Determining you sweat rate will at a minimum give you a pretty good idea of how much fluids you need to take in during any given workout. Determining your sweat rate is the easy part. The hard part is to determine the “correct” electrolyte mix for you. Under-replacing your electrolyte can lead to various problems including dehydration, muscular cramping, headaches, gastrointestinal upset, nausea, fluid retention and hyponatremia. I personally experienced the under-replacing electrolytes during Ironman Louisville, which made for a long run. And if you take in too much water without any electrolytes you could experience a condition call hyponatremia.
How to determine your Sweat Rate:
To determine your sweat rate is somewhat simple. Prior to your workout, with an empty bladder, weigh yourself without any clothes. Go for a 60 minute workout. Immediately after completing your workout, remove your clothes and weigh yourself again. Subtract the difference and convert to ounces (16 ounces per pound). That number is your sweat rate in ounces. If you drink any fluids or use the rest room between the two weight samples, you'll need to include both of these estimated weights in your calculations. Add fluid consumed to the amount of weight lost. Subtract estimated bodily void weight from the total weight lost.
Be sure to record the heat and humidity conditions in your sweat test. Repeat the test in cool and hot conditions. Repeat the test for swimming, running and cycling because sweat rates will vary for each sport and vary with environmental conditions.
The average person sweats anywhere from 27-47 ounces per hour depending on the temperature and humidity. Of course you have those people that are on the extremes, as an example my sweat rate in temperatures in the mid- to high-70s with 80% humidity my sweat rate is 72 ounces per hour.
Now that you know your sweat rates in each sport, you probably imagine that simply drinking enough fluid will replace what you lose to sweat given the environmental situation. If it were only that easy!
The hard thing to determine without extensive lab tests is what is the right amount of electrolyte mix for you. Electrolytes include sodium, chloride and potassium and depending on what article you read, magnesium can be included on the list. Why do you need electrolytes? Electrolytes keep you body’s chemistry in balance and working properly. If your electrolytes are imbalance, you could potentially compromise the success of your workout due to muscle fatigue or cramping. You may experience more frequent muscle cramps in the legs, stomach cramps or sides stitches as a result of an electrolyte imbalance.
When it comes to replenishing electrolytes, every athlete is different. Some athletes are “salty sweaters” and some athletes sweat very little. I am a salty sweater. When I finish working out I can feel the “salt” on my skin and you can see the salt on my skin and clothes. I need to consume more electrolytes than an athlete that sweats very little. I have found that Base Performance Salt works very well for me and I can add as much or as little to the drink as I want. Infinite Nutrition works well too as you can get a custom mix based on your needs. I would avoid commercial off the shelf electrolyte drinks because they add high amounts of simple or artificial sugars to your diet.
So if you cramp a lot or are constantly fatigued (and not overtraining), you need to start trying to crack the code on your sweat rate and your electrolyte needs. Keep in mind that your sweat rate is not just a simple number, but changes based on several factors like your fitness lever, ambient temperature, humidity, clothing, exercise intensity, fatigue level, to name a few.
To crack the code, you need to start recording this data during training to determine what works or doesn’t work for you.