A Review of the Role of Carbohydrates in the Sports Nutrition of Soccer Players

Background & Aims: Soccer is a very dynamic and fast team game with a richness of movement, which is in the group of multi-structured sports games; Soccer is a sport characterized by numerous, complex, and dynamic kinematics activities with rotational or non-rotational movements (1). In this sport, a high level of points can be achieved only in planned training conditions (2). Sports scientists have focused on approximate explanations for excellent athletic performance; or they are looking for factors that affect the athlete's interaction with their environment (for example, diet, and exercise). By understanding these factors, environmental conditions can be manipulated to optimize athletic performance (4). Nutrition strategies are one of the most popular and accessible ways to improve performance, recovery and improve physiological changes in certain sports such as Soccer (5, 7). Despite a correct understanding of the physiological demands of Soccer, and the relationship between preparation and nutritional performance, the eating habits of soccer players are often associated with a lack of training and a lack of knowledge of the scientific methods of sports nutrition (8). The characteristics of contemporary professional Soccer increase the physical demands during the game as well as more matches per season. Now more than ever, aspects of optimizing athletic performance have received much attention from Soccer players and coaches. In this, nutrition plays a special role; because most elite teams try to provide adequate nutrition to ensure maximum performance while ensuring faster recovery from competitions and training. In addition to regular nutrition based on nutritional recommendations, sensible use of dietary supplements may also play a role in optimizing Soccer performance (9). Nutrition of Soccer players is an important issue and its knowledge can help increase the quality of this popular game and prevent possible health problems and injuries in players (10); which shows the importance of applied research on the effect of nutrition on the level of health and athletic performance of soccer players. In view of the above, the purpose of this study was to review the role of sports nutrition in the sports performance of soccer players with emphasis on the role of carbohydrates as one of the macronutrients applied to the sports performance of soccer players. Methods: In the present systematic review study by searching the information obtained from the databases of Google Scholar, Pabmad, etc. from 2000 to 2022, studies that examined the effect of carbohydrates on the physical performance and physical fitness of footba soccer players. Were searched with the keywords Soccer, sports nutrition, macronutrients, carbohydrates and sports performance. The selected studies were reviewed by 3 authors and out of 124 selected articles, 35 articles that met the entry requirements were selected and used. Results: The importance of carbohydrates increases with increasing intensity of exercise, but due to the limited carbohydrate reserves in the body, the reduction of liver and muscle glycogen with intense exercise for a long time is a determining factor (24) in the performance of team sports such as Soccer. . Proper glycogen content plays a major role in athletic performance. As shown by physiological measurements performed in a Soccer match, the bioenergy of this particular sport is quite comprehensive and includes high oxidative capacity, high glycolytic capacity as well as high dependence on the degradation and re-synthesis pathway of ATP and phosphocreatine. Is (25). Due to the high glycolytic component, the content of muscle glycogen is important in Soccer. Proper carbohydrate intake is a key element in dealing with a lot of exercise among professional athletes. Consumed carbohydrates, which are stored as glycogen, are the source of muscle energy during exercise. Carbohydrates stored as glycogen in the liver and skeletal muscle are an important source of energy, both in competition and in training, where carbohydrate availability is a limiting factor during long-term physical activity. Can be effective in athletic performance. Based on the analysis of Soccer matches, the intensity of players' activity is at the level of 70-80 VO2max. Long-term effort at this level is mostly based on glycogen as a substrate for energy metabolism. Adequate carbohydrate intake before, during and after exercise helps maintain and restore glycogen stores, which can affect muscle fatigue and exercise performance (9). During a Soccer season, athletes tend to play intense and light competitions such as crucial and qualifying games. Muscle glycogen stores are a determinant of performance during exercise, and manipulating carbohydrates during the Soccer season to increase muscle glycogen stores can improve the performance of top Soccer players (26). Consumption of carbohydrate courses, depending on the intensity of training and competitions, should include more carbohydrates when competitions or workouts need more intensity and less carbohydrates when they need less intensity. The day before the game (MD-1) is one of the most important times to load up on carbs. Assuming that players have properly loaded muscle glycogen on the day of the match, the role of the pre-game meal should primarily be to promote pre-game hepatic glycogen storage, a goal that is more important for late morning or lunch. In fact, hepatic glycogen may be reduced by up to 50% after one night of fasting and may not fully recover by early evening depending on the frequency and dose of CHO (41). It is wise to allow players to consume the carbohydrate sources they enjoy during MD-1, as long as there are sufficient amounts to reach 6 g/kg (44). From a practical point of view, it is recommended to consume water during and after food before the game until reaching the competition site. Consumption of carbohydrate drinks should be prohibited after meals and re-consumed only after reheating and 5 to 10 minutes before the start of the race. This strategy is to reduce the likelihood of recurrent hypoglycemia in the first 10-15 minutes of the race (44). Carbohydrate nutrition during exercise is likely to improve the performance elements of the race day if fed at 30 to 60 grams per hour (45). Such feeding rates improve the physical aspects of performance such as total running distance, sprinting distance as well as technical performance such as passing, dribbling and shooting (46-49). Taking into account the warm-up time (for example, 20 to 30 minutes) and the game itself (for example, 90 to 95 minutes), this amount corresponds to the absolute dose of CHO equal to 60 to 120 grams per game. Due to the practical problems of refueling during the game and the extent of CHO exogenous oxidation depends on the CHO feeding pattern (50). In this regard, Anderson et al. Suggested that players may consume CHO at the beginning (20-30 g) and end of the warm-up period (20-30 g), between breaks in two halves (20-40 g) as an opportunity to consume Higher doses of CHO will benefit due to the increase in steady-state consumption time and, if possible, the second half (20-30 g) (39). However, such a diet (and indeed the CHO strategy of the optimal race day) has not been experimentally tested. Regarding muscle glycogen re-synthesis, the general consensus is that consumption of 1.2 g / kg / h CHO with a high glycemic index for 3 to 4 hours is optimal to facilitate short-term glycogen re-synthesis (64). The important point is that post-match feeding should start immediately after the game (ie in the locker room) because this is when muscle is most receptive to glucose uptake and glycogen synthesis (39). Due to the time required to complete muscle glycogen (24 to 72 hours), there is also a need to consume enough CHO in the day (s) after the race, often referred to MD + 1. Conclusion: Given the role of CHO as an important substrate for glycolytic and aerobic systems in Soccer, the aim of this study was to provide an overview and theoretical framework of CHO consumption strategies in Soccer. According to research, CHO consumption plays an important role in the quality of training and also the performance of soccer players on the day of the match, which varies according to the physical condition of the athlete, the athlete's position and also the level of competition. CHO intake should be adjusted according to the athlete's training schedule and season. Also, for optimal muscle and liver glycogen stores for athletes' performance, it is necessary to observe nutrition before, during and after competitions and training according to the intervals between competitions and training of athletes. However, nutritional recommendations for athletes of the opposite gender and lower age groups, such as adolescents with developmental needs, may require nutritional revisions, which require further research due to limited information. . Given that Soccer competitions are different according to the level of competition and also the metabolic needs of Soccer according to the conditions of Soccer players (gender, age and position of the player), it shows different physiological needs of these athletes; which indicates the need for further research in this regard.