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Diet and nutrition and their effect on physical activity and performanceWe need food in order to provide ourselves with energy to maintain body functions such as breathing and keeping the body alive; for muscle contraction; for growth and repair.The Seven Classes of FoodCarbohydrate provides energy. The body’s tissues need a constant supply of the carbohydrate glucose, which is used as a fuel. Our main source of glucose is carbohydrate in our diets. Most foods contain some carbohydrate which is digested and converted into glucose and enters the blood. The level of glucose in the blood is kept within narrow limits by the action of the hormone insulin. Excess glucose may be stored as glycogen in the liver and in muscle, but such stores are limited. Any extra glucose that cannot be converted into glycogen and stored as fat.Explain what may happen to the carbohydrates we eat in our diets.Fat is made up of fatty acids and glycerol. Fatty acids are found in the blood. The common storage forms of fat are triglycerides. Fat is a concentrated source of slow-release energy. Fat provides more than double the energy provided by carbohydrate. It is also a carrier for the fat-soluble vitamins A, D, E and K. Fat is only used as an energy source at rest and during low intensity exercise. A high fat intake has been linked with a raised blood cholesterol level, which is one of the risk factors for coronary heart disease. High levels of fat limits our ability to regulate our temperature, as fat is an insulator. Fat layers will also limit flexibility. Fat is excess weight which will limit stamina.List three advantages of having fat in our diet.List three disadvantages of having excessive fat in our dietProtein is necessary for the growth and repair of body tissues. It is also a relatively minor source of energy. The building blocks of protein are amino acids. Protein is broken down by digestion into amino acids, which are then absorbed and used to make other proteins in the body. Athletes who are training in strength/power-type activities will be repairing and developing muscle tissue, and will therefore require sufficient protein in their diet.Why may high-performance athletes need to eat extra protein in their diet?Minerals are inorganic substances required by the body for a variety of functions including:Calcium - the formation of bones and teethSodium - essential constituent of body fluids and tissuesIron?– haemoglobin - red blood cellsVitamins are complex organic substances that are needed in very small amounts for many of the essential processes carried out in the body. Most vitamins cannot be made by the body, so have to be provided by the diet. Vitamin D - normal bone mineralization and structure Vitamin C - production of collagen - the protein in connective tissue Vitamin B12 - required for normal cell division and normal blood formation Vitamin B1 - energy release from carbohydrateVitamin B2 - required to release energy from carbohydrate and fatNiacin - required for the release of energy from foodVitamin B6 - essential in the metabolism of proteinFolic Acid - essential for normal cell division and in the formation of blood cells. Which vitamins are needed for energy to be released from food?Name a vitamin and a mineral concerned with red blood cells. Water is essential for our bodies to work properly.? Water provides the medium in which most reactions in the body occur Water acts as a lubricant for joints, organs and eyesWater helps to regulate body temperature. The amount of water that we need to drink varies and depends on age, time of year, climatic conditions, diet and the amount of physical activity we do.? Dehydration is common amongst athletes, particularly those exercising in hot climates and/or at altitude, and can be very serious. Symptoms of mild dehydration include headache and fatigue.Water replacement is essential, before, during and after exercise. Tap water is suitable for replacing any lost fluid following mild or moderate exercise, but research has demonstrated that strenuous exercise requires carbohydrate and electrolyte replace as well as water.What are the three main functions of water in the body?Water and Electrolyte balanceWater makes up 50-60% of an adult’s body mass. Water is important because it:Regulates body temperature Carries nutrients and oxygen to all cells via the blood plasmaHelps to convert food into energy and absorb nutrients Is required for expiration Removes waste Protects and cushions vital organs and jointsThe body also has a range of electrolytes which have the following functions:Maintaining cell function such as nerve transmissionFor nutrient and waste product exchange Maintaining pH levelsElectrolytes dissolve in water and therefore water and electrolytes in the body are closely linked.Water is regularly lost from the body in different ways:through waste products (urine and faeces)when exhaling when sweatingThe amount of water lost depends on environmental factors such as temperature and humidly, and on the level of exercise.What term is used for a lack of water in the body?The loss of water from the body causes the following:the blood thickens – increasing viscosityblood flow to the skin reducesthe body cannot cool properly body temperature risesExplain why loss of water causes an increase in body temperature.Loss of water will also cause a loss of electrolytes. The liver maintains an electrolyte balance. Loss of electrolytes affects performance by:Causing drowsiness and impairing decision making Muscle weakness and fatigueMuscle crampsInterfere with the nervous control of the heart leading to an abnormal heart rhythmHow does a lack of water and a loss of electrolytes affect performance? Maintaining the water and electrolyte balanceThe level to which a performer needs to consider water and electrolyte balance depends on:The intensity and duration of exerciseThe environmental conditionsThe convenience of taking on board fluids and electrolytes.Drinking plain water is not good. It causes bloating (full stomach), quenches thirst and thus limits further drinking, stimulates more water loss through urine output and affects the body’s level of sodium. It is much better to use drinks that also contain electrolytes. Trouble is water and electrolytes together taste like sea water! Adding carbohydrate makes the drink taste nicer and also adds a valuable energy supply. A simple drink such as a small pinch of salt in a litre of water together with some orange cordial should be sufficient. This should be taken before, during and after exercise to make sure dehydration does not occur.Explain why drinking water is not the best way to combat dehydration.Food supplements CreatineWhat role does creatine have in energy metabolism?High doses of creatine supplement will increase the amount of creatine in muscles. How should extra creatine benefit performers?Creatine supplements should improve the performance of those involved in sprint/power activities, but its long-term effects are unknown and since creatine is excreted by the kidneys there may be effects on that organ, although this has not yet been found. Creatine is not on the UK Sport banned list but is banned in US schools and colleges.Bicarbonate of SodaThe use of bicarbonate of soda (sodium bicarbonate) and the practice of soda-loading can be used to delay the onset of fatigue when engaged in prolonged anaerobic exercise. What is the main cause of fatigue during prolonged anaerobic exercise?The body produces buffers, including bicarbonate, against the effects of the increased acidity caused by the production of lactate in the muscle cells. Increasing the amount of bicarbonate in the body should delay fatigue during anaerobic exercise.Soda-loading, by drinking bicarbonate of soda, should help in events conducted at near-maximum intensity for a duration of 1-5 minutes or in sports that are dependent on repeated anaerobic bursts.The problem of soda-loading is the side-effects. In order to ingest sufficient bicarbonate of soda to have a beneficial effect invariably means too much to permit intensive exercise. The side-effects of large doses are fairly rapid onset of vomiting, stomach cramps and diarrhoea! CaffeineCaffeine is a natural stimulant found in coffee, tea, cola and chocolate. It has been shown that taking caffeine supplements prolong aerobic exercise by increasing the use of fats to provide the energy for ATP re-synthesis, thereby saving the body’s glycogen stores. How would using caffeine benefit marathon runners?Small amounts of caffeine also helps factors like decision-making and reaction time. The benefits of caffeine are less for habitual users or those who have a high carbohydrate diet.How might taking caffeine supplements benefit a games player?Excess caffeine causes anxiety, stomach upsets, restlessness, insomnia, tremors and heart rate abnormalities. Also, caffeine is a diuretic, which could lead to an unnecessary pre-exercise loss of fluid, with problems for temperature regulation. Caffeine is no longer listed as a banned substance by the World Anti-doping Agency (WADA).Glycogen LoadingOne of the main problems for the endurance athlete is that glycogen stores in the body are fairly limited. Why are glycogen stores important for endurance performers?Endurance athletes need to boost their muscle glycogen stores to more than normal, so that they do not have to rely on the much slower fat metabolism for ATP resynthesis during their event. This idea of increasing glycogen stores is called glycogen-loading.There are different ways to increase glycogen stores. Simply increasing carbohydrate intake in the days approaching competition, while training as normal, leads to high levels of muscle glycogen being stored. This works sometimes, but not for every performer. Similarly, carbohydrate free diets in the days leading up to competition, followed by high carbohydrate intake just before the vent will also increase glycogen stores. The alternative and quicker method is to undertake just three minutes of high intensity exercise followed by a 24 hour high-carbohydrate diet, which must begin within 20 minutes of the end of exercise. This is the ‘carbo window’ when glycogen stores are increased dramatically. Describe the ‘carbo window’ method of glycogen loading.AnswersConverted into glucoseSome stored as glycogenExcess stored as fatSlow-release energy source; contains fat-soluble vitamins; insulates; protective; buoyancyExcess fat limits stamina; limits ability to regulate temperature; limits flexibilityMuscle growth and repairB1 and B2Iron and B12 or folic acid Medium; lubricant; regulate body temperatureDehydrationLack of blood to skin – unable to cool properlyIncreased body temperature, muscle weakness, poor decision-making, abnormal heart rhythm Lacks electrolytes – increases water loss through urinePhosphocreatine used as immediate energy sourceAllow more phosphocreatine to be stored/last longer – for maximal exertionLactate build-upAllows longer aerobic exercise/stamina; increases use of fats, saving glycogenIncreased stamina; better decision-making and reaction timeRequired for aerobic (and anaerobic) energy production3 minutes of high intensity exercise followed within 20 minutes of a high carbohydrate diet for 24 hours ................
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