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Consumption of carbohydrates before exercise

 
, medical expert
Last reviewed: 15.05.2018
 
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Athletes are warned about the undesirable consumption of carbohydrates in large amounts before the load. This caution is based on the results of a study conducted by Foster et al. Showed that consumption of 75 g of glucose 30 minutes before the load reduces stamina due to accelerated depletion of muscle glycogen and hypoglycemia. High levels of insulin in the blood, caused by the consumption of carbohydrates before the load, were the cause of these phenomena.

As a result of this study, some practitioners advised athletes to avoid consumption of carbohydrates before loading or use products with a low glycemic index. This advice is based on the fact that products with a low glycemic index (beans, milk) give a slow but continuous release of glucose into the blood, without concomitant release of insulin. For comparison, sugar and foods with a high glycemic index (bread, potatoes, sports drinks and many breakfast cereals) rapidly increase glucose and insulin levels in the blood.

Studies by Hargreaves et al. Contradict the early studies of Foster. Subjects took 75 g of glucose (high glycemic index), 75 g of fructose (low glycemic index) or water 45 minutes before the race to failure. Although glucose intake caused a high level of insulin in the blood and a low blood glucose level, there was no difference in load-to-failure time between arrivals of bicyclists consuming glucose, fructose or water.

Consumption of carbohydrates with a high glycemic index for 1 h before exercise, especially on an empty stomach, can improve performance. Sherman et al. Compared the consumption of beverages containing 1.1 g-kg and 2.2 g-kg carbohydrates per hour before the load. Cyclists rode at 70% V02max for 90 min. At an early stage, the level of serum insulin increased at the beginning of the load and during it, and the blood glucose level initially decreased. But the results of the results increased by 12.5% due to the consumption of carbohydrates, mainly increased their oxidation.

Hyperglycemia and hyperinsulinemia resulting from the consumption of carbohydrates before exercise are temporary and obviously will not affect the outcome if the athlete is not sensitive to lowering blood glucose and does not feel premature muscle fatigue or CNS symptoms indicating hypoglycemia. Athletes should evaluate their reactions to high-carbohydrate foods with both low and high glycemic indexes to determine which is better.

Carbohydrates with a low glycemic index may be the subject of choice for those athletes who are sensitive to lowering blood glucose levels. Thomas et al. Compared the consumption of carbohydrates of lentils (low glycemic index) and water for 1 h before the load. Cyclists rode to exhaustion at 65-70% V02max. Lentils provided a gradual increase and decrease in the level of glucose in the blood in comparison with potatoes, glucose and water. The endurance period provided by lentils (low glycemic index) was 20 minutes longer than in other cases that did not differ from each other.

Athletes who are sensitive to lowering blood glucose levels are given several strategies for choosing.

  • Take carbohydrates with a low glycemic index before the load.
  • Take carbohydrates for a few minutes before the load.
  • Take carbohydrates during exercise.

Consumption of carbohydrates with a high glycemic index (for example, glucose) just before anaerobic load (sprint or weightlifting) does not improve the indices. For these anaerobic loads, enough ATP, creatine phosphate (CRF) and muscle glycogen have been accumulated. Carbohydrates with a high glycemic index do not contribute to the rapid release of energy, allowing athletes to train more intensively. Consuming an excessive amount of carbohydrates before the load can increase the risk of gastrointestinal disorders in the form of seizures, diarrhea and bloating.

Eating before the load

Athletes are advised to take food 2-3 hours before exercise to ensure the necessary time for emptying the stomach. This provision is based on the fact that if there is food left in the stomach, at the beginning of the exercise the athlete may feel nauseous or uncomfortable when blood from the gastrointestinal tract is directed towards the working muscles, so many athletes who train or compete in the morning refuse to eat , and do not get up at dawn for breakfast. This starvation reduces the supply of hepatic glycogen and can worsen the performance of the exercises, especially if the athlete is exposed to a prolonged strain that requires the maintenance of blood glucose levels.

During the exercise, athletes rely mainly on the available supply of glycogen and fat. Although eating before the load does not contribute to instantaneous energy release, it can provide energy when the athlete is working hard for 1 hour or more. Eating also prevents the feeling of hunger, which in itself can worsen the performance. The presence of carbohydrates in food increases the level of glucose in the blood to provide working muscles with energy.

Consumption of carbohydrates for 2-4 h before the morning exercises helps restore the reserve of hepatic glycogen. This allows you to carry loads, provided mainly by blood glucose. If levels of muscle glycogen are also low, carbohydrate intake several hours before the load increases them. If you are concerned about the delay in emptying the stomach, you should use liquid food.

Sherman et al. The effect of 312-, 156- and 45-gram liquid carbohydrate nutrition was assessed 4 hours before the load. Consumption of carbohydrates with a high glycemic index yielded 4.5, 2 and 0.6 g-kg carbohydrates, respectively. A 95-minute bicycle race was held at intervals with subsequent verification of the indicators after a 5-minute rest. A portion of 312 g of carbohydrates improved by 15% despite an increased insulin level at the beginning of the load.

Nuefer et al. Also found that stamina increased when taking mixed food (porridge, bread, milk, fruit juice) giving 200 grams of carbohydrates, 4 hours before the load.

Food rich in carbohydrates, tasty, well tolerated is ideal for eating before exercise. Sherman et al. It is believed that food before the load, containing 1.0-4.5 g-kg carbohydrates, should be taken 1-4 hours before the load. To avoid possible gastrointestinal disorders, the content of carbohydrates and calories should be reduced with a decrease in the interval between meals and exercise. For example, a portion of carbohydrates 1 g-kg is expediently taken 1 hour before the load, and 4.5 g-kg - 4 hours before the load.

Liquid food

The industry has created several types of liquid food specifically for athletes - GatorPro, Nutrament and Exceed Nutritional Beverage.

These products satisfy the need for food before the load: they are rich in carbohydrates, pleasant to the taste and provide the body with energy and liquid. Liquid food, in contrast to the reception of ordinary food, should be taken immediately before the competition, as it promotes rapid emptying of the stomach. This will help to avoid nausea to those athletes who are in a state of stress.

With liquid food stool is lean, which minimizes the increase in body weight immediately after ingestion. This is especially beneficial for wrestlers who must "keep the weight". Liquid food is also convenient for athletes participating in competitions, continuing all day, tournaments and all-around (for example, triathlon).

Liquid food can also be used as a nutritional supplement during intensive training sessions, when the need for calories is extremely high. It gives a significant amount of calories and promotes satiety.

trusted-source[1], [2], [3]

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