WHY IS KNOWLEDGE OF NUTRITION IMPORTANT?

1. A poor diet contributes to a host of modern diseases including heart disease, high blood pressure, diabetes, strokes, obesity, cancer, arthritis, macular degeneration and cataracts

2. The four main determinants of athletic performance are:

• training
• genetic factors
• mental attitude
• nutrition (good eating habits provide energy allowing athletes to train at higher levels for longer periods and to recover faster; nutritional deficiencies and imbalances can reduce the available energy and hence hinder performance, endurance and recovery).

Balanced nutrition will allow an athlete to optimise and maximise their performance.

WHAT TYPE OF FUEL DOES THE BODY USE?

In a car, petrol is the fuel that powers the engine to make the wheels turn. In a human body fuel is provided in the form of a molecule called 'ATP'. This powers all the body's processes e.g.

A small amount of ATP is stored in some tissues (e.g. muscles) in the form of a chemical called creatine phosphate. The majority of ATP is obtained from the consumption and digestion of food:

1. Food is consumed in the form of 3 macronutrients:

• carbohydrates
• fat
• protein

2. Food is digested and broken down into its building blocks:

• carbohydrates > glucose
• fats > fatty acids
• protein > amino acids

3. Substrates are transported via blood stream to all tissues.

4. Substrates are metabolised in the body's cells producing ATP:

Glucose

Amino Acids > ATP

Fatty Acids

WHAT ENERGY SYSTEMS DO MUSCLES USE?

1. CREATINE PHOSPHATE SYSTEM:

• creatine phosphate is stored in muscles in small amounts.
• produces instant energy for sudden movement e.g. a punch or a kick.
• energy stores are used up quickly (within 5-30 seconds) but are also replenished quickly (within 2 minutes).
• weight lifting is an example of an activity using this energy system.
• oxygen is not required to allow the system to work.

2. ANAEROBIC SYSTEM ('Lactic Acid' system)

• the anaerobic system provides energy for intense activity lasting 1/2 – 2 minutes.
• the energy is obtained from the breakdown of stored carbohydrates. Carbohydrate is stored in the body in several forms.

• when glucose/glycogen is metabolised without oxygen (i.e. anaerobically), lactic acid is produced as a by-product.

• if intense exercise continues, lactic acid accumulates in the muscles causing fatigue (e.g. the 'heavy' legs experienced when sprinting up several flights of stairs).

3. AEROBIC SYSTEM

• for longer periods of activity (e.g. endurance events) the body switches to the aerobic system
• energy is obtained from the breakdown of carbohydrate and fat in the presence of oxygen (i.e. aerobically).

How does your body decide which energy system to use?

Athletes have the ability to use one or several of these systems depending on exercise intensity, duration and level of training

i) Exercise Intensity – let us use running as an example:

Type of Activity	Creatine Phosphate	Anaerobic	Aerobic
Explosive speed	70	30	0
Sprint	20	60	20
'V02 Max'	10	20	70
Distance	2	5	83

ii) Exercise Duration

Short (intense) exercise tends to utilise anaerobic systems e.g. sprinting. Prolonged (less intense) exercise tends to utilise aerobic systems e.g. marathon running. In long duration events it is possible to run out of carbohydrate stores completely – this is known as 'hitting the wall' because this is exactly how it feels!

iii) Conditioning – both the carbohydrate storage capacity and fatty acid metabolism can be made more efficient by training.

WHAT ARE THE ESSENTIAL INGREDIENTS OF A BALANCED DIET?

1. Carbohydrates:

• These are either broken down to glucose to give energy or stored as glycogen (in liver/muscles) or as fat (in fat stores).
• Because glucose is the preferred fuel of muscles, carbohydrates are the most efficient and effective source of fuel for athletes.

  Carbohydrates are either simple or complex:

  a) Simple:

  • are often refined products, e.g. jam, honey, table sugar.
  • are easily digested and absorbed and lead to a rapid rise in blood sugar levels.

  b) Complex:

  • natural foods such as cereals, legumes, fruit, vegetables, rice, potatoes, pasta.
  • contain essential vitamins, minerals and fibre.

  Complex carbohydrates should be the main source of energy in an athlete's diet.

  2. PROTEIN

  • principal function is to build, maintain and repair body tissue.
  • have a minor role in energy production when glycogen stores are low.
  • found in most foods, e.g. meat, poultry, fish, eggs, plants, milk products and legumes.
  • most New Zealanders consume [u]twice[/u] the amount of protein required by the body – recommended intake is:

  Type of athlete	Daily Intake (gm/kg body weight)
  Recreational	0.8
  Athlete	0.8 – 1.0
  Endurance	1.0 – 1.2
  Weight Lifter	1.3 – 1.6
  Intense Strength	2.0 – 2.2
  Intense Training	2.0 – 2.2
  Early Phase Training	2.0-2.2

  • The extra protein needs of athletes can easily be provided by a normal and varied diet. This will happen automatically because the increased energy requirements of athletes will generally produce a corresponding natural increase in protein intake sufficient to meet any additional protein requirements.
  • Surrounded by MYTHS!!! The popular view is that muscles being made of protein will get bigger as more protein is eaten. The logic seems to be clear and simple – unfortunately it is not true!! Muscle growth requires hard work at 60 – 80% of maximal capacity and a balanced diet – NOT ADDITIONAL PROTEIN.
  • There is no evidence to suggest that protein supplements on their own improve strength / endurance / performance / muscle mass.
  • in fact the reverse is true – EXCESS PROTEIN IS HARMFUL for the following reasons:

  i) The breakdown products of protein metabolism need to be excreted producing an extra burden on an athlete's liver and kidneys.

  ii) Protein metabolism requires more water than carbohydrate and fat metabolism – this can result in dehydration and increased loss of potassium, magnesium, calcium and iron.

  iii) Excess protein is stored as fat causing obesity and increased cholesterol levels.

  Athletes who need supplements can make their own and save up to 80% of the cost of commercial preparations in the process:

  Ingredients:

  • 1 kg skim milk powder
  • 7 level metric tablespoons sugar
  • 7 level metric tablespoons flavour (Milo, Ovaltine)

  Method: Adjust sugar and flavour to taste Add water to taste

  3. FATS

  • New Zealanders consume too much fat leading to high levels of heart disease, strokes and cancer
  • Convenience foods are loaded with fats (plus salt and sugar)
  • Body stores energy as fat for later use.
  • Are the most concentrated source of food energy (yields twice as much energy weight for weight compared to carbohydrates and protein).
  • Muscles cannot use fat as a primary source of fuel during exercise.
  • Fatty meals are slow to leave the stomach, slow to digest, and can divert blood away from exercising muscles.
  • 3 categories:

  a) Saturated e.g. animal fats (e.g. butter, lard, cream, dripping) and tropical oils (e.g. coconut and palm oils) – harmful in excess.

  b) Monounsaturated e.g. olive oil and avocado oil – beneficial in moderation.

  c) Polyunsaturated e.g. fish oils and plant oils (e.g. sunflower and sesame oils). Deep sea oily fish (e.g. tuna, trout, salmon, sardines, mackerel and kahawai) are very beneficial because of their omega-3 fatty acid content – aim to eat these 3-4 times a week. Processed plant oils in transparent plastic containers (e.g. sesame, corn, safflower and sunflower) are incredibly harmful to your health and should be avoided at all costs.

  • One of the best all-purpose cooking oils is avocado oil because it can be used as a 'pour on' but can also be used as a cooking oil (because it remains stable at high temperatures – unlike olive oil).

  4. SALT

  • Essential in the body but the amount needed is very small.
  • Because salt occurs naturally in many foods and New Zealanders eat 10 times more salt than is required there is no need for supplements.
  • Athletes only get salt depletion in extreme circumstances e.g. intense ultra endurance events in hot conditions. Salt depletion is not the cause of leg cramps.
  • Excess salt can be harmful, resulting in nausea, vomiting, dizziness and dehydration.
  • Buy ORGANIC SEA-SALT (commercial salt has had all the micronutrients removed and aluminium added to stop it from clogging when moist).

  5. WATER

  • Adequate water must be present in the body tissues before, during and after training.
  • Do not wait till feeling thirsty before drinking (thirst indicates dehydration and can take 24 hours to correct).

  Inadequate water intake or replacement can result in dehydration, impaired performance and overheating.

  6. ALCOHOL

  • Has a dehydrating effect and reduces blood glucose levels and therefore should be avoided for 48 hours before an event.

  7. VITAMINS, MINERALS AND ANTI-OXIDANTS

  • Are essential for good health and will be the subject of my next article.

  Knowledge of these food groups allows us to construct a food pyramid

  

  WHAT SHOULD I EAT BEFORE, DURING AND AFTER TRAINING?

  1. Pre-training/Pre-Competition:

  • Food eaten within a few hours of training/competing will not affect the body's energy stores. These are determined by carbohydrate intake several days prior to the event.
  • The main aim of pre-training nutrition is to ward off hunger and to provide optimum hydration for the event.
  • Food should be high in complex carbohydrates and low in fat, protein and simple sugar (a pre-event snack that is high in simple sugar can paradoxically lower blood sugar level resulting in fatigue and impaired performance).
  • Food should be eaten 2-3 hours before training (if eaten immediately before training blood may be redirected from the muscles to the digestive tract, and athletes may feel uncomfortable, sick and faint).
  • Fluids can be consumed till 20-30 minutes before an event (in the form of water, diluted fruit juice or electrolyte replacement drinks).
  • Do not try anything new on the day of the event.

  2. During Training/Competition:

  • For activities lasting less than one hour, water is the main requirement.

  3. Between Events:

  • If there are several events during the day (e.g. in a tournament) the timing between the events will determine what should be taken. If breaks between the events are less than 2 hours, liquids are preferable e.g. high carbohydrate drinks (see later).
  • If breaks are longer than 2 hours, light snacks in the form of complex carbohydrates should be taken e.g. crackers/ sandwiches/fruit /muesli bars/creamed rice/high carbohydrate/ moderate protein drinks (see later).

  4. Recovery:

  • Rehydration should commence immediately after exercise using water or electrolyte sports drinks. It can take 36-48 hours to replace fluids after a hard training session.
  • Muscles are most receptive to fuel replacement for the 1st hour after activity. Carbohydrate-rich foods should therefore be taken as soon as possible after exercise. It can take 48 hours for muscle glycogen levels to completely recover after severe exercise.

  WHAT TYPES OF LIQUID FOODS ARE AVAILABLE AND WHEN SHOULD THEY BE USED?

  1. Electrolyte replacement drinks e.g. Replace.
  2. High carbohydrate drinks e.g. Exceed/Gatorade/ Carboplex – delay glycogen depletion therefore useful during endurance events, during activities that last all day, as a recovery fuel and as fuel for people who find it difficult to eat during events or between games.
  3. High carbohydrate/moderate protein e.g. Ensure/ Sustagen/Staminar – have no role in fluid replacement; are used as a liquid meal before or in between events by people who find it difficult to eat solid food; need to be consumed at least 2 hours before exercise.
  4. High protein drinks – not recommended.

  Is Carbohydrate loading necessary for Martial Artists?

  Definitely not! Carbohydrate loading refers to the fact that muscle and liver glycogen stores can be doubled or trebled by increasing the percentage of carbohydrate in the diet to 80% for 3 days prior to an event. This is useful in endurance events as it allows high intensity exercise to continue for longer periods.

  It is not suitable for short events especially where flexibility is important as water is stored with glycogen making the muscles feel stiff, tight and uncomfortable.

  Martial artists should aim for a moderate increase in complex carbohydrates for 3 days prior to an event.

  Does being a vegetarian affect sports performance?

  Sports people can perform well on a vegetarian diet. Additional advantages include lower blood fat levels, and less heart disease, cancer, obesity and constipation.

  Particular care must be taken to avoid deficiencies in iron, calcium, zinc and vitamins B2, B12 and D. This is achieved by combining grains, cereals, fruits, vegetables, seeds, nuts, legumes, milk and eggs.

  WHAT IS THE BEST WAY OF LOSING WEIGHT?

  • Weight loss may be required to allow an athlete to compete in a particular weight division. A sensible programme is required.
  • Fad diets and rapid weight loss programmes should be avoided since they invariably impair performance by causing dehydration, loss of muscle tissue, fatigue, dizziness and impaired concentration.
  • Weight loss should be achieved before competition because it is impossible to train or perform effectively while on a weight loss programme.
  • The aim is to lose weight from fat stores gradually (up to 1 kg/week).
  • This requires decreased energy input and increased energy expenditure (predominantly in the form of aerobic activity).
  • Complex carbohydrates should still provide the mainstay of the diet.
  • Water should never be restricted.
  • Thought should be given to consulting a dietician experienced in sports nutrition.

  ARE THERE ANY GOOD BOOKS ON SPORTS NUTRITION?

  Yes. "Eat to Compete" by Jeni Pearce is an excellent book.

  FURTHER INFORMATION

  • Available on my website (www.drtom.co.nz) under 'Health and Fitness Articles'.