How to do a basic sweat test
Have you ever performed a sweat test? This simple test can give you valuable insight into how much water your body is using during exercise. Being perfectly hydrated throughout a workout and throughout the day will keep you performing your best.
How to check your sweat rate
A couple rules with this test; no eating and no using the bathroom once you weigh in (Step 2). If either of these happen you’ll have to try another day.
Step 1:
Plan a 1-hour workout. NO EATING during your test.
Step 2:
Right before your workout starts you’ll need to weigh yourself naked. If you use the bathroom in between the time it takes to weigh yourself and when you start your workout, weigh yourself again. Write this number down for reference later.
Step 3:
Workout.
Keep track of all the water you drink during your workout in ounces (water bottles are usually between 16-22 ounces and may be marked on the bottom of the bottle). You need to know exactly how much water you drank to complete the test. If you have water left in your bottle at the end of your workout, estimate how much you drank (example: if you drank half of a 16 ounce bottle, you drank 8 ounces of water). If you want to get really science-y with it you could pour the remaining water in to a measuring cup and subtract it from the size of the water bottle. Write down how much water you drank in ounces.
Step 4:
At the end of your workout, weigh yourself naked again, but towel off the sweat before you step on the scale. Write down this number.
Step 5: Math
Now you have 3 numbers - your weight right before your workout, the amount of water you drank in ounces and your weight after your workout.
First subtract your end weight from your starting weight and multiply the result by 16 (see the equations below). This is your weight difference in ounces. Then, add the amount of water you drank during the workout in ounces to your weight difference in ounces. This is your 1-hour sweat rate, which means you need to try to hydrate close to that amount every hour.
Here’s how to crunch the numbers:
a = pre workout weight in pounds
b = post workout weight in pounds
c = water consumed in ounces
a-b = WP (weight lost in pounds)
(WP) x 16 = WO (weight lost in ounces)
(WO) + c = 1-Hour Sweat Rate
If you get a negative number in 1. above, that means you overhydrated and actually GAINED weight. In that case, still add that negative number to how much you water you drank to get an idea of your sweat rate.
Do this test a few times to get an average. This will give you a ballpark estimate of just how much water you need each hour.
If you do different activities you will want to do a sweat test for each activity. So if you’re a triathlete, do 3 separate tests for swimming, biking and running. If you weight lift and cycle, have separate data for the gym and on the bike.
Things to avoid during your sweat test
Some things that can mess with this test are having to use the bathroom during your workout, eating during your workout or taking a long break during your workout. Consistency is best for tests like these so make sure to eliminate these variables - or if they do occur, redo your test the next day.