Energy systems.

PHYSIOLOGICAL REQUIREMENTS OF PHYSICAL ACTIVITY Foods Fuel and Energy Systems

Where does this energy come from? A Roger Federer serve takes 1-2 seconds to perform. It’s fast & explosive. He might do this hundreds of time over a game. Plus he has to run fwd, bkwd and sideways for 1-2 hours. His Muscles requires ENERGY to do this.

Food Fuels our Body 1. CARBOHYDRATES (Glycogen) 2. PROTEIN 3. FATS

CARBOHYDRATES Pastas Cereals Rice Fruit/Veges Breads Sugar Carbohydrates are stored as Glycogen in Muscle & Liver CHO is the body’s preferred fuel during Exercise – breaks down easily, uses little oxygen

PROTEIN Fish Red Meat Poultry Eggs Dairy products GRAINS Protein is stored as MUSCLE and AMINO ACIDS around the body. 5-10% contribution to endurance events: Mainly used for growth/repair

FATS Butter Oils Margarine Nuts Cheese

Food that we ingest is stored and burnt to fuel our muscles This food must be converted into a chemical compound called ATP Without ATP - Muscles cannot contract

A.T.P. Adenosine triphosphate. This is energy for muscle contraction. Energy for movement of muscle fibres is stored in the muscle as a molecule of ATP. Adenosine P P P Adenosine triphosphate

To use the stored ATP + Energy To release the energy, ATP is broken down into ADP + Pi (Adenosine diphosphate + Phosphate molecule) The energy released allows for a muscle contraction. + P P Pi Adenosine Energy

Resynthesis of ATP There is only enough stored ATP for about 1-2 contractions, so….we must resynthesise ADP back into ATP. Fuel and energy for this comes from CHO, Fats, Proteins and Creatine phosphate. These fuel sources resynthesise the free Phosphate molecule (Pi) back to the ADP to reform ATP.

+ CHO, Fats, Proteins, CP P P Pi Adenosine Resynthesises the ADP back to ATP P P Pi Adenosine

ATP is used in all 3 energy systems. The type of energy system used and the interplay between them depends on the frequency, duration, intensity of the activity and fitness levels of the individual.

The 3 energy systems The ATP – PC system The Lactic Acid Systems Aerobic System

For activity lasting: 0-10 SEC ATP-PC SYSTEM 10-30/40 SEC Anaerobic Glycolytic SYSTEM 2MINS + AEROBIC SYSTEM

High Energy Phosphate System

ATP –PC system cont.. ATP breaks down to ADP + Pi to release energy. The ADP + Pi must be reformed to ATP for continued muscle function. PC provides the energy for the free Pi to be re-attached to the ADP molecule to form ATP.

ATP –PC system cont.. PC stored in the muscles breaks down anaerobically (without O2) to form Phosphate and Creatine. This releases energy for the resynthesis of ATP. It takes 2 PC molecules to resynthesise 1 ATP molecule (one PC = 0.7 ATP). NOTE: The resynthesis of PC (Phosphate + Creatine = PC) occurs in the recovery phase.

ATP-PC SYSTEM CP instantly available, but runs out quickly Uses stores of CP (Creatine Phosphate) to REMAKE ATP Used for high intensity Jumps, Throws, Sprints Only have 10 seconds of CP in muscles If activity lasts longer than 10 sec, ATP must be REMADE by some other means…..

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

Summary Each ATP molecule is made up of an adenosine part and three phosphate groups. Besides ATP, there is still another high-energy compound called phosphocreatine (PC) inside the human muscle cells. When PC is broken down, energy is released for the resynthesis of ATP.

Summary Cont… However, the total amount of PC stored in the human body is also extremely limited. The energy released from the breaking down of ATP is also required to resynthesize PC. Nevertheless, this process will be carried out when the human body is in the recovery stage. The complete ATP-PC system can only supply 5.7 to 6.9 Kcal of energy, which can maintain about 10 seconds of maximal efforts.

Summary cont… The importance of the ATP-PC system is that it is the instant energy source in the human body. The ATP-PC system does not require oxygen in the muscles for proper functioning. Besides, the required fuels (ATP and PC) have already been stored in the muscle cells The chemical reactions involved when PC is broken down are fewer than the other two energy systems. The ATP-PC system is particularly important for high-intensity and high- speed activities that need to be completed in a few seconds (e.g., starting, jumping, throwing, and weight lifting).

Anaerobic Glycolytic SYSTEM Body uses stored fuel of GLYCOGEN to REMAKE ATP Need Oxygen to do this properly About 2-3 hours of glycogen stored in body. Downside – by-product called Lactate. Hydrogen Ions also released which inhibit muscle contraction Happens because of lack of enough Oxygen to break down Glycogen 400m run, 800m at high intensity

The Anaerobic Glycolytic System

Glycolysis A biochemical process that releases energy in the form of ATP from glycogen and glucose Anaerobic process (in the absence of oxygen) The products of glycolysis (per molecule of glycogen): - 2 molecules of ATP - 2 molecules of pyruvic acid The by-product of glycolysis (per molecule of glycogen): - 2 molecules of lactic acid

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

The Anaerobic Glycolytic 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

Substrates for the anaerobic energy system The primary source of substrates is carbohydrate Carbohydrates: primary dietary source of glucose primary energy fuels for brain, muscles, heart, liver

Gluconeogenesis Carbohydrate breakdown and storage Complex Carbohydrates Digestive system Glucose Blood Stream Glucose stored in blood Gluconeogenesis Circulation of glucose around body Glycogen Glycogen stored in muscle or liver

Effect of Training on the Anaerobic Glycolytic System Rate of lactate accumulation is increased 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

Review of Anaerobic Systems Video Review

Used in longer, sub-max activities. Long run, swim, cycle. AEROBIC SYSTEM Plenty of Oxygen available to remake ATP . So no LA or H+ is accumulated Used in longer, sub-max activities. Long run, swim, cycle. Like the LA system, the Aerobic uses Glycogen to remake ATP. Oxygen supply meets demand We use this system at REST (Now!) – except we burn… Will keep suppling ATP for as long as Fitness levels allow FAT!!!!

Aerobic Oxidative System

The Aerobic Oxidative System The most important energy system in the human body 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

The Oxidative Phosphorylation System Two Pathways: Krebs Cycle & Electron Transport Chain Biochemical process used to resynthesize ATP by combining ADP and P in the presence of oxygen Takes place in mitochondrion (contains enzymes, co-enzymes) Energy yield from 1 molecule of glucose is 36 ATP molecules Energy yield from 1 molecule of fat up to 169 ATP molecules By-products of this reaction: carbon dioxide, water

Cori Cycle Lactic acid is taken to the liver to be metabolized back into pyruvic acid and then glucose

Aerobic Review Video Review

The Power Of The Aerobic System Evaluated by measuring the maximal volume of oxygen that can be consumed per kilogram of mass in a given amount of time This measure is called aerobic power or VO2 max (ml/min/kg) Factors that contribute to a high aerobic power: a) arterial oxygen content (CaO2) - depends on adequate ventilation and the O2-carrying capacity of blood b) cardiac output (Q = HR x stroke volume) - increased by elevation of the work of heart and increased peripheral blood flow c) tissue oxygen extraction (a-vO2 diff) - depends upon the rate of O2 diffusion from capillaries and the rate of O2 utilization

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

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

BUT, need 3 minutes rest to get all CP back! During REST Any rest, short OR Long, CP is being replenished, so we can ‘sprint’ again. BUT, need 3 minutes rest to get all CP back! Any Lactate and Hydrogen Ions are removed from muscles & blood stream too.

All 3 turn on at once no matter what the activity. Things to remember: All 3 turn on at once no matter what the activity. However, depending on intensity and duration of the activity, ONE system will contribute more than the other TWO. The 3 Energy Systems are not like TRAFFIC LIGHTS. One does not switch off and another goes on.

Energy Systems Video Overview

The Role of Three Energy Systems During an All-out Exercise Activity of Different Duration

Discussion Questions: 1. What are the differences between the 3 energy systems? 2. List one advantage and one disadvantage of each of the 3 energy systems. 3. Give an example of three activities or sports that use each of (a) the high energy phosphate system, (b) the anaerobic glycolytic system, and (c) the aerobic oxidative system as their primary source of energy (one sport for each energy system). 4. What is the most important source of fuel in the body for all types of energy production - a substance also known as the energy currency of the body? 5. Define ATP turnover and ATP resynthesis. 6. Describe how each of the three energy systems could be trained most efficiently.