21: Applied Sport & Exercise Physiology

Transcription

1 21: Applied Sport & Exercise Physiology 21.1 Introduction This unit explores the stress that heat and cold place on an athlete s body and how the body is able to maintain a constant core temperature. The effects of altitude are also studied. This unit will also examine how an athlete s gender, race and age impact on their sporting ability and therefore dictate the requirements of their training programme. It is widely known that many athletes today try to enhance their performance by using ergogenic aids. Many different types of ergogenic aids are available; some are acceptable means of improving performance, while others are banned, and any athlete found to be taking these aids will be disqualified from competing. The pros and cons of taking some of these aids will be examined in this unit. By the end of this unit you should: know how temperature and altitude affect exercise and sports performance know about the physical differences between people of different gender and race, and their effect on exercise and sports performance know the impact that the physiological effects of ageing have on exercise and sports performance know the effects and implications of using ergogenic aids for exercise and sports performance.

2 BTEC Level 3 National Sport Assessment and grading criteria To achieve a PASS grade the evidence must show that the learner is able to: To achieve a MERIT grade the evidence must show that, in addition to the pass criteria, the learner is able to: To achieve a DISTINCTION grade the evidence must show that, in addition to the pass and merit criteria, the learner is able to: P1 describe the responses of the body to temperature, and their effects on exercise and sports performance M1 explain the effects of the physiological differences between athletes of different gender on exercise and sports performance D1 analyse the effects of the physiological differences between athletes of different gender and race on exercise and sports performance P2 describe the responses of the body to high altitude, and their effects on exercise and sports performance M2 explain the effects of the physiological differences between athletes of different races on exercise and sports performance D2 analyse the impact of the physiological effects of ageing on exercise and sports performance P3 describe the physiological differences between athletes of different gender, and their effects on exercise and sports performance M3 explain the impact of the physiological effects of ageing on exercise and sports performance D3 analyse the effects and implications of six different ergogenic aids used for exercise and sports performance. P4 describe the physiological differences between athletes of different races, and their effects on exercise and sports performance M4 explain the effects and implications of six different ergogenic aids used for exercise and sports performance. P5 describe the impact of the physiological effects of ageing on exercise and sports performance 2 P6 describe the effects and implications of six different ergogenic aids used for exercise and sports performance.

3 Applied Sport & Exercise Physiology 21.2 Temperature and Altitude and their Effects on Sports Performance P1 P2 Athletes train and compete in different countries and this can mean that sometimes they are exposed to different environments to what they are used to; this may have a significant effect on the body and therefore on sporting performance. The Effects of Temperature on Sports Performance The skin temperature of the body can vary a great deal. If the core temperature is increased or decreased by 1 C or more, this will affect an athlete s physical and mental performance. Larger changes in core temperature lead to hypothermia or hyperthermia, both of which can be fatal. To assess the core temperature of a person, there are a number of places a specialised thermometer can be placed: in the mouth, ear or rectum, or under the arm. For sports scientists, the ear is the most common site for measuring core temperature. If the exercise allows, the rectal thermometer is used, as this gives the most accurate reading of the true body core temperature. Key terms Thermoregulation: the process of controlling the body core temperature. Hypothermia: lower than normal core temperature. Hyperthermia: higher than normal core temperature. Fig 21.1 The body core via conduction. If it feels hot, you are gaining heat by conduction. Conduction involves the direct transfer of heat from one object to another. Normally, this method of heat loss is not significant unless a person is exercising in cold water. This is because water conducts heat away from the body approximately 25 times more quickly than air. At the same temperature, a person in water will lose heat from the body two to four times faster than in air. Convection Blow air over your hand. How does your hand feel? Your hand will probably feel cooler after having air blown over it. This blowing of air molecules across your hand is the basis of convection. As air molecules are moved across the body, heat will be lost because convective air currents carry the heat away. Wind will increase the flow of air over the skin, thus increasing the amount of heat lost through convection. This is why a breeze feels good on a hot day, and why we use fans to help keep us cool. Heat Transfer There are four different methods of heat transfer, some of which can be used to rid the body of excess heat and some of which can be used to gain heat: Conduction Convection Radiation Evaporation of sweat. Conduction Place your hand on the desk in front of you. How does it feel? If it feels cold, you are losing heat to it Fig 21.2 Cooling of the body by convection 3

4 BTEC Level 3 National Sport Radiation At rest, radiation is the main method of heat loss. It is the process by which heat is lost (via electromagnetic waves) to cooler objects in the environment, such as the floor, walls, trees, and so on. How much heat a person loses through radiation is determined by their size, mass and body composition. A person with a high body fat percentage will lose less heat through radiation than a person with a low body fat percentage, because body fat acts as an insulator to radiative heat loss. In contrast, a tall, slim person will lose more heat through radiation than a short, stocky person. In warm climates, the sun radiates heat to the body, which increases its temperature. This makes getting rid of excess heat during exercise more difficult, because the sun s heat must also be dissipated. Evaporation of sweat In humans, evaporation of sweat from the body is the major method of heat dissipation, particularly during exercise. Heat is transferred continually to the environment as sweat evaporates from the skin surfaces and produces a cooling effect. If the environment is humid, evaporative heat loss is reduced. Heat is only lost when sweat evaporates, which it will not do in humid conditions. Therefore, on a hot, humid day, an athlete can be dripping with sweat, but because the sweat is not evaporating, this does not cool them down. Fig 21.4 Cooling of the body by sweating Fig 21.3 Cooling of the body by radiation Student activity minutes P1 4 The aim of this activity is to determine the core temperature and the skin temperature of a person. You will need the following equipment: Oral thermometer Skin thermometer Sterilising fluid Pen and paper. Follow the method set out below and record your results in the table; then answer the questions that follow. Place a sterile thermometer under your tongue and leave it there for a few minutes. Take the thermometer out of your mouth and record the temperature reading. Place a skin thermometer on your hand and record the temperature reading. Place the skin thermometer on your neck and record the temperature reading. If you have time, take external readings from other parts of your body.

5 Applied Sport & Exercise Physiology Disinfect/sterilise all thermometers before allowing another person to use them. 1 Is your core temperature the same as that of the person sitting next to you? If not, why do you think this is? 2 Why is your skin a different temperature to your core temperature? 3 Is there a difference between skin temperature readings taken from different sites on your body? If so, try to explain why this is. Core temperature (8C) Hand temperature (8C) Neck temerature (8C) Responses of the Body to High Temperature Exercise increases metabolic rate by 20 to 25 times, and could increase core temperature by 1 C every six minutes if heat loss did not take place. This would result in death from hyperthermia if exercise continued. Therefore, with the added stress of a hot environment, an exercising athlete has to maximise heat loss in order to perform optimally and avoid hyperthermia. The hypothalamus acts as a thermostat and initiates the responses that protect the body from overheating. It receives information about the temperature of the body via two sources: Indirectly from the thermal receptors in the skin Directly by changes in blood temperature. Methods of heat loss in a hot environment Heat loss through radiation is not possible if the environment is hotter than the person exercising. Therefore, there are only three forms of heat loss available to a person exercising in a hot environment: Conductive heat loss occurs by the peripheral blood vessels dilating and bringing blood close to the skin s surface. Key term Peripheral: close to the surface of the skin. This results in the rosy-coloured skin associated with Caucasian hot athletes. The heat from the blood warms the air molecules around the person and any cooler surfaces that come into contact with the skin. Conductive heat loss works in conjunction with convective heat loss. Convective heat loss occurs much more rapidly if there is increased air flow around the body if it is windy or a fan is being used. If there is little air movement, the air next to the skin is warmed and acts as a layer of insulation that minimises further convective heat loss. If the warmed air surrounding the body is frequently changed due to increased air currents, heat loss through convection will continue to remove excess body heat. Evaporative heat loss provides the main source of heat dissipation. As the sweat evaporates, it cools down the skin surface. This has the effect of cooling the blood as it travels through the blood vessels that are close to the skin surface. For evaporative heat loss to occur maximally, the person must be hydrated and have normal levels of salt and electrolytes in their body. The circulatory system is vitally important in ensuring that these three methods of heat loss can occur. Not only does the blood have to supply the muscles with oxygen and nutrients, it also plays a major part in thermoregulation. The blood is redirected to the periphery by dilatation of peripheral blood vessels. In extreme conditions, 15 to 25 per cent of the cardiac output is directed to the skin. As a result of these two cardiovascular demands, the heart rate is higher when exercising in the heat than in normal conditions. Heart rate is also elevated because of the slight to severe dehydration that often occurs while exercising in the heat. If the person is dehydrated, the plasma volume is decreased. A decreased plasma volume will lead to a decreased stroke volume. Therefore, as we know: Cardiac output 5 Heart rate 3 Stroke volume Q (l per min) 5 HR (bpm) 3 SV (ml) In order for cardiac output to remain the same, heart rate has to increase to make up for the decreased stroke volume: Q 5 HR 3 SV 5

6 BTEC Level 3 National Sport Effects of High Temperature If the body is unable to lose the excess heat generated from exercising and/or from the environment, the person will suffer from hyperthermia. There are three major forms of hyperthermia: Heat cramps Heat exhaustion Heat stroke. Heat cramps These are muscle spasms caused by heavy sweating. Although heat cramps can be quite painful, they do not usually result in permanent damage. Student activity minutes P1 The aim of this activity is to see how blood vessel dilatation and constriction affect the colour of the skin. (The outcomes of this activity will apply only to Caucasian learners.) You will need the following equipment: Large beakers Thermometer Hot water Paper towels Ice cubes Skin thermometers (if available). Follow the method set out below and record your results in the table; then answer the questions that follow. Working in small groups, fill a large beaker with warm/hot water. Ensure the water is not too hot for you to place your hand in! Take the temperature of the water and write it down. Look at your hand and make a note of its colour. Temperature of water (8C) Hot Cold Place your hand in the water for about three minutes. Remove your hand from the water, towel it dry, then record the skin temperature. Note down the colour of your hand. Fill a large beaker with cold water and add a few ice cubes. After two minutes, take the temperature of the water and note it down. Ensure the water is not too cold for you to bear. Place your hand in the water for about three minutes. Remove your hand from the water, towel it dry, then record the skin temperature. Note down the colour of your hand. 1 Why did your hand turn the colour it did after being placed in hot water? 2 Why did your hand turn the colour it did after being placed in cold water? 3 By what process was your hand trying to lose heat when it was placed in the hot water? Colour of hand 6

7 Applied Sport & Exercise Physiology Student activity hours P1 The aim of this activity is to see how the effect of exercising in hot conditions affects the cardiovascular system. Ensure that this activity is supervised by a qualified tutor and that a risk assessment has been carried out prior to participation. You will need the following equipment: Bleep test Sports kit (shorts and T-shirt for test 1 and tracksuit bottoms, sweatshirt, woolly hat and gloves for test 2) Tape recorder Heart-rate monitors Weighing scales Results table Sports hall. Follow the method set out below and record your results in the table; then answer the questions that follow. Test 1: Normal conditions Each person is weighed wearing shorts and a T-shirt. Working in pairs, place a heart rate monitor on the first person taking the test. The first person takes part in the bleep test. At the end of each stage, the exercising person calls out their heart rate while their partner records this number and the appearance of the exercising person. Once the exercising person has exercised to voluntary exhaustion, they towel down, put on a clean T-shirt and record their body weight. The process is repeated for the second person. Test 2: Hot conditions This test should be carried out at least 72 hours after test 1. Ensure each person taking part is fully hydrated before taking part in this test. Each person is weighed wearing shorts and a T-shirt. Working in pairs, place a heart rate monitor on the first person taking the test. The person taking the test then puts on tracksuit bottoms, a sweatshirt, woolly hat and gloves. The first person takes part in the bleep test. At the end of each stage, the exercising person calls out their heart rate while their partner records this number and the appearance of the exercising person. Once the exercising person has exercised to voluntary exhaustion, they remove their tracksuit bottoms, sweatshirt, hat and gloves, towel down and put on a fresh T-shirt and shorts. The person is then weighed. Test 1 Weight before: Stage Heart rate Appearance Test 1 Test 2 Test 1 Test

8 BTEC Level 3 National Sport Weight after: Weight difference: Test 2 Weight before: Weight after: Weight difference: Plot the heart rates for the normal and hot conditions on a line graph. 1 Was there a difference in the heart rates at each stage in the two tests? 2 Was there a difference in the person s appearance in the two tests at each stage of the bleep test? Was there any difference between the weight loss in test 1 and test 2? 3 Did the person manage to reach the same stage in the bleep test in both tests? Explain your results. 8 Heat exhaustion This is more serious than heat cramps. It occurs primarily because of dehydration and loss of important minerals. To lose body heat, the surface blood vessels and capillaries dilate to cool the blood. When the body is dehydrated during heat exhaustion, the blood volume is reduced, so there is not enough blood to supply both the muscles and the skin with their required blood supply. This results in the peripheral dilated blood vessels constricting, which significantly reduces heat loss. This can be observed in Caucasian athletes. If you look at the face of a Caucasian athlete suffering from heat exhaustion, it will suddenly change from a red, rosy appearance to a much paler colour or white. Heat stroke If a person ignores the symptoms of heat exhaustion and continues to exercise, they will suffer from heat stroke, which is a life-threatening condition and has a high death rate. It occurs because the body has depleted its supply of water and salt, and results in the person s body temperature rising to dangerous levels. If the core temperature of the body reaches 43 C or more, the proteins start to break down and change their structure permanently. Imagine cooking an egg. The egg white is mainly made up of protein. When the egg white reaches a certain temperature (around 43 C), its structure changes from a runny, viscous medium to a solid. The same principle applies to the body s proteins, such as the enzymes and hormones. Once heated to a certain temperature, the structure of the body s proteins permanently changes and is no longer able to function. Therefore, it is vitally important that the core temperature is not elevated to this degree. Responses of the Body to Low Temperature When humans are exposed to a cold environment at rest, the body attempts to prevent heat loss as well as increase heat production. It does this via three main physiological mechanisms: Constriction of the peripheral blood circulation Non-shivering thermogenesis Shivering. First of all, the body decreases the blood supply to the peripheral circulation by constriction of the peripheral blood vessels (vasoconstriction). The purpose of this is to keep the blood close to the body core and redirect it away from the body s extremities and skin surface, where it would be cooled down by the environment. In humans, vasoconstriction can reduce heat loss by up to a third. The presence of subcutaneous fat also aids in maintaining the heat of the blood, as fat is a very good insulator. Key term Subcutaneous: under the skin. Second, a person will experience an increase in their metabolic rate, which is brought about by an increased release of the hormones thyroxin and adrenaline. An increased metabolic rate will generate body heat. This process is called non-shivering thermogenesis. Lastly, a person will experience a rapid involuntary cycle of contraction and relaxation of skeletal muscles, which is called shivering. The process of shivering can actually increase the metabolic rate to four to five times above resting levels. A person can also conserve heat by adding clothing, which is a behavioural mechanism for minimising heat loss. Effects of Cold Temperatures The effect of a cold environment on exercise performance depends largely on the severity of the cold and the type of exercise performed. Exposure to a moderately cold environment may actually have a positive effect on performance, as the cardiovascular system no longer has to divert blood to the periphery

9 Applied Sport & Exercise Physiology for heat loss in addition to supplying the exercising muscles with blood. This results in less stress being placed on the heart than when exercising in the heat. Therefore, it is not surprising that record performances during long-distance running and cycling are usually achieved in cool climatic conditions. Exposure to a very cold environment may cause frostbite or hypothermia. Frostbite usually occurs in a person s fingers or toes. It happens when a part of the body becomes extremely cold, significantly reducing blood supply to the area, which results in the body tissue freezing. The ice crystals that form rupture and destroy the body s cells. The region involved turns a deep purple or red colour and has blisters usually filled with blood. This tissue will then have to be amputated to prevent infection from spreading to other parts of the body. Hypothermia is defined as a drop in the body s normal core temperature to 35 C or below. The condition usually comes on gradually and its severity varies in relation to how low the body core temperature drops. If it drops to 30 C or below, this can lead to cardiac and respiratory failure, which is soon followed by death. Fig 21.5 Frostbite Student activity minutes P1 1 Produce a poster with written text that describes how the body responds to different temperatures. 2 Produce a second poster, with written text, that describes how different temperatures affect exercise and sports performance. Effects of High Altitude on Exercise and Sporting Performance Anywhere more than 1500 m above sea level (5000 ft) is considered to be at high altitude. The further above sea level you travel, the lower the barometric pressure becomes. This means that the higher up you go, the thinner the air becomes, as there are fewer air molecules in the atmosphere. Therefore, although the percentage of oxygen, carbon dioxide and nitrogen within the air remains the same (20.93 per cent, 0.03 per cent and per cent, respectively), every breath of air you take contains fewer and fewer molecules of oxygen (and carbon dioxide and nitrogen). As a result, a person must work harder to obtain the same quantities of oxygen compared with when they are at low altitudes. This means that an athlete who exercises or competes at high altitude will have to breathe much faster to take in enough oxygen for their energy systems to work normally than when they exercise at lower altitude. In 1968, the Olympic Games were held in Mexico City, which stands at an elevation of 2300 m and is therefore classed as being at high altitude. In order to try to overcome the effects of the thinner air, the athletes went through a period of acclimatisation, during which they trained at high altitude for a number of weeks. The body responds physiologically by adapting to cope with the decreased levels of oxygen in the air. Responses of the Body to High Altitude The body undergoes a number of changes to increase oxygen delivery to cells and improve the efficiency of oxygen use. This response usually begins immediately and continues for several weeks. The body s initial responses to being at high altitude are: An increase in respiratory rate (hyperventilation) An increase in heart rate (tachycardia). When a person arrives at high altitude, their respiratory rate and depth increase. The increased breathing rate has the effect of causing more carbon dioxide to be expired and more oxygen to be delivered to the alveoli. The respiratory rate peaks after about one week of living at high altitude, and then slowly decreases over the next few months, although it tends to remain higher than its normal rate at sea level. 9

10 BTEC Level 3 National Sport 10 Heart rate also increases because the body s cells require a constant supply of oxygen. As there is less oxygen available in the blood, the heart beats more quickly to meet the cells demands. Heart rate will also start to decrease as more time is spent at high altitude. Effects of High Altitude After a person has spent a number of weeks at high altitude, their body adapts by making cardiovascular and metabolic changes. The cardiovascular adaptations are: Decreased maximum cardiac output Decreased maximum heart rate Increase in the number of red blood cells Increased haemoglobin concentration Increased haematocrit Increased capillarisation. The bone marrow contributes to acclimatisation by increasing red blood cell production and, therefore, the blood s haemoglobin concentration. This increase is triggered by the kidneys increased production of erythropoietin (EPO). New red blood cells become available in the blood within four to five days, and have the effect of increasing the blood s oxygencarrying capacity. An acclimatised person may have 30 to 50 per cent more red blood cells than a counterpart at sea level. The cardiovascular system also develops more capillaries in response to altitude. This has the effect of improving the rate of diffusion of oxygen from the blood and into the muscles by shortening the distance between the cells and the capillary. All these adaptations in the weeks following exposure are aimed at increasing oxygen transport to the body cells. This results in a reduction in the cardiac output required for oxygen delivery during rest and exercise compared with pre-acclimatisation. The metabolic adaptations are: Increased excretion of bicarbonate via the kidneys An increase in 2,3-diphosphoglycerate (DPG) within the red blood cells An increase in the number of mitochondria and oxidative enzymes Increased levels of lactic acid leading to reduced levels of lactic acid production. The increased breathing rate means that more carbon dioxide than normal is breathed out, resulting in the body becoming more alkaline. To compensate for the body s increasing alkalinity, the kidneys excrete bicarbonate (an alkaline substance) in the urine. This adaptation occurs within 24 to 48 hours. Within the blood cells DPG increases. This is an organic phosphate that helps oxygen to dissociate (unload) from the haemoglobin to the body s cells much more easily. The increase in DPG helps to compensate for the blood s reduced oxygen level. The increased number of mitochondria and oxidative enzymes appears to be due to the switch in the body s preferred fuel for energy production. At low altitude, carbohydrate is the usual energy source, but at altitude fat is the preferred fuel. This change is not well understood, but may be due to the fact that a reduced oxygen supply causes a higher lactic acid level in the muscles and bloodstream. Carbohydrate metabolism also leads to increased production of lactic acid, but fat metabolism does not produce lactic acid as a by-product. Therefore, the change of the main metabolic fuel from carbohydrate to fat results in a reduced level of lactic acid production. The body s adaptation to high altitude helps significantly, but does not fully compensate for the lack of oxygen in the air. There is a drop in VO 2 max of 2 per cent for every 300 m elevation above 1500 m, even after full acclimatisation. Methods of Adaptation to High Altitude Athletes can acclimatise prior to competition at high altitude in a number of ways. The most common approach is for the athlete to spend a period of no Fig 21.6 High-altitude chamber

11 Applied Sport & Exercise Physiology less than two weeks training and living at the competition altitude prior to the event. Some problems do arise in this approach. Primarily, the athlete is not able to train to such a high intensity as when they are at sea level because of the reduction in oxygen molecules in the air. Therefore, their VO 2 max is reduced. They may also suffer from slight insomnia that would have an impact on their recovery from training. Some athletes acclimatise by training at low altitude and then sleeping at a high altitude or in a high-altitude chamber (see Figure 21.6). The reasoning behind this is that the athlete can train at maximal levels if they are at low altitude; they are then exposed to hypoxic stress while sleeping, thus increasing the production of red blood cells and other physiological adaptations. Key term Hypoxic stress: lower than normal oxygen levels. Student activity minutes P2 A major sporting event is due to be held in a city that is classed as being at high altitude. Write a leaflet that can be given out to athletes who are due to compete at the games to describe how their body will respond to high altitude and how it will affect their training and sporting performance. Key learning points 1 Body core temperature is 37 C; a change of 1 C can affect physical and mental performance. Heat is transferred through convection, conduction, radiation and evaporation. Body heat is lost at a greater rate in water than on dry land. In hot conditions, blood is directed to the periphery. Heart rate is higher when exercising in hot conditions. High altitude is classed at more than 1500 m above sea level. At high altitude the body responds by increasing breathing rate, increasing heart rate. Adaptations to high altitude include: increased number of red blood cells, increased capillarisation, increased haematocrit. Q Quick quiz 1 1 Name the method(s) of heat loss in the following conditions: (a) Swimming in cold water. (b) Running on a cloudy, windy day. (c) Cycling on a hot sunny day. 2 Why is heart rate higher when exercising in hot conditions compared to cooler conditions? 3 What is frost bite and how does it occur? 4 Name two ways in which a person can acclimatise to high altitude. 5 How does the body respond to high altitude? 21.3 Gender and Exercise and Sporting Performance P3 M1 D1 Males and females rarely compete against each other in the sporting arena. Aside from the obvious differences between genders, there are a range of physiological differences that mean one gender would have an unfair advantage over the other hence the need for single-sex competitions. Body Composition One of the main differences between the genders that affects athletic performance is the difference in body composition. Males tend to have greater muscle mass and lower fat mass compared with females. A high percentage of body fat is not always a hindrance in sport. As females have a greater 11

12 BTEC Level 3 National Sport Composition (%) Body Tissue Male Female Muscle Bone Essential fat 3 12 Storage fat Other tissue Total Table 21.1 Differences in body composition between the sexes 12 percentage of fat than males, they are more buoyant (body fat weighs much less than muscle mass), so they use up less energy than males staying afloat. Therefore, using the same amount of energy, females will be able to swim faster than males. This, together with their increased insulation from the cold, makes females more suited to open-water swimming, such as swimming the Channel. Maximal Oxygen Consumption An untrained male will have an average absolute VO 2 max of 3.5 litres per minute. An untrained female will have an average absolute VO 2 max of 2 litres per minute, which is 43 per cent lower than a male s. The main reasons for this difference are that males are usually bigger than females and the difference in body composition between the genders. Females have approximately 10 per cent more body fat than males, which will reduce their VO 2 max because fat mass hinders performance. Females also have a lower blood haemoglobin content than males. This means that their blood has a lower oxygen-carrying capacity than a male s, affecting aerobic energy production. Research has shown that the female heart is slightly smaller relative to body size than the male heart. A relatively smaller heart would mean that a female s stroke volume is relatively lower than a male s. As cardiac output is the product of heart rate multiplied by stroke volume, for a female to maintain a certain cardiac output, her heart must beat faster than a male s: Q 5 HR 3 SV Therefore, body size and fat percentage, the difference in oxygen-carrying capacity of the blood, plus differences in the size of the heart might explain the gender differences in VO 2 max. Thermoregulation If you study males and females sweat rate per kilogram of body weight, women usually have lower sweat rates than men. Therefore, on average, males are able to lose more heat through evaporative heat loss than females. However, as females have a higher ratio of body surface area to volume than males, they are able to lose more heat through radiation. Research has shown that these variations in heat loss between the sexes evens out, so that there is no real difference in the ability to dissipate heat. Flexibility Females are usually much more flexible than males, especially in the hip, shoulder and elbow joints. This could be due to the fact that females usually have less muscle tissue than males, which means there is less resistance provided for stretching. Muscle Strength and Power If you were to extract exactly the same amount of healthy muscle from a male and from a female, and then test the muscle tissue for the amount of force it could produce, there would be no difference between the two. Therefore, there is no difference in the strength of the muscle tissue between the sexes. However, on average, males are stronger than females because of the difference in body composition. The average female has less muscle mass than the average male. The reason for this difference is largely due to the hormone testosterone. Testosterone acts on the body in a number of ways, including increasing muscle growth. Studies have shown that females who have taken testosterone injections for a period of time increased their muscle mass and decreased their body fat percentage. The females involved in this study also began to develop secondary male characteristics, such as growth of facial hair, deepened voice and increased aggression.

13 Applied Sport & Exercise Physiology Fig 21.7 Male and female body builders Studies have also shown that the number of slowtwitch and fast-twitch fibres is no different in the male and female populations. Therefore, it is not the muscle quality that differs between the sexes, but the muscle quantity. Training Differences Between Males and Females Research suggests that males and females should not take on the same volume of training. It would appear that elite female athletes perform optimally at a training volume that is around 10 to 15 per cent lower than that observed in elite male athletes. If the volume of training is increased for a female, it often does not improve performance and can lead to overtraining. This is due to the hormone testosterone. Testosterone is responsible for aiding muscle growth and is also critical for tissue repair. As training results in the breakdown of tissues, males are able to recover much more quickly from training than females because of this hormone. It is important to note that all these differences are based on average results taken from males and females. In reality, there are many individual women with significantly higher VO 2 max values, strength, endurance and training ability than individual men. Student activity minutes P3 M1 The aim of this activity is to determine if there is a difference in strength between the males and females in your class. Differences in upper body and lower body are also compared. You will need the following equipment: Multigym or free weights Pen and paper Weighing scales. Follow the method set out below and record your results in the table; then answer the questions that follow. The whole class should warm up thoroughly before taking part in any strength tests. Working in pairs, go round the multigym or use the free weights. Lift an amount you feel comfortable with, then continue adding weights until you have reached your 1 rep max. Ensure that you have short breaks between lifts. Write this weight down. Record your body weight. Work out what weight you lifted (kg) in relation to your body weight (kg). This can be calculated by: weight lifted (kg) body weight (kg) Complete a table that takes into account the whole class s results. Then work out the average weight lifted in each exercise for males and for females. Repeat this, but use weight lifted in relation to body weight. 1 Was there a difference in the average weight lifted by each sex? If so, can you explain why this difference exists? 2 Which exercise produced the greatest difference between the sexes? Why do you think this is? 3 Why is body weight sometimes taken into account when comparing the amount of weight a person can lift? Exercise Weight lifted (kg) Percentage of body weight 13

14 BTEC Level 3 National Sport Student activity minutes P3 M1 D1 Write a report that describes, explains and analyses the physiological differences between male and female athletes. Include in your report a description, explanation and analysis of how these physiological differences affect their exercise and sports performance Race and Exercise and Sporting Performance P4 M2 D1 Take a look at the 2008 Olympic 100 m sprint semifinal (Figure 21.8). What do you notice about the line-up? Now carry out research to find out who won the endurance races in the 2008 Olympics. Where were the winners from? What about the swimming competition (Figure 21.9)? What do you notice about the race of the swimmers? It seems clear that athletes of certain races are better suited to certain sports. At present, the top athletes for both short- and long-distance running events tend to come from Africa. West African athletes At the time of writing (January 2010), every men s world record from 100 m to 1 mile belongs to a runner of African descent. In sprinting, the last time a white athlete held the world record for the 100 m was in The 10-second time barrier for sprinting 100 m has been broken 200 times, but always by black athletes. This would lead us to believe that athletes of African origin have a natural athletic advantage for this discipline over competitors whose ethnic origin lies elsewhere. Research suggests that this theory does hold true, and that the physique of athletes from this region is better suited to sprinting. These athletes generally have lower body fat, longer legs in comparison with the rest of their bodies and narrow hips. They also tend to have greater muscle mass, higher bone mineral density, higher levels of testosterone, a higher percentage of fast-twitch muscle fibres and more anaerobic enzymes. Research strongly suggests that no amount of training can break through the percentage of genetically inherited fast-twitch muscle fibres. The greater the number of fast-twitch fibres an athlete has, generally the better they will be suited to speed events. Therefore, if an athlete does not have a certain proportion of fast-twitch muscles, they cannot hope to be a champion sprinter or jumper. This would suggest that sprinters are born and cannot be made. Fig 21.8 Fig 21.9 East African (Kenyan) Athletes With regard to the middle- to long-distance running events, the East Africans, particularly the Kenyans, are dominant. The top 60 times for the 3000 m steeplechase are all held by Kenyan athletes. Kenyan athletes also hold more than half the top times for the 5000 and 10,000 metres.

15 Applied Sport & Exercise Physiology The vast majority of top Kenyan runners come from one area of the country, the Kalenjin region. Athletes from this part of Kenya have won more than 70 per cent of Kenya s Olympic medals in world running. The fact that the Kalenjin region is at high altitude has made many scientists believe that their adaptation to living there has given them an increased athletic prowess at endurance events. These athletes have been shown to have a greater number of red blood cells, a larger lung capacity, a high proportion of slow-twitch muscle fibres and more energy-producing enzymes in their muscles, which are better able to utilise oxygen than those of athletes living at normal altitudes. These adaptations would increase the athlete s oxygen-carrying capacity and would certainly aid the athlete in endurance running events. Fig Fig Caucasian Athletes White people (Caucasians) tend to have more natural upper-body strength, and to have evolved with a mesomorphic body type and relatively short arms and legs. As a result, they dominate weightlifting and wrestling. They also excel at field events and hold 46 out of the top 50 throws for shot-put and hammer. Caucasian people also tend to dominate swimming events very few African athletes reach any swimming final. This could be due to the fact that African athletes tend to have heavier skeletons and smaller chest cavities, which would leave them at a disadvantage when competing in water. Indian Athletes Athletes of Indian origin excel in a number of sports in particular, cricket. This is probably due to social and cultural influences rather than a physiological predisposition to the sport. Research clearly shows that genetic evolution has strongly influenced the physiological make-up of people living in different environments, which may well determine if a person has the chance to be an elite athlete. However, dedication, commitment and good fortune are also factors that play a major role in determining if the athlete will win or lose. As well as the physiological traits of athletes coming from different ethnic origins, it is also necessary to take into account the social, cultural and economic factors of the country the person grew up in, as these have a huge effect on determining whether a person will take up certain sports. This may help to explain why some races excel in some sports but not in others. 15

16 BTEC Level 3 National Sport Student activity minutes P4 M1 D1 Research the world records for the following events: Men s marathon Men s 100 m sprint Women s 5000 m Men s shot-put Women s 200 m Men s 100 m freestyle swim Women s m freestyle swim. Find out the ethnic origin of each world record holder and try to explain why this person may be more physiologically suited to the event. Student activity minutes P4 M2 D1 Athletes from certain races do appear to dominate in specific athletic events, which could be explained in part by differences in their physiological make-up. Examine the following events: 100 m sprint Long-distance running Swimming Weightlifting. Write a report that describes, explains and analyses the physiological differences between athletes of different races and how it appears to have an effect on their sporting performance. Key learning points 2 In general, males and females have differences in body composition, with males having more muscle mass than females. In maximal oxygen consumption, males are usually higher. Females are usually more flexible. Body strength and power in males is stronger than in females. Training programmes females should have a volume of around per cent less than males. Athletes from different races appear to have physiological differences that can affect their sports performance. West African athletes excel in sprinting events. East African athletes excel in long-distance running events. Caucasian athletes excel in swimming, weightlifting, wrestling and athletic field events. 16

17 Applied Sport & Exercise Physiology Q Quick quiz 2 Choose a term from the following list to answer each of the questions below: Fast-twitch muscle fibres Testosterone Large lung capacity 2 litres per minute 3.5 litres per minute Open-water swimming Upper body strength Thermoregulation. 1 A high percentage of body fat is of benefit for this sport. 2 An average male will have an average absolute VO 2 max of this amount. 3 An average female will have an average absolute VO 2 max of this amount. 4 There appear to be no real differences in male and female ability to perform this process. 5 The difference in the amounts of this hormone in males and females is largely responsible for the differences in the muscle mass of males and females m sprinters need to have a high percentage of these muscle fibres to do well in their sport. 7 Long-distance runners would benefit from having this. 8 Caucasian athletes tend to have more of this than other races Ageing and Exercise and Sporting Performance P5 M3 D2 Any person who plans to work in the sports industry may find themselves dealing with people of varying ages. People of different ages have differing needs in terms of their training requirements and sporting and exercising abilities. Most people are aware of how a typical adult responds to exercise and training programmes, but few know how children and older adults (50-plus) respond. The Younger Person Contrary to popular belief, children are not mini adults. They grow and mature at their own rates and their chronological age may differ greatly from their biological age. For girls, puberty may take place between the ages of 8 and 13, and for boys from 9 to 15 years. Understanding of how children respond to exercise is limited, because measurement techniques and equipment developed for use with adults are often not appropriate for use with young people. However, it is clear that children should take part in exercise on a regular basis. The National Association for Sports and Physical Education recommends that school-age children should take part in 60 minutes or more of physical activity every day. It is better for the child if the activity is broken down into sessions of around 15 minutes. Any person supervising exercising children should be suitably qualified. Coaching qualifications for specific sports, combined with first aid and an awareness of children s exercising needs, are usually adequate. Anyone wishing to supervise children who are exercising in a gym, using weights or taking exercise classes should have specialist knowledge and qualifications, to demonstrate a sound understanding of children s physiology as an absolute minimum. Strength Training for Children A child s strength-training programme should not be a scaled-down version of an adult s weight-training programme. The reason behind this is that children are still growing. An inappropriate strength-training programme could damage their growth plates at the end of their bones, which could result in growth problems. A suitably qualified person should design a programme for the child. One of the most important aspects of this programme is to ensure that the child has the correct lifting techniques. Children should aim to lift lighter weights with a high number 17

18 BTEC Level 3 National Sport of repetitions. A strength-training programme for children should not attempt to increase muscle bulk until the child has passed through puberty. Thermoregulation and Children Children are much more prone to overheating than adults. This is partly because they do not have a fully developed sweating mechanism, and also because they have a much higher ratio of surface area to volume. This means that they will gain (or lose) heat much more quickly than adults. Therefore, if you are supervising children who are playing or exercising on a hot day, be sure to have lots of rest periods, lots of drinks, sun hats and sun cream, and try to stay out of the sun whenever possible. The Older Person People today are living on average much longer than they did than before. At the beginning of the twentieth century, only 4 per cent of the population was aged 65 or older; by 1996, this number had increased to 16 per cent, and it is predicted that, by 2026, 41 per cent of the population will be over 65. This is partly due to better nutrition, medicine and sanitation. Fig Skeletal Cardiorespiratory Body composition Changes related to older age Gait Neuromuscular 18 Posture Fig Changes related to older age

19 Applied Sport & Exercise Physiology The quality of a person s life as they get older can be greatly improved through exercise participation. When a person gets older, they face a variety of anatomical and physiological changes, which can be reversed or slowed down through regular physical activity. Skeletal Changes Once you reach the age of 30, your skeleton should be at its strongest. From then on, there is a gradual loss of bone mass, which means that the skeleton becomes weaker and more prone to fractures. Women are particularly vulnerable to weaker skeletons after the menopause, as they no longer produce the same levels of oestrogen, which helps make the skeleton strong. There is also a reduction in a person s flexibility as they get older. This reduced range of movement is due to the ligaments becoming thicker, with less elastic connective tissue. It has been estimated that around 80 per cent of older adults suffer from arthritis, which is not only uncomfortable, but can also significantly impair a person s mobility. Neuromuscular Changes A person is at their strongest and most powerful when they are in their thirties, and this remains relatively constant until they reach their fifties. After this, around 280 grams of muscle mass is lost every year. By the age of 70, both males and females will have a 40 per cent reduction in their muscle mass. This reduction in muscle mass is partly due to a reduced production of the hormone testosterone. Not only does muscle mass decline with age, but the number of functioning fast-twitch muscle fibres also decreases. Research has found that there is a link between a loss of muscle strength and an increased risk of falling. Connective tissue also becomes less elastic, resulting in increased stiffness, which is also a common complaint in people as they get older. Cardiorespiratory Changes Cardiorespiratory function declines after the age of around 25. If person does not remain physically active, their VO 2 max will drop by 1 per cent every year after the age of 25. Key terms Arthritis: inflammation of a joint or joints, causing pain, swelling and stiffness. VO 2 max: the ability to take up and use oxygen. This decline is due to a reduction in maximal heart rate. As maximal heart rate age, it is clear to see that the older you become, the lower your maximal heart rate will be. A person s arteries and arterioles are also affected by ageing. They become less elastic and can become thickened. This has the effect of increasing a person s blood pressure. The oxygen-carrying capacity of the blood is reduced as haemoglobin levels drop. A person s lungs become less effective as they become older. They become less elastic, and there is an increase in residual volume and a reduction in the number of alveoli in which gaseous exchange takes place. Body Composition As a person gets older, they lose muscle mass and gain body fat. Muscle mass is lost because of a reduction in testosterone production. As muscle uses up more calories than fat tissue, when a person starts to lose muscle tissue their basal metabolic rate slows down. Unless a person reduces the amount of calories they take in, they will gain body weight in the form of fat. As people get older, few actually do consume fewer calories than when they were younger, which results in weight gain in the form of body fat. Body Posture A person s body posture is important to help maintain balance and for efficient mobility. As the skeleton becomes weaker, a person s body posture changes. The shoulders become rounder and the head comes further forwards, known as kyphosis. This, together with a decline in eyesight, leaves older people more susceptible to falls. Gait Gait is the term used to describe how a person walks. As a person gets older, their gait pattern will alter. Speed of walking and stride length decrease, with an increase in pelvic tilt, more time in double leg support (i.e. stationary, with two feet on the ground) and decreased movement at the ankle. Physical Activity and the Older Person Physical activity will have a positive impact on all the aforementioned anatomical and physiological effects of ageing. Regular participation in a range of different types of exercise will help to delay the impacts of ageing. 19

20 BTEC Level 3 National Sport Skeleton Regular weight-bearing activity and/or resistance exercises, such as walking, jogging or weight training, will help to maintain the strength of the bones of the skeleton, which will make them less likely to break. Neuromuscular Decreased muscle strength has been linked to an increased incidence of falling. Older adults who regularly take part in resistance exercises find that they increase or preserve muscle strength. Cardiorespiratory Physical activity of moderate intensity has been shown to prevent or reduce the effects of ageing on the cardiorespiratory system. Body Composition Regular moderate aerobic and resistance physical activity has been shown to effectively increase or maintain the muscle mass of an older person. This helps to decrease the amount of body fat gained as a person gets older. Body Posture Regular physical activity helps a person to maintain a good body posture as they get older. Weight-bearing exercise or resistance exercises help to keep the skeleton and muscular systems strong. This helps to keep a person s back in the correct position, and thereby helps to maintain a good body posture. Gait Regular physical exercise will help an older person maintain their walking pattern. Resistance training will help to strengthen the abdominals, which helps to reduce pelvic tilt. Regular mobility exercises will help to maintain a good range of movement in the ankle. Moderate aerobic exercises will help to maintain stride length and frequency. Key learning points 3 Children should take part in 60 minutes of exercise every day. Children should lift light weights at high repetition and not aim to increase muscle bulk. Children are more prone to overheating than adults. Muscle mass and bone mass decrease after the age of 35. Flexibility decreases as ligaments become less elastic. After the age of 25, cardiorespiratory function decreases. Body posture and gait are affected as a person gets older. Q Quick quiz 3 1 What sort of things would you plan to take into account when leading a sports activity session in: (a) Hot conditions (b) Cold conditions. 2 Carry out research to find out about three different coaching qualifications available that are specific to coaching children. 3 Why do you think that there are more sports and activity sessions available for the older adult today, as opposed to 30 years ago? 4 At what age does your skeleton start to become weaker? 5 Describe how a person can maintain their skeletal and muscular systems as they get older. 6 What is gait and how is it affected as a person gets older? 20