Water is the most plentiful compound in the human body. All biomechanical reactions occur in water, and the water is an active contributor in these reactions. Water is the most important nutrient for the human body.
In line with oxygen humans need water to survive. The human body is made up of 2/3 of water, which means it is vital that to take in as much water as you can. Water practically fills every space in the body’s cells and even between them. Water molecules don’t only fill space in the cells; it also helps form structures of macromolecules such as protein and glycogen. Water is deemed to be the primary fluid in the body, which serves as a solvent for minerals, vitamins and glucose and many other nutrients which are required for the body. Drinking water regularly helps keep our bodies healthy, and it is essential for many functions of the body for example it helps with digestion, regulation of body temperature, blood circulation, the carrying of nutrients and oxygen to the cells within the body, and it also helps to remove toxins from the body. There is no system in our bodies that does not depend on water from energy production; joint lubrication to reproduction water is an essential nutrient.
Most importantly consuming water throughout the day will prevent dehydration. By consuming water daily it helps the body maintain its regular functions easily and effectively.
A 2% loss in water surrounding our cells can result in a 20% drop in energy levels, this leads to a drop in blood volume, when this occurs the heart has to work harder in order to move blood through the bloodstream. Consuming water regularly keeps the body hydrated. Dehydration can occur in any athlete and can have detrimental effects on their body’s functions. When an athlete is dehydrated their body has to work twice as hard to ration and distribute the amount of water available. Staying properly hydrated can delay fatigue and muscle soreness. Sweat evaporation provides the most important possibility of heat loss during vigorous exercise in warm hot weather, for that reason sweat loss can be important. As well as containing water sweat also contains electrolytes, which are also lost during vigorous exercise.
It has been proven time after time that athletes are using ergogenic aids, to aid their performance in any slight way at all, in the hope of achieving an edge on their opponent. Some people tend to classify Ergogenic aids as only drug use, and there are techniques used in sport to increase energy production and performance. There are those which are used regularly and safely e.g. nutritional and psychological, but there are these types of aids like electrolyte solutions vitamins and stress management that are over looked more so than for several years are the pharmacologic and physiological aids, such as doping and steroids etc. Water is classified as an ergogenic aid, because when a well hydrated athlete for example in a football match, is up against an athlete which did not take on as much fluid, then the better hydrated athlete already has an edge over their opponent. Throughout this review it aims to address the rationale behind volume of fluid intake, the electrolytes and amount of sodium (Na+) needed to rehydrate athletes in enough time to regain hydration before their next training session.
Water and electrolyte balance are critical for the function of all organs and, indeed, for maintaining health in general (Sawka, 1988 & Mack et al, 1996). Water is the intermediate for biomechanical reactions within cell tissues and is necessary for maintaining an adequate blood volume and consequently the integrity of the cardiovascular system. The body reallocates water within its fluid compartments so that it can provide a reservoir to reduce the effects of water shortage. People often mistake being dehydrated during exercise in the heat to the difference of thirst and their fluid requirements. Athletes perform physical activity throughout a range of environmental conditions, for example, the temperature, humidity, the sun and wind exposure. All depending on one person’s metabolic rate, the environmental conditions plus the clothes in which the athlete is wearing during exercise can have and stimulate significant rise in body temperature. Because sweat is a hypotonic solution, in heat-acclimatized distance runners have low sodium chloride content, but sodium chloride losses during prolonged exercise are comparatively minor, in which they do not pose a threat to an athlete’s health as does the dehydration that attends the sweat losses. Consequently, Costill and Miller (1974) have stated that ‘during prolonged, heavy sweating, the need to replace body water is greater than any immediate demands for electrolytes’. When exercising in excess heat, and when the body temperature increases too much then performance will be reduced, an example would be the increase usage of muscle glycogen, which will potentially speed up fatigue. Due to the result in body temperature increasing this can have a consequence effect in premature fatigue, in fact due to the effect of an increase in temperature upon the brain.
Sweat is invariably hypotonic relative to plasma, and the primary electrolyte present is sodium, the major cation present in the extracellular space (Maughan et al, 2000). Water is not the only source of fluid lost when sweating, electrolytes and other solutes are also lost. When an athlete exercises in warm weather and a huge amount of sweat it lost then this may lead to an increase in plasma osmolality and to hypernatraemia.
Athletes may tend to think that training in a cooler environment may reduce their risk of dehydration, this in fact is not the case as, Rehrer and Burke (1996) has reported mean sweat rates of 1000ml h71 for football players at an ambient temperature of 108C, with a slightly higher mean sweat rate (1200ml h71) at 258C. This suggests that average sweat rates in cool conditions may not be very different from those in warmer environments this could possibly be because of different intensities in which the athletes are training and even the type of clothing worn by the athletes.
But there is little evidence to prove that training in cooler environments reduces sweating. There have been a few studies in which athletes were tested for their fluid losses on warmer conditions as it is harder to maintain fluid intake therefore there are more studies in this area more so than in cooler conditions.
Maughan et al (2004) also proposed a similar study which showed sweat losses when training in a cooler environment from those who trained in a comparable standard training but in much warmer conditions. There are some huge factors to accommodate with sweat loss, the intensity of the exercise, the state of fitness of the athlete and of course heat acclimation. Greenhaff and Clough (1989) suggest that, there is also a large inter-individual variability in both sweating rate and sweat composition, and this is apparent even when these factors are kept constant. Within Maughan et al, (2004) study there was also a comparison of salt and electrolyte composition in both warm and cooler conditions. It is evident that athletes training in warmer climates prefer to consume cooler drinks and at a larger volume, than those training in cooler climates. Maughan et al (2004) shows that the athletes training in cooler climates consumed lower levels of fluid and in his study while the thirst sensation was low during training in the cold, the extent of dehydration which occurred in the athletes was the same as those who were training in a warmer climate.
Recently Coyle (2004) argued that the tolerable level of dehydration will depend on a number of variables, including the environmental conditions, the exercise duration and intensity, and the aerobic fitness and state of heat acclimation of the individual. Coyle (2004) and other researchers have shown that dehydration in any athlete of 1-2% may be tolerable in some temperature environments, but the loss of 2% may be more tolerable in cooler environments. Adolph et al (1948) in the earlier studies also suggested that completely replacing fluid losses in any athlete is not essential and that when the environment was less challenging (cooler) that their levels of dehydration were acceptable. Training in cold or hot climates any athlete who is already dehydrated by 2% pre-exercise may not be able to tolerate the loss of fluids when he/she begins exercising, which leads us to believe that the athlete should be well hydrated before exercising. The aim for any athlete is to minimise any risk to health through dehydration, while trying to maximise their exercise performances.
It is important for athletes to keep an eye on their dehydration state and the amount of fluid intake they have, they need a simple way of doing this. They cannot carry around a huge machine with them to training and matches. In today’s society there is no universally accepted field method that exists to determine if an athlete is well hydrated or not, but in saying that there are different techniques have been examined. It has been known to the athlete that one way of keeping an eye on their fluid intake is the use of urine colour, it is easy to use, and they can carry it in their training bags, although it is not supported by any serious scientific paper, it is still useful for athletes to keep themselves in check. It has been once said that you should monitor urine colour and your frequency of urination, pale yellow urine is a good sign that your are hydrated and that frequent urination is another positive sign that the athlete has a good amount of fluid within his/her body. Within Maughan et al (2004) study they show a mean osmolality from the athletes urine sample pre training was 872+177. Within the 17 elite soccer players, 6 players provided a high rate of osmolality, which shows that these players prior to the test has consumed a large volume of fluids, apart from these 6 players there was no significant difference between the pre-exercise urine sample and the volume of fluid consumed during training.
Athletes who have exercised for a considerable amount of time and have lost a substantial amount of fluid and electrolytes are generally advised to rehydrate as soon as possible post exercise. It is essential that athletes who may have to conduct two training sessions in one day, that they have to replace the necessary fluids to rehydrate. It has been shown that to accomplish complete rehydration is to consume a greater volume of fluids that were lost during your exercise. Each body water compartment contains electrolytes, their concentration and compositions are significant for moving fluid between intracellular and extracellular compartments and are also used to maintain membrane electrochemical potentials. Mitchell et al (2000) showed that their primary findings into their investigation was that when 25 mM Na+ was consumed and compared to 50mM Na+, the Na+ content of the rehydration beverage did not influence whole body rehydration, on the other hand the ingestion of 150 vs. 100% of fluid lost significantly improved the level of rehydration. With the findings gathered they did not show any interaction between Na+ and volume was experimental. Although, the difference was in Na+ content and volume as it showed to have an effect on the level of extracellular vs. intracellular rehydration.
There have been rehydration protocols which have all been designed to investigate the influence of electrolyte content and the fluid volume on speedy rehydration. There have been quite a few conflicting findings in regards to the amount of Na+ and volume necessary to produce the optimal rehydration. The protocols in which Maughan et al (2004) and Sheriffs et al (1996) presented included the ingestion of large volumes of fluid in a really short period of time their athletes consumed 2-3 liters of fluid in approximately 30-60 minutes. In comparison with Maughan and Sheriffs study, Mitchell et al (1999) study had their athletes consume either 100 or 150% fluid replacement over a 2.5 hour stage, which was consumed in consecutive intervals of 30 minutes. A number of studies have shown that, fluid replacement with any amount of Na+ less than 25 mM will not completely rehydrate any dehydrated athletes, therefore these findings show that the optimal level of Na+ is somewhere above 25 mM, in saying that Mitchell et al (1994) showed that when doubling the consumption to 50mM of Na+ that it actually did not improve rehydration. This leads us to believe that Na+ may not help with rehydration as shown in Mitchell et all (1994) is shows that the relatively large Na+ deficit in the high volume and low Na+ condition did not interfere with fluid restoration, since 100% rehydration was achieved. As there seems to be a disagreement in whether high or low Na+ consumption with a high or low volume consumption is in adequate, then this may be because in Mitchell ‘s (1994) study with 25 and 50 mM levels of Na+ were used, it may be due to 25 mM is a sufficient amount of Na+ and when this level of Na+ is increased that it may become a more powerful factor in extracellular rehydration, but scientists have to be aware that the subjects may not be able to consume a high amount of Na+ concentration, as it may not be palatable for them. Shirreffs et al (1996) found that subjects were still hypohydrated 6 hours after ingestion of a low sodium drink in an amount equivalent to 150 and 200% of their body weight. And is another case it showed the opposite effect when a high sodium drink was consumed.
Kovacs et al (2002) showed in their study that a high rate of fluid ingestion resulted in a higher rate of plasma volume and fluid balance restoration during the first 4 hours of rehydration, keeping in mind that there were large amounts of urine excreted. Also in this study is was shown that when consuming a high carbohydrate-electrolyte solution at either a high or low rate did not result in a complete rehydration after the 6 hours allowed for recovery. Also in Kovacs et al (2002) study showed that sodium balance was negative in both of their trials, which suggests that sodium output was greater than sodium replacement. This shows an indication why the subjects were still dehydrated at the end of the experiment, even when the participants consumed fluids corresponding to 120% of sweat loss.
Athletes need to take a much more controlled approach on their water intake whilst exercising. For example the ironman triathlon, athletes were encouraged to take on as much water as they possibly could when on their bikes. When the race was finished, a study bySpeedy et al (1999) reported that 18% of the 330 race finishers at the 1997 New Zealand Ironman triathlon were hyponatremic. This was due to excessive water drinking throughout the triathlon. In further studies of other triathlons also showed that some of the athletes were also hyponatremic. Hypernatraemia is caused by over hydrating in water and due to this the loss of Na+ from within the body is much high, John W Gardner (2002), showed that on a warm summer days in the military in 1995 there was a series of 9 cases of Hypernatraemia in healthy Marine Corps, some of their sodium levels dropped to a staggering 125mmol/l, whereas normal Na+ levels should range from 136-145.
In conclusion it has been demonstrated that all athletes become dehydrated when exercising if they have not consumed enough fluids. Studies have shown that to regain 100% rehydration you need to consume >25 mM of Na+ and a 150% of fluids which are lost when exercising. When training sessions and competitions are days apart, it is easy for an athlete to regain rehydration, by consuming fluids and foods which provide fluids. The majority of papers show that dehydration can be harmful to athletes. Therefore they must replace fluids, electrolytes and Na+ to regain rehydrate. Although throughout my research there was some confusion into how much Na+ is needed to be completely hydrated, therefore I feel like there is much needed research into the amount of Na+ and fluid volume needed to rehydrate. Because hypernatraemia is a huge factor in athletes today, it is documented that athletes should have a controlled intake of fluids before, during and after training.
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