CHAPTER 6 THE THREE ENERGY SYSTEMS WORKING TOGETHER TO PRODUCE ATP

recovery of ATP-PC SYSTEM

-ATP and PC are stored at the muscles -PC replenishment requires a passive recovery. -Full PC replenishment will take 3 minutes -Once PC at the muscle has depleted ATP is resynthesized via the anaerobic glycolysis system.

Glycaemic Index

-Carbohydrate foods can be measured on a glycaemic index (GI) on a scale of 0-100 of how quickly the carbohydrates are digested and absorbed into the blood. -High GI foods are rapidly digested and absorbed. E.g white bread, sports drink -Low GI foods are digested more slowly and provide longer lasting energy. E.g oats, mixed grain bread

ATP-PC energy system

-Does not require oxygen to produce energy (anaerobic) -The ATP-PC system provides the most rapidly available source of ATP. -Depends on PC being broken down to P + C. -Enough stored ATP to last 2 - 3 secs -Enough PC to last 10sec

Aerobic energy system

-Produces ATP with the presence of oxygen -Produces ATP at the slowest rate due to the complex chemical reactions -Capable of producing the most energy out of the 3 systems -It requires oxygen, which can be provided (90% of VO2 max) within 60 seconds preferably breaks down carbs rather than fats. releases no toxic/fatiguing by-products. contributes significant amounts of energy during high intensity/maximal activity 1-2mins.

Advantages of the ATP-PC system

-Simple, anaerobic energy pathway -Provides energy at an explosive rate -Allows for maximal intensity effort EG. 100m, 50m pool

Anarerobic glycolysis energy system

-The anaerobic glycolysis system produces ATP without oxygen. -Supplies ATP at a slower rate due to longer chemical reactions -It also contributes energy from the start of intense exercise -Contribution during maximal activity for 10 - 75 seconds -Involves the incomplete breakdown of glycogen -Lactic acid and H+ (hydron) are a byproduct of this. -Lactic acid is then broken down to lactate and further ATP is produced.

ATP (adenosine triphosphate)

ATP provides energy for movement. ATP is being broken down and rebuilt 24/7. ATP is broken down to provide energy for muscular contractions.

chemical fuels

Adenosine triphosphate (ATP) is the major source of energy. Energy is released when 1 phosphate molecule splits off, this results in ATP ADP. Enough ATP stored in the muscle to supply energy for 2 - 3 seconds.

predominant energy system

After about 1 minute of maximal intensity effort, the main supplier of ATP shifts from the anaerobic glycolysis system to the aerobic system. After 10 seconds of intense muscular activity, the energy system providing the majority of the energy shifts from the ATP-PC system to the anaerobic glycolysis system.

Energy continuum

All three systems contribute to ATP production. One system contributes more than the other two systems at any one point, depending on: intensity, duration, availability of oxygen and availability of fuel sources.

Advantages of anaerobic glycolysis

Also an anaerobic energy pathway Provides energy at a fast rate Allows for high intensity effort Provides energy in larger amounts than ATP- CP eg. 400m, 100m pool,

Why are carbohydrates a more efficient fuel source?

Carbohydrate is a more efficient fuel source than fat when you consider the amount of ATP produced per unit of oxygen consumed. This means more oxygen is available for working muscles when using carbohydrates vs. fats.

Disadvantages of aerobic glycolysis

Delay in aerobic responses at start of exercise Slow rate of energy production Submaximal intensity only allowed for muscular effort.

Oxygen debt

EPOC (Excess Post - Exercise oxygen consumption) - Occurs during recovery whilst oxygen levels remain above resting levels - largely aerobic energy system. the amount of oxygen required after physical exercise to convert accumulated lactic acid to glucose

Phosphcreatine

Energy from the breakdown of Phosphocreatine (PC) is used to re-join ADP to inorganic phosphate. The stored muscle PC lasts around 10 seconds of maximal intensity.

Food fuel

Everything we eat is broken down and either used immediately, excreted or stored as chemical energy, which must be used to rebuild ATP.

oxygen uptake and deficit

Oxygen deficit is associated with anaerobic ATP production Oxygen uptake is associated with aerobic ATP production Oxygen uptake and oxygen deficit for an elite 800-metre runner during an event lasting approximately 2 minutes:

Advantages of aerobic glycolysis

Provides an "endless" amount of energy Allows sustained, long duration effort Produces non-toxic by-products Ability to oxidise lactic acid eg. 800m, 200m pool, endurance

Disadvantages of anaerobic glycolysis

Relatively small amounts of energy produced By-product of H+ ions lead to fatigue

how does ATP create energy?

The 'energy' comes from breaking the bond holding the three phosphates together. We need to rebuild or recharge ATP, and this occurs by using Phosphocreatine (PC), Carbohydrates (CHOs), fats and sometimes proteins. When these are broken down, they release energy to enable ATP to be recharged/ rebuilt. ATP is breaking down and being rebuilt '24/7' with the only difference being how fast this occurs.

aerobic lipolysis

The Aerobic Use of Fat (Lipolysis). This energy pathway involves the breakdown of fat - especially fatty acid to supply energy for work in the presence of oxygen. The key factor about this energy systems is that it too needs OXYGEN for energy release.

The cross-over concept

The cross-over concept and glycogen sparing both involve the delay of carbohydrates becoming the major fuel rebuilding ATP. This means that fats are used for longer from the start of continuous activities.

Disadvantages of ATP-PC System

There is only a limited supply of phosphocreatine in the muscle cells, (eg. it can only last for 10seconds). Only one molecule of ATP can be regenerated for every molecule of PC PC regeneration can only take place in the presence of oxygen (eg. when the intensity of exercise is reduced)

3 energy systems

We have two anaerobic energy systems: The ATP-PC system & The Anaerobic Glycolysis system As well as one aerobic energy system: The Aerobic system

Proteins

are rarely used to recharge ATP because of an abundance of other fuel sources. If they do recharge ATP, they are the slowest because they are also the largest fuel molecules.

Fats

can only be broken down aerobically and because these are 'huge' molecules, they take a long time to recharge ATP. Preferred fuel source at rest and for prolonged submaximal exercise.

glycemic index ratings

high GI- 70+ eg sports drink Moderate GI- 55-70 eg muffin Low GI- 55 or below eg pasta

oxygen deficit

occurs when oxygen supply lags behind oxygen demands - typically at the start of exercise and when exercise intensities rapidly increase - mainly anaerobic energy systems

steady-state oxygen uptake

oxygen supply equals oxygen demand. The aerobic system is the predominant supplier of ATP

Energy System Interplay

refers to the concept that more than one energy system is contributing to ATP resynthesis at one time. all three systems contributing to ATP production, but to varying amounts. As one system increases its energy contribution, the other two energy systems are also affected. One must decrease and the other can either increase or decrease, depending on stage of activity.

VO2 maximum

the maximum oxygen that can be taken up, transported and used by working muscles.

Carbohydrates

the starches and sugars present in foods Carbohydrates are the body's preferred exercise fuel. Carbohydrated can be broken down both anaerobically and aerobically. During high intensity exercise carbohydrates are the primary source once PC is depleted. During aerobic glycolysis energy comes from the break down of carbohydrates and then fats. Fats are also used to provide energy at rest.