energy systems

what is the difference between aerobic and anaerobic exercise

aerobic:

• respiration with the use of oxygen

• exercise over 10 seconds

• low intensity and high duration

anaerobic:

• respiration without the presence of oxygen

• exercise/skill less than 10 seconds

• high intensity, low duration

what are the three different energy systems

ATP-P system (under 10s) - 100m sprint

anaerobic glycolytic system (10s - 3mins) - 400m sprint

aerobic system (3mins +) - marathon run

describe the energy continuum related to exercise duration

• when we start exercising the demand for energy will rise rapidly

• the energy continuum is a term used to describe which energy system is being used for different types of physical activity

• it refers to the contribution that different energy systems make to the production of energy depending on the intensity and duration of exercise

• the 3 energy systems don’t work independently- just one has more prominence than the others

how can the energy continuum be explained in terms of thresholds

The ATP-PC/anaerobic glycolytic threshold is the point at which the ATP-PC system is exhausted and the anaerobic glycolytic system takes over

the anaerobic glycolytic/aerobic threshold is the point where the anaerobic glycolytic system is exhausted and the aerobic system takes over

define VO2 max

the maximum volume of oxygen that can be taken up and utilised by the working muscles per minute

what are the benefits of having a high VO2 max

more oxygen can be taken up and utilised by the working muscles to provide energy to enable a high rate of exercise

delayed onset of OBLA, so performer can work at a higher intensity for a longer period of time

what factors improve VO2 max

training- aerobic training can improve VO2 max by 10-20%

Genetics- VO2 max is genetically inherited

Gender- males have a higher VO2 max than females (20%)

age- VO2 max increases until around the age of 30, where as age increases VO2 max decreases

body composition- having a low body fat percentage will increase VO2 max

lifestyle- smoking can decrease VO2 max

physiological- greater HR range, cardiac hypertrophy and bradycardia will increase VO2 max

what are the 4 different measures of energy expenditure

indirect calirometmery

lactate sampling

respiratory exchange ratio (RER)

VO2 max test

what is indirect calorimetry

• gives an accurate estimate of energy expenditure through gas exchange

• it measures how much CO2 is produced and how much O2 is consumed at rest and during aerobic exercise

• calculating the gas volumes also enables us to find out the main substrate being used for aerobic exercise (fats or carbohydrates)

• the accuracy of this test is very reliable as it gives a precise calculation of oxygen and VO2 max

what is lactate sampling

• an accurate and objective measure of lactate in the blood

• it can also be used to measure exercise intensity as the higher the exercise intensity is when the performer hits the lactate threshold, the fitter the performer is considered to be

• this is helpful as allows the performer to identify their level of fitness and enables the performer to train relevant training zones

• regular lactate sampling allows the performer and coach to see whether improvements have occurred- indicates a higher lactate threshold, improved HR recovery, improved power

what is respiratory exchange ratio

the ratio of CO2 produced to O2 consumed

it’s used as a measure of exercise expenditure

provides information about fuel usage during exercise

what do the different RER values stand for

1+ anaerobic respiration- more CO2 is being produced than O2 is being consumed (PC is fuel)

1 anaerobic glycolytic (glycogen is fuel)

0.7 aerobic exercise (less CO2 is produced than O2 consumed) (fats are fuel)

describe the VO2 max test

provides for valid and reliable results as it uses direct gas analysis

can be performed on bike, treadmill, or rowing machine to suit athletes needs

test protocol:

• minute increments of speed, measuring RPE and blood lactate at the end of each minute until exhaustion

• expired air is processed by a computer to calculate how much O2 is being used by the athlete

what is plyometric training and what is it’s impact on energy systems

• improves power and speed (anaerobic energy system)

• involves high intensity hopping, bounding, and depth jumping

• uses fast twitch muscle fibres

• it works on the concept that muscles can produce more power if they have previously been stretched (stretch shortening cycle)

describe the stretch shortening cycle

3 phases

Phase 1- eccentric phase/pre loading phase- muscle performs an eccentric contraction where it lengthens under tension

Phase 2- amortisation phase- is the time between the eccentric and concentric contractions. This time needs to be as short as possible, so the stored energy from the eccentric contraction isn’t lost. When a eccentric contraction occurs, a lot of the energy required to stretch or lengthen the muscle is lost as heat, but some of the energy can be stored and is then available for the subsequent concentric contraction

Phase 3- concentric/muscle contraction phase- uses the stored energy to increase the force of contraction

what is SAQ training and what is its impact on energy systems

improves the anaerobic system as SAQ training uses activities performed with maximum force at high speed (so energy needs to be provided anaerobically)

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

• agility- the ability to move and position the body quickly and effectively whilst under control

SAQ training aims to improve multidirectional movement through developing the neuromuscular system e.g. using zig zag runs and ladder work

a ball can be added e.g. football or basket ball, to make SAQ training more sport specific

what is altitude training and what is its effect on energy systems

altitude training is usually carried out at over 2500m above sea level where the partial pressure of oxygen is lower

this means that not as much O2 diffuses into the blood, so haemoglobin is less saturated with O2 than when at sea level- this lowers the oxygen carrying capacity of the blood

since less O2 is delivered to the working muscles, there is a reduction in aerobic performance and VO2 max- leads to a quicker onset of anaerobic respiration

what are the advantages of altitude training

• increased number of red blood cells

• increased concentration of haemoglobin

• enhanced O2 transport- more O2 delivered to the working muscles

• delayed onset of OBLA

• increased lactate tolerance/ higher lactate threshold

what are the disadvantages of altitude training

• difficult to train at same intensity due to the decrease in partial pressure of O2- leads to loss of fitness

• altitude sickness- can’t train- loss of fitness

• psychological problems due to being away from home (homesickness)

• benefits can be lost quickly upon return to sea level

what is HIIT training and what is its impact on energy systems

can improve both the aerobic and anaerobic energy systems

a form of training where periods of work are interspersed with recovery periods

involves short periods of maximum intensity exercise (anaerobic) followed by a recovery period of low-moderately intense exercise (aerobic)

the performer can make HIIT training specific by altering the:

• duration of work intervals

• duration of recovery intervals

• intensity or speed of work intervals

• number of work and recovery intervals

HIIT training also works as a fat burner as HR remains elevated during recovery periods, so we are working aerobically which means O2 is available that can burn fats

describe the lactate threshold

as the intensity of exercise increases the body starts to work anaerobically as the demand for O2 can’t be met

the lactate threshold is the point at which there is an exponential increase in blood lactate

what is OBLA

the onset of blood lactate accumulation

when blood lactate goes above 4 mmol

measuring OBLA can give an indication of endurance capacity

describe the ATP-PC system

It’s an anaerobic process

The energy we use for muscular contractions comes from ATP

ATP hydrolase is used to break the bonds between the phosphate groups on the ATP molecule

ATP is broken down into ADP and Pi + energy

Phosphocreatine (PC) is the fuel for the ATP-PC system

PC is broken down to Pi and creatine + energy (this energy is used in a coupled reaction to resynthesise ATP from ADP and Pi)

describe the replenishment of PC

3 minutes to replenish fully (100%)

30 seconds to replenish 50%

what are the advantages of the ATP-PC system

no fatiguing by-products such as lactic acid

energy released immediately

provides energy for high intensity short duration exercise

the ATP-PC system can be extended through the use of creatine

ATP can be resynthesises quickly

PC stores can be replenished quickly- 3 minutes for 100% and 30 seconds for 50%

what are the disadvantages of the ATP-PC system

only lasts up to 10 seconds due to limited supply of PC in muscle cells

only produces 1 ATP

PC stores can only be re-synthesised in the presence of oxygen (during rest)

what is phosphocreatine

the fuel for the ATP-PC system

an energy rich phosphate compound

found in the sarcoplasm of muscles

describe the anaerobic glycolytic system

Glycogen is the fuel and is stored in the liver and muscle cells

when PC stores are low in the muscle glycogen stored in the liver and muscles is broken down into glucose via the glycogen phosphorylase enzyme

glucose is then broken down into pyruvic acid via the enzyme phosphofructokinase- which produces 2 ATP molecules

if oxygen isn’t available/present then pyruvic acid will be converted into lactic acid

what are the advantages of the anaerobic glycolytic system

provides energy for high intensity short duration exercise

provides energy for up to 3 minutes

what are the disadvantages for the anaerobic glycolytic system

only produces 2 ATP molecules

produces fatiguing byproducts (lactic acid)

describe the stages of the aerobic system

3 stages that have a net production of 38 ATP

Glycolysis (2 ATP)- glucose is broken down ichemiosmosis, which provides the energy for ATP to be resynthesisedyl coenzyme-A, which combines with oxaloacetic acid to produce citric acid

Electron transport chain (34 ATP)- electron carriers are oxidised and electrons are carried down an electron transport chain, providing the energy to actively transport hydrogen ions and set up a hydrogen ion concentration gradient. The electrons are accepted by oxygen to form water. Hydrogen ion gradient drives the process of chemiosmosis, which provides the energy for ATP to be resynthesised

describe the Krebs cycle

• beta oxidation breaks down fatty acids (as O2 is present) to form acetyl coenzyme-A which enters the Krebs cycle and diffuses from the sarcoplasm into the mitochondrial matrix

• Acetyl coenzyme A (2C) combines with oxaloacetate (4C) to form citrate/citric acid (6C)

• after this CoA is recycled and goes back to the link reaction to pick up another acetyl group

• Citrate (6C) is then decarboxylated and dehydrogenated into alpha ketogluterate (5C)- the hydrogen is used to reduce NAD into NADH, and CO2 is given off

• alpha ketogluterate (5C) is converted into a 4C molecule as dehydrogenation and decarboxylation happen again so CO2 is given off, 3 hydrogen molecules are lost in total which produces 2 NADH and one FADH

• ATP is also formed from ADP and Pi by substrate level phosphorylation (1 ATP molecule per cycle)- there are 2x Krebs cycles per glucose molecule

• After all of the dehydrogenation and decarboxylation reactions have occurred oxaloacetate (4C) is formed- ready to combine with acetyl co enzyme-A during the next cycle

describe the electron transport chain

electron carriers are oxidised and electrons are carried down an electron transport chain

this provides the energy to actively transport hydrogen ions and set up a hydrogen ion concentration gradient.

The electrons are accepted by oxygen to form water.

Hydrogen ion gradient drives the process of chemiosmosis, which provides the energy for ATP to be resynthesised

this process produces 34 ATP

process occurs across the cristae of the mitochindria

what are the advantages of the aerobic system

high yield of ATP (38 ATP)

no fatiguing byproducts because O2 is available

provides energy for low intensity high duration exercise

what are the disadvantages of the anaerobic system

can’t use for the first 10 seconds of exercise because O2 isn’t available straight away

why are fats the preferred source of energy in the aerobic system over carbohydrates?

More ATP can be produced from one molecule of fatty acids, than one molecule of glucose.

Hence why low intensity, long duration, fatty acids is the predominant energy source

what does EPOC stand for

excess post oxygen consumption

define EPOC

the amount of oxygen consumed during recovery above that at rest

what is sub maximal oxygen debt

at the start of exercise oxygen isn’t available straight away so the increase in demand for oxygen can’t be met

therefore oxygen is provided anaerobically until the mitochondria and circulatory system can meet the oxygen demand to produce energy

what is maximal oxygen deficit

maximal accumulated oxygen debt

the higher the intensity the larger the demand for oxygen, therefore the larger the oxygen debt is

draw the graph for submaximal and maximal oxygen debt

what are the two different components of EPOC

fast component- restore ATP and PC stores + resaturate myoglobin with O2

slow component- remove lactic acid

describe the fast component of EPOC

restore ATP and PC stores in the muscles

PC stores- 3 mins for 100% and 30 seconds for 50%

resaturates myoglobin with oxygen

myoglobin has a high affinity for oxygen

myoglobin resaturation uses 0.5L of O2 and takes 2 minutes

describe the slow component of EPOC

The slow component starts as soon as lactic acid appears in the blood

removes lactic acid

LA accumulates during exercise where the demand for O2 can’t be met so energy is provided anaerobically

During slow component BR and HR is maintained and glycogen stores are replenished

during recovery LA needs to be removed- full LA removal can take around 1h

LA can be removed via:

• O2

• cori cycle

• through sweat and urine

• converted into protein

• cool downs

how is lactic acid removed via the presence of O2

Lactic acid is oxidated and converted back into pyruvate, CO2 and water in the inactive muscles and organs

Pyruvate can be used by the muscles as an energy source

how is lactic acid removed via the cori cycle

LA is transported to the liver via the blood where it’s converted into blood, glucose, and glycogen

how is lactic acid removed via cool downs

lactic acid is oxidised in the muscles by the mitochondria

during a cool down HR and BR are maintained and capillaries stay dilated →increases blood flow to muscles → more O2 to muscles/mitochondria

this helps to oxidise lactic acid that has accumulated in the muscles into pyruvate, CO2 and water

what factors affect the rate of lactic acid accumulation

exercise intensity

muscle fibre type

rate of blood lactate removal

the respiratory exchange ratio

fitness of performer

how does exercise intensity affect the rate of lactic acid accumulation

the higher the intensity, the faster the rate of LA accumulation will be

how does muscle fibre type affect the rate of lactic acid accumulation

fast twitch muscle fibres (type IIx) have a faster rate of lactate accumulation

how does the rate of blood lactate removal affect the rate of lactic acid accumulation

the faster the rate of blood lactate removal, the slower the rate of blood lactate accumulation will be

how does respiratory exchange ratio affect the rate of lactic acid accumulation

a respiratory exchange ratio close to 1 indicates anaerobic respiration and therefore a higher rate of lactate accumulation

how does the fitness of the performer affect the rate of lactic acid accumulation

if the performer is fitter then the rate of blood lactate accumulation will be slower

which athletes benefit from buffering

elite sprinters and power athletes as they can cope with higher levels of lactate

how does buffering provide an advantage

buffering is a process that aids the removal of lactic acid which helps to maintain acidity levels in the blood and prevent them from going to high

This allows athletes to work at higher intensities for longer and tolerate higher levels of lactate in their blood

buffering causes a change in the working muscles- greater size of mitochondria, greater capillary density and more myoglobin