Why do we need to replenish glycogen and carbohydrates before endurance sports competitions?

Nutritional recommendations for game days vary widely between sports, and also vary widely between game days and non-game days within the same sport. When approaching a competition, the most important dietary principle is to give the body more energy and avoid gastrointestinal discomfort. Different sports have different requirements for water and electrolyte balance for optimal performance, and also have their own eating timing and food composition principles. In heavyweight sports, there is a process of safely dehydrating the body that should be carefully planned and executed; and replenishing water, electrolytes and nutrients in time to compete after dehydration is very important for athletic performance.

Endurance sports competitions

Glycogen supercharging is an important difference between endurance sports and other sports, but its importance is often exaggerated. As long as there are adequate glycogen stores before the game, the exact method used to replenish the stores is not really important. The characteristic of nutrition strategy for endurance sports is that the recommendations for carbohydrate, water and electrolyte intake during training are relatively complex. As long as these suggestions are met, you can flexibly adjust them according to your personal preferences.

The response to nutritional strategies during competition varies from person to person and can significantly affect performance, so endurance athletes must try nutritional strategies during training to assess their body’s response and adjust their strategies for future competitions.

【One week before the race】

Only for events lasting more than three hours does it need to use glycogen super-replenishment in the week before the competition. In the week of the competition, it is necessary to ensure that the calories consumed are sufficient for recovery and glycogen refill. A hypocaloric diet should not be implemented at this time, and it is recommended to switch some of the caloric source from fat to carbohydrates to ensure optimal restoration of glycogen. This is also a good time to practice your nutrition strategy for the race. If the race lasts more than three hours, start increasing your carbohydrate intake two or three days before the race, consuming about 4 to 6 grams more per kilogram of body weight than usual. Try to choose foods with a medium to high glycemic index and avoid consuming too much fiber. Carbohydrate intake slightly above the recommended amount may be beneficial for cycling performance. Cycling events are less weight-constrained than running, so even if you add a few extra pounds to your body due to glycogenolysis, water, and food in your intestines, it is unlikely to affect the benefits of intact glycogenolysis stores.

[The day before the race]

In order to continue using glycogen supercharging for races over three hours (and for events around two hours), it is recommended to increase carbohydrate intake the day before the race, consuming approximately 6 to 11 grams per kilogram of body weight more than usual, and spread this intake evenly throughout the day, preferably continuing it until the evening before the race. If you are participating in a competition lasting less than an hour, you do not need to supplement a large amount of carbohydrates. You only need to slightly increase your intake the day before the competition, about 1.1 grams more per kilogram of body weight than usual.

【Pre-race diet】

If the race is longer than two hours, try to consume as many carbohydrates as your stomach can hold without causing stomach upset. The amount of intake varies from person to person. Some people may need 2.2 grams of carbohydrates per kilogram of body weight, while others may not exceed 1.1 grams. As discussed previously, practicing your pre-race meal before a long training session will give you a better idea of ​​how much carbohydrate you need to consume before a race. It is recommended to experiment early and often, otherwise rebound hypoglycemia (a sharp drop in blood sugar) will cause intense hunger, tremors, sweating, dizziness, nausea, fatigue and other reactions, which are not conducive to athletic performance. It is usually recommended to take your pre-game meal one and a half to two hours before the game starts, and eating some easily digestible carbohydrates within fifteen minutes before the game starts or warm-up will also have a good effect.

【Match Day】

Carbohydrate recommendations

When determining carbohydrate needs during training, endurance athletes must consider whether they will experience gastrointestinal discomfort and the absorption rate of the selected carbohydrate source. The maximum rate of carbohydrate absorption during exercise is approximately 90 grams per hour, and studies have shown that absorption rate has little to do with the athlete's weight or body size, but can vary by as much as 20% between individuals. However, consuming more than 90 grams of carbohydrates per hour will not help improve performance. The longer the exercise duration, the higher the rate of carbohydrate intake must be.

Table 14.1 lists the minimum, recommended, and maximum carbohydrate intakes for various exercise durations. You can start with the "recommended" intake and then slowly increase to the "maximum" intake to find the intake that achieves optimal performance. If your stomach starts to have problems, consider reducing your intake towards the minimum, but it is not recommended to go below the minimum value, otherwise your performance may be affected.

(Photo provided by Caishi Culture)

Some of the above recommended values ​​are slightly higher than the research data, because a slight excess of carbohydrate intake may help to replenish glycogen, which is very helpful for long-term endurance events.

Inevitably, the rate of carbohydrate intake cannot keep up with the metabolic demands of long-duration endurance competitions, because the rate at which the intestines absorb carbohydrates is limited during sustained exercise. Therefore, it is important to consume the most carbohydrates possible per unit time by adding more fructose to your carbohydrate drink during training. The greater the amount that needs to be absorbed per hour, the higher the ratio of fructose to glucose, up to a maximum of 1:2.

Hydration recommendations

With a steady intake of water, most athletes can consume a liter of fluid per hour during exercise without experiencing gastrointestinal discomfort, but this requires that the concentration of sugars and electrolytes in the water is lower than that in the body, as this will slow down the rate at which the stomach empties. Sometimes you can increase the sugar concentration in water to give the body more energy, although this will slightly affect water replenishment. This is a complex topic, but it is recommended to start with liquids that contain 6% to 8% sugar. Drinks with higher sugar content should be consumed with caution and tested before the race to ensure that they are still hydrated. Paradoxically, acute dehydration also slows the rate at which the stomach empties, so once dehydration sets in, the body's ability to absorb water is also affected.

Extreme endurance athletes must work hard to avoid dehydration. The fuller the stomach space (to the point of discomfort), the faster the stomach empties. Athletes can take advantage of this by drinking water regularly to maintain the occupied stomach space (it is recommended to drink water every ten minutes, up to fifteen minutes). If you wait more than fifteen minutes to drink water, it may lead to a decrease in gastric emptying rate, making it more difficult to maintain hydration during endurance exercise, and may even cause hypoglycemia. Some people stop drinking water near the end of a race to achieve peak performance, but this approach is probably only suitable for advanced athletes who are striving for extreme performance—and even then there are risks.

This article is from Caishi Culture's book "Muscle Gain x Fat Loss: A Complete Book of Scientific Diet"