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HUMAN ENERGY SYSTEMS 1 The Chemistry of Energy Production Energy in the human body is derived from the breakdown of complex nutrients like carbohydrates, fats, and proteins. The end result of this breakdown is production of the adenosine triphosphate (ATP) molecule. ATP provides energy necessary for body functions Breakdown of Energy currency Carbohydrates Fats Proteins Biochemical processes Muscular Work ATP Thermoregulation Digesting Food 2 a) ATP breakdown (ATP turnover) ATP + H 2O ADP + Energy + P 1. Hydrolysis of the unstable phosphate groups of ATP molecule by H2O 2. Phosphate molecule (P) is released from ATP (ATP ADP) 3. Energy is released 3 c) ATP resynthesis ADP + Energy + P ATP 1. Initial stores of ATP in the muscles are used up very quickly and ATP must be regenerated 2. ATP is formed by recombination of ADP and P 3. Regeneration of ATP requires energy (from breakdown of food molecules) 4 5 The Anaerobic Alactic System Overview Primary energy source: Stored ATP, CP Duration of activity: 7-12 s Sporting events: Weight lifting, high jump, long jump, 100m run, 25m swim Advantages: Produce very large amount of energy in a short amount of time Limiting factors: Initial concentration of high energy phosphates (ATP, PC) FPEH University of Toronto 6 ATP System P ENERGY Creatine ADP + Pi ATP FPEH University of Toronto 7 Training the High Energy Phosphate System a) Interval training: - 20% increase in CP (creatine phosphate) stores - no change in ATP stores - increase in ATPase function (ATP -> ADP+P) - increase in CPK (creatine phosphokinase) function (CPK breaks down CP molecule and allows ATP resynthesis) b) Sprint training: - increase in CP stores up to 40% - 100% increase in resting ATP stores FPEH University of Toronto 8 The Anaerobic Lactic System Overview Primary energy source: Stored glycogen, blood glucose Duration of activity: 12 s – 3 min Sporting events: 800m run, 200m swim, downhill ski racing, 1500 speed skating Advantages: Ability to produce energy under conditions of inadequate oxygen Limiting factors: Lactic acid build up, H+ ions build up (decrease of pH) FPEH University of Toronto 10 The Anaerobic Lactic System Glycogen ENERGY Lactic Acid ADP + Pi ATP FPEH University of Toronto 11 Anaerobic Threshold The exercise intensity at which lactic acid begins to accumulate within the blood The point during exercise where the person begins to feel discomfort and burning sensations in their muscles Lactic acid is used to store pyruvate and hydrogen ions until they can be processed by the aerobic system FPEH University of Toronto 12 Anaerobic Lactic System cont . Starts when: – the reserves of high energy phosphate compounds fall to a low level – the rate of glycolysis is high and there is a buildup of pyruvic acid FPEH University of Toronto 13 Substrates for the Anaerobic System The primary source of substrates is carbohydrate Carbohydrates: – primary dietary source of glucose – primary energy fuels for brain, muscles, heart, liver FPEH University of Toronto 14 Carbohydrate Breakdown and Storage Complex Carbohydrates Digestive system Glucose Blood Stream Circulation of glucose around body Glucose stored in blood Gluconeogenesis: Creation of new glucose when absent. Glycogen Glycogen stored in muscle or liver FPEH University of Toronto 15 Effect of Training on the Anaerobic Lactic System Rate of lactic acid accumulation is decreased in the trained individual This rate can be decreased by: a) reducing the rate of lactate production - increase in the effectiveness of the aerobic oxidative system b) increasing the rate of lactate elimination - increased rate of lactic acid diffusion from active muscles - increased muscle blood flow - increased ability to metabolize lactate in the heart, liver and in non-working muscle FPEH University of Toronto 16 The Aerobic System Overview Primary energy source: Glycogen, glucose, fats, proteins Duration of activity: > 3 min Sporting events: Walking, jogging, swimming, walking up stairs Advantages: Large output of energy over a long period of time, removal of lactic acid Limiting factors: Lung function, max.blood flow, oxygen availability, excess. energy demands FPEH University of Toronto 18 Aerobic System O2 Glycogen Fat ENERGY Protein ADP + Pi ATP Carbon Dioxide Water FPEH University of Toronto 19 The Aerobic System The most important energy system in the human body Blood lactate levels remain relatively low (3-6mmol/L bl) Primary source of energy (70-95%) for exercise lasting longer than 10 minutes provided that: a) working muscles have sufficient mitochondria to meet energy requirements b) sufficient oxygen is supplied to the mitochondria c) enzymes or intermediate products do not limit the Kreb’s cycle Primary source of energy for the exercise that is performed at an intensity lower than that of the anaerobic oxidative system 20 The Substrates for the Aerobic System Carbohydrates ( glycogen and glucose) and fats (triglycerides and fatty acids) Fats: – found in dairy products, meats, table fats, nuts, and some vegetables – body’s largest store of energy, cushion the vital organs, protect the body from cold, and serve to transport vitamins – each gram of fat contains 9 calories of energy 21 Effect of Training on Aerobic Systems Endurance training is the most effective method (long duration several times per week): - increases vascularization within muscles - increases number and size of mitochondria within the muscle fibres - increases the activity of enzymes (Krebs cycle) - preferential use of fats over glycogen during exercise Endurance training increases the max aerobic power of a sedentary individual by 15-25% regardless of age An older individual adapts more slowly FPEH University of Toronto 22 Summary of the Energy Systems Characteristic Other names Fuel source(s) High energy phosphate phosphagen, ATP/CP stored ATP, PC Enzyme sytem used in breakdown Muscle fibre type(s) recruited Power output requirement Metbolic byproducts maximum rate of ATP production (mmol/min) Time to maximal ATP production Maintenance time of maximal ATP production Time to exhaustion of system ATP production capacity (mol) single enzyme Anaerobic glycolytic lactic acid stored glycogen, blood glucose single enzyme Aerobic oxidative steady state glycogen, glucose, fats, proteins multiple enzymes SO, FOG, FG high ADP, P, C 3.6 SO, FOG, FG high lactic acid 1.6 depends on level of effort low CO2, H2O 1 1 sec 5-10 sec 2-3 min 6-10 sec 20-30 sec 3 min 10 sec 0.6 3040 sec 1.2 5-6 min theoretically unlimited Relative % ATP contribution to efforts of 10 sec Relative % ATP contribution to efforts of 30 sec Relative % ATP contribution to efforts of 2 min Relative % ATP contribution to efforts of 10 min Time for total recovery (sec) Time for one half recovery (sec) Ultimate limiting factor(s) 50 35 15 15 65 20 4 46 50 1 9 90 3 min 20-30 sec 1-2 hr 15-20 min 30-60 min 5-10 min Depletion of ATP / creatine phosphate stores Lactic acid accumulation resulting from production exceeding buffer capacity. Depletion of carbohydrate stores, insufficient oxygen, heat accumulation 23 Energy Systems During Max Activity 24 Factors Affecting Physical Performance Somatic Factors Sex Age Body distribution State of health Drugs Strength Fibre type distibution Nature of the Work Intensity Duration Technique (efficiency) Body position Mode Type Work:rest schedule Psychic Factors Attitude Motivation Environmental Factors Diet Temperature Air pressure (hypobaric and hyperbaric) Air pollution Noise