KS4 Physical
Education
The Effects of Exercise
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Learning objectives
Learning objectives
What we will learn in this presentation:
The immediate effects of exercise on the
respiratory system
The immediate effects of exercise on the
circulatory system
How levels of lactic acid, water and heat are
affected by exercise
How the body recovers from exercise
Recovery rates
The long term effects of exercise on the heart,
lungs, skeleton and muscles
How different components of fitness can be
tested.
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The immediate effects of exercise
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Immediate effects on the respiratory system
Exercise causes the muscles to use more oxygen.
This means that the lungs must work harder and faster to
keep the body supplied with oxygen and also to exhale the
carbon dioxide that is produced. This is why exercise
makes you out-of-breath.
Breathing rate increases from around 18 breaths per
minute to up to 80!
The amount of air inhaled and exhaled in each breath also
increases from around 0.5 litres to up to 4.5 litres.
During aerobic exercise, the lungs are able to work
fast enough to supply the muscles with oxygen.
During anaerobic exercise, the lungs can’t supply
enough oxygen. Once the exercise is over,
breathing remains fast to repay the ‘oxygen debt’.
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Immediate effects on the circulatory system
During exercise, the circulatory system’s most important
function is transportation.
The heart and blood vessels work to transport the oxygen
from the lungs to the muscles where it is needed. Glucose
and other substances needed by the muscles are
transported in the blood too.
The by-products of respiration, including carbon dioxide
and lactic acid, are also carried away from the muscles.
carbon
glucose + oxygen
energy +
+ water
dioxide
glucose
energy + lactic acid
If these by-products build up in the muscles,
they can cause them to stop working.
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Immediate effects on the circulatory system
In response to exercise, the heart beats not only faster,
but stronger.
Heart rate increases from around 70 bpm to up to 200 bpm.
Stroke volume (the volume of blood pumped per beat)
increases from around 50 ml to around 120 ml. In highly
trained athletes, stroke volume can reach 200 ml.
The arteries respond to the body’s increased demands by
widening slightly to allow more blood to pass through them.
Blood is also diverted away from systems that are not
involved in the activity, for example, the digestive system.
Write a paragraph explaining how the roles of the
heart and lungs in supporting exercise are connected.
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The immediate effects: lactic acid
Lactic acid is produced during anaerobic respiration.
This happens when there is not enough oxygen for
normal aerobic respiration to take place.
glucose
energy + lactic acid
Lactic acid is a mild toxin. It is responsible
for the pain you feel in your muscles when
they get tired.
When too much of it builds up in a muscle,
it can prevent the muscle contracting. At
this point, the performer’s muscles will
cramp and they will be forced to stop.
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The immediate effects: heat loss
The body has two main ways of getting rid of the extra
heat produced by muscles during exercise.
1. Vasodilation
The capillaries close to the surface of the
skin dilate, allowing more blood to flow into
them. Because the blood is closer to the
skin, more heat is lost to the environment.
2. Sweating
Sweat glands in the skin excrete
sweat – a mixture of water, salts and
urea. As the sweat evaporates, it
takes heat away with it.
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The immediate effects: water loss
When you sweat, water is lost from the
body. Water is vital to maintaining proper
body functions.
The body produces less urine to
compensate, but during prolonged exercise
or in hot weather, this is often not enough.
Extra water must also be consumed.
The body does not only lose water – it also loses important
salts called electrolytes. These are necessary in many
areas of the body, including the nervous system.
Salts can be replaced during exercise by drinking isotonic
drinks, or eating foods rich in these minerals.
Severe salt depletion can lead to cramps,
fainting and, in extreme cases, death.
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Immediate effects of exercise
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Recovery rates
Your recovery rate is how quickly your body returns to
normal following a period of exercise.
Recovery rate is a good indicator of fitness. The quicker
you recover, the fitter you are.
As you recover from exercise, changes happen in the
following areas:
Heart rate
Lactic acid levels in the blood
Glycogen stores
Muscles
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Heart rate
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Lactic acid
Lactic acid is produced when the body cannot supply the
muscles with enough oxygen.
In this situation, the body builds up an oxygen debt – this is
repaid by continuing to breathe heavily for a period after
exercise ceases.
As more oxygen becomes
available, it reacts with the
Resting
recovery
lactic acid to form
harmless substances.
The rate at which lactic acid
is removed can be increased
by performing a cool-down
at the end of a session.
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Active
recovery
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Glycogen stores
Food is converted to
glycogen by the body and
stored in the muscles and
liver as an energy reserve.
As you exercise, muscle
glycogen is used up and it
takes some time to replace.
After prolonged exercise, for
example a marathon, it can
take more than 48 hours for
the glycogen stores to fully
recover.
This graph shows glycogen levels
during and after a marathon.
You can increase the rate at which glycogen is
replenished by eating a carbohydrate rich diet.
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Muscles
Strenuous exercise can cause slight
damage to the muscle fibres.
It is actually through this process of damage
and repair that muscles become stronger.
As you would expect, your body needs time
to repair the damage done to muscles
during exercise or training.
After exercise, we sometimes experience
stiffness or soreness for a period of time
until our muscles have fully recovered.
This soreness can also be caused by lactic
acid remaining in the muscles.
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Recovery time
When you plan your training,
ensure that you allow your
body enough time to recover
between training sessions.
It you train hard every day,
try and alternate between
heavy sessions and light
sessions to aid recovery
Always ensure that you have
the appropriate rest periods
or you run the risk of injury
through overtraining.
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Recovery
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Testing recovery – the Harvard Step Test
The Harvard Step Test is a fitness test that uses recovery
rate to help assess a performer’s aerobic endurance.
To undertake this test, you will require:
a gym bench (approx 45 cm or 18 inches high)
Ensure that the bench is firmly fixed and will not slip.
a stop watch
someone to help you
keep the required pace.
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Procedure – Harvard Step Test
Before you start, record your resting heart rate.
Step up onto the bench once every two seconds for five
minutes (150 steps in total).
At the end of the five minute period of stepping, rest for one
minute and then check and record the number of times
your heart beats in the next 30 seconds.
Two minutes after you have finished exercising, count your
heart beats again for 30 seconds.
Three minutes after you have finished exercising, count
your heart beats again for 30 seconds.
You can then use these three
figures to work out your score.
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Recording – Harvard Step Test
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The long term effect of exercise
As you would expect, training causes the body to adapt
and grow stronger.
The following areas are particularly affected:
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the heart
the skeleton
the lungs
the muscles.
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The long term effect of exercise – the heart
Aerobic exercise strengthens the heart.
The heart becomes bigger.
The walls become thicker and
stronger.
The stroke volume increases.
The result is that the heart
becomes a more efficient pump.
Your resting heart rate gets slower as you get fitter, because
the heart needs fewer beats to pump blood round the body.
Training also results in new capillaries growing to improve
the supply of blood to the muscles.
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The long term effect of exercise – the lungs
Training makes the lungs more effective
at supplying the body with oxygen.
New capillaries
grow around the
alveoli, making
gas exchange
more efficient.
The muscles involved in
breathing in and out become
stronger and can work for longer.
Vital capacity (the maximum
amount of air that can be inhaled
in one breath) increases.
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The long term effect of exercise – the skeleton
Exercise has been shown to increase
bone density and strength.
Stronger, denser bones are better
at carrying weight and more
resistant to injury.
The increase in bone density is
specific to the activity – walking
will strengthen your leg bones,
but not your arm bones.
Both aerobic exercise and weight
training are effective in increasing
bone strength, but the activity must
be weight-bearing.
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The long term effect of exercise – the muscles
Training obviously has a large effect on the muscles.
New capillaries grow in and around the
muscles to supply them with blood.
The other effects will depend on the type of training.
Weight and power training
increases the strength of muscles.
The number of fast twitch fibres
increase. Muscles increase in size.
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Endurance training makes
muscles able to work for
longer. The number of slow
twitch fibres increase.
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The effects of exercise
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Testing cardiovascular fitness
The best way of measuring cardiovascular fitness is to
calculate a performer’s VO2 max. – this measures the
maximum amount of oxygen the body can take in.
However, calculating VO2 max. requires very
specialized equipment.
An alternative is the bleep test.
Performers have to do 20 metre shuttle
runs, keeping pace with a series of
recorded bleeps which gradually get
faster. The point at which the
performer has to drop out is recorded.
The easiest test is the 12 minute run. Performers simply
run for 12 minutes and the distance covered is recorded.
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Testing speed, flexibility and balance
Speed is easy to test. Simply record how fast a
performer can sprint a short distance. 100 metre
and 60 metre distances are often used.
Flexibility can be tested by
measuring a performer’s range of
movement. A common test for
flexibility is the sit and reach test.
How far the performer can reach relative to their feet is
measured on a ruler.
Balance can be tested using the stork stand test. The
performer stands on one leg, with their free foot on their
standing knee. How long they can hold the position for is timed.
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Testing agility and muscular endurance
Agility can be tested by setting up
an agility run and timing how long it
takes for a performer to complete it.
When retesting performers to
measure improvement, you must
take care that the agility run is set
up exactly the same as before.
Muscular endurance can be tested
easily by seeing how many times a
performer can repeat a movement
requiring strength. Sit-ups and
press-ups are often used.
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Exam-style questions
1. Describe the changes that occur in the functioning of the
cardio-respiratory system during moderate, sustained
exercise.
2. List two ways in which each of the following structures
are affected by training.
a) The lungs
b) The skeleton
3. Neena has just completed a 10 km fun run.
a) Explain how the run will have affected the levels of
lactic acid and glycogen in her body.
b) Suggest two things that she could do to aid her
recovery.
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