KS4 Physical Education

Transcription

1 KS4 Physical Education The Effects of Exercise These icons indicate that teacher s notes or useful web addresses are available in the Notes Page. This icon indicates that the slide contains activities created in Flash. These activities are not editable. 1 of 30 For more detailed instructions, see the Getting Started presentation.

2 Learning objectives 2 of 30 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.

3 The immediate effects of exercise 3 of 30

4 4 of 30 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.

5 Immediate effects on the circulatory system 5 of 30 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.

6 6 of 30 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.

7 The immediate effects: lactic acid 7 of 30 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.

8 8 of 30 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.

9 9 of 30 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.

10 Immediate effects of exercise 10 of 30

11 11 of 30 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

12 Heart rate 12 of 30

13 13 of 30 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 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. Active recovery Resting recovery

14 14 of 30 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.

15 15 of 30 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.

16 16 of 30 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.

17 Recovery 17 of 30

18 Testing recovery the Harvard Step Test 18 of 30 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.

19 Procedure Harvard Step Test 19 of 30 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.

20 Recording Harvard Step Test 20 of 30

21 21 of 30 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 heart the skeleton the lungs the muscles.

22 22 of 30 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.

23 23 of 30 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.

24 24 of 30 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.

25 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. EMPICS Ltd Endurance training makes muscles able to work for longer. The number of slow twitch fibres increase. EMPICS Ltd 25 of 30

26 The effects of exercise 26 of 30

27 27 of 30 Testing cardiovascular fitness The best way of measuring cardiovascular fitness is to calculate a performer s VO 2 max. this measures the maximum amount of oxygen the body can take in. However, calculating VO 2 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.

28 28 of 30 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.

29 29 of 30 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.

30 30 of 30 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.