Increasing glycogen reserves and maintaining its level during training sessions requires a diet rich in carbohydrates. If an adequate amount of carbohydrates is not consumed daily between exercise periods, the content of muscle glycogen before loading gradually decreases and the exercise performance during training or competition deteriorates. Daily restoration of carbohydrate reserves of the body should be a priority for athletes who are training intensively.
Costill et al. Glycogen synthesis based on a 45% carbohydrate diet was evaluated for three consecutive days of 16.1 km run at 80% V02max. The level of muscle glycogen initially was 110 mmol-kg and decreased to 88 mmol on the second day and to 66 mmol-kg on the third day. Another study showed that a diet providing 525-648 grams of carbohydrates promoted the synthesis of glycogen to 70-80 mmol-kg and provided an almost maximum recovery of muscle glycogen for 24 hours.
Fallowfield and Williams also evaluated the importance of carbohydrate intake for their recovery after a prolonged load. Their subjects ran at 70% V02max for 90 minutes or until fatigue. For the next 22.5 hours, runners consumed an isocaloric diet containing 5.8 or 8.8 g carbohydrate-kg. After rest, they ran with the same intensity to determine endurance, and got 8.8 grams of carbohydrates-kg could run for the same time as in the first race. And although these two diets were isokaloriynymi, the running time of athletes who received 5.8 grams of carbohydrates-kg, decreased by 15 minutes.
For many athletes, energy needs and carbohydrates during training sessions are more than during the competition. Some athletes can not (unintentionally) increase the absorption of calories to meet energy needs during intensive training sessions. Costill et al. Studied the effect of a 10-day workout, increased in volume and intensity, on muscle glycogen and indices in swimming. Six swimmers themselves chose a ration containing 4,700 calories per day and 8.2 grams of carbohydrates-kg per day, and four swimmers chose a diet containing only 3,700 kcal and 5.3 grams of carbohydrates-kg per day. These four swimmers could not overcome the increased demands of training sessions and sailed much more slowly, presumably as a result of a 20% reduction in glycogen in the muscles.
The feeling of lethargy associated with the depletion of muscle glycogen is often called overwork, the cause of which is overtraining. Athletes who train hard for several consecutive days should consume enough carbohydrates to reduce the threat of fatigue due to the combined depletion of muscle glycogen.
Glycogen depletion associated with training sessions can occur during classes that require repeated near-maximal explosive efforts (football, basketball), as well as with endurance exercises. The symptom of glycogen depletion is manifested in the inability of the athlete to maintain the normal intensity of the load. Depletion of glycogen can be accompanied by a sudden loss of body weight of several pounds (caused by the loss of glycogen and water).
A review of the literature by Sherman and Wimer casts doubt on the assumption that a high-carbohydrate diet optimizes adaptation to training and sports performance. In their opinion, the relationship between the depletion of muscle glycogen and the exhaustion of the athlete is the strongest in moderate training (65-88% V02max (maximum oxygen consumption is an indicator of the maximum capacity of the human body to transport and use oxygen during exercise)). However, they also mention the established fact that low blood glucose concentrations and muscle and / or liver glycogen can cause fatigue while performing other types of exercises. Since dietary carbohydrates are involved in maintaining carbohydrate stores in the body, Sherman and Wimer recommend that athletes continue to consume foods high in carbohydrates, and observe signs of lethargy during training and take note of those athletes whose addictions in food make them more prone to depletion of glycogen.
Strongly trained athletes need to consume 7-10 grams of carbohydrate-kg per day. A typical American diet involves 4-5 g of carbohydrate-kg per day. Consumption of 6-7 grams of carbohydrates-kg per day is sufficient for the athlete's intense training (about 70% V02max) for about one hour a day. Consumption of 8-10 g of carbon-water per kg per day is recommended for intensive training of athletes for several hours a day.
Some athletes should reduce their fat intake to 30% of the total calories to get 8-10 grams of carbohydrates-kg per day. The amount of sugar can be increased to meet the increased demand for carbohydrates, but most of the carbohydrates should be represented by complex carbohydrates. They are more nutritious and, in comparison with food containing sugar, include more B vitamins needed for energy metabolism, as well as more dietary fiber and iron. Many foods high in sugar also contain a lot of fat.
In addition to carbohydrates, athletes should consume enough calories. Consumption of a diet that reduces energy production will worsen endurance due to depletion of muscle and liver glycogen. Adequate intake of carbohydrates is also important for athletes who, with increased physical exertion (eg, wrestling, gymnastics, dancing) have reduced body weight as a result of negative energy balance.
Those wishing to reduce body weight and consume low-energy foods are prevalent among athletes exposed to heavy loads. Negative energy balance can reduce their performance due to deterioration of acid-base equilibrium, reduced levels of glycolytic enzymes, selective atrophy of type II muscle fibers, an abnormal function of the sarcoplasmic network. Adequate intake of carbohydrate food can reduce some of the damaging effects that result from limiting energy intake to the muscles.
For athletes participating in competitions requiring superhardness (lasting more than 4 hours), the need for carbohydrates is very high. Saris et al. Studied food consumption and energy costs during the "Tour de France" cycling race. In this 22-day race for 2,400 miles, cyclists consumed an average of 850 grams of carbohydrates per day or 12.3 g-kg per day. About 30% of all consumed energy was provided by high-carbon beverages. Brounc et al. Assessed the impact of the simulated study of the Tour de France on food and fluid intake, energy balance and substrate oxidation. Although cyclists consumed 630 g of carbohydrates (8.6 g-kg per day), 850 g of carbohydrates per day were oxidized (11.6 g-kg per day). Despite the arbitrary intake of regular food, cyclists have not received enough carbohydrates and calories to compensate for the increased expenditure of their energy. When 20% of carbohydrate drinks were added to the diet, carbohydrate intake increased to 16 g-kg per day, and carbohydrates oxidized to 13 g-kg per day.
Athletes who specialize in super sports and require an additional 600 grams of carbohydrates a day to meet their carbohydrate and energy needs must supplement their diet with high-carb drinks if they do not eat enough. Saris and Brauns recommend such athletes during training sessions and competitions to consume 12-13 g of carbohydrates per 1 kg of body weight per day. They also believe that this portion gives the maximum contribution of carbohydrates to energy supply during extreme loads that require greater endurance.
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