of Corn Flakes: 112 cal

Check out www.whatsinsideguide.com www.brianmac.co.uk/energyexp.htm www.weightlossresources.co.uk/calories/calorie_counter www.bmi-calculator.net

WORK = force x distance moved Force = a push or pull that alters, or tends to alter, the state of motion of a body. Measured in Newtons. measured in joules (J)

Work WORK = force x distance moved A rugby players spear tackles a stationary 95kg opponent. He drives him back 2 metres? How much work did he do before he was sent off and banned for 3 months?

Power is the rate at which we can work or work/time the energy used per second POWER = work/time Considered a combination of strength and speed unit = watt (W)

ATP ATP is adenosine triphosphate. This compound is the only immediately usable form of energy stored in our bodies. We have other energy rich compounds such as phosphocreatine and glycogen.

Types of Energy CHEMICAL ENERGY is energy that is produced by a complex series of chemical reactions Stored as ….. which can then be made available as : KINETIC ENERGY is energy due to movement which results from muscular contractions POTENTIAL ENERGY is stored energy waiting to happen. eg. ATP does nothing until P group is released with the help of ATPase.

ATP However, ATP is the only one that can be utilised by the muscles to create movement. ATP is stored within the muscle cell Total mass of 85g within the body Enough to last for about 2 seconds of exercise. To maintain exercise, ATP has to be re-synthesised from adenosine diphosphate (ADP) and a phophate group (‘P’ of ‘Pi’)

High-energy bond Adenosine P P P Adenosine P P The energy is stored in the bond between the last two phosphate groups. When this bond is broken by the action of the enzyme ATPase, energy is released that can be used by the muscle cell to contract. P ATPase

ATP re-synthesis ATP re-synthesis is achieved by 3 energy systems: The Phosphocreatine system Lactic acid system Aerobic system The amount of ATP re-synthesis is done by each system will depend purely on the intensity of the exercise. Two systems can be working at the same time.

The Phosphocreatine system This system uses another high-energy compound known as phosphocreatine to provide energy to combine ADP and P. PC = P + C + energy (exothermic) Energy + ADP + P = ATP (endothermic) Advantages Disadvantages Provides ATP re-sythesis very quickly because the PC is stored in the sarcoplasm of the muscle cell and there are very few steps in the reaction There is only a small amount of PC stored in the muscle cells. O2 is not required, therefore there is no delay to wait for oxygen to be supplied from the lungs Only one mole of ATP is re-synthesised from one mole of PC It can provide energy for very high-intensity exercise. It will only provide energy for a maximum of ten seconds Recovery times for this system are very quick, as PC will re-synthesise quite quickly. There are no harmful by products that will cause fatigue.

Lactic acid system Another anaerobic system The fuel used is CHO. takes place in the sarcoplasm The fuel used is CHO. Stored in the muscles and liver as glycogen. CHO is converted to glucose by the enzyme glycogen phosphorylase and undergoes a series of reactions known as anaerobic glycolysis. This is started by the enzyme phosphofructokinase (PFK) until eventually it is converted into pyruvic acid. During this process 2 moles of ATP are re-synthesised. Due to the lack of oxygen, the pyruvic acid is converted to lactic acid by the enzyme lactodehydrogenase.

Lactic acid system Advantages Disadvantages Glucose PFK 2 ATP Lactic acid Pyruvic acid LDH Advantages Disadvantages There is a relatively large supply of glycogen stored in our bodies and so ths system can supply more ATP than the PC system The bi-product, lactic acid, reduces the pH of the muscle cell, making it more acidic; this prevents the enzymes from functioning properly, causing fatigue. ATP can be provided quickly for high-intensity activities that last from anywhere from 15-180 secs. O2 is not required, therefore there is no delay to wait for oxygen to be supplied from the lungs

The Aerobic system Requires Oxygen as a fuel alongside glycogen or fat to re-synthesise ATP First part of the system is identical to the lactic acid system. However the pyruvic acid is not converted into lactic acid. Instead it is taken by the co-enzyme acetyl CoA into the Kreb’s Cycle. Here a series of chemical reactions occurs, further breaking down the CHO compound. This takes place in the matrix of the mitochondria. Once this series of reactions is completed, Carbon Dioxide and Hydrogen ions are produced. The CO2 is removed via the lungs The hydrogen ions enter the electron transfer chain. This occurs in the cristae of the mitochondria. Electrons are removed from hydrogen and passed down the elctron transfer chain providing energy to resynthesise 34 moles of ATP. The hydrogen is combined with oxygen to produce water.

Mitochondria (matrix) Electron transfer chain Mitochondria (cristae) Glucose PFK 2 ATP Lactic acid Pyruvic acid Sarcoplasm LDH Acetyl CoA Kreb’s Cycle 2 ATP 2 CO2 Mitochondria (matrix) H e- Electron transfer chain 02 24 ATP H20 Mitochondria (cristae)

The Aerobic system Advantages Disadvantages A large amount of ATP can be resynthesised 36 to 38 moles can be produced from one mole of glycogen. Activity can last for hours There are no harmful by-products of the chemical reactions Disadvantages Due to the need for oxygen, the system cannot resynthesise ATP immediately; there is a delay while oxygen is transported from the lungs Cannot provide ATP whilst working at higher intensities.

Energy Thresholds The threshold of any system is the point at which that energy system is unable to provide energy. PC system Approx. 10 seconds Lactic Acid system Approx. 15 -180 secs Aerobic system Onset of Blood lactate accumulation (OBLA) When blood lactate levels goes above 4mmol per litre or the point at which there is a rapid increase in this value. OBLA ranges from 50% VOs max in untrained individuals to 85% VO2 max in highly trained athletes. Due to increased ability to remove waste products and supply oxygen to working muscles.

The Energy Continuum In an given situation our energy systems rarely work in isolation. E.g a footballer Movement at low intensity whilst jogging back into position Sudden high intensity movement – break down the wing. Energy is provided by all three systems, and the contribution is determined by the intensity and the duration of exercise.

Duration of maximal exercise The Energy Continuum Duration of maximal exercise Seconds Minutes 10 30 60 2 4 120 90 80 70 50 35 15 5 1 20 65 85 95 98 99 Percentage anaerobic Percentage aerobic

The Energy Continuum Aerobic Anaerobic 100m sprint 200m sprint 100m swim boxing 800m 1500m / hockey game 400m swim rowing 2000m 3000m run Cross-country run Marathon 10 20 30 40 50 60 70 80 90 100 100 90 80 70 60 50 40 30 20 10 Adapted from Davis et al (2005) - Physical Education and the study of Sport

References Carnell et al (2002), Advanced PE for OCR AS Davis et al (2005), Physical Education and the Study of Sport.