Water overload and extreme long-distance running

Hyponatremia is a rare condition known as "water intoxication". It is the opposite of dehydration, and is often associated with endurance athletes. It is important to state here that for most beginner to intermediate runners, the dangers connected with hydration are a lack of water rather than too much. However, for a small minority of runners running long-distance events, hyponatremia can be an issue.

The following shocking account is but one of an increasing trend in endurance sports where participants, especially women, are suffering symptoms ranging from nausea to vomiting, collapse, seizures, hospitalisation… and yes, even dying. But it has nothing to do with dehydration. In fact it is the complete opposite, a case of “over hydration”. And that’s the incredible thing; so dependant are we on fluids for performance, who would ever have imagined that endurance athletes could ever suffer from what is very much a case of getting too much of a good thing.

True running story
Nearing the 22-mile mark of 2002’s Boston Marathon, 28-year-old Cynthia Lucero is starting to struggle. For all but the last 15min she had felt fine. Careful to stay as hydrated as possible she had walked while she drank at every aid station and while others struggled, she had taken Boston’s infamous Heartbreak Hill in her stride. But in the time that it took her to run the next 3km, Cynthia Lucero’s life unravelled.

At the 22-mile mark of America’s most famous race she was walking, felt nauseous and told a friend she must be dehydrated. Then in the next breath the friend watched as the walk turned to a wobble and she collapsed. Going into seizure, worried spectators called for an ambulance but by the time she arrived at a hospital Cynthia Lucero was in a coma. Two days later she died.

What is Hyponatremia?
Hyponatremia, according to New Zealand’s Dr Dale Speedy, “Is a lowering of sodium concentration in the blood due to water overload.” Speedy is the pioneer in research into hyponatremia, one of the first to recognise it as a serious health risk. “What actually happens,” he says, “is waterlogging of the cells and brain, which is why people with hyponatremia suffer confusion and in severe cases seizures. People can and have died from this!”

Indeed, the Boston Marathon tragedy outlined above is not an isolated incident. In 1993 a 32-year-old women died during California’s Big Sur Marathon and in 1998’s Chicago Marathon a 43-year-old women died, both from complications associated with after finishing the race in a hyponatremic state.

Speedy began studying hyponatremia as a result of his involvement as medical director of the Ironman New Zealand triathlon during the mid-1990s. In 1997 he put the entire field through medical screening and found that 18% of the finishers were technically hyponatremic. “The majority had no major symptoms, he says. “But 16 people ended up in hospital!”

In the years since, similar figures have been recorded in endurance events all over the world. Athletes are reported to have died in South Africa, and the advent of water as something of a fashion has even seen hyponatremia show its ugly face amongst the casual recreation crowd. In 1997, 27 walkers were helicoptered out of the Grand Canyon suffering hyponatremia.

What causes Hyponatremia in runners?
For the most part, studies indicate water overload as and sodium concentration scenario as the principal cause of hyponatremia. The woman who died in the Chicago Marathon is reported to have drunk, “gallons and gallons of water daily,” in the two weeks prior to the Windy City race. In his Ironman studies, Dale Speedy has come across hyponatremia cases where athletes have drunk as much as 23 litres of fluid during the race.

However, despite the strong correlations between water overload, Speedy admits that there is a lot still unknown about what are the causes behind it all. Right now, for example, expert opinion is divided as to the relationship between over hydration and the loss of sodium via sweat. In an address to a sports nutrition conference in February 2001, Dr E. Randy Eichner, M.D., promoted the role of salt loss to sweat as a contributing cause to hyponatremia.

 

“Studies have shown that athletes can lose two or more grams of salt per litre of sweat,” said Eichner, who is a Professor of Medicine at the University of Oklahoma Health Sciences Centre. “If you consider that athletes may lose up to a litre or more of sweat each hour, you can see that over a long endurance event it is not unimaginable that an athlete could sweat out 30 or 40 grams of salt. Replacing this loss of sodium during an event is critical to performance and safety.”

Dale Speedy admits that the logic appeals, but says the scientist in him isn’t sold because, “studies really don’t support this.” Speedy thinks the real answer lies with finding out why the body cannot absorb or expel this excess fluid during exercise. John Hellemans, a sport medicine physician, coach and world champion triathlete tends to agree, saying: “It seems to be tied to blood supply to the kidneys being shut down because blood flow is pulled away to supply the working muscles.”

Both Hellemans and Dale Speedy also wonder if it this absorption problem might have something to do with believe that part of the cause behind hyponatremia may relate to athletes adopting race day hydration regimes that they have not accustomed their body to in training.

Speedy’s extreme case of an Ironman athlete suffering hyponatremia after drinking 23 litres on race day is a classic example. With the average finisher clocking around 11 hours 30min, this equates to a massive two litres of fluid per hour! Not only is that too much says Speedy, but, “when athletes train usually they usually don’t have the large amounts of fluid available to them like at races. So when they flood the body with fluid on race day perhaps the body can’t cope.”

How to avoid Hyponatremia in running
The key is replacing fluids at the exact same rate that they are being lost, and then balancing the dilution of the bodies sodium content by replacing it with drink containing sodium. Generally most people use between 500ml and 1000ml of fluid an hour when exercising. But in long events this is too broad a range because someone at the lower level could be overhydrating by 100%.

Who is most at risk from Hyponatremia?
In 1997’s Ironman New Zealand a massive 45% of the women suffered some form of hyponatremia, while studies at the San Diego Marathon revealed female finishers as having the lowest sodium levels.

In general, however, hyponatremia appears to be a condition associated mostly with people who are competing for periods longer than four hours. Indeed, studies from 2002’s San Diego Marathon reveal that no hyponatremia case finished in less than four hours. What this means for runners, is that the people most at risk are mid-pack marathoners and ultra-distance athletes, and especially women because they actually require less fluids than men.

How do I recognise hyponatremia in my running?
The deadly irony with hyponatremia is that it actually shares many of the same symptoms as the direct opposite condition of dehydration. In 2002’s Houston Marathon eight-time marathoner Kathy Schatte was one of four people who suffered hyponatremia. But in Schatte’s case it almost resulted in death after she was presumed dehydrated.

Schatte tanked up liberally both before and during the event. But Houston is not known as a hot marathon, so she was taking in far more than her body needed and she finished suffering severe swelling in fingers and hands (basic water intoxication), severe cramps and vomiting. Presumed dehydrated she was put on an IV, which immediately sent her into seizure and eventually into a coma from which she didn’t wake for two days.

When she did wake, doctors said they had taken eight litres of fluid out of her and that the fluid had got into her lungs. It was another three days until her sodium levels were deemed safe for her to be released and three weeks before she could stay awake long enough to go to work.

The early warning signs of hyponatremia are often subtle and may be similar to dehydration, with nausea, muscle cramps, disorientation, slurred speech and confusion. But in an article in Sports Medicine Digest Dr E. Randy Eichner said symptoms more specific to hyponatremia were: “bad headache, vomiting, bloating, puffiness from water retention (shoes tight, rings tight, wristband tight), confusion, and seizure.”

And yet, despite hyponatremia being much more problematic than dehydration, it is not as widely recognised or warned against. Dr John Hellemans isn’t willing to take it so lightly, warning, “as a health risk, overloading is much worse than underloading!” So don’t let hyponatremia turn you into a statistic – know when to say when with water...

Symptoms of hyponatremia include:
Fatigue, despite adequate fluid intake
Loss of mental focus
Nausea
Confusion
Vomiting
Low body temperature
Weight gain during exercise
Fitting and/or seizures
Loss of consciousness
In extreme cases, coma and/or death