Glycemic Index is a guideline for the rate at which carbohydrate foods are digested, absorbed and raise blood glucose levels. Foods are generally catergorized as having a high, medium or low glycemic index. Carbohydrate foods which contain fiber especially soluble fiber have lower glycemic indexes. Glycemic index does not take into account consuming foods that also contain protein and fat such as eating a baked potato with butter and sour cream or as part of a meal. The heart muscle is aerobically oriented and does not do well during low oxygen availability.
Glycolysis also utilizes fructose and galactose in small amounts .
However, the higher the level of aerobic training the athlete has attained, the longer he will be able to use fat as an energy source through aerobic metabolism. When lactate is produced it migrates out of the muscle cell and is absorbed into the vascular system. The liver removes lactate from blood and resynthesizes glucose which is then released back into the vascular system where it may be used for glycolysis. Using lactate to synthesize glucose is one form of gluconeogenesis. Their is an immediate increase in glycogenolysis when muscle begins to contract.