The predominant function of carbohydrates in the human body is as an energy source.  Carbohydrates are used short term like the fuel in your car’s petrol tank. The types and amounts of carbohydrates and the timing of their intake are therefore crucial to one’s performance.

Although the body can use fat reserves and amino acids catabolised from muscle tissue as sources of energy, it is always carbohydrate reserves that are the limiting fuel source.  Insufficient carbohydrate supplies will result in you running out of fuel in a flash. An effective way of achieving good carbohydrate nutrition is to ensure optimum carbohydrate intake before, during and after exercise.

Scientific studies have confirmed that the level of carbohydrates in the way of body glycogen stores before you start exercise is the most important fuel determinant of your performance.  The primary goal in terms of carbohydrate loading then should be to maximise glycogen reserves before the start of the event.

When the body’s glycogen stores are depleted during exercise, fatigue sets in and athletic performance is reduced. It has been scientifically proven however, that when glycogen stores are depleted and then properly replenished (“re-loaded”), more glycogen can be stored than prior to depletion. This glycogen (carbohydrate) loading helps endurance athletes compete for longer periods of time without hitting the wall.

Muscles use glucose as their main source of energy during exercise. When carbohydrates are consumed and digested they are broken down into smaller components including glucose. Glucose that is not required for immediate energy is converted to glycogen and stored in the muscles and liver for future use. When a need for energy arises, the glycogen is then reconverted to glucose.

Carbohydrates become the more important source of fuel for muscles as the body becomes more active. At very high training intensities, carbohydrates are the most important source of fuel for the muscles.

The more glycogen your body can store, the better it is for your performance, for the following reasons:

  1. Once glycogen stores run low, your body turns to its fatty acid supply as a source of energy. Athletic performance is then negatively affected, as fats are not as an “efficient” energy source as carbohydrates.
  2. When glycogen stores are depleted, the body uses more amino acids from muscle tissue for energy and to manufacture glucose. This increases muscle catabolism.

For the above reasons, effective carbo-loading offers great benefit to endurance athletes.


Carbohydrate loading generally consists of 2 phases:


During this phase, the body’s glycogen stores are depleted by manipulating the diet by moderately restricting carbohydrate intake and maintaining training intensity. The simplest method of carbo-loading does not require completely depleting glycogen stores.  By moderately restricting carbohydrate intake about 7 days out from competition, combined with daily training, glycogen stores naturally deplete. Resistance training by means of using the weight training circuit during this period further assists with the depletion process.


During this phase, the body’s glycogen stores are re-filled beyond normal levels by reducing training intensity and increasing carbohydrate consumption. Three days before competition training duration and intensity is reduced and carbohydrate consumption is increased. Simple carbohydrates should be consumed during and directly after training sessions. This is best achieved by consuming liquid carbohydrate drinks. This carbohydrate drink should be comprised predominantly of glucose polymers with a little additional glucose and fructose. The carbohydrate composition of Pro Nutrition’s Hydra-Sport makes it an ideal choice.

High levels of low glycemic index carbohydrates i.e. complex carbohydrates such as beans, sweet potatoes, pasta, oats, rice, whole-wheat or brown bread etc, should be consumed throughout the day. Additional consumption a glucose polymer “carbo-loading” drink such as Pro Nutrition maltodextrin during this period will help ensure adequate carbohydrate intake. Carbohydrates should make up at least 70% of the diet during this period and a reduced training intensity should be maintained during all 3 days, with the lowest intensity on the 3rd day.

3 days of the above “carbo-loading” strategy is what results in the enhanced glycogen stores needed to maximise performance.


Carbohydrate loading has its place in the athlete’s repertoire. Practised correctly, it can dramatically enhance performance.

Additional Tips For Race Day

  • Before the event it is important to try to raise blood glucose levels as this has been shown to improve performance.  This is best achieved by consuming a carbohydrate drink such as Hydra-Sport or Carb-Up 2-3 hours before the race.  It is suggested that you practice in training leading up to the race by starting with 30-40 grams of carbohydrates taken before each training session and gradually building up to around 100g of carbohydrates taken 2-3 hours pre-event.
  • Once the race begins the minimum level of carbohydrate intake you should be looking at is 40 grams per hour although research indicates that 70-90 grams per hour is optimum.  The best way to achieve this is to use a 5%-10% carbohydrate rehydration drink (such as Hydra-Sport) or carbohydrate gel sachets followed by an appropriate amount of water.  Using a sports drink such as Hydra-Sport would mean aiming for around 1 litre per hour.