btec-national-sport-level-3-sample-pages-9781444111989.pdf

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Sport&ExercisePhysiology Q Quick quiz 3 1. List three reasons why fatigue can occur. 2. How much glucose do we have in our bloodstream? 3. What is the main by-product of anaerobic glycolysis? 4. At what blood pH is muscle and neural function affected? 5. Which ions are required for muscle contraction? 6. What does EPOC stand for? 7. After a bout of vigorous exercise, what five events must occur before a muscle can operate again? 8. What is alactacid debt? 9. What is lactacid debt? 2.5 HowtheBodyAdaptsto Long-termExercise P6 P7 M4 D3 Long-term exercise is also known as chronic exercise and means that a person has been participating in regular exercise for long periods of time (a minimum of eight weeks). This regular participation affects the body in a number of ways that make it more able to cope with the stresses of the exercise. This results in the person being able to exercise at higher intensities and/or for longer periods of time. This process is called adaptation. Cardiovascular Adaptations The main adaptations that occur to the cardiovascular system through endurance training are concerned with increasing the delivery of oxygen to the working muscles. If you were to dissect the heart of a top endurance athlete, you would find that the size of the walls of the left ventricle are markedly thicker than those of a person who does not perform endurance exercise. This adaptation is called cardiac hypertrophy. Keyterm Cardiac hypertrophy: the size of the heart wall becomes thicker and stronger. Adaptation occurs in the same way that we increase the size of our skeletal muscles – the more we exercise our muscles, the larger or more toned they become. In the same way, the more we exercise our heart through aerobic training, the larger it will become. This will then have the effect of increasing the stroke volume, which is the amount of blood that the heart can pump out per beat. As the heart wall becomes bigger, it can pump more blood per beat, as the thicker wall can contract more forcibly. As the stroke volume is increased, the heart no longer needs to beat as often to get the same amount of blood around the body. This results in a decrease in heart rate which is known as bradycardia. Keyterm Bradycardia: decreased resting heart rate. Fig 2.13 The athlete’s body has adapted to strength training 47 BTEC National for Sport and Exercise Sciences uncorrected first proofs issued by marketing 9/7/2013. This material is © Hodder Education 2013 and should not be redistributed.
BTEC Level 3 National Sport & Exercise Sciences 48 An average male adult’s heart rate is 70 beats per minute (bpm). However, Lance Armstrong, a Tour de France champion, had a resting heart rate of 30 bpm! As stroke volume increases, cardiac output also increases, so an endurance athlete’s heart can pump more blood per minute than other people’s. However, resting values of cardiac output do not change. An endurance athlete has more capillaries, allowing more blood to travel through them. This process, called capillarisation, aids in the extraction of oxygen. An increase in haemoglobin due to an increase in the number of red blood cells (which contain the haemoglobin) further aids the transport of oxygen. Though haemoglobin content rises, the increase in blood plasma is greater, and consequently the blood haematocrit (ratio of red blood cell volume to total blood volume) is reduced, which lowers viscosity (thickness) and enables the blood to flow more easily. Strength training produces very few adaptations to the cardiovascular system, as this training does not stress the heart or oxygen delivery and extraction systems for sustained periods of time. Respiratory Adaptations The respiratory system deals with taking oxygen into the body and also with helping to remove waste products associated with muscle metabolism. Training reduces the resting respiratory rate and the breathing rate during sub-maximal exercise. Endurance training can also provide a small increase in lung volumes: vital capacity increases slightly, as does tidal volume during maximal exercise. The increased strength of the respiratory muscles is partly responsible for this as it aids lung inflation. Endurance training also increases the capillarisation around the alveoli in the lungs. This helps to increase the rate of gas exchange in the lungs and, therefore, increase the amount of oxygen entering the blood and the amount of carbon dioxide leaving the blood. Strength training produces very few adaptations to the respiratory system, as this type of training uses the anaerobic energy systems, whereas the respiratory system is only really concerned with the aerobic energy system. Neuromuscular and Energy Systems’ adaptations Endurance training results in an increase in the muscular stores of muscle glycogen. There is increased delivery of oxygen to the muscles through an increase in the concentration of myoglobin and increased capillary density through the muscle. The ability of skeletal muscle to consume oxygen is increased as a direct result of an increase in the number and size of the mitochondria and an increase in the activity and concentration of enzymes involved in the aerobic processes that take place in the mitochondria. As a result, there is greater scope to use glycogen and fat as fuels. Slow-twitch fibres can enlarge by up to 22 per cent, which gives greater potential for aerobic energy production. Hypertrophy of slow-twitch fibres means that there is a corresponding increase in the stores of glycogen and triglycerides. This ensures a continuous supply of energy, enabling exercise to be performed for longer. These adaptations result in an increased maximal oxygen consumption (VO 2 max) being obtained before the anaerobic threshold is reached and fatigue begins. High-intensity training results in hypertrophy of fast-twitch fibres. There are increased levels of ATP and PC in the muscle and an increased capacity to generate ATP by the PC energy system. This is partly due to the increased activity of the enzymes which break down PC. ATP production by anaerobic glycolysis is increased as a result of enhanced activity of the glycolytic enzymes. There is also an increased ability to break down glycogen in the absence of oxygen. As lactic acid accumulates, it decreases the pH levels of the blood, making it more acidic. This increased level of hydrogen ions will eventually prevent the glycolytic enzyme functioning. However, anaerobic training increases the buffering capacity of the body and enables it to work for longer in periods of high acidity. Energy System Adaptation Aerobic training will increase the number of mitochondria in slow-twitch muscle fibres. This will allow greater production of ATP through the aerobic energy system. Greater amounts of glycogen can be stored in the liver and skeletal muscle. Aerobic training results in an increase in the number of enzymes required for body fat to be broken down, and more body fat is stored in muscle tissue, which means that more fat can be used as an energy source. Anaerobic or strength training predominantly uses the PC and lactic acid energy system. Chronic anaerobic/strength training increases the body’s tolerance levels to low pH. This means more energy can be produced by the lactic acid energy system, and the increased production of lactic acid can be tolerated for longer. BTEC National for Sport and Exercise Sciences uncorrected first proofs issued by marketing 9/7/2013. This material is © Hodder Education 2013 and should not be redistributed.
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