Water and Sport
Efficient dehydration in sport is critical in order to produce optimum performance. By drinking water in correct quantities before, during and after sport can help minimize and delay dehydration allowing us to perform at peak levels and recover more quickly.
Optimum fluid levels promote muscle contraction and faster transmission of nerve impulses it also promotes generation of energy in the brain allowing us to think faster and better in order to respond more rapidly to the stimuli that we are presented with in our sports.
The volume and concentration of blood is vital in the transportation of oxygen and nutrients to the working muscles and depletion of waste products. Without efficient dehydration blood concentration increases making the speed of blood flow decrease, which means delayed delivery of oxygen and nutrients to the working muscles. With a delay in transportation and decrease in blood flow speed it becomes more difficult for waste products to be flushed out which is when lactic acid begins to amass in muscles causing pain, cramp and fatigue.
Dehydration also means a decrease in electrolytes, which includes calcium and sodium.
Calcium is required for muscle contraction and with absence of calcium it gradually becomes more and more difficult for the athlete to perform the techniques and skills in the manner in which they need too. Sodium also promotes absorption of water alongside glucose so with lack of sodium it is more difficult for fluids to be absorbed and utilized.
Dehydration also means a more difficult pathway for nerve impulses and a decrease in energy generation in the brain, which means it, is more difficult for us to concentrate and react both physically and mentally.
The first sign of dehydration is thirst, but by the time we are thirsty we are already mildly dehydrated, however this will already have caused a significant affect on performance as when only 2% dehydrated performance begins to be impaired. Water is easily lost in sport as we are dehydrated at even one percent and if most training sessions or competitive games last from one hour onwards it is not difficult to become dehydrated. The main cause of dehydration in sport is sweating and if we play a football match lasting 90 minutes involving constant movement between trotting, walking and sprinting then we will most definitely sweat. The more we sweat the more fluids we must replace in order to prevent dehydration. It is recommended that we sip water continuously throughout exercise rather than drink huge quantities at several periods of time; otherwise we will suffer water imbalance causing bloating in the abdominal area. Isotonic sports drinks are also recommended in order to replace not only lost fluids but also electrolytes and energy production promoting carbohydrates.
So it is vital that we remain efficiently dehydrated in sport otherwise our performance will decrease both physically and mentally. Whereas if we manage to remain hydrated we can perform to our peak levels both mentally and physically.
Electrolytes
Electrolytes are elements or chemicals required in order to enable the body and heart to function properly. The main electrolytes are sodium, chloride and potassium. Each of these electrolytes plays key role in the body especially in temperature and fluid regulation.
Electrolytes are particularly important as they maintain voltage across cell membranes especially nerve and heart, carrying electrical impulses for muscle contractions etc, from one cell to another. To do so the kidneys maintain levels of electrolytes in the blood at a constant despite the changes that may occur for example during exercise. During exercise or sport as our muscles contract constantly heat is produced therefore causing sweating which in turn means a loss of electrolytes, these electrolytes must then be replaced in order for the body to function correctly.
Fluid is lost through skin, lungs, faeces, urine, sweat and kidneys as part of every normal day life, which is why it is important to keep fluid, and electrolyte levels at an optimum. Electrolyte imbalance can cause problems such as -
- Breathing: - changes in rate and depth of breathing
- Pulse irregular: - heartbeat, changing pulse rate and faintness.
- Abdomen: - bloated with cramps
- Elimination: - unable to urinate, diarrhea or constipation
- Head and Neck: - headache, thirst, and neck pains.
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Behavior: - confusion
- Skin: - very dry.
This is why it is important to stay well hydrated with balanced levels of electrolytes. This is especially important in sport as the higher the intensity of exercise the higher the level of energy production required and therefore the higher the level of fluid replacement required due to a greater loss of electrolytes through sweat. During moderate exercise we lose more fluid than electrolytes but we need to be more careful about higher intensity exercise in hot temperatures i.e. a 5000m endurance run in 24 degree heat is very dangerous.
Gastric Emptying
Gastric emptying can be defined as the movement of liquid and or food out of the stomach into the small intestine. Before being absorbed the fluids must be emptied from the stomach to the small intestine. This is a major factor with regards to sport as the faster gastric emptying can take place the faster the required nutrients can be absorbed. There are several factors, which can effect gastric emptying.
The osmolality of the fluid consumed can affect the rate at which the fluid is emptied and absorbed. The greater the content of carbohydrates or sugar in the drink the slower the rate of gastric emptying, so the recommended carbohydrate content is 7%, which allows gastric emptying to be almost at the same rate as water.
This also means that gastric emptying is also affected by the composition and volume of the liquid being consumed, so if the liquid is low in nutrients it will be emptied more quickly, whereas if the fluid is rich in carbohydrates or other nutrients it will take longer to empty.
A volume of 250ml is recommended every 15 mins during exercise. Consuming fluids rich in concentrated sugars can be dangerous when participating in sports in high temperature environments. The temperature of the fluid consumed can also influence gastric emptying. The colder the liquid the more quickly it will be emptied and absorbed.
The main aim of fluid replacement is to –
- Maintain plasma volume in order to encourage optimum circulation and sweating in order to maintain moderate body temperature
- Fluid intake should always match fluid loss.
- Monitor fluid loss by evaluating body weight before and after exercise.
- Prevent dehydration and high body temperature, which could result in hypothermia.
The purpose of fluid ingestion during sport is to replace the fluid lost during sweating, helping to maintain plasma volume and prevent dehydration or hypothermia. Sports drinks such as lucozade, powerade etc not only replace this lost fluid but can also provide additional nutrients that prove useful for producing energy in sport such as carbohydrates and electrolytes. Consumption of such drinks can have positive effects on performance in sport however it is important that the correct drinks are consumed at the correct times during exercise.
There are 3 main types of sports drinks – Isotonic, Hypotonic and Hypertonic.
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Isotonic – Fluid, electrolytes and 6-8% carbohydrates.
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Hypotonic – Fluids, electrolytes and low levels of carbohydrates.
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Hypertonic – High levels of carbohydrates.
The fluids required during exercise will depend on the intensity of the sport regarding replacement of water and fuel for example in strenuous activity lasting for long periods of time an isotonic drink is most appropriate as it contains moderate levels of carbohydrates yet its osmolality remains around blood plasma level. Hypotonic drinks would have a lower osmolality than isotonic drinks and hypertonic drinks have a greater osmolality than isotonic drinks.
Isotonic drinks replace fluids lost by sweating and supply the body with carbohydrates to produce energy. This drink is most suitable for endurance athletes and intermittent sports as glucose is the predominant source for energy production in the body and their carbohydrate source is glucose. Isotonic drinks include – Lucozade, Powerade etc. Hypotonic drinks also quickly replace fluids but do not provide the body with any extra nutrients and are therefore suitable for athletes that experience less strenuous exercise such as gymnasts or darts players. They are also suitable for consumption during participation in sports in high temperature environments as increased consumption of high osmolality fluids can be dangerous. Hypertonic drinks contain large amounts of carbohydrates and are most suitable for very strenuous activity for prolonged periods of time.
High energy levels are required for sports such as the 5000m or marathons etc, which is why hypertonic drinks are suitable for these types of events. Hypertonic solutions are also suitable for increasing glycogen stores in the muscles. In all sports carbohydrates are generally in the source of glucose as this minimizes the osmolality preventing any negative influences on gastric emptying. Sodium is also usually present for several reasons.
Energy Bars
Sports energy bars can be beneficial to an athlete providing they are consumed at the correct time and quantity. These nutritional supplements are convenient, easily consumed, taste good and often provide enough carbohydrates to restore glycogen depletion in the muscles following training or to provide additional energy if consumed before training. However sports bars should not play a major role in an athlete’s diet because the same energy can also be gained from regular foods that we consume everyday. These bars contain major sources of carbohydrates, carbohydrate content, protein content, fat content, sodium content and potassium content. There are thousands of different brands and types of these bars all varying much like the sports drinks.
Most energy bars are aimed at athletes or people following diets or weight loss programs. Due to the fact that these bars are low in fat yet high in carbohydrates they do offer some advantages for athletes or people trying to lose weight and also for the fact that their portions are limited discouraging over eating.
Most nutritional bars have nutritional fortification in order to provide the body with its requirements, which is where energy bars differ from sweets or chocolate bars such as galaxy, snickers bars etc. Although this would seem a much healthier option in comparison to chocolate bars over consumption of these bars could cause more damage than good.
Energy bars contain extra vitamins and minerals so it is important that we monitor our vitamin and mineral intake before consuming any energy bars in order to avoid exceeding the recommended daily value for any minerals or vitamins as this could cause health problems. Although these bars contain high quantities of minerals, vitamins, carbohydrates etc the quality of the nutrition may not be as good as to that of a real meal for example a bar may contain high portions of protein, however this protein would not be as rich as the protein we would receive through eating red meat. Athletes should be careful in which bars they select as some contain stimulants such as caffeine, ginseng, guarana etc that can be dangerous if they suffer from any health conditions.
Nutritional bars are not adequate for replacing meals during the day but however would play a much better role in the diet in comparison to sweets, chocolate or crisps. So instead of eating unhealthy snacks between meals, especially if an athlete, a nutritional energy bar would be recommended. Although these bars contain the majority of athlete’s nutritional requirements they contain little calories, which is why it is important that they do not replace proper meals. Energy bars are most suitable for a small snack before training to give them a small boost of energy, and also after training to help replace the body’s energy sources.
Class Notes
Books
Sport and PE, Advanced level study. Published 1998, Kevin Wesson, Nesta Wiggins, Graham Thompson, Sure Hartigan. London
Web Sites
http://www.medicdirectsport.com/sportsnutrition/default
http://www.lucozadesport.com/lucozade_logo.gif
http://www.nulifevitamins.com/productimages/md-images/52717.jpg
http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/stomach/regions
http://www.utexas.edu/features/archive/2004/graphics/nutrition2.jpg
