Carbohydrate ingestion before, during and after competition.

 
Research on the benefits of ingesting high glycemic carbohydrates, such as sugar, less than one hour before competition is inconclusive.

One theory is that ingesting high glycemic carbohydrates negatively affects performance during endurance events. The sudden surge of glucose passing into the blood causes an over secretion of insulin. This sudden increase in insulin secretion actually depletes the blood sugar level and disturbances in nervous system functions. High insulin levels increase the use of carbohydrate as a fuel in muscles and decreases the mobilisation of fat. It is believed that less fat mobilisation and increased carbohydrate use tends to prematurely deplete glycogen levels in the muscle and cause early fatigue.

SInce the results are inconclusive it is advised that high glycemic carbohydrates be consumed one hour before exercise.
It is important to keep a stable concentration of insulin in the blood in order to stabilise blood sugar levels and enable fat mobilisation which together help preserve glycogen reserves. Low glycemic carbohydrates, such as high fibre brown bread, ingested more than 30 minutes before exercise enables for slow release of glucose into the blood from the digestive tract.

During exercise an intake of 60 grams of carbohydrate each hour benefits high intensity exercise of long duration.

After exercise it is important to speed up replenishment of glycogen. Athletes should consume up to 75 grams of high glycemic carbohydrates every two hours until a maximum of 10 grams per kilogram of body mass. A period of rest after intense exercise enhances the rate at which glycogen is replenished.

Carbohydrate loading is a particular combination of diet and exercise designed to increase the amount of stored glycogen well above the levels achieved by normal carbohydrate intake. Bodybuilders use this technique prior to competition to enhance muscle size.

Normally 1.7 grams of glycogen is packed into 100 grams of muscle tissue. However carbohydrate loading pushes the glycogen stores to approximately 5 grams of glycogen per 100 grams of muscle tissue. For well nourished, active individuals, who participate in non-endurance events this practice has little benefit.

Below is a two stage carbohydrate loading procedure(from Essentials of Exercise Physiology 3rd Ed p 117).. It is designed to deplete the body stores of glycogen and then to allow synthesis and storage of glycogen by ingesting a carbohydrate rich diet. The body responds by storing a greater amount of glycogen than present prior to depletion. Three grams of water is stored with every gram of glycogen which causes a significant increase in mass. This can be a hindrance for an athlete competing in activities such as running.

Seek proper medical approval before commencing on this program.

Stage 1 Depletion.
Day 1. Perform exhaustive exercise to deplete glycogen in specific muscles. Preferably the muscle groups used for the event.
Day 2, 3, 4 Maintain low carbohydrate ( up to 100 grams per day) intake by substituting carbohydrate for protein and fat while training at moderate intensity to further deplete glycogen stores.


Stage 2
Day 5,6,7 Increase the amount of carbohydrate (up to 700 grams per day) and maintain normal levels of protein and fat.
Competition day - Ingest a high carbohydrate precompetition meal.