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Fluid Intoxication

DEL_5592_THUMB Photo: Delly Carr


The science of hydration has been turned on its head and if you are racing long course triathlon it is in your best interests to be privy to this new information.

Recent research indicates that endurance athletes should discredit any previous general recommendations regarding fluid intake during events. 

Such guidelines have pointed us in the direction of consuming anything from 150-300ml of fluid every 15-20 minutes during training and racing. These guidelines have encouraged drinking to a schedule and have suggested that if we reach a point where we are in fact thirsty during exercise we are already dehydrated and at risk of having left drinking too late. 

Tim Noakes, a medical doctor and well respected professor of exercise physiology believes strongly in listening to our bodies. He states, “We evolved an almost fail-safe mechanism to ensure that we do not endanger ourselves during exercise. We become thirsty and develop sensations of fatigue.” In essence the human body’s natural mechanisms will hold us in good stead. Dehydration is now viewed by many as a natural physical state and drinking too much is far more dangerous to one’s health than delaying drinking and waiting for your thirst to tell you that you need to drink.

An ever growing group of well-respected scientists believe that in the early 1980s the sports drink industry quite possibly developed a disease for which their companies could produce the only known cure. And so the concept of ‘dehydration’ was introduced, for which they provided a cure –
a sports drink to be drunk ‘as much as tolerable’.

What is dehydration? 

Dehydration is NOT a medical condition. It is rather a physiological term indicating a reduction in total body water content. When the reduction in body water causes the sodium concentration in our blood to rise, the brain detects this change and develops the symptom of thirst. Thus the sole consequence of dehydration is to make you thirsty! Only if fluid was not available at this point would fluid losses become so great that it would become life threatening (for example out at sea or in the desert). However in athletic events, fluid is available at the endless number of aid stations along the way. The issue is rather a case of too much as opposed to too little.

Sports drink companies called for the “zero
per cent dehydration rule”, encouraging athletes
to believe that if they lose even a gram of water during endurance events, they are likely to suffer consequences eventually leading to heatstroke
and overwhelming muscle cramps, but these recommendations have created the opposite problem, that is an increased risk of developing “exercise-associated hyponatreamia (EAH)” – a true medical condition and one with dire consequences.

What is EAH?

EAH is simply when the body retains too much water and is caused by overdrinking. Many individuals are able to excrete this excess fluid however a small proportion of the population (~30%) who overdrink, retain the fluid and become ‘waterlogged’. Fluid accumulates in the blood,
in the fluid surrounding cells and inside cells
themselves. Blood sodium concentrations therefore begin to fall and simultaneously brain cells swell causing brain function to become progressively impaired. Eventually, EAH will cause the athlete to lose consciousness, possibly slip into a coma and,
if left untreated, death may result.

The third consideration: heat stroke

Consider that in the years since the first official marathon at the 1896 Olympic Games in Athens, there have been very few cases of heatstroke in endurance athletes. Reports of heatstroke have been more commonly associated with short distance races, where runners are competing at high speeds. These athletes are not dehydrated and thus it is argued that heat stroke has little to do with the hydration status of an athlete and more to do with the speed of the activity.

In the sixty years between 1921 and 1981 the Comrades Marathon (ultramarathon) runners adopted an approach of very little fluid intake. Drinks were provided by ‘seconds’ as and when one felt thirsty. During this period there were no cases of EAH. It was only when aid stations were introduced every 1.6km along the course that elaborate medical care was required to be provided at the finish line. Initially it was thought these athletes were suffering from heat illness and dehydration (however paradoxical this may appear) – it was later established that most athletes were suffering from a degree of EAH.

The current model of encouraging ‘excessive’ amounts of fluid intake doesn’t explain how marathoners and ultramarathoners of the early part of the twentieth century were able to survive, let alone run record times, when they drank very little during races. 

But the real tragedy is that this incorrect treatment i.e. ingesting fluid at high rates, for a rare condition (heatstroke in endurance athletes) that is not even caused by the condition (dehydration) for which the treatment has been prescribed, eventually spawned a whole new disease for a generation of runners who were never at risk in the first place! These recommendations have cost the lives of exercisers who were simply following the advice they believed to be true.

All the evidence now points to the fact that as an athlete, you should drink according to thirst. If you are seeking specific drinking guidelines, it is suggested to stick to no more than 400-800ml per hour. It has even been suggested that drinking ‘ahead’ of thirst may impair performance.

Interestingly enough, a study conducted by K.A. Sharwood et al., in the 2000 and 2001 South African Ironman triathlon, found a significant relationship between body-weight changes and the total performance time in 736 competitors. The fastest finishers were among the triathletes who lost the most weight due to fluid losses! This data conflicts directly with the theory that any weight loss during exercise impairs exercise performance.

We’ve been told to ‘push fluid intake’, and to ‘drink more than your thirst dictates, since thirst may be an unreliable index of fluid needs during exercise’. This information has now clearly been discredited. Listen to your body and act accordingly.

Conclusion: ‘Man can sweat like a horse but cannot drink like one’ – E.C. Scott  

By Anonymous     Posted 1/1/0001 5:00:00 PM