Proper hydration during exercise

One of the most important factors which determines the success of an athlete’s performance is how much water he or she loses during an event and how successfully these fluid losses are replenished during and after exercise.

Strenuous physical exertion results in massive losses of water through sweat and can lead to dehydration, which in turn can cause fatigue and serious negative effects, including hyperthermia, kidney failure, collapse and even death.

Athletes that compete in hot weather are particularly vulnerable to dehydration. High temperatures and humidity (which suppresses sweating) can cause the body to overheat when an athlete is doing strenuous physical exercise.

Studies indicate that water losses of as little as 2% of the athlete’s body weight can already impair performance by as much as 45%. It is, therefore, in the best interest of any athlete to ensure that he or she is well hydrated. Monitor your fluid losses by weighing yourself before and immediately after each exercise session.

Drinking water and other liquids during exercise helps to lower the core temperature of the body, increases blood flow to the skin which promotes sweating, and regulates overall body temperature.

Loss of electrolytes
Sweating also results in a loss of compounds called electrolytes (sodium, potassium, calcium, magnesium and chloride) from the body.

Sodium is probably the most important of the electrolytes in relation to sports performance. When the body loses sodium due to exertion and the athlete uses low-sodium drinks such as water and cola drinks for hydration purposes, a condition called hyponatraemia (low sodium levels in the body) may develop.

When coupled with dehydration, this loss of sodium can land an athlete in the emergency tent at the end of long races, which are often undertaken in hot weather. These exhausted, dehydrated athletes are generally treated with saline (sodium-containing) and glucose drips.

Although it is not generally regarded as essential for all athletes to drink fluids containing salt or sodium, participants in ultra-marathons, which last for eight hours or longer, can benefit from using sodium-supplemented drinks, such as Energade, Powerade and other sports drinks, instead of plain water or cola and standard cold drinks or fruit juices.

How much liquid?
The amount of liquid an athlete ingests during an event depends on the type of activity and its intensity, the length of the event, the ambient temperature and humidity, the physiological characteristics of the athlete (some athletes sweat much more than others) and physical reactions to fluid ingestion (e.g. some sports drinks may cause gastric discomfort or cramps and bloating during the event).

Every athlete should determine how much liquid he or she requires for superior performance during training and not at a big event.

a) Short events
Short, non-endurance events, which do not exceed 30 minutes, do not usually require the athlete to replenish lost fluid during the event. It is, however, always important to make sure that you are well hydrated before you start exercising.

Don’t cut out fluids just before an event. If you have to ‘make weight’ and have restricted your fluid intake and used diuretics to achieve the required weight, start rehydrating yourself as soon as possible after the weigh-in. For athletes who participate in a number of short events on the same day, rehydration between events is vital.

b) Events lasting up to one hour
Start in a well-hydrated state and replenish fluid losses at the rate of approximately 150-300 ml every 15-20 minutes (Burke and Deakin, 2000). According to Burke and Deakin, the total volume of liquid ingested during an event is more important than the timing.

There are certain factors that will enhance fluid uptake during an event, such as using a cool, but not a cold beverage which contains some carbohydrate (30 to 60 g per hour) and starting to hydrate early on in the event.

No sodium replacement is usually required during shorter events, but research shows that liquids which contain sodium are more easily absorbed and taste better. Experiment with the sports drinks that are available to find out which one enhances your performance best.

c) Endurance events lasting one to three hours or longer
The same recommendations as mentioned under point b) also apply to long endurance events, but sodium replenishment becomes more important as the length of an event increases.

Athletes who compete in ultra-marathons such as the Comrades, should try out combinations of sports drinks and snacks, water and fruit juices during their training sessions to determine which regimen provides them with the optimum hydration, carbohydrate and sodium supply to sustain the extreme effort they will be making in conditions that are often hot and dry.

Don’t dehydrate yourself before an event, do drink plenty of liquids during the event, preferably those that also supply some carbohydrate so that you obtain liquid and fuel from the drink, and rather avoid ordinary cold drinks and cola beverages as they do not contain any sodium and can contribute to dehydration.

Hydrate yourself before, during and after every event and exercise session to ensure top performance and good health. – (Dr I.V. van Heerden, DietDoc)

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