Calculating Your Sweat Loss
Every runner is different in regard to rehydration and replenishing electrolytes after training. Some runners are “salty sweaters” and some people sweat very little and there’s a fine line between not drinking enough and drinking too much. Consuming the right amount — and right kind — of fluids during and after running will help you avoid an upset stomach from drinking too much, becoming a victim of hyponatremia, or not drinking enough and becoming dehydrated.
Unfortunately, most generalized advice doesn’t cut it when it comes to how much you need to rehydrate: some experts say drink to thirst, which may not keep up with your own body’s sweat loss rate if you’re a heavy sweater, while others say to consume 8-10 ounces of fluid per hour, which doesn’t factor in temperature, humidity, or environmental factors.
Rehydrating properly during and after a run can sound sound daunting and confusing, but calculating your exact fluid loss in any given temperature and humidity is actually quite easy if you use a sweat loss calculator and create a reference chart. All you need to input is your weight before and after each run, any fluid taken or lost (when going to the restroom), and the distance/time you ran. The calculator will do the hard work for you.
Use this calculator a few times in different temperatures and record your results. You’ll now have an easy reference chart to see exactly how much fluid you need replenish on any given run and in any temperature. This will help you avoid dehydration, over-hydrating, or getting a sloshing stomach while on the run this summer.