Many long-distance swimmers "carb-load" before an endurance event like a 5 km swim. Carbohydrate loading involves eating carbohydrate-rich meals several days to one week before the event. In fact, many groups sponsor dinners the night before a race and serve high-carbohydrate foods like pasta. However, studies are mixed about the usefulness of this practice. One problem in practice is that it is difficult to consume such a high level of carbohydrates over several days. Event distance is a factor. Also, studies have failed to consistently show that performance - speed and/or endurance - improves, even when the diet is followed. Although some athletes report improved performance, it is possible that this is a placebo effect. Genetic and gender differences may also play a role. Regardless of its efficacy, what is the reasoning behind carbohydrate loading?
1. Excess glucose enables the body to produce more ATP. which is stored in the body and can be used during the event.
2. Decreasing the amount of fat and protein in the diet helps with weight loss, which can improve endurance and speed.
3. Excess glucose is stored as muscle glycogen, reducing the amount of lactate generated in muscle during the event.
4. Excess carbohydrates are stored as triacylglycerols, which can be oxidized during anaerobic metabolism.
5. Glucose is stored as glycogen, which can be broken down to supply energy during the event.

Carbohydrate loading is for contant supply of energy as ATPs for the skeletal muscles cells to sustain contraction during high intense activity, (e.g. long distant swimming), to reduce fatigue, and increase performance for upmost performance.

The mechanism of carbohydrate load involved; the increase in intake of high carbohydrate meals a few weeks before the commencement of the sporting activities. The excess carbohydrate is stored as muscle glycogen, liver glycogen and brain glycogen.

During intense physical activites the body depends on the muscle glycogen. This is converted to glucose -6-phopahate which enters into glycolysis, and Krebs’s cycle to generate ATPs.

The use of muscle glycogen during strenuous exercise reduces blood glucose uptake, and ensured that its level is at a relatively constant value for the body homeostatic conditions, without exogenous carbohydrate intake.