Energy Systems ©Subject Support 2010. Learning Objectives To understand the different energy systems To understand each energy systems use in sport and exercise REMEMBER Energy can be defined as the capacity to do work! Grading Criteria P7 – Describe the three different energy systems and their use in sport and exercise activities M4 – Explain the three different energy systems and their use in sport and exercise activities D2 – Analyse the three different energy systems and their use in sport and exercise activities Unit Content Energy systems – Phosphocreatine; Lactic Acid; Aerobic energy system Amount of ATP produced by each systems Sports that use these systems to provide energy Recovery time Energy Systems • ATP-PC System (anaerobic) • Lactic Acid System (anaerobic) • Aerobic Energy System ©Subject Support 2010. Energy Systems The use of each system depends on the intensity and duration of each activity: If the activity is short in duration (less than 10 seconds) and high intensity, we use the ATP-PC system If the activity is longer than 10 seconds and up to 3 minutes at high intensity, we use the lactic acid system If the activity is long in duration and submaximal pace, we use the aerobic system Energy Continuum Sometimes we need to use all three systems to regenerate ATP because the demands of an activity are varied. For example, in rugby: A short sprint to tackle a player uses the ATP-PC system A long sprint the length of the pitch to score a try uses the lactic acid system Positional play will use the anaerobic system Adenosine Triphosphate (ATP) ATP is vital for muscle contraction it is the only form of useable energy in the body The body only has enough ATP stored for 1 explosive act (about 3 seconds) After that there is none left Then energy has to be created by other means ATP (1 explosive act) = ADP (adenosine phosphate) ATP – Adenosine TriPhosphate ADENOSINE PHOSPHATE High energy bond PHOSPHATE PHOSPHATE ADP – Adenosine DiPhosphate ADENOSINE PHOSPHATE PHOSPHATE ENERGY PHOSPHATE Phosphocreatine Energy System (ATP/PCr System) ADP + Creatine Phosphate (PCr) = ATP Lasts about 10 seconds High intensity maximum work Extremely efficient Does not need oxygen Has no waste products Think 100 meters Advantages ATP-PC System Phosphocreatine stores can be regenerated quickly (50% replenishment in 30 s; 100% in 3 mins) No fatiguing by-products Creatine supplementation extends the time that the ATP–PC system can be utilised Disadvantages There is a limited supply of phosphocreatine in the muscle cells, i.e. it can only last for 10 s Only 1 molecule of ATP can be regenerated for every molecule of PC PC regeneration can only take place in the presence of oxygen (i.e. when the intensity of the exercise is reduced) Lactic Acid Energy System ADP + Glucose = ATP When PCr runs out, the muscles call upon stores of glucose (glycogen). Lasts between 10-60 seconds. Has a waste product called pyruvic acid If not enough oxygen is breathed in to break pyruvic acid down (oxygen debt) it converts into lactic acid This is also called anaerobic glycolysis Think 400m Lactic Acid Energy System Glycogen in Liver Carbohydrate in Food Glucose in bloodstream Muscle Sarcoplasm ANAEROBIC Glucose in Muscle 2 ATP Glycolysis Pyruvic Acid Lactic Acid (1) + O2 Acetyl Coenzyme A Lactic Acid (1) Lactic Acid System Advantages ATP can be regenerated quite quickly because few chemical reactions are involved. In the presence of oxygen, lactic acid can be converted back into liver glycogen, or used as a fuel by oxidation into carbon dioxide and water. It can be used for a sprint finish (i.e. to produce an extra burst of energy). Lactic Acid System Disadvantages Lactic acid is the by-product! The accumulation of acid in the body denatures enzymes and prevents them increasing the rate at which chemical reactions take place. Only a small amount of energy (5%) can be released from glycogen under anaerobic conditions (as opposed to 95% under aerobic conditions). Aerobic Energy System Starts similar to the Lactic Acid system ADP + P + Glucose = ATP + Pyruvic Acid As oxygen is present the pyruvic acid does not convert into lactic acid but into another 34 molecules of ATP Long term low intensity exercise Carbon dioxide (CO2) and water (H2O0 are waste products of this system Think long distance running Aerobic Energy System O2 The aerobic system of energy production needs oxygen. Breaks down carbohydrates & fats into CO2, H20 and ENERGY Takes approx 3 mins to extract 95% of energy from glucose molecule This supplies the body with a prolonged and steady supply of energy. Aerobic Energy System Immediate energy production, therefore comes from the other two anaerobic systems used. Heart rate and ventilation rate increase during exercise. The vascular system distributes more oxygenated blood to our working muscles. Within 1-2 mins the muscles are being supplied with enough oxygen to allow effective aerobic respiration ATP (1 burst of energy) =ADP ADP+ PCr = ATP (3-10s of work) = ADP ADP + Glucose= ATP (10-60s of work) = ADP + Pyruvic Acid (No oxygen = lactic acid) ADP + P + Glucose = ADP + Pyruvic Acid + Oxygen =34 ATP + CO2 + H20 ANAEROBIC Muscle Sarcoplasm Pyruvic Acid Acetyl CoA Muscle Mitochondria O2 AEROBIC 2 ATP Glycolysis + Oxaloacetic Acid 2 ATP Citric Acid Krebs Cycle Hydrogen Electron Transport Chain Carbon Dioxide Electron Transport Chain The Aerobic System Advantages More ATP can be produced — 38 ATP from the complete breakdown of one glucose molecule. There are no fatiguing by-products (only carbon dioxide and water). Stores of of glycogen and triglyceride are plentiful, so exercise can last for a long time. The Aerobic System Disadvantages This is a complicated system so it cannot be used immediately. It takes time for enough oxygen to become available to meet the demands of the activity and ensure glycogen and fatty acids are completely broken down. Fatty acid transportation to muscles is low and fatty acids require 15% more oxygen to break them down than glycogen. Food Fuels Food is the basic form of energy for ATP regeneration. The main energy foods are: carbohydrates — stored as glycogen and converted into glucose during exercise glycogen — a complex sugar supplied from muscle or liver stores glucose — a simple sugar supplied from the blood fats — stored as triglycerides in adipose tissue under the skin and converted by the enzyme lipase to free fatty acids when required When are These Fuels Used During Exercise? The intensity and duration of exercise play a huge a role in determining whether fats or carbohydrates are used. The breakdown of fats to free fatty acids requires more oxygen than that required to breakdown glycogen. It is also a much slower process. Therefore, during high-intensity exercise when oxygen is in limited supply, glycogen will be the preferred source of energy.