Saturday, February 5, 2011

Electrolytes & Hydration, Part 1

There are a lot of misconceptions and confusion around ultra-running electrolytes and hydration. There are also many fads or trends that go off on tangents, without collating data already learned from other sports.

Everyone already knows we need to maintain a certain quantity of electrolytes and hydration. The argument is how much? What makes this harder is that everyone is somewhat different.

The last part, about everyone being “different”, has to be taken with a grain of salt (no pun intended {well, maybe a little bit}). What causes everyone to be different are usually measurable things like heart rate and breathing rate. Otherwise we aren’t as different as most people imply. An elite athlete has an astoundingly low Resting-Heart-Rate, incredible VO2Max, and plenty of oxygen-carrying red blood cells. To run up the exact same stretch of trail, at the exact same pace, an elite weighing 130lbs will have a very low heart rate and breathing rate, because they aren’t working very hard. But a 180lbs runner, with twice the RHR, lower VO2Max, and not as many red blood cells, will be gasping for air. Regardless the altitude, the lighter elite athlete will not have to breathe or work as hard.

Unlike calories, electrolytes don’t “burn up”. Calories burn and escape the system via heat. Electrolytes don’t burn. They flush out via sweat and urine. Therefore, an elite who sweats less, wastes less. Urine is going to come out either way. Your body will try to maintain a healthy hydration and electrolyte balance, but if you flood the system with too much or not enough, of water or electrolytes, the body will have a harder time balancing. Way more than optimal salt and too little water – you’re in trouble. Way more salt and way more water, maybe not bad at all, but still making the body work extra to maintain “optimal”. Too much water and too little salt leads to deadly hyponatremia.

Collation 1
Everyone knows that people stranded at sea should never drink sea water, or they’ll get stomach cramps, delirium, and then die. Allegedly, you die of dehydration, no matter how much sea water you drink. The sailors who have lasted the longest aren’t the ones who drank only the survival-ration of on-board fresh water. The ones who lasted well beyond historical expectations were those who mixed sea water with fresh water. Only the optimal ratio is argued today. But why argue? We already know the optimal salinity of human blood. To maintain optimal water-to-salt ratio, you need to drink that same ratio. Each body may react slightly differently to sun and heat. If you sweat more, you’ll lose both water and salt through your pours, but some will lose more salt than others. So what is “optimal” for one person may not have enough salt for another. But sitting still in a boat, humans don’t vary much – only a little. The conditioning of athletes cause wild variations from one person to the next, but sitting still in the shade, people are very similar.

This should be a lesson for ultra-runners who are rabid fans of electrolyte capsules. Too many runners take electrolyte supplements based on the clock, while ignoring their bodies and their environment. It should be no mystery that they eventually drop or crash. They may still finish their race, but only after gutting through hours of self-inflicted agony. If the salt/water ratio is too saline, it’s like drinking sea water. And no matter how much sea water you drink, you’ll be killing yourself.

When you drink sea water, your body will attempt to re-balance the ratio of salt and water in the system back to optimal levels. The only way the body can rid salt is to flush it out with water. That’s why drinking sea water leads to dehydration – it takes more water to flush out the excess salt than was in the volume of water the sailor drank.
Sea water is about 3x’s the salinity of optimal human blood.
Blood = ~2tsp salt/qt (~10gms/qt)
Sea water = ~6tsp salt/qt (~1oz/qt)

Ultra-runners aren’t sitting still in a boat. The harder you work, the faster you breath, which dries you out. Breathing causes you to lose fresh water, but no electrolytes at all. Theoretically, if you didn’t sweat at all, and you were gasping like the Little Engine That Could, you would only have to take in as much salt as you peed-out - not much. (But of course, we always sweat some, even on frigid winter excursions.)
The recommended daily dose for average people is only 500mg/day, but the average person also only needs 2qts/day of fluids. What mainstream people refer to as “active” still ranks as “sedentary” to the average ultra-runner. During a 100-mile event, a middle-of-pack ultra-runner can consume two or more gallons of fluids in a 24hr period. If they get their electrolyte ratio wrong, they can do lots of damage.
FYI: Real (whole) sea salt, from evaporative mining, contains many of the minerals our body needs for optimal health. Salt mined from inland sediments, even if they originated from evaporated seas, often are missing these elements. Many salt-mining companies get most of their profits not from selling salt, but from selling the extracted, refined individual minerals. Beware what you pay extra for – just because its labeled “Sea Salt”.


  1. Excellent post. I find that there are SO many runners that just pop salt tabs all day long without even taking one mind to their body (or what they just ate- usually during long runs) because it is the "thing" to do. I have one bottle of salt tabs that has lasted me forever for the simple fact that I rarely ever use them.


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