Get to Know Your Sweat and Electrolyte Loss Rates
Written by Jim Levesque, Owner and Head Coach at Grit Endurance. Learn more about Jim’s background here!
Getting a solid understanding of your sweat and electrolyte loss rate can be a game changer for endurance sports performance, and the longer the race or workout, the more important it becomes! What makes it tricky to figure out, though, is not only do sweat rate and electrolyte concentration vary widely by person, even the same person can see quite a variance in both, depending on the activity, effort level, and weather conditions. For example, an athlete might have a sweat rate of 15 oz/hr with an electrolyte concentration of 40 mg/oz during one workout, and a sweat rate of 30 oz/hr with an electrolyte concentration of 60 mg/oz in another workout that is either higher effort or hotter conditions!
The great news is that there are now tools out there, like the Nix Biosensor, that can help you get a very dialed in understanding of your numbers. I recently tested this out on a few different workouts, and the results were fascinating! A little caveat, I have a very high sweat rate and very high electrolyte concentration, so these numbers are way above average!
Workout 1 – June 26 – Easy run – 55 minutes – hot and humid
Sweat rate – 31.3 oz/hr
Total electrolyte loss rate – 1354 mg/hr
Estimated sodium loss rate – 636 mg/hr
Workout 2 – June 29 – Easy to moderate long run – 59 minutes – very hot and humid
Sweat rate – 43.8 oz/hr
Total electrolyte loss rate – 2733 mg/hr
Estimated sodium loss rate – 1,285 mg/hr
Workout 3 – June 30 – Moderate indoor long bike ride – 3 hours – hot
Sweat rate – 46.8 oz/hr
Total electrolyte loss rate – 4305 mg/hr
Estimated sodium loss rate – 2023 mg/hr
One thing to note is that the total electrolytes you are losing in sweat, on average will be 47.4% sodium, 47.4% chloride, and 4.7% potassium. This is how I’ve deduced the estimated sodium loss rate from the total electrolyte loss rate. Seeing the difference in sweat rate and electrolyte concentration will be very helpful in planning out a hydration strategy for training and for race day. I plan to do several more tests simulating race effort conditions outdoors, which will help build out a complete picture of the averages across all workouts, but most importantly, it will help me understand the expected sweat rate and electrolyte concentration at race effort and in expected race day conditions.
If this information interests you and you aren’t sure where to start, please reach out, contact us here!
Below is a snapshot of the Nix Biosensor data from minutes 125-140 of the indoor bike ride from June 30:
