Energy systems. And how they work

PHYSIOLOGICAL REQUIREMENTS OF PHYSICAL ACTIVITY Foods Fuel and Energy Systems

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

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

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

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

FATS Butter Margarine Oils Cheese Nuts

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 PPP Adenosine triphosphate

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

Resynthesis of ATP There is only enough stored ATP for about 1- 2 contractions, soooo….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.

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

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 Alactacid system Creatine phosphate system Phosphagen system. The Lactic Acid Systems Anaerobic glycolysis system Lactacid system Aerobic System Aerobic Glycolysis

ATP –PC system 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.

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

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

Summary Each ATP molecule is made up of an adenosine part and three phosphate groups. When 1 mole (1) of ATP is broken down, 7 to 12 Kcal (2) of energy is released. 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. There are altogether 450 to 510 mM PC, or 4.5 to 5.1 Kcal of energy in the human body. 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).

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

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

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.

Things to remember: The 3 Energy Systems are not like TRAFFIC LIGHTS. One does not switch off and another goes on. 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.