Hydration in Sport

Euhydration is the state of being in water balance. The human body is made up of approximately 60% water. It is a component of our cells, blood plasma, spinal fluid, eyes and joints among many other sources. This water content of a person will vary with age and a person who is overweight will contain less water than someone who is slim. This shows the healthier you are the more water your body contains. So hydration is of massive importance in retaining health. A 2005 study suggests “a daily water intake of 3.7L for adult men and 2.7L for adult women meets the needs of the majority of persons” A person who is exercising or performing in sports may require an extra 2-3 cups per day dependant on the fitness levels of the individual. The more fit a person then the more they will sweat and the more water that requires replenishing. However, there is still research to be done regarding the necessary amount of fluid or other beverages in order to be adequately hydrated. There are several variables that need to be taken into account including hydration biomarkers, total body water and water balance.

The occurrence of involuntary dehydration and the delay in the body restoring the water loss by drinking has been described at length but still little is known about the biological mechanism. This occurs in humans when they are open to stresses like exercise, heat and cold, altitude, water immersion, dehydration and others either singly or in combination. The level of dehydration that occurs is normally relative to the degree of stress that the person has been exposed to.

Guidelines are in place that recommends that all athletes should consume enough fluid and also that carbohydrates need to be consumed during prolonged exercise this can be achieved by consuming 600-1200ml/hr fluid. During exercise, athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating (i.e., body weight loss), or consume the greatest amount that can be tolerated. It is suggested that ingested fluids be cooler than ambient temperature and may also be flavoured to enhance sweetness and promote fluid replacement. Fluids should be readily available and served in containers that allow adequate volumes to be ingested with ease and with minimal stoppage of exercise. Research has shown that many athletes do not even nearly meet these goals, research by Cheuvront and Haymes showed that many athletes consume only 400ml/hr which leads to losses of around 2.1-4.5kg during a race. Numerous laboratory-based procedures have shown that dehydration can reduce exercise ability or performance, with deficiencies generally becoming obvious when the fluid deficit exceeds 2% of body mass. After exercise protein and sodium, supplementation has been shown to aid recovery and rehydration. Laboratory-based studies have shown that even mild dehydration adversely affects mood.  Ultra-endurance events such as long-distance cycling often result in mild to moderate dehydration so little research has shown whether the relationship between hydration and mood status also exist in these sports. In one study 119 cyclists were analysed in order to determine the effect that dehydration had on their mood. Each participant was given varying amounts of fluid breaking them into three categories dehydration, euhydration, and hyperhydration. The results showed that the dehydrated participants had greater Fatigue and Pain than euhydrated participants. These findings indicate “dehydration may adversely affect mood state and perceptual ratings during ultra-endurance cycling”

Dehydration occurs in the body when there has not been enough fluid consumed or if there is an excessive amount of fluid loss. In brief, it happens when a person is losing more fluid that they are taking in/absorbing. Sweating is the primary reason for the fluid loss in most people whether it is from exercise or being exposed to high temperatures for an extended period of time. In most cases, dehydration can be easily remedied and doesn’t pose a significant threat. But chronic and severe dehydration that leads to an electrolyte imbalance can cause a surplus of problems if and if left untreated even death.

Dehydration not only reduces athletic performance but also places athletes at risk of health problems and even death. For athletes, monitoring hydration has significant value in maximising performance during training and competition. It also offers medical personnel the opportunity to reduce health risks in situations where athletes engage in intentional weight loss such as weight restrictive sports as featherweight boxing.  Simple non-invasive techniques, including weight monitoring and urine tests, have proved useful. It is recommended that individuals drink about 500 ml of fluid about 2h before exercise to promote adequate hydration and allow time for urination to remove excess ingested water. Pre-exercise hydration status can be assessed from urine markers. Short-term changes in hydration can be estimated from the change in body mass. Sweat salt losses can be determined by collection and analysis of sweat samples which can be done with patches. An appropriate drinking strategy will take account of pre-exercise hydration status and of fluid, electrolyte and substrate needs before, during and after exercise. Another method of determining hydration status is by using salivary osmolarity. This non-invasive retrieval of a sample using this method makes it an ideal method to study the biological functions during occupational, athletic or military tasks. This method is based on the knowledge that osmolarity values increase when dehydration is facilitated by sweat loss. Though this has only been proved in laboratory studies. By using this method it could be seen that the hydration status of an individual changed remarkably after 1min after a brief mouth rinse. 15 minutes was shown to be an adequate time for recovery from dehydration. For this method, the timing of mouth rinse and saliva sample collection is critical which means this method cannot be in use for reliable hydration assessment today. Hydration status is not easily measured, but sometimes hydration status is estimated from body mass change. Changes in body mass are also often used as a measure for sweat losses during exercise. The environment in which the exercise is performed has a large effect on the hydration status of an individual. The ingestion of water and loss through sweat by altering the distribution of water in the body. Loss of hypotonic sweat results in increased concentration of salt in the body fluids. Urine losses can be measured easily, but changes in the amount of water lost to the bladder and the gastrointestinal tract cannot be measured easily. Body mass change is not always a reliable measure of changes in hydration status and substantial loss of mass may occur without an effective net negative fluid balance.

Too much of a good thing, however, can have negative health consequences as insistent drinking in excess of sweating rate can induce hyponatremia. Hypohydration if sufficiently severe adversely affects athletic performance and poses a risk to health. Strength and power events are generally less affected than endurance events such as cycling and team sports that involve repeated intense efforts will be impaired. A study conducted in 2008 showed that hypohydration impairs performance and increases the risk of heat injury this study was conducted based on competitors in tennis. It showed that the consumption of appropriate fluid volumes before, during and after tennis play is important to maintain physiological homeostasis and performance. Tennis is a sport that normally has points lasting fewer than ten seconds and short to moderate rest periods between each work bout. The sequence is repeated over many hours. The study showed that tennis players could sweat more than 2.5 litres per/hour and will replace fluids at a slower rate in competition than in practice. In warm and hot environments, electrolyte-enhanced fluid should be consumed at greater than >200 mL per changeover and ideally closer to 400 mL per changeover. Tennis scientists, coaches, and players need to individualize hydration protocols to arrive at the optimal hydration strategy. Mild hypohydration is not harmful, but many athletes begin exercise already hypo hydrated. Athletes are encouraged to begin exercise well hydrated and – where opportunities exist – to consume fluid during exercise to limit water and salt deficits. In high-intensity efforts, there is no need and may be no opportunity, to drink during competition. Most team sports players do not drink enough to match sweat losses, but some drink too much and a few may develop hyponatremia because of excessive fluid intake. Athletes should assess their hydration status and develop a personalized hydration strategy that takes account of exercise, environment and individual needs.

A study was conducted in order to investigate the fluid and electrolyte balance in 20 Gaelic football players during training. This study was completed in a warm environment similar to that of the tennis study of 16°c to 18°c with 82%-88% humidity. Urine samples were taken from the players before practice determine the hydration status. Before training the players had absorbent patches applied in four different locations in order to collect sweat and analyse the sodium content of it. The mean sweat rate per hour was 1.39 litres and the mean body mass lost was 1.1%. Sodium concentrations were between 19-52mmol. On average the players did not drink enough to match the sweat rates as the hydration status was measured beforehand it is known that the dehydration happened as a result of training. This study showed a wide variation in the body mass loss, sweat loss, and sodium concentrate of the players a single hydration strategy may not be suitable for the entire team even if playing the same or similar positions.  To maximise the performance of the individual players it would be beneficial to accurately quantify individual fluid and electrolyte imbalances.

The inclusion of sodium in the rehydration solution ingested during exercise lasting longer than 1 h is recommended. Its benefits include enhancing palatability, promoting fluid retention, and possibly preventing hyponatremia in certain individuals who are known to drink excessive quantities of fluid. There is a little physical basis for the presence of sodium in an oral rehydration solution for enhancing intestinal water absorption as long as sodium is sufficiently available from the previous meal. Studies have been conducted in this in the case of a half ironman. The results of this study showed that total race time was an average of 26minutes lower than those who had not ingested salt. No change was indicated in the sweat loss and the sodium ions in the sweat. Post-race serum Na and Cl concentrations were higher. This study conclusively showed that oral salt supplementation was effective to lessen the body mass loss (reducing fluid loss) and increase serum electrolyte concentration during a half-ironman. “This positive effect on performance relates to an increase in the concentration of electrolytes in the blood, making them drink more fluids during the race (as salt stimulates thirst) and improves the water and electrolyte balances during the competition”

As well as the hydration guidelines. It is also recommended that all sporting individuals consume a balanced diet and drink adequate fluids during the 24-hr period before an event. Addition of proper amounts of carbohydrates and/or electrolytes to a fluid replacement solution is recommended for exercise events of duration greater than 1 h since it does not significantly impair water delivery to the body and may enhance performance. During exercise lasting less than 1 h, there is little evidence of physiological or physical performance differences between consuming a carbohydrate-electrolyte drink and plain water.

In order to achieve the maximum endurance and performance during training or completive events, strict hydration regime can be followed.  In order to create a beneficial hydration strategy, there are many factors which must be considered, these factors include – BMI, length of exercise, type of exercise, and pre-exercise hydration status. The biggest benefit of considering these aspects is improvement in performance and endurance during events but failing to do so can have very negative impacts on health

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