Body in Action

1. Body in Action Changing Levels of Performance

2. Exercise and Fitness. • When we start to exercise e.g. running or walking up a steep hill our pulse rate and breathing rates increase. • This is because our muscles require more energy which they get from breaking down glucose during aerobic respiration.

3. Equation of Aerobic Respiration • glucose + oxygen carbon dioxide + water + lots of energy • We increase our breathing rate to get more oxygen into our bloodstream at the alveoli. • At the same time our heart rate ( and pulse rate) increases to get the oxygen and glucose to the muscles as quickly as possible.

4. Muscle Fatigue • Whether we are fit or not, strenuous exercise puts a great strain on the body’s muscles and circulatory and breathing systems. • Eventually our muscles tire or fatigue • due to either continuous contraction as in a long distance race or • rapidly repeated muscle contraction as in a sprint race.

5. Causes of muscle fatigue • Muscles fatigue because of • a lack of oxygen and • a build up of lactic acid. • This causes the symptoms of muscle cramp that occur during strenuous exercise.

6. Anaerobic Respiration in AnimalsCREDIT • In the absence of oxygen, animal muscle cells break down glucose into a substance called lactic acid. • Carbon dioxide is not given off and there is only a little energy released. • Equation of Anaerobic Respiration in Animals • Glucose lactic acid + a little energy

7. Lactic AcidCREDIT • Unfortunately lactic acid is a mild poison and its build up makes our muscle ache. Gradually the muscles contract less powerfully. This is called muscle fatigue. • When the exercise is over, lactic acid is broken down into carbon dioxide and water. • Oxygen is needed for this and the volume of oxygen required to get rid of all the lactic acid is called the oxygen debt

8. Importance of Training • Trained athletes and other fit people find that during exercise their breathing and pulse rates do notrise as much as an untrained person. • In addition the level of lactic acid in the blood of an athlete does not rise as much during exercise. • The following graphs below compare the changes in pulse rate, breathing rate and blood lactic acid level in an athlete and an untrained person before, during and after exercise.

9. Pulse Rates Exercise starts Exercise stops

10. Breathing Rate Exercise stops Exercise starts

11. Lactic Acid Exercise starts Exercise stops

12. Pupil A The steeper this line the quicker the persons pulse rate is increasing and the less fit the person is Pupil B Pupil C The shorter this line is the less time the person has taken to recover from the exercise and the fitter they are Exercise stops Exercise starts

13. Recovery Time • Recovery time is the time taken to return to normal levels of pulse rate, breathing rate and lactic acid. • From the graphs, it is obvious that athletes return to these levels much quicker than an untrained person. • The recovery time, following a set period of exercise, can therefore be used as an indication of fitness. • Following a training programme, your recovery time should decrease as you become fitter.

14. Effects of Training and Recovery Time • Training involves vigorous exercise over a period of weeks or months. • It can be measured and monitored by fitness tests such as the Bleep Test in PE • As you train and become fitter then • your pulse rate, breathing rate and blood lactic acid levels will return to normal levels quicker after exercise.

15. Effects of TrainingCREDIT • Training results in improvementof the parts of the body being trained -so your leg and arm muscles obviously get bigger and stronger. • However and perhaps more importantly, as a result of training the efficiency of the lungs and circulationimproves. • Exercise increases the volume of the heart and strengthens the heart muscle. This means that the same volume of blood can be delivered to working muscles using fewer heartbeats. • Since the heart of a trained athlete beats less often but more strongly than that of a non athlete, the athlete’s heart and circulatory system is more efficient. • Exercise increases the number of capillaries per mm2 in heart muscle thus increasing the delivery of glucose and oxygen to hard working heart muscle cells Therefore the efficiency of the heart is increased again.

16. Effects of TrainingCREDIT • With exercise lung volumeincreases, which speeds up the rate of gas exchange at the lungs thus ensuring plenty ofoxygenated blood is produced • This is because, in a trained athlete, oxygen is absorbed into the blood from the lungs and delivered to the working muscles more quickly than before training • As a result, pulse rate, breathing rate and level of blood lactic acid rise less than for an untrained person doing the same exercise. Consequently it will take less time for these levels to return to normal. • In addition, the time taken to pay back the oxygen debt and remove excess lactic acid from the bloodstream is reduced in a trained athlete. It is for these reasons that a highly trained athlete has a short recovery time.