Hydration Practices for Marathon Runners: The Risks of Drinking Too Much Water (Exercise-Associated Hyponatremia)

Here in Winnipeg, days are counting down to the 34th annual Manitoba Marathon which takes place this weekend (3 days!). Weather has been great in the last few weeks, and so I expect that athletes have had a chance to train in the hot & humid weather before this race. If this race turns into a scorcher, we have to really think about water intake levels aka: hydration!

So what do you think I'll tell you? Make sure you are drinking plenty of water before and during the race, and that if you feel thirsty it's already too late and that you are probably dehydrated? Until very recently, I would have probably stated just that. A couple weeks ago, I was brought up to speed by a great therapist in Dartmouth, NS, Daniel Crumback with Paragon Sports Performance (great clinic name Dan!).

With exercise, most of us think if we are going to be doing heavy endurance work over extended periods of time, we will have to consume much water so that we do not dehydrate. If it is really hot out, we think that we need above and beyond what we would normally need. Some may think that we must also hydrate substantially the days before the run.

The question is, can we really drink too much water? Can we be too healthy? Can we actually be hindering our performance in sport and may even be putting our lives at risk?

We may have the best of intentions for our health, but we may have been psychologically conditioned to think that we require copius amounts of fluid when exercising.

History

Before 1969, athletes were regularly advised to avoid drinking water during exercise. Even olympic marathon runners from the early 1900's were quoted writing: "I know from actual experience that the full race can be covered in creditable time without so much as a drop of water being taken or even sponging of the head."

In 1957, Jim Peters (previous 4 time world record marathon runner) trained in this same way. Minimal to no water for training.

Take a step back in time now. 1924. South Africa. Arthur Newton (then ultramarathoner and marathon record holder) created the first sports drink ever! Named, the Corpse Reviver was the drink to have for runs over 26 miles!

Alright, jump forward again: 1965. Dr. Robert Cade, a nephrologist from University of Florida, developed the second sports drink known today as, what else, but GATORADE. Basic fitness tests used in Cade's study then showed that increased fluid uptake by football players reduced the risk of developing heat stroke.

Four years later (1969), a pair of physiologists had a questionable study that said concluded that higher body weight losses during racing must inevitably cause heat stroke. Runners were then told by their athletic association, to consume as much water as felt necessary based on thirst.  This study has since been proven to have errors and incorrect causation.

During this time and until the present, sports drinks have been a massive industry among athletics. Growth was estimated at $217M in 1985 to $2.69B (yes, billion) in 2003.

In 1996, the American College of Sports Medicine (ACSM) had implemented a 'zero percent hydration' rule that dictates: the weight lost during exercises must be replaced if health is to be protected and performance is to be optimized.  It was portrayed that fluid ingestion was the be-all end-all of exercise induced heat illness. They noted that the thirst mechanisms in humans was slow, and that athletes regularly drink too little prior, during, and post exercise. Also, every athlete, regardless of weight, height, etc. was to have the same fluid ingestion guidelines. These may have not been exactly evidence-based.

Hyponatremia

What is it?

Hyponatremia is the state in which there is a low concentration of sodium in the serum. It is not as you think though. It is not exaclty a loss of overall sodium in the system (though we will lose some through sweat and urine), but it is often induced by too much hypotonic fluid uptake. We are essentially diluting the body's serum. Symptoms may or may not be present. Some indiviuals may be symptom-free in early stages, though it may progress to cerebral edema, noncardiogenic pulmonary edema, altered mental status, and death.

History:

The term Exercise-Associated Hyponatremia or EAH was put onto paper by non-other than the wonderful South Africans (yet again!). It was a condition that was described in a handful of superathletes that competed in events over 7 hours.

A recent study in 2002 (of Boston Marathoners) found that of their sample size of 488 runners, that 13% developed EAH (purely diagnosed by serum levels).

There have been a number of accounts of death due to EAH:

• 4+ deaths in the military between 1989 and 1996 - recruits were encouraged to consume 1.8L of fluid per hour of time spent in temperatures above 30C.
• 2 USA physicians - too healthy??
• 2002 had 2 female runner deaths, one each in Boston and Washington Marathon
• 2 college students died participating in a hazing requiring downing gobs of water
• 2007 - a 28 year old female died while competing to see if she could drink 2 gallons in a short period of time, without going to the bathroom

 Who's at Risk?

A couple of nephrologists from the University of Virginia have outlined some of the risk factors based on current evidence:

• Exercise duration over 4 hours, or slow running/exercise pace
• Female gender - postulated that it may be moreso due to body mass
• Lower body weight
• Excessive drinking (>1.5 L.h) during the event
• Pre-exercise overhydration
• Abundant availability of drinking fluids at the event
• Use of NSAID anti-inflammatory medications
• Extreme hot or cold environments

What do we do? Drink or no drink?

If you are serious about running in a race, you will have to practice your long distance runs before the race date. Weigh yourself before your run, monitor exactly how much water you have ingested during your run (drinking only when feeling thirsty), then weigh yourself immediately after the run.

There should be a net loss of body weight or an unchanged body weight. If your weight has increased during the run, you have consumed too much water and are at risk of EAH. Try to figure out the amount of fluid you will need through the run with this test.

DO NOT overhydrate the day before the race. During the race, I was explained that you should grab the small amounts of electrolyte solution (small amounts, to maintain the small amounts of salt lost), and take the water handed out and throw it onto your head (helps cool you down!).

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This seems like a topic that I can write forever upon! I normally would write up the reference list, but wil hold off for now, because it has gotten pretty late! If interested, send me a message and I'll compile the list for you!

TO ALL THE WEEKEND RUNNERS:

Thanks for reading!!