During exercise muscle uses energy to contract.
During exercise lasting from several minutes to several hours, carbohydrate and fat are the most important fuels, both of which can be mobilised from stores within the body.
Carbohydrate stores are limited within the body, therefore the aim is to maximise these stores to allow for greater exercising potential with reduced possibility of early fatigue.
It is important to maximize the body’s store of energy for optimal performance through good nutrition

Introduction:
At rest and during low intensity exercise fat is often the substrate of choice but as the intensity of exercise increases your carbohydrate stores, in particular the glycogen stores in muscles become more important with muscle glycogen being the most important energy source at intensities of 70-90% VO2max i.e. exercise of a high intensity.
Carbohydrate is stored in the body in the form of glycogen in liver and muscle and is broken down in exercise to supply muscle with energy to contract.
Inadequate carbohydrate in the diet leads to inadequate glycogen stores in the body which will lead to earlier fatigue and so can affect performance.
The larger your glycogen stores are, the longer you can exercise without feeling fatigue.
Depletion of body carbohydrate stores is a cause of fatigue or performance impairment which is seen both peripherally (muscle fatigue) and centrally (effects on the brain and nervous system).

Recommended amount of carbohydrate:

Example a 65g athlete exercising for on average 1 hour per day would require a daily intake of 455g CHO

Food carb-content table:

Maintaining a high carbohydrate diet can take some thought and effort.

Tips to increase your carbohydrate intake;

• Base all of your meals around high carbohydrate foods such as cereals, breads, pasta, rice, noodle, potatoes
• High carbohydrate snacks such as scones, toast with banana, crackers, cereal bars etc….
• Use thicker slices of bread
• Go for deep pan pizza
• Add potatoes to soups etc
• Have pasta and rice salads
• Fruit fresh or dried to cereal
• Fruit juices and other carbohydrate containing drinks during the day and with meals
• Use jam/ honey on bread or add honey to cereals

PROTEIN:

General:

Athletes require protein in their diet to help build and repair muscle tissue however protein is not the main energy source for exercising muscles. Muscle is gained through training (resistance exercise) as long as there is sufficient energy and carbohydrate in the diet to fuel exercise.
Protein requirements:
Endurance requires 1.2g protein per kg of body weight, therefore a 65kg athlete will require 78g protein.
This can be easily reached within the context of a normal diet and there should be no need for protein supplements.
See table below for food protein-content.

Food protein-content table:

FATS

Even the leanest athlete will have sufficient fat stores, so it is not a component of the diet which needs to be increased for good exercise performance.
A certain amount of fat in the diet is necessary for good health however too much fat and the wrong type of fat may lead to weight gain as well as an increased risk of heart disease.
Fats slow-down your absorption of carbs.
Filling up on foods which are higher in fat may decrease you appetite for foods which are high in carbohydrate which will more positively affect your exercise performance.

• Use low fat milk and dairy products
• Use a low fat spread
• Use a good quality vegetable oil for cooking
• Trim fat from meat and skin from chicken before cooking where possible
• Avoid heavily processed meats as they can have a very high fat content
• Use low fat mayonnaises and salad dressings
• Be aware that many products which may be high in carbohydrate such as pastries,
chocolate, chips are also high in fat.
• Don’t rely on high fat snacks such as chocolate and pastries or biscuits,
choose lower fat high carbohydrate snack option as cereal bars, scones, bagels, fruit, juices, smoothies etc.

FLUIDS

General:
Approximately 50-60% of the body is comprised of water.
Exercising muscles cause an increase in heat production through contraction.
If the body is not cooled, body heat will rise to dangerous levels very quickly.

Accompanying this rise in heat is greater strain on the cardiovascular system for example an increased heart rate.
Sweating is the most important heat loosing mechanism as the action of evaporation of sweat from the skin has a cooling effect.
However, sweating results in the loss of water from the body, leading to a risk of dehydration.
Major consequence of dehydration is an increased in core temperature which will rise
Progressive dehydration impairs the ability of the body to sweat; therefore it is very important to prevent dehydration as much as possible to regulate body temperature.

Effects of Dehydration:
Dehydration of as little as 1-2% loss of body weight compromises physiological function and negatively influences performance.
Losses of 4-5% of body weight can decrease capacity to work by 20-30%.

Signs of Dehydration:
It is vital to recognise the signs of dehydration, as thirst is a poor indicator of dehydration:
Look out for fatigue, dry mouth, headache irritability, flushed skin, dark scant urine, weakness, dizziness, cramp or profuse sweating. Recommendations

Pre exercise:
Athletes should begin training session or event well hydrated.
To ensure pre exercise hydration an athlete should consume 500-600mls every 2-3 hours

During Exercise:
During exercise the body uses 30-60g carbohydrate per hour.
Ideally the carbohydrate in fluid should be 6-8% with small quantities of sodium which may enhance palatability, retention,
stimulate thirst and therefore promote drinking (see home made drinks).
Aim to drink 150-200mls every 10-15 minutes.
.

Post Exercise:
Post-exercise hydration should correct any fluid lost during exercise.
This fluid should ideally be replaced within 2 hours.
The fluid temperature can influence the amount consumed, studies have shown that the ideal temp for drinks is 10-15 degress C as it stimulates the athlete to drink more during excerise.
Aim to drink 450-675mls for every 0.5kg lost during exercise.

Home made Drinks:
Sports drinks are comprised of 3 main components; water, carbohydrate and sodium:
Water for fluid, carbohydrate for energy, and sodium to aid water absorption and retention.
Presences of small amount of sodium and carbohydrate in fluid will increase the rate of fluid absorption in the intestine better than plain water alone.
Electrolytes are added to sports drinks to increase palatability, and maintain thirst thereby promoting drinking.

Recipe:

40-80g sugar/glucose powder, 1L water (previously boiled and cooled) and 0.5g salt
500mls fruit juice, 500mls water (previously boiled and cooled) and 0.5g salt
200mls fruit squash/cordial, 800ml water (previously boiled and cooled) and 0.5g salt

Make sure you wash all containers well with warm soapy water after use!!!

VITAMINS and MINERALS

A balanced diet should contain sufficient nutrients for an athletes needs.
Supplementation with single micronutrients is discouraged unless under supervision of a doctor or dietitian.
Taking one single nutrient alone may do more harm than good as a single nutrient in high doses can interfere with the absorption of other nutrients.

Iron:
Iron is necessary for the formation of Haemoglobin which is the oxygen carrying component of the red blood cells.
Chronically low intakes of iron in the diet can lead to anaemia and low energy. Include high iron sources in your diet daily, good sources are:

• Red meat
• Poultry and fish
• Eggs
• Beans and lentils
• Green leafy vegetables
• Fortified breakfast cereal

The iron contained in vegetable or grain foods is not as efficiently absorbed as that contained from animal foods such as meat, poultry fish and eggs.
To enhance the absorption of iron from these foods, include a source of vitamin C.
Good sources of Vitamin C include citrus fruits and juices as well as most other fruit and vegetables.

Zinc:
Zinc plays a role in growth building and repair of muscle tissues and energy production.

The following foods are high in zinc;

•Meat and meat products
•Milk and milk products
•Whole grains
•Shellfish.

Calcium:
Calcium is important for building and the repair of bone tissues.
Low intakes will lead to an increased risk osteoporosis and stress fractures.
Adults should aim to include 3 servings of calcium rich foods daily

One serving;

• 1 glass of milk
• 1 yoghurt
• 30g (1 matchbox-sized portion of cheese)

Whereas milk and milk products are the highest sources of calcium other foods such as fortified cereals and cereal bars,
soya products fortified with calcium, baked beans, and tinned fish and bread also contain calcium.

MEAL TIMING

Pre exercise:
Ideally a high carbohydrate meal should be consumed 2-4 hours before exercise.
The aim of this meal is to provide fluid, maximise carbohydrate stores in the liver and muscle, contain some protein and not have high amounts of fibre or fat. High amounts of fibre or fat can slow down the emptying of foods from the stomach and may make exercising uncomfortable.

Pre-event food examples:

• Breakfast cereal with low fat milk and fresh/canned fruit
• Muffins/crumpets with jam/honey
• Pancakes and Syrup
• Creamed rice
• Rolls or sandwiches with Banana filling
• Spaghetti with pasta or tomato sauce
• Baked potato with cottage cheese
• Cereal bars or sports bars

During exercise:
During exercise the goal is to replace fluid and prevent dehydration and provide carbohydrate for energy. (See home made drinks)

Post exercise:
Post excercise, the goal is to replace muscle glycogen with sufficient energy in the form of carbohydrate.
Eat within 2 hours or 30 minutes if exercising next day.
Aim 1g carbohydrate /kg body weight along with 0.2g protein/kg body weight.
E.g. a 65kg athlete will require a meal containing 65g of carbohydrate and 13g protein.

SUPPLEMENTS

Ergogenic (practices that improve performance) aids/ supplements should be used with caution.
Ref.: www.eirpharm.ie for a list of substances prohibited by the International Olympic Committee (IOC).
“Marketing of these products is an international multimillion dollar business that preys on the desires of athletes to be the best, and when one item does not work or is discredited by research, another comes along to take its place”: American Dietetic Association

Carnitine:
L-carnitine is a natural substance present in moderate quantities in meat.
Several claims exist for carnitine however numerous studies have shown that oral supplementation does NOT increase carnitine concentration in muscle and does not affect muscle metabolism at rest or exercise, does not increase VO2 max and does not reduce lactate accumulation during exercise.

Chromium:
Chromium is a trace element present in foods such as Brewer’s Yeast, mushroom, wheat germ.
It has been claimed that chromium increases muscle bulk and reduces body fat levels however the vast majority of studies carried out demonstrate that chromium supplements are not effective in increasing lean body mass.

Coenzyme Q10:
Coenzyme Q10 is also known as ubiquinone and plays an integral part in energy production.
It has been claimed that Coenzyme Q10 increases VO2Max and increases ‘stamina and energy’.
Studies have shown that although supplementation will lead to increases in plasma levels the levels in muscle where it will be most effective remain unaltered, therefore claims are likely to be unfounded.

Creatinine:
Creatinine is a naturally occurring compound in found in meat and fish and is again involved in energy production.
Creatinine store in muscle can be depleted with exercise (long duration, endurance) and some studies have shown that carnitine supplementation can an effect has been seen only in repeated bouts of short-lasting, high intensity exercise, no studies shown an effect on endurance performance.

Glycerol:
Glycerol has been investigated as a way to ‘hyper hydrate’ prior to exercise.
Glycerol is a small molecule which when ingested with large amounts of water (1-2 L) has been found to improve water absorption and water retention as well as leading to an overall decrease in heat stress has been seen as indicated by lower heart rate and body temperature.
Generally studies with positive effects have used ~1g of glycerol/kg body weight with 1-2 Litres of water.
Side effects nausea, heartache, blurred vision, headaches, gastro-intestinal problems, dizziness, light-headedness plus large volumes just before exercise can cause feelings of bloatedness.