What is Carbohydrate Loading?
Carbohydrate loading or carbo-loading, is a term used to describe a nutrition technique used by endurance athletes in an attempt to prolong optimal athletic performance and delay the onset of fatigue, or, ‘hitting a wall’.
The Transformation of Food into Energy
When we eat carbohydrate containing foods, they arrive at our stomach and begin to break down. From the stomach, the partially broken down food travels to the small intestine where it completely breaks down into many compounds, one being glucose. From the small intestine the glucose is absorbed into the blood stream. A hormone called insulin which is secreted by our pancreas, accompanies the glucose from the blood to our liver and muscle cells, where it is stored in the form of glycogen. From this stored form, the body can transform glycogen back into glucose through a process known as glycolysis, and use it for energy when needed.
When is Carbohydrate Loading Appropriate?
Carbohydrate loading has been shown to only be beneficial for athletes competing in endurance events lasting longer than 90min. This includes events like marathon running and triathlons. The reason carbohydrate loading is indicated only for endurance events lasting more than 90min is due to the body stressing its aerobic energy system and depleting all of its stored energy. What do I mean by this? Our body naturally reserves some energy in the form of glycogen for daily activity and these stores can last us a modest duration of light-moderate intensity activity e.g. netball game, tennis game, a run or a jog. As exercise intensity increases, so to does the rate of glycolysis in the liver. i.e. as the intensity of the exercise increases, the rate at which glycogen from the liver is broken down into glucose to be used as energy, also increases. This glucose is transported to the muscles where together with muscle glycogen, it is utilised for energy.
However, when the body is active for 90 minutes or longer, those energy stores from our regular diet begin to exhaust and the body turns to other, less efficient energy supplies like fat. So, in order to maintain optimal athletic performance and delay the onset of fatigue, endurance athletes engage in carbohydrate loading.
How to Do It
Previously, the carbohydrate loading technique involved vigorous exercise and little carbohydrate intake so as to deplete all glycogen stores for a few days leading up to the event. Then one day prior to the event, zero exercise and high carbohydrate intake so as to saturate liver and muscle glycogen stores.
The most recent research into techniques of carbohydrate loading are as follows:
Three days prior to the event, the athlete must increase his/her carbohydrate intake to 7-10g/kg body weight in order to saturate glycogen stores to around 150-200% of their normal levels. Secondly, during these days, training must decrease. Thirdly, the day before competition, the athlete must completely rest in order to ensure minimal energy expenditure, and hence maximal glycogen storage.
Do’s and Don’ts
It is important to note that different meal plans can have differing effects on the body. For this reason, it is imperative that the athlete trial different foods prior to the event, to ensure no unforseen gastrointestinal disturbances during the event. High fibre foods like grain breads, wholemeal pasta and brown rice, without an adequate fluid intake, can cause gastrointestinal upset including constipation, flatulence and bloating which are all very uncomfortable sensations, particularly during vigorous exercise. So in order to maximise carbohydrate intake whilst not over doing your fibre intake, one should include simple carbohydrates as part of the diet as well. Simple carbohydrates are derived from foods like fruit and milk and also white varieties like white bread and white pasta.
However, gastrointestinal upset is not uniform amoungst all athletes. If it does apply to you, an alternative diet could substitute the wholemeal options with white, simple carbohydrate alternatives, which as mentioned above are lower in fibre. The reason they are called simple carbohydrates is because they are not as complex for the body to digest. They release glucose (energy) into the blood stream much faster as a result of the body being able to digest them quicker than the high fibre, complex carbohydrates mentioned above. This is either because of their innate chemical composition which allows them to be broken down faster, as is in the case of fruit and milk. Otherwise, as is in the case of some processed food products like bread and pasta, most of the processing is done during food production, so the body doesn’t have to work as hard or for as long to break them down. Thus, these foods are digested faster in the gut, providing instant, short bursts of energy as opposed to a more consistent, sustained energy release as is in the case of complex carbohydrates like wholemeal bread and wholemeal pasta, oats and corn.
According to Asker E. Jeukendrup although our fat stores account for about 92% of energy stores and carbohydrate account for around only 2%, glycogen (from carbohydrate) is a much more readily available, efficient form of energy. So to ensure your body is equipped with the most efficient energy stores, ensure the bulk of your carbohydrate intake, particularly the night before an event, is from complex carbohydrate sources as these foods are believed to improve athletic performance by 2-3%. However, to achieve that 10g/kg body weight of carbohydrate intake, which for a 70kg athlete is 700g carbohydrate, simple carbohydrates are what is going to get you over the finish line.
An Extra Top Up
Another way of topping up on energy during an event, is to drink sports drinks like Gatorade or PowerAde. They not only supply instant energy in the form of simple carbohydrates, but they also hydrate and replenish electrolyte losses. Below is a table comparing the nutritional value of a range of sports drinks.
|Gatorade||Gatorade Endurance||Powerade||Powerade Zero||Maximus||Staminade|
|Fat – total|
Remember, carbohydrate loading is only useful for events which demand it. For a short duration or power sport, this technique will be useless as these activities do not demand the body to utilise extensive glycogen stores.