Energy Systems


Energy Transfer in the Body

A constant supply of energy is needed to perform everyday tasks - tissue repair and muscle growth

We use energy from adenosine triphosphate - ATP - only useable form of chemical energy in body

Enzymes are used to break down compounds and ATPase is used to break down ATP leaving ADP

Body constantly rebuilds ATP by converting ADP and P back into ATP.

Resynythesis of ATP occurs in three different chemical reactions in the muscle cell - fuelled by phosphocreatine

Conversion of fuel takes place in the: aerobic system, ATP-PC system or anaerobic glycolitic system.

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The Aerobic System

Low intensity exercise is low and oxygen supply high - aerobic system is used

Breaks down glucose into carbon dioxide and water - which with oxygen is highly efficient

Complete oxidation of glucose can produce 38 molecules of ATP.

Fats and proteins can also be broken down - products of these are reduced to acetyl coenzyme A that enters the Krebs Cycle.

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How the Aerobic System Provides Energy

Three stages:

Glycolosis - first stage is anaerboic so takes place in sarcoplasm. Glycolosis is the breakdown of pyruvic acid. For every molecule of glucose undergoing glycolosis, 2 ATP are formed.

Krebs Cycle - the two acetyl groups diffuse into mitochondria and reactions occur. Acetyl groups combine with oxaloetic acid, forming citric acid. Citric acid then undergoes oxidative carboxylation - meaning carbon and hydrogen is given off. The carbon forms carbon dioxide which is transported to the lungs. The hydrogen is taken to the ETC.

Electron Transport Chain - hydrogen is carried to ETC by hydrogen carriers. occurs in cristae of mitochondria. Hydrogen splits into hydrogen ions and electrons - charged with potential energy. Hydrogen ions are oxidised to form water. Hydrogen electrons provide the energy to resysnthesis ATP. 34 ATP are formed.

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Beta Oxidation

Stored fat is broken into glycerol and fatty acids for transportation by the blood.

Fatty acids undergo beta oxidation - converted into acetyle coenzyme A - used in Krebs Cycle

From here, fats follow same path as glycogen.

More ATP is produced from a molecule of fat than glucose - which is why fats are predominant energy source for long duration events.

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The ATP-PC System

Uses PC as fuel. Broken down quickly to release energy to resysnthesise ATP - limited to 10s

How It Provides Energy:

System is anaerobic - no oxygen

It resysnthesises ATP when creatine kinase detects high levels of ADP.

Breaks down PC in the muscles to P and C, releasing energy

For every molecule of PC broken down, 1 ATP is produced - there are no fatguing by products.

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Anaerobic Glycolitic System

Provides energy for high intensity activity - longer than ATP-PC system

System can last up to 3 mins but can peak at 45s

How it Provides Energy:

When PC is low, glycogen phosphorylase breaks glycogen into glucose.

Glucose is then broken into pyruvic acid by phosphofructokinase.

No oxygen is availabe meaning pyruvic acid is broken into lactic acid by lactate dehydrogenase.

2 ATP molecules are produced per 1 molecule of ATP

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Energy Continuum of Physical Activity

During start of exercise demand for energy increases rapidly.

Energy continuum - describes different energy systems for each type of physical actvity

All energy systems work together - when one reaches its threshold the next takes over

ATP-PC System - 10s - 100m and Shotput

8-90s - ATP-PC and anaerobic glycolitic - 200m, 400m

90s-3mins - Anaerobic glycolitic and aerobic - 1500m, round of boxing

3mins + - Aerobic - marathon

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Differences in ATP between Fast and Slow Twitch Mu

Slow Twitch - Type 1 - Main pathway for ATP production - aerobic system

                                  - Max ATP per glucose molecule - 36ATP

                                  - Less likely to fatigue

Fast Twitch - Type 2 - Main pathway for ATP production - anaerobic energy systems

                                  - ATP = 2 molecules - insufficeint yield

                                  - Likely to fatigue

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Oxygen Consumption During Exercise - Maximal and S

Body uses oxygen to produce energy to resynthesise ATP.

Oxygen consumption is the amount we use to produce ATP and is referred to as VO2.

At rest we consume oxygen at 0.3-0.4L per minute

During exercise this rises to 4-6L

When exercise starts, insufficient oxygen is distributed to the tissues for all energy to be provided aerobically.

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Oxygen Consumption During Recovery - Excess Post E

When a performer finishes exercise, oxygen consumption still remains high in comparison with oxygen consumption at rest.

This is because extra oxygen has to be taken in and used to help the performer recover.

This is known as EPOC

EPOC is the amount of oxygen consumed during recovery above tht which would have been consumed at rest during the same time.

There are two components of EPOC

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The Fast Component of EPOC

Uses the extra oxygen that is taken during recovery to restore ATP-PC and to resaturate myoglobin.

Complete restoration of PC takes 3mins but 50% of stores are replenished in 30s.

Myoglobin has a high affinity for oxygen.

It stores oxygen in the sarcoplasm that has diffused from the haemoglobin.

The excess oxygen supplied through EPOC helps replenish these stores, taking 2mins and 0.5L of oxygen

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The Slow Component of EPOC

Removal of Lactic Acid - full recovery takes up to 1h - removed by - oxygen being present, transporation from blood to the liver, converted into protein and removed in sweat and urine

Maintenance of Breathing and Heart Rate - heart and respiratory muscles need oxygen to work. To keep breathing and HR high after exercise, muscles need extra oxygen. Aids recovery as it helps replenish ATP stores, resaturate myoglobin and reduce lactic acid.

Glycogen Replenishment - Glycogen is the main energy provider - fuel for aerobic and anaerobic system. Replacement of glycogen depends on carbs consumed after exercise. In the first 20 mins after exercise - carbs and protein should be consumed in a 3:1 ratio.

Increase in Body Temperature - when body temperature is high, respiration rates stay high. This helps oxygen consumption, but you need oxygen to fuel this increase in temperature

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Energy Transfer During Short Duration High Intensi

Lactate and lactic acid are not the same

Using the anaerobic glycolitic system produces the by-product lactic acid as a result of glycolosis

The higher the exercise intensity, the more lactic acid produced.

The lactic acid breaks down, releasing hydrogen ions.

The remaining compound combines with potassium or sodium to form the salt lactate.

As lactate accumulates in the muscles, more hydrogen ions are present and this causes acidity.

This slows down enzyme activity, affecting the breakdown of glycogen causing muscle fatigue

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Lactate Threshold and Onset Of Blood Lactate Accum

Lactate threshold is the point in which lactic acid accumulates in the blood.

As the intensity of exercise increases, there is a lack of oxygen meaning lactate isnt broken down.

OBLA and lactate threshold are the same thing.

At rest, 1-2 millimoles of lactate can be found in the blood.

During exercise this rises to 4 millimoles - OBLA occurs

Lactate threshold is expressed as a % of VO2 max.

As fitness increase, lactate threshold is delayed.

Average performers have a lactate threshold of 50-60% of their VO2 max.

Elite performers have a lactate threshold of 70-90% of their VO2 max.

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Factors Affecting The Rate of Lactate Accumulation

Exercise Intensity - greater demand for energy

Muscle Fibre Type - slow twitch have less lactate then fast twitch

Rate of Blood Lactate Removal

Respiratory Exchange Ratio - ration of carbon dioxide to oxygen production - when 1:0 glycogen is preferred fuel

Fitness - trained athletes can delay OBLA

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Lactate Producing Capacity and Sport/Power Perform

Elite athletes will have a better anaerobic endurance that non-elite performers.

Their bodies have adapted to cope with higher levels of lactate.

In addition a process called buffering allows them to lower their lactate levels

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Factors Affecting VO2 Max and Aerobic Power

VO2 Max - the maximum vloume of oxygen that can be used per minute.

Physiological Factors - increased cardiac output, increased SV, greater HR ranges, more O2 available, increased haemoglobin and RBC count, increased glycogen, increased myoglobin, increased capillary count, increased mitochondria, alevoli surface area increase and increased lactate tolerance.

Training - VO2 max can increase by up to 20% following aerobic training

Genetics - Inherited from parents if they are trained athletes

Age - Increase in age - decline in V02 max - body not as efficient

Gender - Men have a greater VO2 max - due to being naturally bigger

Lifestyle - Smoking reduces VO2 max

Body Composition - High body fat % decreases VO2 max

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Measurements of Energy Expenditure

Gives an indication of the intensity of exercise, levels of fitness, dietary requirements and training programme effectivness.

Indirect Calorimetry - measures the production of CO and the consumption of O2. Provides an estimate of energy expenditure through gaseous exchange

Lactate Sampling - taking a blood sample and analysing lactate present. Measures exercise intensity

V02 Max Test - Bleep Test - direct gas analysis measures the concentration of O2 inspired and CO2 that is expired

Respiratory Exchange Ratio - the ratio of CO2 produced compared to O2 consumed - used to measure exercise intensity - provides info about fuel used during exercise

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Impact of Specialist Training Methods on Energy Sy

Altitude Training - done at 2500+m above sea level - PP of O2 is lower. Reduction in diffusion gradient of O2 between the air and lungs and the alveoli and blood. Not as much O2 diffuses into blood so haemoglobin is at full capacity.

HIIT - used for aerobic and anaerobic training - periods of work followed by rest. Four variables are  used - duration of work interval, intensity of work, duration of rest, number of work and rest intervals

Plyometrics - repeated rapid stretching and contracting of muscles to increase power. Three phases - Eccentric phase - on landing muscle performs an eccentric contraction - Amortisation Phase - time between eccentric and concentric muscle contractions - time needs to be as short as possible so energy is not lost. Muscle contraction phase - uses stored energy to increaee contraction force.

Speed, Agility and Quickness

Speed - how fast a person moves over a set distance

Agility - the  ability to change direction effectivley whilst under control.

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