Hydration in Football
The problem of Dehydration
Dehydration as low as 1-2% of bodyweight can impair both exercise performance and mental functioning; both of which are crucial components of high intensity intermittent sports such as football. Dehydration greater than 3% has the potential to be extremely dangerous and therefore measures should be implemented to reduce this amount of mass loss.
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Hydration and Football
Research has shown that athletes commonly become dehydrated during training and competition, therefore, efforts to maintain a level of normal hydration (i.e., not dehydrated or over hydrated) are vital when aiming to optimise performance and avoid health problems. Decades of previous research has focused upon a variety of interventions to examine both the negative effects of dehydration and possible strategies to counteract these effects upon the performances of high intensity exercise and skill execution. It is generally assumed that consuming adequate volumes of fluid at regular intervals during exercise easily prevents dehydration; however, in football it may be difficult to achieve such aims due to the stop and go nature of the sport. Additionally, the high intensity periods common in football (>80% max) have been shown to reduce the rate at which fluids are emptied from the stomach into the small intestine (gastric emptying). Thus, the exercise intensity as well as other factors such as; hydration status, the temperature, the volume, and the composition of ingested beverages, all have a significant bearing upon the rates of gastric emptying and the amount of fluid that is subsequently absorbed into the blood.
Volume Consumed: The most important factor concerning the rate at which a fluid is emptied from the stomach is the volume ingested. The rate at which fluid is emptied from the stomach is proportional to the volume consumed, however, an upward limit of 600 ml of ingestion has been proposed.
Type of Beverage: It is generally accepted that a glucose/sucrose beverage of 6-10% carbohydrate (i.e. between 6 and 10 g of carbohydrate per 100 ml of drink) is appropriate for ingestion during exercise. Although increasing the carbohydrate content of a beverage above 10% tends to slow its absorption into the bloodstream, addition of carbohydrate to a sports drink provides an energy source which can account for a large percentage of the energy used during exercise, whilst simultaneously addressing the issue of hydration. Much interest has focused upon the addition of carbohydrate, in the form of glucose, when aiming to examine the effectiveness of certain beverages during exercise; however, other beverages such as plain water have also been investigated.
Plain Water: Research recommends consuming plain water for any exercise lasting less than 60 min or where weight loss is the main goal in training longer than 60 min but not exceeding 90 min. During competition, drinking plain water will obviously help a player to rehydrate as compared to not drinking at all; however, water also increases urine production. The amount of urine produced by the body partly depends on the level of electrolytes in the blood; as sweat contains both water and electrolytes (mainly sodium but smaller proportions of chloride and potassium). If the rehydrating fluid contains only water, thus not replacing the electrolytes lost in the sweat, then the level of electrolytes in the blood will drop due to a dilution effect, therefore, urine production will increase and the athlete delays rehydration. One study highlights this point; whereby three hours of cycling in a warm environment when participants ingested either water or a properly formulated sports drink resulted in better hydration and less urine production when the sports drink was consumed.
Carbohydrate-Electrolyte Provision: A great deal of research confirms that sports drinks are superior to water at improving performance during both intense and prolonged exercise. As plain water provision is not supported by performance and skilled studies, and a lot of literature supports the use of carbohydrate supplementation in delaying fatigue, it is therefore not surprising that carbohydrate-electrolyte solutions are amongst the most commonly used supplements in sport. The primary goals of consuming a carbohydrate-electrolyte beverage during competition are to replace the water and electrolyte losses incurred during exercise, whilst simultaneously providing energy to supplement the body's stores; both of which act to delay fatigue.
The addition of Protein to Carbohydrate-Electrolyte Drinks: Research indicates that drinking a carbohydrate and protein beverage during training can also enhance muscle synthesis, as well as maintain hydration and energy provision, even when subjects have been consuming regular meals during the day.
Summary and recommendations
Due to the interaction of various factors including weather, clothing and player individualisation, it is difficult to recommend specific hydration regimes due to the variation in sweat rates that exists. However, it must be acknowledged that thirst is not a good enough indicator to prevent dehydration as player's can already be 2% dehydrated by the time that they become thirsty.
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