9. Carbohydrate Loading for Endurance Athletes
Time required for an endurance athlete to carb-load, without exercising
Carbohydrate loading in human muscle: an improved 1 day protocol (Bussau VA, Fairchild TJ, Rao A, Steele P, Fournier PA.) This study examined whether or not trained athletes could store maximal amounts of muscle glycogen within a shorter period of time than the traditional 3 days of carbohydrate-rich diet. Eight endurance-trained male athletes were asked to remain physically inactive and eat 10 g.day(-1).kg(-1) body mass of high-carbohydrate foods having a high glycaemic index over 3 days. The results showed that muscle glycogen content increased significantly after only 1 day, and remained stable afterwards despite another 2 days of carbohydrate-rich diet. This study concluded that combining physical inactivity with a high intake of carbohydrate enables trained athletes to attain maximal muscle glycogen contents within only 24 hours. Full summary below.
It is commonly known that increasing the amount of glycogen in the muscles before an event can increase the time to exhaustion and enhance performance for endurance athletes. Previous carbohydrate loading strategies included the classic 3-day loading where an athlete would perform glycogen-depleting training, followed by 3 days of high carbohydrate diet without training. Although 3 days does not seem like much time, it can be difficult for endurance athletes to completely alter their routine to adjust to this carb-loading strategy.
To determine if an endurance athlete could carb-load for less time, such as 24 hours, a study was conducted on 8 male endurance athletes. The goal was to see how quickly these athletes could obtain maximal muscle content of glycogen by consuming 10 grams per day per kilogram of body mass. Muscle biopsies were performed on 3 muscle types to determine if each group of fibers equally attained maximal glycogen concentration, if at all. Key discoveries from the study included:
Experienced athletes can maximize their muscle glycogen stores within 24 hours by remaining inactive and consuming a large number of carbohydrates.
All 3 muscle fibers studied exhibited maximal amounts of glycogen stores within 24 hours. (Muscle fibers included I, II, and IIb.)
Glycogen-depleting exercise before carb-loading will extend the timeframe from 24 hours to at least 48 hours. However, if a short, high-intensity exercise is completed before carb-loading so that current glycogen stores are not fully depleted, an athlete will be able to obtain maximal glycogen stores within 24 hours.
To reach optimal levels of glycogen stores within 24 hours, athletes are recommended to consume carbohydrates that have high glycemic indexes such as white rice, white bread, or whole wheat bread.
These discoveries are advantageous to athletes that don’t have the typical 3-day preparation time before an event to carb-load, due to traveling, diet restrictions, or other life commitments. Plus, this study proves that trained endurance athletes don’t have to overdo it in the days leading up to an event. It should be noted that athletes can also implement this strategy 3 days before an event and still obtain maximal muscle glycogen levels. If an athlete decides to cease training 3 days before an event and carb-load on day one, but return to their normal diet on the last 2 days before the event, they will still see the desired glycogen levels in their muscles.
In summary, experienced endurance athletes can obtain maximal muscle glycogen levels within 24 hours if they remain inactive and carb-load adequately. This means that athletes can wait until the day before an event to complete their carb-loading and still obtain the desired results. Also, athletes can implement the 3-day strategy without continuous carb-loading. In the 3-day strategy, an athlete can cease exercising and carb-load on the first day, then resume their normal diet for the remaining 2 days before the event. This discovery allows endurance athletes more freedom in the days leading up to an event and adaptability for their unique lifestyles.
Bussau, Vanessa & Fairchild, Timothy & Rao, Arjun & Steele, Peter & Fournier, Paul. (2002). Carbohydrate loading in human muscle: An improved 1 day protocol. European journal of applied physiology. 87. 290-5. 10.1007/s00421-002-0621-5.