Hydration Guidelines: Dehydration a Myth?

To drink or not to drink? 

“Drink before you’re thirsty.” “Drink only when you’re thirsty.” “Losing just 2% of your body weight due to dehydration leads to heat related illnesses and impairs performance.” “Over drinking can lead to Hyponatremia (water intoxication) and death.” Have you heard these phrases before?

How about this quote from runnersworld.com?

“Far more interesting (and reliable) is this nugget: [researchers] measured [Haile Gebrselassie] before and after he won Dubai [Marathon] in 2009, and despite drinking at a fairly high rate, he lost 9.8% of his starting body weight...” -Alex Hutchinson (Runner’s World)

Hmmm...shouldn’t Geb be comatose and not setting world record marathon times then? After all, that’s what our hydration guidelines have taught us, right? — that losing weight during exercise can lead to all sorts of catastrophic outcomes.

I’ve been confused by this topic for many years but, after reading Waterlogged: The Serious Problem of Overhydration in Endurance Sports by Dr. Tim Noakes, my lens is finally coming into focus. I was taught from early on to drink before you are thirsty, top off fluids before you start your run and replace all fluid lost in sweat while on the run.

I followed this advice for years and experienced nausea, bloating and headaches following my long runs. I thought I was dehydrated, so I would continue to drink afterwards and never felt like I was recovering. Eventually, I started to take electrolyte capsules and/or sports drinks which seemed to bring a little relief. The “drink as much as tolerable” advice never made any sense to me though.

In reading Waterlogged, I have found the most sensible information I’ve ever read on hydration. Dr Noakes has presented compelling evidence that becoming “dehydrated” during endurance sports is the body’s natural way of maintaining electrolyte balance and does not lead to heat related illnesses or a diminished performance. In fact, he believes dehydration is a myth that developed from misinterpretation of a study published in the early 70s.

Overhydrating, however, has caused many cases of Exercise-Associated Hyponatremia (EAH) since the sports drink industry influenced the development of hydration guidelines in the 70s. Some athletes have died as a result of EAH Encephalopathy where the cells in the brain swell, but have no room to expand. Dr Noakes writes, “...12 athletes or soldiers are known to have died in this way. All deaths would probably have been prevented if the pressure inside the skull had been rapidly reduced with the use of hypertonic (3-5%) saline solutions administered intravenously.”

Here’s the part of the theory that I love: During hunter-gatherer times, man would kill large prey on the African Savannas by running them to exhaustion. This was only possible because man’s cooling system (sweating) is more efficient than large prey’s like antelope (panting), but the animals had to be chased during the hottest part of the day for them to overheat and be killed. Because there were no water stations, like in our big city marathons, hunters would become “dehydrated” during the chase, but would re-hydrate later while dining on antelope.

According to Dr Noakes, the only symptoms of dehydration are thirst, so in our training for and participation in endurance events, we should drink when we become thirsty. Drink when we are thirsty? Hmmm....so what you are telling me is that my body will know when and how much to drink. Isn’t that a novel concept?

Here are some other important points that I took away from reading Waterlogged:

• Front runners and race winners are often the most dehydrated (5-10% weight loss).
• Drinking sports drinks with added electrolytes will not prevent Hyponatremia or “heat cramps”, but the added carbohydrates may increase performance.
• Maintaining zero dehydration while exercising does not prevent overheating.
• Heat related illnesses such as heat stroke are likely to occur in shorter duration races where the pace is faster instead of in marathons and ultras.
• The brain slows the body’s pace when it begins to overheat.
• Collapse of runners at the end of races is usually due to Exercise-Associated Postural Hypotension (low blood pressure). Blood pools in the legs when exercise ends, so the runner should lie down with pelvis and legs higher than the heart. Symptoms will disappear in a few minutes when more blood flows to the upper extremities.
• Medical personnel should not give Intravenous (IV) for “dehydration” until blood sodium levels have been checked. If the runner is overhydrated, a normal saline solution (0.9%) can make the situation worse.
• If the athlete is suffering from EAH Encephalopathy giving an IV of hypertonic saline solution (3-5%) can reduce brain swelling in minutes and save the victims life. 
• Endurance athletes should follow the fluid recommendations published by the International Marathon Medical Director’s Association. (IMMDA) (See link below)
• The only way to prevent water intoxication is to NOT OVER DRINK!

To test Noakes’ findings on hydration, I modified my fluid intake on several “heat training” workouts since we have been having triple digit highs in West Texas this month. On one run where the temperature was over 100 degrees, I drank 24 ounces of water during a one hour run and felt nauseous and sluggish by the end.

The next week I ran the same course in 104 degree weather and drank nothing. I lost 2.8% body weight (4 lbs) and, other than being hot, felt fine all the way to the end of the run.

Several long training runs took me to the top of two 7,000 ft mountains, North and South Franklin Peaks, to get ready for my Kendall Mt Run. This race is a half marathon route that ascends a 13,000 ft summit in Silverton, CO, but I signed up for the double climb for a full 26 miles of amusement.

On one adventure, I climbed and descended both N. and S. Franklin peaks in four hours. I drank around 3 liters of water and took electrolyte capsules as well as a Hammer Gel/chia seed mixture for energy. I was very sore for the next few days due to all the steep ups and downs and had a headache afterwards which could be an indication that I drank too much.

The next week I ran a 20 mile course in the Franklin Mts State Park known as the Scenic Loop. I also added a climb to the top of N. Franklin Peak to build some character. On this outing, I drank only to thirst and again took the gel/chia seed mixture for energy. The weather was warm, but breezy so I was able to stay cool for most of the run and actually felt very comfortable in the higher elevation.

By the end of the run though, I was very hot because the temperature was reaching 90 and there was no wind on the lower slopes. My pace slowed considerably and I was thirsty following my run. Perhaps I should have drank a little more towards the end, but I finished my training in 4:30 and recovered after some rest and rehydrating. 

This shows that there is no exact formula as to how much you should drink and it won’t always be perfect. The bottom line is to drink when you become thirsty, slow down or stop if you overheat, and lie down if you feel faint. Your body will tell you what to do if you just listen.

See you on the trail.

Further reading:
Waterlogged: The Serious Problem of Overhydration in Endurance Sports by Tim Noakes (Human Kinetics, May 2012)


Updated Fluid Recommendation: Position Statement from the IMMDA: Read Statement

Statement of the Second International Exercise-Associated Hyponatremia Consensus Development Conference, New Zealand, 2007: Read Statement