The Test: Hydration

In my last post I outlined the importance of hydration for training and racing while living in the heat and humidity of the Southeast, USA. So I scheduled a test for myself through the company Precision Hydration to find out just how much sodium I am losing in my sweat.

Before making the drive up to Asheville, North Carolina, my coach had decided it would be fun to schedule some killer workouts in the morning. I’m pretty sure he was trying to make sure I had no sweat left for the test, but I was assured by the center that my previous workouts would have no bearing on the results of the test. It was just over a 2-hour drive to get to the location and I listened to some good podcasts on the way and of course some Avett Brothers songs once I got into North Carolina. Everyone was super nice upon my arrival and we soon got down to business!

No sweat, yet…

The first part of the test was to get me to sweat. While you may think they may put me in some torture chamber and yelled at me to work to exhaustion, it was actually quite simple. After giving my arm a rub down, two straps with little electrodes were attached to my forearm. Then, a barely recognizable electrical current was sent through them to stimulate my sweat glands just below the skin.


After a few minutes that small spot on my arm sure enough started to sweat just a little. The straps were then replaced with a single strap. The job of this strap was to collect just enough of the sweat into a skinny little tube that had a blue dye to measure how much had been collected. Once we had enough, this was connected to a device that would then measure the concentration of sodium in that sweat. So after about 5 minutes, the entire testing procedure was over!

Once the device had given us an initial number, it was plugged into Precision Hydration’s database and came back with the result. According to the test I am listed as a “Moderately Salty” sweater, with a concentration of 819 mg of sodium per liter of sweat. So what does this number mean exactly and how can I use it?

Along with my result was also a full handout on how to go about hydrating before, during, and after training sessions and races in order to stay adequately hydrated using Precision Hydration products. It is extremely thorough and it is obvious that they have thought out every aspect of this very important part of the sport. One thing that is still a variable, though, is the amount of sweat that is actually produced during exercise. I now know that if I sweat at 1 liter per hour during exercise that it would be ideal for me to aim to replace exactly 819 mg of sodium. But what about when it’s warmer and I sweat 1.5 liters in an hour? Or 2? Luckily, this data will be a good starting point for me to track my sweat rate and sodium losses in different climates and at different intensities so that I can best make adjustments in the moment.

Based on this information, it seems to me that my previous hydration plan may not have been too far off. But that certainly doesn’t mean I can’t improve. In about 25% of my long distance races, I ended up having some sort of GI distress during the run resulting in a significant bathroom stop. There could be a number of reasons for this, but I’m not satisfied with having this problem in 1 out of every 4 of my races. Therefore, I will continue to tweak both my hydration and my nutrition plans until I find what works best for me.

Down the road I intend to do another write up detailing the plan that I have settled on for my races for this year after testing a number of options during training. So stay tuned!

One thought on “The Test: Hydration

  1. This is pretty interesting to read about. I think it’s neat they made you sweat naturally instead of having you work out first, though. I wonder if that makes the test more accurate somehow?

    It sounds like it was a productive trip and test. I am with you, stopping for bathroom or having GI issues in 1 out of 4 races would be really, really frustrating. Especially at your level- because you’re likely doing a good job of controlling what you put in your body and not eating crazy foods, getting drunk, etc the night before a race. Good to get some answers early- before tri season!


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