Sports and Hydration: What you should know

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Proper hydration means getting the right amount of water and electrolyte before, during and after exercise. About 60% of your body is water and thus plays a vital role in every bodily function such as joint lubrication as well as transporting nutrients to give your body energy and health. When you exercise, you lose a lot of fluid as much as a litre or two an hour mainly through sweating and breathing. Thus, if you do not replace the fluid you can get dehydrated and this can have a negative effect both on the sporting performance and health of the athlete. Usually a dehydrated athlete will present with symptoms such as:

1. Increased resting heart rate

2.Impaired aerobic capacity

3.Impaired concentration and decision making

4.Slow reaction times

5.Impaired judgement

6.Early fatigue

Adequate hydration is even much more important in Tropical climates such as Nigeria where athletes are exposed to humid conditions for most part of the year. Asides from the ambient temperature other factors which can determine the extent to which an athlete should hydrate include the type of sport, the health status of athletes and the metabolic rate of the athlete.

From a sports perspective, a loss as little as 2% of your body weight in fluids can cause a significant deterioration in sporting performance. In fact, dehydration of more than 3% of your body weight could predispose you to severe issues such as heat exhaustion and heatstroke. Therefore, for any athlete minimising fluid loss to not more than 2% of your body weight is a good rule to optimise performance.

Fluid replacement strategies

Before exercise: It is important to note that you should be fully hydrated before exercise to perform well during the game and also to avoid a fluid deficit during the game. Consequently, if you are dehydrated before exercising your core temperature will rise faster and your heart will have to work harder than usual. This invariably will affect your performance and could also lead to heatstroke. Drinking before a game is even much more important in sports where an opportunity might not exist for a water break during the game.

Though there is no consensus on how much fluid one can take before exercising, it is generally advised that you aim to drink around 500ml of fluid at least four hours before you exercise. In the 10 to 15 minutes before you exercise, top up your fluid levels by drinking about half this amount again. It is important to note that these amounts of fluid should be adjusted to the weather conditions and how much you sweat.

During the game: Fluids consumption during exercise is necessary to replace body fluid deficit while also making the athlete feel comfortable. You will rarely need to drink water during an exercise session that lasts less than 40 minutes, but athletes oftentimes report a feeling of satisfaction just by gaggling their mouth with cold water. However, studies have shown that the longer the workouts get (usually above an hour) the more the dehydration level rises and invariably a significant deterioration in performance.

While athletes are often advised to consume fluid only when thirsty, this might not be a reliable guide. Why? The rule guiding the opportunities to drink fluids in many sports may not correspond with the times that thirst hits. Instead, a feasible and targeted approach is to develop a fluid plan that is peculiar to the sport, the individual athlete and the ambient weather conditions.

As a starting point, the athlete should try to drink at a rate that replaces enough of their sweat losses so that the overall fluid deficit for a training session or competition is kept to no more than about a 2% loss of body mass (i.e. 1.0 kg for 50 kg person, 1.5 kg for a 75 kg and 2 kg for a 100 kg person).

It is important to note that in warm environments the risk of impaired performance and associated heat illnesses secondary to dehydration from sweat loss is very high. In fact, the rate of sweat loss is very high and it is not always practicable to drink sufficient fluid to replace the fluid deficit. What is practicable in this instance is simply to minimise the rate of dehydration by ensuring water breaks during the competition.

What if I over-hydrate?

It is not uncommon to see athletes taking more fluid compared to sweat loss. If this is not checked, water intoxication occurs leading to a potential life-threatening problem called dilutional hyponatremia (dilution of blood sodium concentration). This will present with symptoms such as nausea, vomiting, confusion, seizures, and coma.

Rehydration after exercise

A core component of recovery following sport is the replacement of water and salt loss via sweating. It is expected that athletes drink about 1.2-1.5 litres of fluid for each kg of weight loss in training or competition to compensate and fully restore fluid losses

Practical ways to access and manage rehydration

1.   Start the exercise session hydrated. Checking your urine colour is a good approach to access the extent of hydration. If your urine colour becomes darker than what is normal for you, you are likely not drinking enough. Having a urine colour chart will be helpful

2.   Develop an individualised drinking plan. Having an understanding of how much fluid is lost via sweat will help provide an estimate of how much fluid should be replaced. The sweat test provides a practical way to get this done and this entails:

a. Before exercise weigh yourself nude or wearing minimal clothing and barefooted.

b.     After exercise, towel dry and weigh yourself again before eating, drinking and going to the toilet.

For example: Pre-exercise weight= 80kg

Post-exercise weight= 78kg

Fluid deficit: 80-78=2kg

c.      Estimate the weight of any fluid or foods you have consumed during the workout. For instance, a 300mL of water=300g or 0.3kg

d.      Calculate the sweat loss. This is calculated as: 

 Sweat loss (Litres) = Body mass before exercise (in kg) – Body mass after exercise (kg) + weight of fluids/foods consumed.

Using our assumed values, sweat loss: 80kg –78kg + 0.3kg = 2.3kg

Thus, we have a sweat loss of 2.3kg or 2300ml

e.      To convert to a sweat rate per hour, divide by the exercise time in minutes and multiply by 60.

f.      Your weight deficit at the end of the session provides a guide to how well you hydrated during the session, and how much you need to rehydrate afterwards.

When do I need more than water?

Workouts that elicit fatigues and last for more than 1 hour will require the consumption of fluid with carbohydrate and sodium contents. The use of commercial sports drink with electrolyte and carbohydrate content of about 4-8% (4-8 g/100 ml) allows carbohydrate and fluid needs to be met simultaneously in most events. This carbohydrate can come from sugars such as sucrose, fructose, and glucose).

In low resource settings such as Nigeria where the average athlete may not be able to afford commercially prepared sports drink, an oral rehydration solution will suffice (ORS). ORS is an effective solution for hydration because it contains the right balance of sodium and glucose.

Finally, just as training and competition strategies should be individualised based on the uniqueness and needs of the athletes, so should their drinking and eating choices be individualised also. Thus, athletes and athletes support personnel should adapt these recommendations to their realities.

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