effects of exercise

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Learning objectives

What we will learn in this presentation:

Lear

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The immediate effects of exercise on the respiratory systemThe immediate effects of exercise on the circulatory systemHow levels of lactic acid, water and heat are affected by exerciseHow the body recovers from exerciseRecovery ratesThe long term effects of exercise on the heart, lungs, skeleton and musclesHow different components of fitness can be tested.


The immediate effects of exercise


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’.


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.

If these by-products build up in the muscles, they can cause them to stop working.

glucose + oxygen energy carbon dioxide+ + water

glucose energy + lactic acid


Immediate effects on the circulatory system

Write a paragraph explaining how the roles of the heart and lungs in supporting exercise are connected.

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.


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.

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.

glucose energy + lactic acid


The immediate effects: heat loss

The body has two main ways of getting rid of the extra heat produced by muscles during exercise.

1. VasodilationThe 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. SweatingSweat glands in the skin excrete sweat – a mixture of water, salts and urea. As the sweat evaporates, it takes heat away with it.


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.


Immediate effects of exercise


Recovery rates

Muscles

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


Heart rate


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.

The rate at which lactic acid is removed can be increased by performing a cool-down at the end of a session.

As more oxygen becomes available, it reacts with the lactic acid to form harmless substances.

Resting recovery

Active recovery


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.

You can increase the rate at which glycogen is replenished by eating a carbohydrate rich diet.

This graph shows glycogen levels during and after a marathon.


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.


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.


Recovery


Testing recovery – the Harvard Step Test

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.

The Harvard Step Test is a fitness test that uses recovery rate to help assess a performer’s aerobic endurance.

a stop watch

someone to help you keep the required pace.


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.


Recording – Harvard Step Test


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:

the heartthe lungs

the skeletonthe muscles.


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.

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.

The result is that the heart becomes a more efficient pump.


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.


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.


The long term effect of exercise – the muscles

Training obviously has a large effect on the muscles.

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.

New capillaries grow in and around the muscles to supply them with blood.

Endurance training makes muscles able to work for longer. The number of slow twitch fibres increase.

© EMPICS Ltd

© EMPICS Ltd


The effects of exercise


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.

The easiest test is the 12 minute run. Performers simply run for 12 minutes and the distance covered is recorded.

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.


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.

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.

How far the performer can reach relative to their feet is measured on a ruler.


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.


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 lungsb) 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.

effects of exercise

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