Energy systems

How does the ATP-PC system work?

This is an anaerobic energy system that uses the energy rich compound phosphocreatine which is found in the sarcoplasm of cells as its fuel.

The enzyme creatine kinase detects high levels of ADP. it breaks down the phosphocreatine in the muscles to phosphate and creatine and releases energy in the process. The energy provides energy to resynthesize 1 ATP from ADP + Pi

What are the advantages of the ATP-PC system?

• ATP can be synthesized rapidly using the ATP-PC system

• Phosphocreatine stores can be synthesized quickly (50% in 30s and 100% in 3 minutes)

• There are no fatiguing by products

• It is possible to extend the time ATP-PC system can be utilized through use of a creatine supplement

What are the disadvantages of the ATP-PC system?

• limited supply of phosphocreatine in the muscle cell

• Only one molecule of ATP can be resynthesized

• PC re-synthesis can only take place in the presence of oxygen (the intensity of exercise can be reduced)

What is the anaerobic glycolysis system?

This anaerobic system lasts longer than the ATP-PC system (2-3 minutes) however how long this system lasts for depends on the intensity and fitness of the performer.

When the PC stores are low, the enzyme glycogen phosphorlyse is activated to break down the glycogen into glucose. Which is then further broken down into pyruvic acid by the enzyme phosphofructokinase, this releases energy for 2 ATP molecules to be resynthesized.

Since this is an anaerobic process pyruvic acid is broken down into lactic acid by the name lactate de hydrolyase

What are the advantages of the anaerobic glycolytic system?

• ATP can be re-synthesized quite quickly due to very few chemical reactions

• Last longer than the ATP-PC system

• In the presence of oxygen lactic acid can be converted back into liver glycogen or used as a fuel through oxidation into carbon dioxide and water

• it can be used for a sprint finish to produce an extra burst of energy

What are the disadvantages of the anaerobic glycolytic system?

• Produces lactic acid as the by product. The accumulation of acid in the body denatures enzymes and prevents them increasing the rate of chemical reaction

• Only a small amount of energy can be released from glycogen under anaerobic conditions (5% as opposed to 95% under aerobic conditions)

What is the 1st step of the aerobic system?

This is used when intensity is low and oxygen supply is high.

• Before pyruvic acid is produced in glycolysis it is oxidized into 2 aceytl groups and is then carried into the Krebs cycle by coenzyme A

What is the 2nd step of the aerobic system?

The 2 aceytl groups diffuse into y he matrix of the mitochondria. The aceytl groups combine with oxaloacetic acid forming citric acid. Hydrogen is removed from the citric acid and the rearranged form of citric acid undergoes oxidative carboxlyation which means hydrogen and carbon and given off. Carbon dioxide forms carbon dioxide and is breathed out. This process results the energy release to resynthesize 2 molecules of ATP

What is the 3rd step of the aerobic system?

Electron transport chain, hydrogen (from the Krebs cycle) is carried into the electron transport chain by hydrogen carriers. This occurs in the cisterns of the mitochondria and the hydrogen splits into hydrogen ions and electrons and they are charged with potential energy. The hydrogen ions are oxidized to form water while hydrogen electrons provide energy to resynthesize ATP. This gives energy for 34 molecules of ATP to be formed

What is beta oxidation?

Fat is broken down into glycerol and free fatty acids for transportation in the blood. These fatty acids undergo a process called beta oxidation whereby they are converted into aceytl coenzyme A, which is the entry molecule for the Krebs cycle.

More ATP can be made from one molecule of fatty acids than one molecule of glucose which is why in long duration, low intensity exercise fatty acids will be the predominant energy source but this does depend on the intensity and fitness of the performer

What are the advantages of the aerobic system?

• 36 Molecules of ATP can be produced

• There are no fatiguing by products

• Lots of glycogen and triglyceride stores so exercise can last for a long time

What are the disadvantages of aerobic system?

• fatty acid transpiration to muscles is low and also requires 15% more oxygen to be broken down than glycogen

• This is a complicated system so cannot be used straight away it takes a while for enough oxygen to become available to meet the demands of the activity and ensure glucose and fatty acid are completely broken down

What is the energy continuum?

The energy continuum is a term used to describe which energy system is used for different types of physical activity. It refers to the contribution that the different energy’s systems make to the production of energy, depending on the intensity and duration of exercise.

The energy continuum is often explained in terms of threshold the point at which ATP-PC system is exhausted the anaerobic glycolic system will take over when this system is exhausted the aerobic system will take over

How is energy generated in the slow twitch muscle fibers?

Slow twitch

• the main pathway for ATP production is in the aerobic system

• It produced the maximum amount of ATP abalone from each glucose molecule

• Production of ATP is slow but these fibers are more endurance based so less likely to fatigue

How is energy generated in the fast twitch muscle fibers?

• main pathway for ATP production is via the lactate anaerobic energy system

• ATP production in the absence of oxygen is not efficient only 2 molecules of ATP can be produced per glucose molecule

• Production of ATP is fast but have little resistance to muscle fatigue

What is oxygen consumption during exercise?

When we exercise the body uses oxygen to produced energy to resynthesize ATP. Oxygen consumption is the amount of oxygen we used to produce ATP (VO2 max).

At the start of exercise we use more oxygen to provide more ATP so our oxygen consumption increases. As intensity of exercise increases so does the amount of oxygen consumed until a performer reaches maximal oxygen consumption (VO2 max) which is the maximum volume of oxygen that an be taken up and used by the per muscles per minute.

What is sub-maximal oxygen deficit?

When we start exercise oxygen is distributed to the tissues for all the energy to be provided aerobically. This is because it takes time for the circulatory system to respond to the increase in demand for oxygen and it also takes time for the mitochondria to adjust to the rate of aerobic respiration needed. As a result energy is provided anatomically to satisfy the in ease in demand for energy until the circulatory system and mitochondria can cope

What is EPOC?

Excess post oxygen consumption is the amount of oxygen consumed during recovery to bring the body back to its resting state.

What is the fast component of EPOC?

The fast replenishment stage uses extra oxygen that is taken in during recovery to:

• restore ATP and phosphocreatine takes 3 minutes and 3L of oxygen

• resaturate myoglobin with oxygen takes 2 minutes and 0.5L of oxygen

What is the slow component of EPOC

• removal of lactic acid

Removal of lactic acid

• Lactic acid is converted back into pyruvic acid and oxidized into carbon dioxide and water in the inactive muscles and organs. This can be used by the muscles as energy source

• Transported in the blood to the liver where is it converted to blood glucose and glycogen (Cori cycle)

• Converted into proteins

• Removed in sweat and urine

How can performing a cool down help remove lactic acid?

Majority of lactic acid can be oxidized into carbon dioxide the mitochondria so performing a cool down can accelerate its removal. This is because exercise keeps the metabolic rate high and keeps capillaries dilated, which means oxygen can be flushed through removed the accumulated lactate.

This begins as soon as lactic acid appears in the muscle cell and will continue using breathed oxygen until recovery is complete, this can take up to 5-6L of oxygen in the first 30 minutes and remove up to 50% of lactic acid

What is the slow component of EPOC

• maintenance of breathing and heart rates

Maintaining breathing and heart rate required extra oxygen to provide the energy needed for the respiratory and heart muscles.

This assists recovery as extra oxygen is used to replenish ATP and phosphocreatine stores, re saturate the myoglobin and remove lactic acid

What is the slow component of EPOC

• glycogen replenishment

Glycogen is the main energy provider as it is fuel for both aerobic system and anaerobic system. Glycogen can be replenished via:

• Cori cycle - lactic acid is converted back to blood glucose and glycogen in the liver

• Eating a high carbohydrate meal will accelerate glycogen restoration

What is the slow component of EPOC

• Increase in body temperature

When temperature remains high, respiratory rates will also remain high and this will help the performer take in more oxygen during recovery. However extra oxygen is needed to fuel this increase in temperature until the body returns to normal

What is lactate accumulation?

Using the anaerobic glycolic system produces the by product lactic acid as a result of glycolysis. The higher the intensity of exercise the more lactic acid is produced.

What is the result of lactic acid in the cells?

Lactic acid breaks down releasing hydrogen ions, the remaining compound then combines with sodium or potassium ions to form the salt lactate. As lactate accumulates in the muscles so do more hydrogen ions, that increases acidity. This slows down enzyme activity which affects the breakdown of glycogen causing muscle fatigue.

What is lactate threshold and OBLA?

Lactate threshold - The point during exercise at which lactic acid quickly accumulates in the blood.

OBLA - the point when lactate levels go above 4 milomoles per liter

how does lactate accumulate and OBLA occur?

As intensity of exercise increases the body moves from working aerobically to anaerobically, the body produces lactate and is unable to produce enough oxygen to break down lactate. The levels of lactate build up (accumulate) and this results in OBLA

OBLA gives an indication of endurance capacity. Some individuals can work at higher levels of intensity than others before OBLA and can delay when the threshold occurs.

What is V02 max?

The maximum amount of oxygen that can be taken up and used by the body per minute.

Average v02 max for a level students is around for males 45-55ml/kg/min and for females 35-44ml/kg/min. Tour de France winner Greg Lemond has a V02 max of 92.5ml/kg/min. This means he has more oxygen going to the muscles and can utilize this oxygen to provide energy to enable a high rate of exercise. This is possible because the body has adapted as a result of training to take up more oxygen.

How is lactate threshold expressed?

Lactate threshold is expressed as a percentage of V02 max. As fitness increases the lactate threshold increases and also becomes delayed. Average performers may have a lactate threshold that is 50% of their v02 max whereas elite performers may have lactate threshold that is 70% of their v02 max.

The fitter we are the higher our lactate threshold as a percentage of our v02 max and therefore the harder we can work

What are the factors that affect lactate accumulation?

• exercise intensity - the higher the exercise intensity the greater the demand for energy and faster the OBLA occurs

• Muscle fiber type - slow twitch fibers produce less lactate than fast twitch fibers because glycogen is broken down much more effectively and with little lactate production

• Rate of blood lactate removal - if the rate of lactate removal is equivalent to the rate of lactate production then the concentration of blood lactate remains constant, if lactate production increases then lactate will start to accumulate

• Respiratory exchange ratio - it is the ratio of carbon dioxide produced compared to oxygen consumed

• Fitness of the performer - a person who trains regularly will be in a better position to delay OBLA as adaptions occur in the trained muscles. Increased numbers of mitochondria and myoglobin, together with an increase in capillary density improve the capacity for aerobic respiration and therefore avoid the use of the anaerobic glycolytic system

What are physiological factors that affect V02 max?

physiological

• increased maximum cardiac output

• Increased stroke volume and ejection fraction

• Greater heart rate range

• Less oxygen being used for the heart muscle so more available for the muscles

• increased levels of hemoglobin and red blood cell count

• Increased stores of glycogen and triglycerides

• Increased myoglobin content

• Increased capillarisation around muscles

• Increased number and size of mitochondria

• Increased surface area

• Increased lactate tolerance

What are other factors that affect V02 max?

• Training - can be improved by up to 10-20% following a period of aerobic training

• Genetics - inherited factors of physiology limit possible improvement

• Lifestyle - smoking, poor diet and fitness and sedentary lifestyle can all reduce v02 max

• Body composition - a higher percentage of body fat decreases Vo2 max

• Gender - Men generally have approx 20% higher v02 max than women

• Differences in age - as we get older our v02 max declines as our body systems become less efficient

What is altitude training?

Usually done at 2500m+ above sea level where the partial pressure of oxygen is lower. Therefore there is a reduction in the diffusion gradient of oxygen between the air and lungs and between the alveoli and blood, this means that not as much oxygen diffuses into the blood so hemoglobin is not as fully saturated with oxygen which results in lower 02 carrying capacity of the blood. As less 02 is therefore delivered to the working muscles there is a reduction in aerobic performance and v02 max and quicker onset of anaerobic respiration.

What are the benefits of altitude training?

• increase number of red blood cells

• Increase in the concentration of haemoglobin

• Increase in capillarisation and EPO resulting in enhanced oxygen transport

• Increase in lactate tolerance

What are the disadvantages of altitude training?

• very difficult to train at the same intensity due to the reduction in the partial pressure of oxygen so there can be a loss of fitness

• Altitude sickness

• The benefits gained from altitude training can be lost very quickly in return to sea level and the body can only produce a limited amount of EPO.

• Living away from home can also result in psychological problems such as homesickness

What is HIIT training?

It is a form of training in which periods of work are interspersed with recovery periods. Four main variables are used to ensure the training is specific

• duration of the work interval

• Intensity or speed of the work interval

• Duration of recovery interval

• Number of work intervals and recovery intervals

The work interval is anaerobic and recovery is aerobic. Pushing you body to the max during intervals increases the amount of calories you burn as it takes longer to recover from each work session.

HIIT involves

• different number of high intensity work intervals and low intensity recovery intervals

• Different lengths of time for the work and recovery intervals

• Different exercise intensity for the recovery interval

What is plyometrics?

Training involves high intensity explosive activities such as hopping, bounding and depth jumping, if used fast twitch fibers. It works on the concept that muscles can generate more force if they have previously been stretched.

• eccentric stage - pre loading stage, on landing the muscle performs a eccentric contractions where it lengthens under tension

• Amortization phase - stage between the eccentric and concentric muscle contractions. This time needs to be as short as possible so energy stored from the eccentric contraction is not lost

• Concentric - contraction phase, uses the stored energy to increase the force of the contraction

What is SAQ training?

Speed, agility, quickness

Speed - how fast a person can move over a specified distance or how quickly a body part can be put into motion .

Agility - ability to move and position the body quickly and effectively while under control, good agility requires a combination of speed, co-ordination balance and flexibility, these are all important fitness components for a games player and can be developed through SAQ training

What does SAQ training improve?

This type of training aims to improve multi directional movement through developing the neuromuscular system. Drills include zig zag runs and foot ladders and often a ball is introduced so passing occurs throughout the drill making it more sport specific. As SAQ training uses activities performed with maximum force at high speed, energy is provided anaerobically