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Exercise Physiology
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Energy Systems
energy – the ability to perform work (joules)
chemical energy - food
kinetic energy – movement
potential energy – stored
work – force x distance (joules)
power – work performed over a unit of time (watts).
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Adenosine Triphosphate
Adenosine triphosphate, more commonly referred to as ATP, is the only usable form of energy in the body. The energy we derive from the foods that we eat, such as carbohydrates, has to be converted into ATP before the potential energy in them can be used. ATP consists of one molecule of adenosine and three phosphates:
Adenosine
P P P
Energy is released from ATP by breaking down the bonds that hold this compound together.
Adenosine
P P P
Enzymes are used to break down compounds and in this instance ATPase is the enzyme used to break down ATP into ADP + P.
Adenosine
ATP-ase
P P P
ADP + P + energy
The type of reaction that occurs here is an endothermic reaction. This is because energy is released. A reaction that needs energy to work is called an endothermic reaction. Re-building or resynthesising ATP from ADP + P is an endothermic reaction.
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As there is only a limited store of ATP within the muscle fibres it is used up very quickly (about 3 seconds) and therefore needs to be replenished immediately. There are three energy systems which re-synthesise/replenish ATP:
1. The ATP-PC system
2. The lactic acid system
3. The aerobic system
Each of these energy systems is suited to a particular type of exercise depending on the intensity and duration and whether oxygen is present. The higher the intensity of the activity the more the individual will rely on anaerobic energy production from either the ATP-PC or lactic acid systems. The lower the intensity and the longer the duration of the activity will result in the use of the aerobic system.
Fuels for ATP re-synthesis
When we exercise we need energy. The more exercise we do the more energy required.
Phosphocreatine is used to re-synthesise ATP in the first 10 seconds of intense exercise. It is easy to break down and stored within the muscle cell but its stores are limited
Food is also used for ATP re-synthesis. The main energy foods are:
Carbohydrates – stored as glycogen in the muscles and the liver and converted into glucose during exercise. During high intensity anaerobic exercise glycogen can be broken down without the presence of oxygen, but it is broken down much more effectively during aerobic work when oxygen is present.
Fats – stored as triglycerides and converted to free fatty acids when required. At rest two thirds of our energy requirements are met through the breakdown of fatty acids. This is because fat can produce more energy per gram than glycogen.
Protein – approximately 5-10% of energy used during exercise comes from proteins in the form of amino acids. It tends to be used when stores of glycogen are low.
Carbohydrates and fats are the main energy providers and the intensity and duration of exercise plays a huge a role in determining which of these are used. The breakdown of fats to free fatty acids requires more oxygen than that required to breakdown glycogen so during high intensity exercise when oxygen is in limited supply glycogen will be the preferred source of energy. Fats, therefore, are the favoured fuel at rest and during long endurance-based activities.
Stores of glycogen are much smaller than stores of fat and it is important during prolonged periods of exercise not to deplete glycogen stores as some needs to be conserved for later when the intensity could increase, for example, the last kilometre of the marathon.
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ATP-PC System.
PC is an energy rich phosphate compound in the sarcoplasm of the muscles and is readily available. Its rapid availability is important for providing contractions of high power such as in the 100m or in a game during a short burst of intense activity e.g., a smash in tennis or a slam dunk in basketball. However there is only enough PC to last for up to 10 seconds and it can only be replenished when the intensity of the activity is sub-maximal.
The ATP-PC system re-synthesises ATP when the enzyme creatine kinase detects high levels of ADP. It breaks down the phosphocreatine to phosphate and creatine, releasing energy. This energy is then used to convert ADP to ATP in a coupled reaction. For every molecule of PC broken down there is enough energy released to create one molecule of ATP. This means the system is not very efficient but it does have the advantage of not producing fatiguing bi-products and its use is important in delaying the onset of the lactic anaerobic system.
Adenosine
P P P
Advantages of the ATP-PC system
ATP can be re-synthesised rapidly using the ATP-PC system
Phosphocreatine stores can be re-synthesised quickly – (30secs =50% replenishment and 3 mins = 100%)
There are no fatiguing bi-products
It is possible to extend the time for the ATP-PC system through use of the creatine supplementation
Disadvantages of the ATP-PC system
There is only a limited supply of phosphocreatine in the muscle cell, ie. it can only last for 10 seconds
Only one mole of ATP can be re-synthesised through one mole of PC
PC resynthesis can only take place in the presence of oxygen (ie. the intensity of the exercise is reduced)
Phosphocreatine
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The Lactic Acid System
Once PC is depleted the lactic acid system takes over and re-synthesises ATP from the breakdown of glucose. Glucose is stored in the muscles and liver as glycogen. Before glycogen can be used to provide energy to make ATP it has to be converted to glucose. This process is called glycolysis and the lactic acid system is sometimes referred to as anaerobic glycolysis due to the absence of oxygen. In a series of reactions the glucose molecule is broken down into two molecules of pyruvic acid which is then converted to lactic acid because oxygen is not available. The main enzyme responsible for the anaerobic breakdown of glucose is PFK (phosphofructokinase), activated by low levels of phosphocreatine. The energy released from the breakdown of each molecule of glucose is used to make two molecules of ATP.
Glycogen
Phosphofructokinase Glycolysis
Glucose
2 ATP
Pyruvic acid no lactic
Oxygen acid
The lactic acid system provides energy for high intensity activities lasting up to 3 minutes but peaking at one minute, for example, 400m.
Advantages of the lactic acid system
ATP can be re-synthesised quite quickly due to very few chemical reactions
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 (ie., to produce an extra burst of energy)
Disadvantages of the lactic acid system
Lactic acid as the by-product! The accumulation of acid in the body de-natures enzymes and prevents them increasing the rate at which chemical reactions take place.
Only a small amount of energy can be released from glycogen under anaerobic conditions (5% as oppose to 95% under aerobic conditions)
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The Aerobic System.
This system breaks down glucose into carbon dioxide and water which, in the presence of oxygen is much more efficient. The complete oxidation of glucose can produce up to 38 molecules of ATP and has three stages:
1. Glycolysis. This process is the same as anaerobic glycolysis but in the presence of oxygen, lactic acid is not produced and the pyruvic acid can be converted into a compound called acetyl–Coenzyme-A (CoA)
2. Krebs Cycle. Once the pyruvic acid diffuses into the matrix of the mitochondria (the powerhouse of muscle cells) forming CoA, a complex cycle of reactions occur in a process known as Krebs cycle. Here CoA combines with oxaloacetic acid forming citric acid. The reactions that occur result in the production of two molecules of ATP where carbon dioxide is formed which is breathed out and hydrogen which is taken to the electron transport chain.
Acetyl-Coenzyme-A
Oxaloacetic acid
2 ATPCarbon dioxide
Citric acid
Hydrogen
3. Electron Transport Chain. Hydrogen is carried to the electron transport chain by hydrogen carriers. This occurs in the cristae of the mitochondria and the hydrogen splits into hydrogen ions and electrons and they are charged with
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potential energy. The hydrogen ions are oxidised to form water while the hydrogen electrons provide the energy to resynthesise ATP. Throughout this process 34 ATP are formed.
Hydrogen
34 ATP
water
Electron Transport Chain
Advantages of the aerobic system
More ATP can be produced -36 ATP
There are no fatiguing by-products (carbon dioxide and water)
Lots of glycogen and triglceride stores so exercise can last for a long time.
Disadvantages of the aerobic system
This is a complicated system so cannot be used straight away. It takes a while for enough oxygen to become available to met the demands of he activity and ensure glycogen and fatty acids are completely broken down
Fatty acid transportation to muscles is low and also requires 15% more oxygen to be broken down than glycogen
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Glycogen
S Phosphofructokinase Glycolysis
A
R
C
O energy
P 2 ATP
L
A Pyruvic acid no lactic
S Oxygen acid
M
Acetyl-Coenzyme-A
(matrix)
M Oxaloacetic acid
I energy 2 ATP T Carbon dioxide
O Citric acid
Glucose
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C
H O (cristae) Hydrogen
N
D energy 34 ATP
R water
I
A
Electron Transport Chain
The Energy Continuum
When we start any exercise the demand for energy will rise rapidly. Although all three energy systems are always working at the same time, one of them will be the predominant energy system. The intensity and duration of the activity are the factors that decide which will be the main energy system in use, for example, jogging is a long duration sub-maximal exercise so the aerobic system will be the predominant energy system. A highly explosive, short duration activity such as the 100m will use the ATP-PC system. However in a game there will be a mix of all three energy systems and the performer will move from one energy system to another. This continual movement between the threshold of each energy system is known as the energy continuum.
ATP-PC – lactic acid threshold = the point at which the ATP-PC energy system is exhausted and the lactic acid system takes over.
Lactic acid – aerobic threshold = the point at which the lactic acid system is exhausted and the aerobic system takes over. This can be highlighted in a graph:
% of energy Lactic aerobic supplied ATP-PC acid
10 1 3 secs min min
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The continuum below indicates the aerobic and anaerobic percentages of certain activities. Fill in the blank spaces:
0102030405060708090100
aerobic
100m?
rugbyhockeyfootball
?
?
1009080706050403020100
anaerobic
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Maximising energy for ATP re-synthesis
By following an appropriate diet and training programme it is possible to enhance the production of energy from each of the energy systems
Glycogen-loadingThis is a form of dietary manipulation involving maximising glycogen stores. Six days before an important competition a performer eats a diet high in protein and fats for three days and exercises at relatively high intensity to burn off any existing carbohydrate stores. This is followed by three days of a diet high in carbohydrates and some light training. This will greatly increase the stores of glycogen in the muscle.
Advantages: Increased glycogen synthesis Increaseed glycogen stores in the muscle Delays fatigue Increases endurance capacity
Disadvantages: Water retention which results in bloating Weight increase Fatigue During the depletion phase-irritability
Creatine monohydrate A supplement used to increase the amount of phosphocreatine stored in the muscles. Allows the ATP-PC system to last longer and can help improve recovery times. Possible side effects could be dehydration and slight liver damage
Soda Loading
Drinking a solution of sodium bicarbonate increases the pH of the blood and makes it more alkaline. This then increases the buffering capacity of the blood so it can neutralise the negative effects of lactic acid.
Training can improve the efficiency of each of the three energy systems, causing adaptations that will impact on ATP re-synthesis:
ATP-PC system – Sprint interval training, plyometrics and weights (90% of maximum load) will increase the stores of ATP and PC and increase enzyme activity (ATP-ase and creatine kinase).
Lactic acid system – interval, fartlek and weight training (80% of maximum load) will cause an increase in muscle glycogen stores and increase the number of glycolytic enzymes (PFK)
Aerobic system – continuous training will increase the stores of muscle glycogen and triglycerides and will increase the number of oxidative enzymes.
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Causes of Fatigue and the Recovery Process
There are many causes of fatigue and these will depend on the intensity and duration of the activity, for example, a marathon runner will fatigue through glycogen depletion wheras an 800m runner will fatigue through lactic acid build up! These causes will now be discussed:
Glycogen depletion-glycogen stores are limited and the body has enough to last approx 90 minutes. When this happens athletes are said to ‘hit the wall’ as the body tries to metabolise fat but is unable to use fat as a fuel on is own.
Lactic acid build-up-An accumulation of lactic acid releases hydrogen ions These hydrogen ions increase the acidity of the blood causing acidosis. This inhibits enzyme action and irritates nerve endings causing pain.
Reduced rate of ATP synthesis-when stores of ATP and PC deplete there is insufficient ATP to sustain muscular contractions.
Dehydration-water is lost through sweating during exercise and if it is not replaced then dehydration occurs. Dehydration can have an effect on blood flow to the working muscles and result in a loss of electrolytes such as calcium which help muscular contractions.
Reduced levels of calcium-an increase in hydrogen ions decreases the amount of calcium that is released from the sarcoplasmic reticulum, thus affecting muscle contraction.
Reduced levels of acetylcholine-this is a neurotransmitter that can jump the synaptic cleft (gap which separates the nerve ending from the muscle fibre) and initiate muscular contraction
Thermoregulation
Heat is generated in the body as a result of all the chemical reactions that take place to produce energy. The heat is then transported to the surface of the skin by the blood where it is lost through radiation, convection or through the evaporation of sweat. During prolonged exercise or when the body is dehydrated total blood volume can decrease as more blood is redirected to the skin, This reduces both the volume of blood and the amount of oxygen available to the working muscles and therefore affects performance. In hot conditions the this situation is exacerbated so it is important to acclimatise so the body can modify the control systems which regulate blood flow to the skin and sweating
Offsetting fatigue
Train the relevant energy system by using the appropriate training method
Spare glycogen levels-ie, a marathon runner needs to pace themselves, going too fast will speed up glycogen metabolism.
Try glycogen loading to optimise levels of glycogen before an event to enable an endurance based activity to last for longer
Keep hydrated-drink fluid through a performance with a carbohydrate level of no more than 6% carbohydrate to boost blood glucose levels.
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The Recovery Process
The Oxygen Defecit.
When we start to exercise insufficient oxygen is being distributed to the tissues for all the energy production to be met aerobically, so the two anaerobic systems have to be used. This is known as the oxygen defecit (or the amount of oxygen that the subject was short of during the exercise).
The recovery process involves returning the body to the state it was in before exercise. The reactions that take place and how long the process takes depends on the duration and intensity of the exercise undertaken and the individual’s level of fitness.
Complete the table to below to show the changes that take place during exercise:
Factor ChangeATP
Phosphocreatine
Glycogen
Triglycerides
Carbon Dioxide
Oxygen/myoglobin stores
Lactic acid
Temperature
Therefore after strenuous exercise there are four main tasks that need to be completed before the exhausted muscle can operate at full efficiency again:
1. Replacement of ATP and phosphocreatine2. Removal of lactic acid3. Replenishment of myoglobin with oxygen4. Replacement of glycogen.
These first three tasks require a large amount of oxygen. Therefore, during recovery the body takes in elevated amounts of oxygen and transports it to the working muscles to maintain elevated rates of aerobic respiration. This surplus energy is then used to help return the body to its pre-exercise state. This is known as EPOC (excess post-exercise oxygen consumption). The term oxygen debt is no longer used to explain the whole of the recovery process as it is commonly thought that other processes occur in addition to those covered by oxygen debt. The term EPOC incorporates oxygen debt together with those processes requiring an elevated rate of respiration.
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Increase in heart rate and breathing after exercise
Increased Excess Post-Exercise Restoration activity of Oxygen Consumption of oxygen and hormones myoglobin
stores
Restoration Increase in of glycogen Oxygen debt body temperature
Restoration of Removal of
Muscle phosphagens lactic acid
Oxygen Debt.
This is the amount of oxygen consumed during recovery above that which would have been consumed at rest during the same time. It has two components:
1. The Alactacid Component
This is often referred to as fast replenishment and involves the restoration of ATP and phosphocreatine stores. Elevated rates of respiration continue to supply oxygen to provide the energy for ATP production and phosphocreatine replenishment. Complete restoration of phosphocreatine takes up to three minutes but 50% of stores can be replenished after only thirty seconds, during which time approximately three litres of oxygen is consumed. The graph over the page shows the relationship between recovery time and the replenishment of muscle phosphagens after exercise:
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100 90
8070
% of PC 60replenished 50
40302010
| | | | | | 30 60 90 120 150 180 Recovery time
This knowledge is useful for a coach or performer who will want to prevent the use of the lactic acid system with its fatiguing bi-product. A time-out in basketball will allow for significant restoration of PC stores. However, in most team games it is possible to create a 30 second rest to replenish PC stores. Can you think of three instances when you could employ these tactics:
1._____________________________________________________________
2._____________________________________________________________
3._____________________________________________________________
2. The Lactacid Component
This is concerned with the removal of lactic acid. It is the slower of the two processes and full recovery may take up to an hour, depending on the intensity and duration of the exercise. Lactic acid can be removed in four ways:
DestinationApproximate %
lactic acid involved
Oxidation into carbon dioxide and water
65
Conversion into glycogen – then stored in muscles/liver
20
Conversion into protein 10
Conversion into glucose 5
The lactacid oxygen recovery 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 5-6 litres of oxygen in the first half hour of recovery removing up to 50% of the lactic acid.
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O2 Requirements
A
B
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C
D
A = Oxygen defecitB = Oxygen uptake during exerciseC = alactacid componentD = Lactacid component
Myoglobin and replenishment of oxygen stores.
Myoglobin has a high affinity for oxygen. It stores oxygen in the muscle and transports it from the capillaries to the mitochondria for energy provision. After exercise oxygen stores in the mitochondria are limited. The surplus of oxygen supplied through EPOC helps replenish these stores, taking up to two minutes and using approximately 0.5 litres of oxygen.
Glycogen.
Glycogen, as the main fuel for the aerobic system and lactic acid system will be depleted during exercise. In addition the stores of glycogen in relation to the stores of fat are relatively small, so it is important to conserve these in order not to cross the lactate threshold. The replacement of glycogen stores occurs when an individual eats a carbohydrate meal. It has been suggested that eating a high carbohydrate meal within one hour of exercise will speed up the recovery process
Increase in breathing and heart rates.This is important to assist in the process of expelling carbon dioxide.
Increased activity of hormones.An increase in activity will keep aerobic respiration high
Increase in body temperatureWhen temperature remains high respiratory rate rates will also remain high and this will help the performer take in more oxygen during recovery.
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Rest Exercise Recovery
Factors that contribute to successful endurance performance
There are many factors that contribute to successful endurance performance. These are now discussed:
Significance of maximum oxygen consumption in sporting performance
VO2(max)
This is the maximum volume of oxygen that can be taken in and used by the muscles per minute. A person’s VO2(max) will determine endurance performance in sport. Average VO2(max) for an A-Level student is around 45-55ml/kg/min for males and 35-44ml/kg/min for females. Paula Radcliffe’s VO2(max) is around 80ml/kg/min.
VO2(max) depends on:
1. How effectively an individual can inspire and expire2. Once they have inspired how effective the transportation of the oxygen is from the
lungs to where it is needed.3. How well that oxygen is then used.
Evaluation of VO2(max)
There are various methods of evaluating VO2(max). The Douglas bag is one very accurate method carried out under laboratory conditions. An individual runs on a treadmill to exhaustion while the air that is expired is collected in a Douglas bag. The volume and concentration of oxygen in the expired air is then measured and compared with the percentage of oxygen that is in atmospheric air to see how much oxygen has been used during the task. This test requires access to expensive and hi-tech equipment so less expensive predictive tests (indirect tests) have been developed to estimate the performer’s VO2(max)
One such test is the multi-stage fitness test developed by the NCF. Here an individual performs a 20 metre progressive shuttle run to a beep, until they reach complete exhaustion. The level that is reached can be compared with a standard results table. This test gives only an estimate of VO2(max) and is nowhere near as accurate as the Douglas bag. However, it does provide a guide from which progress can be monitored and is easy to set up. The equipment required is limited making it a cheap alternative. It is also possible to test large numbers simultaneously so it is not as time consuming as the Douglas bag.
Harvard step test
Here a performer steps up and down from a bench in time to a set rhythm for five minutes. Recovery heart rate is recorded and used to predict VO2(max)
PWC170 cycle ergometer test
A performer carries out three consecutive workloads on a cycle ergometer. Heart rate is measured each minute for four minutes for each workload. The heart rate for each workload is graphed and a line of best fit is drawn. The test is sub-maximal.
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Coopers 12 minute run
Here the perfomer runs as far as they can in 12 minutes and the distance they cover is recorded and compared to a standardised table such as the one shown below. In this test the performer runs to exhaustion.
Factors affecting VO2(max)
Differences in gender.
A male long distance runner will have a VO2(max) of approximately 70ml/min/kg wheras female long distance runners will have a VO2(max) of around 60ml/min/kg. This is because the average female is smaller than the average male so the following will occur: females have a smaller left ventricle and therefore a lower stroke volume females have a lower maximum cardiac output females have a lower blood volume which will result in lower haemoglobin levels females have lower tidal volumes and ventilatory volume
Differences in age.
Unfortunately most things decline with age and the same is true of human beings. As we get older our V02(max) declines as our body systems become less efficient: Maximum heart rate drops by around 5-7 beats per minute per decade. An increase in peripheral resistance results in a decrease of maximal stroke
volume Blood pressure increases both at rest and during exercise Less air is exchanged in the lungs due to a decline in vital capacity and an increase
in residual air
LifestyleSmoking, sedentary lifestyle and diet can all reduce VO2(max) values.
Training
VO2(max) can be improved by up to 10-20% following a period of aerobic training (continuous, fartlek and aerobic interval)
Body Composition
Research has shown that VO2(max) will decrease as the % of body fat increases.
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Onset blood lactate accumulation (OBLA)
The multi-stage fitness test is a good practical example to illustrate this. The performer eventually reaches a point due to the increasing intensity of this test where energy cannot be provided aerobically. This means the performer has to use the anaerobic systems to re-synthesise ATP. Blood lactate levels start to increase until eventually muscle fatigue occurs and the performer slows down or is no longer able to keep up with the bleep!
The multi-stage fitness test is a good practical example to illustrate OBLA. The performer eventually reaches a point due to the increasing intensity of this test where energy cannot be provided aerobically. This means the performer has to use the anaerobic systems to re-synthesise ATP. Blood lactate levels start to increase until eventually muscle fatigue occurs and the performer slows down or is no longer able to keep up with the bleep!.
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Onset blood lactate accumulation (OBLA)
Point where lactate accumulates in the
blood
Depends on aerobic fitness of performer
Occurs at 4mmol/l or above
Untrained individual at approx 50% of VO2(max)
Highly trained individual at approx 85% of VO2(max) Buffering.
A trained performer can cope with higher levels of blood lactate and speeds up removal through effective buffering
Factors affecting the rate of lactate accumulation
Exercise intensity.
The higher the exercise intensity the greater the demand for energy (ATP). Fast twitch fibres are used for high intensity exercise and can only maintain their workload with the use of glycogen as a fuel. When glycogen is broken down in the absence of oxygen, lactic acid is formed.
Muscle fibre type.
Slow twitch fibres produce less lactate than fast twitch fibres. When slow twitch fibres use glycogen as a fuel, due to the presence of oxygen, the glycogen can be 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 in the blood till we reach OBLA
The trained status of the working muscles
Adaptations occur to 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 lactic acid system.
Gender Differences in Athletic performance.
Gender difference Reasons why
Women have a 15-20% lower VO2(max) Lower levels of haemoglobin
Lower blood volume
Smaller heart size
Greater % of body fat which increases the non-functional weight thus using up more oxygen during exercise
Smaller lung capacity
Up to 50% lower in strength and power measures
Less muscle mass
Lower capacity for anaerobic glycolysis
7-10% more body fat Due to the female hormone oestrogen
Biomechanical differences Women have a wider pelvis and forward orientation of the pelvis which can affect running and cycling efficiency
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Physiological Adaptations
Physiological adaptations are long lasting changes that occur in the body as a result of following a training programme. These changes take place to allow improvement in fitness. The type of training you choose to do will result in specific adaptations.
Physiological adaptations to aerobic training
If you perform continuous, fartlek or aerobic interval training over a period of time, physiological adaptations take place that would make the initial training sessions appear very easy. This is because your aerobic capacity/VO2(max) has improved as the following adaptations have taken place:
HeartHypertrophy of the
myocardium (heart gets bigger and stronger)
Increase in stroke volume and maximum cardiac output
Decrease in resting heart rate
Lungs Maximum minute ventilation increases
Respiratory muscles more
efficient
Increase in resting lung
volume
Diffusion rates
improve
Blood Blood volume will increase due mainly to an increase in blood plasma and a small increase in red blood cells
Blood less acidic at rest but more acidic during
exercise due to the greater tolerance to lactic acid
Vascular system
Aerobic training can increase the elasticity of the arterial walls making it easier to
cope with fluctuations in blood pressure
Increased density of the capillary networks
surrounding the lungs and skeletal muscle
MusclesIncrease inmyoglobin
HypertrophyAnd
hyperplasia of slow
oxidative fibres
Increase in mitochondria
Increase in the number
of oxidative enzymes
Increase in energy stores in the muscle
cell (glycogen
and triglycerides)
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Responses to anaerobic training
Hypertrophy of fast
oxidative glycolytic and fast
glycolytic
Cardiachypertrophy(thickness of
the ventricular
walls through strength training)
Increase in ATP and PC stores in the muscle
cell
Increase in glycogen stores
Greater tolerance of lactic acid(enhanced buffering capacity)
Short-term responses of the body to exercise.
Cardiovascular Responses
Heart rate Stroke volume
Cardiac output
Blood pressure
Vascular shunt
Blood acidity
Muscular Responses to Exercise
Energy Production
Lactic acid production
Oxy-myoglobin
Carbon dioxide
Temperature
Respiratory Responses
Minute ventilation Oxygen consumption a-VO2diff
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Planning Training Regimes for Elite Performers.
Principles of TrainingIn order to improve fitness it is important to follow an effective training programme that includes the principles necessary for improvement. These are:
Overload (F.I.TT.)This is achieved by increasing one or more of the following:
Frequency - The number of times that you train per week. Intensity - how hard you work. If you wish to increase aerobic fitness it is important to increase the intensity of the exercise by training above the aerobic threshold but below the anaerobic threshold. Training zones help us to do this and one of the most recognised methods of calculating this is the ‘Karvonen Principle’. He suggests a training intensity of between 60-75% of maximum heart rate, using the following calculation:
60% = Resting heart rate + 0.6 (max heart rate – resting heart rate)75% = Resting heart rate + 0.75 (max heart rate – resting heart rate)
Time - This is the length of the session. Type – What type of training are we using?
ProgressionThis involves the application of overload. It is important to overload the body in order to improve fitness but this should be done gradually.
SpecificityHere the training should be relevant to the sport the individual is training for, for example, a sprinter will do strength training on the muscles required for his event and will do speed training to improve the efficiency of the energy system he uses when competing.
ReversibilityThis is often referred to as detraining. If you stop training the adaptations that have occurred as a result of training will deteriorate. Although it is suggested that the aerobic adaptations are lost more quickly than strength adaptations
ModerationDon’t overdo it! Over training can lead to injury
VarianceA training programme needs to have variety in order to maintain interest and motivation.
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Types of Training
The following types of training are all methods that can be undertaken by an elite performer to improve performance
Continuous TrainingThis involves exercise without rest intervals and concentrates on developing endurance, therefore placing stress on the aerobic energy system. Examples include exercises such as cycling, jogging and swimming. In order to gain any improvement in aerobic fitness it is important to apply the principles of training
Fartlek TrainingThis is slightly different method of continuous training where the word ‘fartlek’ means speed-play. Here the performer varies the pace of the run to stress both the aerobic and anaerobic energy systems. This is a much more demanding type of training and will improve an individual’s VO2 (max) and recovery process. A typical session will last for approximately 40 minutes with the intensity ranging from low to high.
Interval trainingInterval training can be used for both aerobic and anaerobic 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:
1. The duration of the work interval2. The intensity or speed of the work interval3. The duration of the recovery period4. The number of work intervals and recovery periods.
Energy system
Duration/distance of work interval
Intensity of work interval
Duration of recovery
Number of work intervals/recovery periods
ATP-PC 60m High intensity (10secs)
30 seconds
10
Lactic acid
200m High intensity (35 seconds)
110 seconds
8
Aerobic 1500m Submaximal(6 minutes)
5 minutes
3
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Strength trainingSome individuals do a form of strength training to improve performance in their chosen activity. Improvements in strength result from working against some form of resistance. In this instance it is also important to make any strength training programme specific to the needs of the activity. To do this the following factors must be considered:
what type of strength is to be developed – maximum, elastic or strength endurance
the muscle groups you wish to improve the type of muscle contraction performed in the activity – concentric, eccentric
or isometricOther individuals do strength training for muscle growth and need to ensure that any exercises they perform will overload the anaerobic energy systems which will result in hypertrophy of fast twitch fibres.Strength can be improved by doing the following types of training: weights, circuits, pulleys and plyometrics.
Weights.Weight training is usually described in terms of sets and repetitions. The number of sets and repetitions that you do and the amount of weight you lift will depend on the type of strength you wish to improve. If maximum strength is the goal, it will be necessary to lift high weights with low repetitions. However if strength endurance is the goal it will be necessary to perform more repetitions of lighter weights. The choice of exercise should relate to the muscle groups used in sport, both the agonists and antagonists.
Circuit training.In circuit training the athlete performs a series of exercises in succession. These exercises include press-ups, sit-up squat thrusts to name a few. The resistance used is the athlete’s body weight and each successive exercise should concentrate on a different muscle group to allow for recovery. A circuit is usually designed for general body conditioning and it is easily adapted to meet the needs of an activity.
Plyometrics.If leg strength is crucial to successful performance, for example, long jump and 100m sprint in athletics or rebounding in basketball, then plyometrics is one method of strength training that improves power or elastic strength. It works on the concept that muscles can generate more force if they have previously been stretched. This occurs in plyometrics when, on landing, the muscle performs an eccentric contraction (lengthens under tension) followed immediately by a concentric contraction as the performer jumps up.
PNF
This stands for proprioceptive neuromuscular facilitation where the muscle is stretched to the limit of its range of movement then isometrically contracted for a period of at least 10 seconds (either on its own or with a partner). It then relaxes and is stretched again, usually going further a second time. By contracting the muscle isometrically signals from the golgi tendon organ negate excitory signals from the
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muscle spindle apparatus which delay the stretch reflex. This causes further relaxation of the muscle so it can be stretched further .
Altitude trainingAt altitude the pressure/concentration of O2 is reduced, usually by up to 50% at an altitude of 5000m. Therefore there is a reduction in the diffusion gradient and haemoglobin is not fully saturated, which results in the lower O2 carrying capacity of the blood. As less O2 is delivered to working muscles there is an earlier onset of fatigue. This results in a decrease in performance (of aerobic activities).
Advantages:
Increase in the number of red blood cells
Increased concentration of haemoglobin
Enhanced oxygen transport
Disadvantages:
Expensive
Altitude sickness
Difficult to train due to the lack of oxygen
Detraining due to the fact that training intensity has to reduce when the performer first trains at altitude due to the decreased availability of oxygen.
Benefits can be quickly lost on return to sea level
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Periodisation
This is a key word when planning a training programme. This involves dividing the year into periods, blocks or cycles where specific training occurs. It enables an athlete to peak physiologically and psychologically during major competition:
(a) Off season(b) Pre-season(c) Competitive Season
This seasonal approach is now commonly adapted to macro, meso and micro cycles that describe periods of time that are more prescriptive for individual needs:
Macro - the ‘big’ period which involves a long-term performance goal. For a footballer it may be the length of the season or for an athlete it could be four years as they build up to the Olympics.
Meso – this describes a short-term goal within the macro cycle which may last for 2– 8 weeks.
Micro – this is normally just a description of one week of training that is repeated throughout the length of the mesocycle.
Macrocycle
This should be focused around peaking for major competitions. In its simplest form the macrocycle is made up of three distinct periods:
The preparation period
This is often referred to as pre-season training and is divided into: General conditioning training (phase 1). This should consist of high volume,
low intensity work. Athletes should aim to develop aerobic and muscular endurance, general strength and mobility.
Competition specific training (phase 2) is when there should be an increase in the intensity of training. During this time strength and speed work should be done. This phase also introduces technique and tactical work so the performer is prepared for the first day of the competitive season.
The Competition periodThe main aim of this phase is to optimise competition performance. Levels of fitness and conditioning should be maintained as should the competition specific aspects of training. Within this phase volume of training is decreased but intensity of training is increased. The competition period can be divided into the following phases:
Phase 3 (6 to 8 weeks). The typical competition period - reduction in the volume of training but an increase in the intensive competition specific training. Trials and qualifying competitions fall within this phase.
Phase 4 (4 to 6 weeks). During a long competitive season it is a good idea to have a mini period where competitions are eliminated altogether and the level of competition specific training is reduced. This allow the body to recover and prepare for phase 5
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Phase 5 (3 to 4 weeks). This is the end of the training year where all the major events and competitions fall. Competition specific training is maintained and tapering for peak performance should take place. Tapering is where there is a reduction in the volume of training prior to major competition. This allows the athlete to reach peak performance. The coach’s task is to ensure that peak performance occurs in a window between the removal of training-induced fatigue and the reversal of the training effect. A typical taper will last between 10 and 21 days but can vary between sports and performers.
The transition or recovery period (phase 6)This is the final phase of the year but probably the most important. It is the recovery phase where the athlete recharges physically and mentally and ensures an injury free start to the season. General, fun exercise should be carried out through this phase.
Mesocycle
Mesocycles are blocks of training that last 2-8 weeks in duration. They are closely related to the performance goals of the particular cycle. They may have a component of fitness as their focus, eg strength or cardio-respiratory endurance.
Microcycle
This is a training week. Microcycles are planned around the aims of a mesocycle ad contain the detail of the weeks training programme in terms of intensity, volume and sequence of training programmes. (ie. What the performer is going to do Monday to Sunday including rest days, usually on a 3:1 ratio).
The training unit
This is a description of one training session which will be following a key training objective.
In the table below describe what activities you might do to satisfy the aims of the session
Training aim Details of training session
A session to improve lactate tolerance
A session to improve strength in the upper
body
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Double Periodisation
Some sports require an athlete to peak more than once in a season. A long distance athlete, for example may want to peak in winter during the cross country season and then again in the summer on the track. In this case the performer has to follow a double periodised year.
The table below summarises periodisation:
Month 1 2 3 4 5 6 7 8 9 10 11 12
Periodisation phase
Preparatory 1 Preparatory 2 Competitive Trans
General
Preparation
Specific
Preparation PC
Competition
Maintenance
Taper Light
Rec
activity
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Structure of Skeletal muscle
Skeletal muscle is often referred to as voluntary, striped or striated muscle. A skeletal muscle is surrounded by a layer of connective tissue called the epimysium. This mainly consists of collagen fibres and its function is to provide a smooth surface so that other muscles can glide against this. Skeletal muscle is made up of bundles of muscle fibres which are enclosed in a connective tissue sheath called the perimysium. Then each of these individual muscle fibres are made up of many smaller fibres. These are called myofibrils and are covered by a very thin layer of connective tissue or endomysium.
The epimysium, perimysium and endomysium are all connected to one another so that when the muscle fibres contract movement occurs through their links with the tendons and their attachment to bones at joints.
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Types of muscle fibre.
Three main types of muscle fibre can be identified, namely type I slow oxidative, type IIa fast oxidative glycolytic and type IIb fast glycolytic. Our skeletal muscles contain a mixture of all three types of fibre but not in equal proportions. This mix is mainly genetically determined. These fibres are grouped into motor units where only one type of fibre can be found in one particular unit.
The relative proportion of each fibre type varies in the same muscles of different people, for example, in an elite endurance athlete there will be a greater proportion of slow twitch fibres in the leg muscles and in the elite sprinter a greater proportion of fast twitch fibres in the leg muscles. Also postural muscles tend to have a greater proportion of slow twitch fibres as they are involved in maintaining body position over a long period of time.
All three fibre types have specific characteristics that allow them to perform their role successfully. These can be found in the table below. Discuss each characteristic with a partner or in a small group and relate these to each of the fibre types.
Characteristic Type I Type IIa Type IIb
Contraction speed
Size
Force produced
Fatiguability
Mitochondria
Myoglobin
Glycogen store
Capillaries
Aerobic capacity
Anaerobic capacity
Elasticity
The effect of training on fibre type.
Fibre type appears to be genetically determined. However it is possible to increase the size of muscle fibres through training. This increase in size (hypertrophy) is caused by an increase in the number and size of myofibrils per fibre, with a consequent increase in the amount of proteins, namely myosin. As a result there will be greater strength in the muscle.
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Worksheet
1. From the table place the characteristics into the following categories:
Structures Functions
2. State whether the following activities use predominantly slow or fast twitch fibres:
a. Marathon
b. distance
c. basketball
d. endurance cycling
e. long jump
f. sprinting
3. What difference, if any, is there between male and female performers in these sports in terms of fibre type?
4. Will a 40 year old runner have a different fibre type to when he was a 20 year old runner?
5. Why is a warm-up important with regards to fibre type?
6. How can you adapt training sessions so that you just overload either slow or fast twitch fibres?
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The Motor Unit
For muscle to contract it has to be sent an impulse from the cerebrum or spinal cord. These impulses travel along nerves to the muscle. A motor unit is the whole system with which the impulse travels from the cell to the nerve to the muscle for the muscle to contract. This can be seen in the diagram below:
Here the dendrites receive impulses from other neurones and pass them on to the cell body. The cell body sorts out the information and sends an impulse down the muscle nerve called the axon or motor neurone. These impulses are electrical impulses and similar to electric currents in a wire. To protect them an insulator called the myelin sheath, made up of fatty material, surrounds the axon. This myelin sheath is absent at intervals along the axon. These breaks are called nodes of Ranvier. The impulse travels from one node of Ranvier to the next, which results in it travelling quicker. The thicker the myelin sheath the faster the impulse is conducted.
As the impulse reaches the end of the axon it triggers the release of acetycholine at the neuromuscular junction (where the axon connects with the motor end plate of the muscle).
One motor neurone cannot stimulate the whole muscle. Instead a motor neurone will stimulate a number of fibres within that muscle (between 15 and 2000 fibres). This is called a motor unit. Each motor unit only contains one kind of muscle fibre, e.g., all slow oxidative fibres.
The All-or-None Law.
Here a minimum amount of stimulation called the threshold is required to start a contraction. If an impulse is equal to or more than the threshold then all the muscle fibres in a motor unit will contract. However, if the impulse is less than the threshold
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then no muscle action will occur. As such the motor unit exhibits an all or none response.
Gradation of contraction.
Here the force exerted by a muscle is dependent on the following:
a) Recruitment. The more motor units that are recruited the more muscle fibres that contract, therefore increasing the force that can be produced.
b) Frequency. The greater the frequency of stimuli, the greater the tension developed by the muscle. This is often referred to as wave summation where repeated activation of a motor neurone stimulating a given muscle fibre results in summation.
Force
Single
Twitches
Time
S S
Force
A higher frequency of
Multiple stimulation = greater tension
Summation
S S S S S S Time
If the stimuli occur very infrequently the calcium concentration in the sarcomere returns to resting levels before the arrival of the next stimuli. When the stimuli occur frequently not all the calcium released in response to the first one is taken back into the sarcoplasmic reticulum. As a result summation occurs.
c) Timing. If all the motor units are stimulated at exactly the same time then maximum force can be applied. This is sometimes referred to as spatial summation or synchronisation.
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Control of Muscular Contraction
Muscle action has to be controlled in order for movement to be effective. There are several internal regulatory mechanisms that make this possible.
Proprioceptors: these are sense organs in the muscles, tendons and joints that inform the body of the extent of movement that has taken place.
Muscle Spindle Apparatus: These are very sensitive proprioceptors that lie between skeletal muscle fibres. They provide information about the changes in muscle length and the rate of change in muscle length. When the muscle stretches the spindle also stretches and this sends an impulse to the spinal cord. If the muscle is stretched too far the muscle spindle apparatus will alter tension within the muscle, causing a stretch reflex which automatically shortens the muscle.
Golgi tendon organs: are thin pockets of connective tissue between where the muscle fibre and tendon meet. They provide information to the central nervous system concerning the degree of tension or stretch within the muscle. When stretched they trigger both the reflex inhibition of the muscle that is contracting and stretching the tendon as well as the reflex contraction of the antagonist muscle.
Neuromuscular adaptations to resistance training:
Resistance training will result in some long-term physiological responses to the neuromuscular system
Recruitment of more motor units
Muscle hypertrophy-muscle gets bigger due to an increase in the size of the fibres
Evidence suggests that muscle fibres can split resulting in hypertrophy
Conversion of type 2b to type 2a fibres – some research has suggested that type 2b fibres in a trained muscle can decrease in favour of type 2a fibres. This could delay fatigue in prolonged training.
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Biomechanics
Linear Motion – this is when a body moves in a straight or curved line with all parts moving the same distance in the same direction at the same speed
Some concepts and definitions used when describing motion include speed, velocity, mass, weight, displacement, momentum, distance, inertia, vector quantity, scalar quantity and acceleration
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IS 3 Motion and Movement
Force
A force can be described as a ‘push or pull’. It can cause a body at rest to move or cause a moving body to stop, slow down, speed up or change direction.
A force can be measured in terms of:1. The size or magnitude of the force. This is dependent on the size and number
of muscle fibres used.2. The direction of a force. Here if a force is applied through the middle of an
object it will move in the same direction as the force.
3. The position of application of a force. This is an important factor in sport.
Applying a force straight through the centre will result in movement in a straight line (linear motion)
Applying a force off-centre will result in spin (angular momentum).
A force can be either internal or external. Internal forces are provided by concentric and occasionally eccentric muscle contraction. External forces include:
a) gravity – the force that draws all bodies on the earth towards the centre of the earth.
b) air resistance – this opposes the motion of objects through the air.c) friction – the resistance to motion caused by contact between two surfaces.d) reaction – for every action force there must be a reaction force equal and
opposite to it.
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WS 1 Motion and Movement
1. Screw up a piece of A4 paper into a tight ball.
2. Throw the ball into the air so that it does not spin. Mark the centre of gravity on the ball below and then show both the point of application of the force and the direction the force is acting.
3. Now throw the ball up again and this time give it some back spin. Draw the point of application of the force and the direction the force is acting.
4. Now throw the ball up one more time and this time try to make it spin forwards. Again draw the point of application of the force and the direction in which the force is acting.
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IS 4 Motion and Movement
Centre of Gravity
The centre of gravity is the point of concentration of mass, or more simply, the point of balance. In the human body the centre of gravity cannot be defined so easily due to its irregular shape. In addition the body is constantly moving so the centre of gravity will change as a result. In general the centre of gravity for someone adopting a standing position is in the hip region.
X
In order to be in a balanced position the centre of gravity needs to be in line with the base of support. If you lower your centre of gravity you will increase stability but if your centre of gravity starts to move near the edge of the base of support you will start to over balance. A sprinter in the ‘set’ position will have their centre of gravity right at the edge of the area of support. As they move when they hear the starting pistol they will lift their hands off the ground and become off balanced. This will allow the athlete to fall forward and will create the speed they require to leave the blocks as quickly as possible. Below are some other sporting pictures showing the changing positions of the centre of gravity.
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WS 2 Motion and Movement
1. Stand against a wall with your back and the back of your heels touching it. Now try to touch your toes.
2. Can you do this?
3. Any reasons why?
4. Now kneel on the floor with your bottom touching your heels.
5. Place both elbows at the front of your knees and keep your hands flat on the floor.
6. Place a pen/pencil horizontally from one hand to the other at the point that is furthest away from your body.
7. Transfer your weight back onto your feet and then with your hands behind your back see if you can pick up your pen with your teeth. (You are allowed to lift your bottom up into the air but you cannot move out of the kneeling position).
8. Are you able to do this
9. Can you give reasons why?
Newton’s Laws of Motion
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Newton’s First Law of Motion
Every body continues in its state of rest or motion in a straight line, unless compelled to change that state by external forces exerted upon it.
Newton’s Second Law of Motion
The rate of momentum of a body (or the acceleration for a body of constant mass) is proportional to the force causing it and the change that takes place in the direction in which the force acts.
Newton’s Third Law of Motion
To every action there is an equal and opposite reaction.
Complete the table below giving an example of how each of the laws can be applied to a sport of your choice.
Newton’s Laws Application
Law of inertia
Law of acceleration
Law of reaction
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