The Sweat Rate Test

9 Jul 2015

Woman working out text "Sweat rate test"

Sweat Rate Testing. Most athletes this time of year find themselves measuring and analyzing things like VO2 Max, Lactic Threshold, etc. On the hydration side of this is Sweat Rate testing. Understanding the amount of fluids your body uses and loses on a per hour basis can give you a much better understanding of how many ounces of fluids you need to be replacing each of activity. Below is a great way to find what your sweat rate is.

The Sweat Rate Test

Here is a proticol for doing a sweat rate test. Do this on a training day when the weather/conditions will be similar.

Worksheet B: Determining Sweat Rate

The goal is to see exactly how much dehydration you incur during your workout and in turn, determine your hourly fluid replacement needed for euhydration.

1. Empty you bladder and record you weight (nude or swim suit)

2. Pre-exercise weight = ___________ lbs.(A)

3. Do your usual workout, and drink like you normally would.

4. Record the approximate volume of fluid consumed during exercise.

How much you drank = ___________ fluid ounces (E)
*Note: Each mouthful of fluid is ~1 ounce.

5. Towel dry, empty your bladder and then record your weight (nude or swim suit)
Post-exercise weight = ___________ lbs.(B)

6. Subtract your post-exercise weight from your pre-exercise weight to get the number of pounds you lost during exercise.
Weight lost = _____lbs.(A) - ______lbs(B) = ________lbs.(C)

7. To find out how many fluid ounces of water you have lost, multiply pounds x 16
_____lbs(C) x 16 = ________ fluid ounces of water you lost during exercise (D)

8. To determine hourly fluid replacement needs, add number of fluid ounces you lost during exercise (D) to the number of fluid ounces you consumed during exercise (E) and divide by total number of hours spent training.

(_____fluid ounces (D) + ___fluid ounces (E)) ÷ ___hours =_____fluid ounces needed each hour

Conditions that will increase sweat rate include heat, humidity, and elevated heart rate (high intensity training). Athletes should measure sweat rate across several workouts to determine their fluid replacement needs in various environmental conditions. On race day, based on the forecast, the athlete than can go back to their log and know exactly what fluid they need to plan on ingesting to prevent performance declines associated with dehydration. Deaths have occurred when the air temperature was less than 75 degrees F (24 degrees C) but the relative humidity was above 95%. Humidity levels over 75% will contribute to an increased risk of heat injury.

*Note that a factor of 1.2-1.6 can be multiplied to hourly replacement needs when heat & humidity (>75%) are extreme.

9. To find out what percentage of your weight you lost during exercise,
_____lbs. (C) ÷ ______lbs. (A) X 100 = ________ % Body weight lost