Fuel during Sport

During most sport your body will steadily burn a fuel mixture of carbohydrate (as glycogen) and fat.  If your sport is no longer than an hour, you will perform well without having to replace those fuels until you have finished.  Your next meals, if well chosen, will replace all the fuel you have used.  On the other hand, you will be sweating and losing fluid very soon after you begin any exercise.  This fluid must be replaced as soon as possible during exercise, because even minor dehydration can impair your performance. 

If your sport or training takes longer than an hour then you may benefit from consuming some carbohydrates during sport in addition to fluids eg sports drinks.  The decision will depend on the:

• Intensity of the exercise (higher intensity burns more glycogen more quickly)
• Duration (the longer the event, the more glycogen burned)
• Ambient temperature (the hotter it is, the quicker glycogen will be burned)
• How well you have eaten before sport (more pre-event carbohydrate means more available glycogen).

Carbohydrate consumed during an event may improve endurance by:

a)  Sparing muscle glycogen.  In low intensity exercise the carbohydrates taken during the event can be re-made into glycogen for later use.

b)  Keeping blood glucose (sugar) levels normal during moderate to high intensity exercise and providing extra fuel for empty muscles, so delaying fatigue.

Fluids

Fluids, there is no doubt you need them.  Water is good for replacing fluid losses.  However, sports drinks have a number of advantages, including a taste that encourages better fluid intake, and the addition of carbohydrates for glycogen fuel replacement.  Glycogen replacement is beneficial if the event is an hour or more.  Drink before, during and after exercise.  Don’t wait until you are thirsty.  If you feel thirsty then you are already too dehydrated to perform at your best. 

Events less than 90minutes

A sports drink provides some carbohydrates as sugars can help delay fatigue in a short event or team game.  It should not be necessary to eat any solid food in events less than 90minutes duration, as eating well beforehand will have a big impact on sports performance, and a sports drink provides plenty of opportunity to refuel during the event.  If you fatigue during the event, then probably you haven’t:

• Eaten enough carbohydrates beforehand.
• Taken enough sports drink.
• Trained enough you have overtrained.

Events Longer than 90minutes / Multi events.

Most fit people can exercise for 90minutes or more if they are well fuelled with carbohydrates before they start.  Unfortunately, there isn’t a never ending supply of glycogen fuel, so in endurance events it is recommended that extra carbohydrate is consumed, usually in the form of a sports drink or easy to eat food bar or sugar confectionery.

The sugars found in a sports drink will help to delay fatigue and allow you to compete at your optimal pace for a longer time.  If you eat solid food to supply additional carbohydrate, then it will need to be a choice that you feel comfortable with. 

Examples include:

• 50g jelly beans/jelly snakes etc
• 1 python snake
• 1 banana
• 1 fruit muesli bar
• 1 sports bar eg. Powerbar
• 3 fruit strips
• 50g carbohydrate gel

Studies of athletes show that around 30-60g of carbohydrates per hour should be consumed in an endurance event to delay fatigue. You should experiment to find a fuel replacement schedule that suits your individual needs.

Summary points

• During sporting activities, it is important to replace lost fluid as soon as possible
• In longer activities, both fluids and carbohydrates will need to be replaced to enhance endurance ability
• Consume 30-60g carbohydrate per hour during endurance events

By Jodie Barker