2.1a diet and nutrition

• the government recommends that 19-50 year olds in the UK should consume

  • for men 2550 calories a day
  • for women 1940 calories a day
  • approximately 55% carbohydrates
  • approximately 15% protein
  • no more than 30% fats
  • varied foods, including five portions of fruit and vegetables a day
• carbohydrates are used for energy production, active transport and formation of molecules and cell division. they are the preferred fuel for exercise and account for around 75% of energy requirements and come in several forms

  • starches, such as rice and potatoes, which are stored as glycogen in the liver and muscles
  • sugars, such as fruit and honey, which circulate in the blood stream as glucose

  glycogen and glucose provide fuel for aerobic and anaerobic energy production. excess glucose, associated with a high sugar diet is converted into triglycerides (body fat)
• carbohydrate

  sugars and starches stored in the body as glycogen and converted to glucose to fuel energy production
• proteins are found in milk, eggs, meat and soya. amino acids from proteins are needed for growth and repair of cells and tissues. they're used to make muscle proteins, haemoglobin, enzymes, antibodies and collagen, and can also be broken down to provide energy aerobically if no other fuel is available. athletes have higher protein requirements than sedentary people to build new muscle cells and compensate for the increased muscle breakdown during and after intense activity
• protein

  amino acids essential for the growth and repair of cells and tissues
• enzymes

  biological catalyst which increases the speed of chemical reactions
• fats are an important part of the diet and serve to insulate nerves, form cell membranes, cushion organs and provide an energy store. they provide essential fatty acids and the fat soluble vitamins A, D and E. fats also can be broken down for aerobic energy production and have twice the energy yield of carbohydrates
• saturated fatty acids are a type of fat molecule typically solid at room temperature, mainly found in animal products. for example butter and bacon have saturated fatty acids and should be limited to reduce the risk of cardiovascular disease.
• unsaturated fatty acids are a type of fat molecule typically liquid at room temperature and can help to lower cholesterol. for example, avocados and fish oil contain omega-3s and may be beneficial to athletes, boosting the delivery of oxygen, improving endurance and recovery rates and reducing inflammation and joint stiffness
• minerals are essential inorganic nutrients required in small quantities to maintain healthy body functions. they are necessary for bone and tooth health, controlling body fluids, enzyme formation, breaking down food to release energy and normal nerve function. essential minerals are found in meat, cereals, fish, dairy foods, vegetables, fruits and nuts and include:

  • calcium: for bone health, muscle contraction, blood clotting and nerve transmission
  • iron: for the formation of haemoglobin, enzyme reactions and the immune system
  • phosphorus: for bone health and energy production
• vitamins are essential organic nutrients required in small quantities to maintain healthy body functions. even for performers undertaking intense exercise, there is no need for supplementation, providing sufficient energy is consumed through a varied, balanced diet. there are two types of vitamins, fat and water soluble
• fat soluble vitamins are stored in the body and found mainly in fatty foods and animal products, such as vegetable oils, dairy products and eggs:

  • vitamin A: antioxidant and important for eye health, cell and bone growth
  • vitamin D: important for bone health and protects against cancer and heart disease
  • vitamin E: antioxidant and important for skin, eye and immune system health
  • vitamin K: important for blood clotting and bone health
• water soluble vitamins are not stored and require regular intake. they are found in fruit, vegetables, grains, milk and dairy products:

  • vitamin C: important for skin, blood vessel, tendon, ligament and bone health
  • vitamin B: important for the breakdown of food, haemoglobin formation and skin, eye and nervous system health
• fibre

  dietary fibre is found in food such as bread, cereal, beans, lentils, fruit and vegetables. it is an important component of a balanced diet for the normal function of the large intestine. a high fibre diet can reduce cholesterol, risk of diabetes and obesity
• water

  accounts for two thirds of body weight and is essential to allow chemical reactions and dissolve and move substances around the body. it is also required to regulate temperature by moving heat to the skin surface for evaporation (sweating) or to the lung tissue for expiration as water vapour

  essential for hydration before, during and after training and competition, especially in hot climates and endurance activities. dehydration can result in decreased plasma volume, stroke volume and increased temperature and heart rate. endurance and strength will suffer as a result.
• energy

  the ability to perform work (joules or calories)
• energy expenditure

  the sum of basal metabolic rate, the thermic effect of food and energy expended though physical activity
• basal metabolic rate (BMR)

  the minimum amount of energy required to sustain essential physiological function at rest, which can account for as much as 75% of total energy expenditure
• thermic effect of food (TEF)

  the energy required to eat, digest, absorb and use food taken in, which accounts for a very small percentage of the total energy expenditure
• physical activity energy expenditure

  the total number of calories required to perform daily tasks, which can be estimated using MET values
• metabolic equivalent value (MET)

  the ratio of a performer's working metabolic rate to their resting metabolic rate
• energy intake

  the total amount of energy from food and beverages consumed and measured in joules or calories
• energy balance

  the energy balance is the relationship between energy intake and energy expenditure:

  • if energy intake matches energy expenditure, weight will be maintained
  • if energy intake is greater than energy expenditure, weight will be gained and the percentage of body fat may rise, having negative health performance implications
  • if energy intake is lower than energy expenditure, weight may be lost. this may be beneficial as a part of a weight loss programme, but must be carefully monitored with an athlete to minimise loss of muscle mass and performance
• ergogenic aid

  a substance, object or method used to improve or enhance performance
• pharmacological aids

  a group of ergogenic aids taken to increase levels of hormones or neural transmitters naturally produced by the body, including anabolic steroids, erythropoietin and human growth hormone
• what are anabolic steroids

  • a group of synthetic hormones which resemble the male hormone testosterone
  • taken to promote protein synthesis and muscle growth
  • increased quality and quantity of training as well as strength and speed of recovery
  • easily accessible and come in tablet, solution (injection), capsule and cream form
  • use associated with maximal and explosive strength performers, such as sprinters and rugby players
• benefits of anabolic steroids

  • increased muscle mass and strength
  • increased speed of recovery
  • increased intensity and duration of training
• risks of anabolic steroids

  • irritability, aggression and mood swings
  • liver damage and potential heart failure
  • acne and hormonal disturbances
• what is erythropoietin (EPO)

  • EPO is a naturally produced hormone, which produces red blood cells
  • recombinant EPO (RhEPO): illegal synthetic product copying natural EPO, typically used for patients with severe anaemia or kidney failure
  • when injected in athletes, increased red blood cell count increases oxygen transport, aerobic capacity and duration of performance before fatigue
  • associated with endurance performers such as marathon runners and triathletes
• benefits of EPO

  • increased red blood cell and haemoglobin count
  • increased oxygen transport and aerobic capacity
  • increased intensity and duration of performance before fatigue
• risks of EPO

  • increased blood viscosity
  • decreased cardiac output
  • increased risk of blood clots and heart failure
  • decreased natural production of EPO
• hyper-viscosity

  excessively thickened blood with high resistance to flow
• what is human growth hormone (HGH)

  • a synthetic product copying the naturally produced growth hormone, which declines naturally with age and its supplementation increases protein synthesis for muscle growth, recovery and repair
  • increases the metabolism of fats, glucose levels and quality of training, causing increased percentage of lean mass
  • associated with maximal and explosive strength performers such as body builders and sprinters
  • preferred by athletes over testosterone as not associated with hormonal distubances
• benefits of human growth hormone

  • increased muscle mass and strength
  • increased fat metabolism and decreased fat mass
  • increased blood glucose levels
  • increased speed of recovery
  • increased intensity and duration of training
• risks of human growth hormone

  • abnormal bone and muscle development
  • enlargement of the vital organs, potentially leading to multi-organ failure
  • increased risk of certain cancers and diabetes
• physiological aids are used to increase the rate of adaptation by the body to increase performance. some physiological aids are illegal, such as blood doping, and athletes face severe penalties for their use; however, others are legal such as hypoxic training and cooling aids, and are used frequently by a wide range of performers
• what is blood doping

  • illegal method which increases red blood cell content, however is difficult to detect through blood samples if it is the athlete's own blood
  • a volume of blood is removed from the athlete and the red blood cells are frozen around four weeks before competition. the body naturally replenishes lost blood and a couple of hours before an event the red blood cells are reinfused in a saline solution
  • increases the total blood volume and red blood cell count
  • associated with endurance performers such as Tour de France cyclists
• benefits of blood doping

  • increased red blood cell and haemoglobin count
  • increased oxygen transport and aerobic capacity
  • increased intensity and duration of performance before fatigue
• risks of blood doping

  • increased blood viscosity
  • decreased cardiac output
  • increased risk of blood clots and heart failure
  • risk of transfusion reactions and infections such as hepatitis and HIV
• what is intermittent hypoxic training (IHT)

  • when athletes live at sea level but train under hypoxic conditions
  • minimal traveling, expense and disruption to training making it preferable to altitude training
  • can increase red blood cell and haemoglobin volume, and so aerobic capacity, delaying fatigue
  • it also increases mitochondrial density and buffering capacity
  • performed with aerobic and high intensity anaerobic intervals where a mask supplying low pO2 air is worn during work intervals and removed during relief interval
  • beneficial for endurance athletes such as marathon runners