When you exercise, your body must start producing energy very much faster than it does when it is at rest. The muscles start to contract more strenuously, the heart beats faster pumping blood around the body more rapidly and the lungs work harder. All these processes require extra energy. Where does it come from and how can you ensure that your swimmers have enough to last through a training session?


Where does energy come from?

Energy comes from the food that they eat. There are three components of food and drink that are capable of producing energy:






When you eat a meal or have a drink these components are broken down in your digestive system into the various building blocks. Then they are absorbed into the bloodstream. Carbohydrates are broken down into small single sugar units; fats are broken down into fatty acids; and proteins into amino acids. Alcohol is absorbed directly into the blood.

Carbohydrates are used mainly for energy in the short term, while fats are used as a long term energy store. Proteins can be used to produce energy in 'emergencies' (e.g. when carbohydrates are in short supply) or when they have reached the end of their useful life. Sooner or later, all food and drink components are broken down to release energy.


What is fatigue?

Tiredness! Fatigue during exercise can be experienced in many forms. Your swimmers may find it harder to swim certain times at the end of a session, or it may become harder to concentrate on technique, or they may find that they are unable to swim with good technique because they have lost co-ordination. This is fatigue!


How can fatigue be delayed?

Your swimmers can help to delay fatigue in the following ways.-


               Start exercising with full energy (glycogen) stores

Think of it like setting off on a car journey with a full tank of petrol. The more they have to start with, the longer they can keep going. If they start with only half a tank of petrol, they will either have to stop halfway, or go more slowly to conserve your fuel.

               Reduce the rate at which they are using muscle glycogen (energy)

The rate at which they use glycogen depends on the type and intensity of the exercise, their fitness level and the surrounding temperature. Exercising in hot conditions uses up more energy. Try and get them to pace themselves - if they start out too fast then they may run out of fuel before the end of the session!


How does diet help to delay fatigue?

A diet that is rich in carbohydrates will ensure high glycogen (energy) stores. Remember that glycogen is made up of glucose that comes from the carbohydrates in their diet. If they eat a high carbohydrate diet, their glycogen stores are more likely to be full. This will help them to exercise for longer and help them perform at their best.

The general consensus is that you should get approximately 60-70% of your energy from carbohydrates. In practice, to achieve this all meals and snacks should be based around foods which are high in carbohydrates. Carbohydrates are sometimes divided into two types: Simple (sugars) and complex (starches and fibres). Examples of these are shown in the table below-.


High in simple carbohydrates


High in complex carbohydrates


A mixture of simple and complex


Sugar (white and brown)


Flour (brown and white)




Jam, honey and other preserves


Bread (all types) Pasta, rice, noodles


Biscuits Puddings


Fruit (fresh, tinned and dried) Soft drinks


Oats and other grains Unsweetened breakfast cereals


Sweetened breakfast cereals (Frosties etc.) Sweet pastries


Yoghurt Fromage frais


Pulses (beans, lentils, peas)


Pies Flans


Sweets, chocolate






Ice cream, Jelly








Sweetcorn (unsweetened)





One type is not necessarily better than the other is. Different carbohydrates are suitable for different circumstances. Carbohydrate foods that contain a range of other nutrients should make up the main part of the diet. In general foods rich in complex carbohydrates e.g. breads and grains and the naturally occurring simple carbohydrates e.g. fruit and milk have a better nutritional value than foods rich in refined simple carbohydrates e.g. soft drinks, sweets and chocolates. In practice therefore your swimmers should aim to get most of their carbohydrates from foods providing a good nutritional package, i.e. bread, grains, cereals, starchy vegetables, pulses, fruit and dairy products.


What carbohydrate to eat and when?




Before exercise


During exercise


After exercise


Between sessions


How much?






1g/1 kg body weight


60% of energy


Time period


5-30 minutes


Begin after 30 minutes; regular intervals


0-2 hours


Minimum 4-6 meals/ snacks (for twice daily training)














  2-3 bananas

  pt isotonic sports drink & 1 banana

  3oz dried fruit

  jam sandwich (2slices bread with 2tbsp jam)

  1 energy bar


  1 litre diluted squash (3-6%)

  1 litre sports drink

  Energy bar

  2-3 bananas

  2-3oz dried fruit


       Banana sandwich

       3oz raisins

       4-5 low fat biscuits

       250ml glucose polymer drink (20%)

       8oz potato


  Pasta with lentils/ low fat cheese /chicken/fish

  Rice with beans

  Noodles with chicken

  Beans on toast

  Potato with tuna/ cottage cheese



Gl* is the Glycaemic Index of food and it is a measure of the speed of carbohydrate absorption and the rate of the resulting rise in blood sugar.


Eat a balanced diet!

In theory your swimmers should be able to get all the vitamins and minerals they need from a well planned diet. This should include a wide variety of foods from each of the main food groups in the proportions outlined below:




Number of portions per day


Cereals and starchy vegetables




Fruit and vegetables


5 or more


Milk and dairy products




Meat, fish and vegetarian alternatives




Oils and fats





Eat less of the following:

(These foods are high in fat but relatively low in other essential nutrients)

               Butter, margarine and other spreading fats Fried foods

               Fatty meats and processed meat products (e.g. sausages, burgers, meat pies)

               Pastry dishes

               Cakes and biscuits Chocolate

               Crisps and similar potato/com/wheat snacks


Make the following substitutions:

(These foods provide some fat together with other essential nutrients)

               Semi-skimmed or skimmed milk instead of full fat milk

               Low fat spread or peanut butter instead of butter or margarine

               Low or reduced fat cheese instead of ordinary cheese

               Jacket or boiled potatoes instead of chips

               Chicken, fish or lean meat instead of fatty meat, burgers and sausages

               Crackers, rice cakes or fruit bars instead of crisps, biscuits and cakes

               Fresh fruit instead of chocolate


Make the following changes:

(These will reduce fat intake while supplying other essential nutrients)

               Limit frying to stir frying with limited amounts of oil

               Top baked potatoes with fromage frais, yoghurt, half fat creme fraiche or baked beans

               Remove skin from chicken or turkey

               Grill, bake stir fry or boil instead of frying

               Choose lean cuts of meat and trim off as much fat as possible