Running a Marathon | How much Fluid Should you Drink during a Race?

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By janderson99

© janderson99-HubPages

Despite the huge number of people running long distances these days there is no clear advice on how much water or other fluids you should drink during the event.

Does too little harm your performance?

Does too much slow you down or worse threaten to harm you or even kill you?

So what is a right amount to drink during a long running event such as a marathon?

What strategy should you use to keep hydrated and maximize you performance?

There has been considerable variation in attitudes and expert advice and the thinking has changes over the last 15 years.

In the late 1990's the general advice was that runners should begin drinking early in the race and continue to drink at regular intervals (at all the drinking stations; as much as you can). The idea was to avoid dehydration at all cost.

Runners were advised of the need to replace water lost through sweating, or to drink the maximal amount of water that they could. The concept was to stay ahead of your thirst to avoid dehydration sneaking up on you. By the time you started to feel thirsty you may have already started to get dehydrated. Your thirst response lagged behind your actual need for water to avoid dehydration. So the advice was to drink early and regularly as much as you could tolerate.

But recently, several marathoners have actually died as a result of complications from drinking too much fluid, because of a dangerous condition referred to as hyponatremia, or water intoxication. The danger in this condition is due to low blood sodium levels caused by consuming too much water. If you consume more water than you lose through sweating and breathing, and urinating, you can dilute your blood’s sodium levels. The process of osmosis then transfers water from the blood into the cells of the body to maintain sodium levels. The extra water causes the cells to swell, and if the brain cells are affected, it can be fatal.

Many experts have seen the warning signs and marathon runners are now being advised to drink less and to drink only when thirsty. However recent research has shown that many runners are not heeding this advice which has been poorly communicated.

Research published in the journal Sports Health, showed that most of the 419 runners had no plan or strategy about fluid consumption during the race. About two-thirds of the runners aid that they were not worried about the possibility of developing hyponatremia.

A second survey, published in the British Journal of Sports Medicine, showed that 50% of runners appeared to be drinking too much fluid during the race. Only about half of the runners only drank when they felt thirsty. The other half drank fluid using a preset schedule of some kind, and almost 10 % said they drank 'as much fluid as possible.'

A research study on the exercise-associated hyponatraemia in the London marathon was initiated after 14 runners were treated at hospital with symptoms of hyponatraemia several hours the finish the 2003 London Marathon and one young male runner died from severe hyponatraemia complications after finishing a London Marathon event.

The study of 88 volunteers showed that about 12% developed low sodium levels in their blood and symptoms of hyponatraemia. The affected runners had consumed more fluid that the other runners and gained more weight than did non-hyponatraemic runners.

A recent study of runners in the 2010 London Marathon examined hydration strategies used by runners assessed using registration questionnaires.

Most the runners in the survey knew about the need to avoid dehydration and had developed a plan for the race. However about one third of the runners planned to drink volumes of water that posed a risk of hyponatraemia. About 20% or the runners were planning to take a drink from all 24 water stations during the race. Only 25% had a strategy to only to drink when thirsty. About 70% of runners were aware hyponatraemia or low sodium levels, but only about 35% knew what caused it and how it related to their drinking strategies.

Clearly the old 1990's misconception that you drink to stay-ahead of your thirst still persists amongst a large number of runners. This out-dated idea is contrary to modern research, and can be dangerous.

Drinking when you’re thirsty is the recommended strategy to protect yourself against both hyponatremia and dehydration. Despite earlier 'myths' - Thirst is a very good and reliable indicator of the hydration status of your body and provided there are lots of drinking stations this is the best strategy - Drink only when you feel thirsty.

© janderson99-HubPages

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