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How to Perform a Sweat Test to Determine Hydration Needs for Runners

Proper hydration for runners is important, but how much exactly do you need to be taking in? As always, it depends — in this case, on your weight, your physiology, and how intense your workouts are. Fortunately, a relatively easy sweat test can help give you an idea of how much water and electrolytes you’ll need to keep yourself well hydrated. And, you’ll want to; staying properly hydrated is important for the following reasons:

  • Body temperature regulation
  • Joint lubrication
  • Optimal performance
  • Reduced risk of fatigue
  • Increased strength and stamina with no muscle cramps, dizziness, or soreness

How much water does a runner need?

  • Drink to your thirst. There are no exact rules for how much water or electrolytes one needs because so many factors can affect hydration, such as environment, weather, altitude, and genetics.
  • Check your urine. Urine should be colorless or light yellow which is an indicator of adequate hydration. Dark yellow or amber coloring can be a sign of dehydration.
  • The average person needs 8 to 10 cups (64-80 ounces) of water per day with no exercise.
  • Exercise results in more hydration required.
  • During intense activity or activities lasting more than 90 minutes, drink about 5 to 10 ounces of water every 20 minutes.
  • Post workout, drink enough fluid to replenish water and electrolyte loss.

Perform a Sweat Test

A sweat test can help determine how much water loss you have on an average workout. To perform the test, weigh yourself naked right before the exercise. Once you weigh yourself, do not eat or drink anything during the activity. Ideally, this is done during a training session of 60 minutes or less in normal weather and environmental conditions. After the workout, weigh yourself naked again. For every pound of weight lost, drink an additional 16-24 ounces of water.

For example, initial weight is 160 pounds pre-workout. Post workout weight is 158 pounds. You lost 2 pounds of water weight during the exercise. 2 pounds x 24 ounces = 48 additional ounces of water per day.


Water is important, and so are electrolytes. Electrolytes include sodium, potassium, calcium, magnesium, chloride, and hydrogen phosphate, and they help regulate muscle function, blood pressure, blood pH, and hydration. Balancing electrolytes in the body will help with proper muscle contractions and enhance performance.

Tips to Include Electrolytes During Activity

  • Drink an electrolyte drink during extended workouts of more than 90 minutes or during extremely sweaty workouts.
  • Drink a combination of water and electrolyte drinks during an intense workout to maintain hydration and electrolyte levels. Switch it up with one drink water, one drink with electrolytes.
  • Eat a regular diet that includes electrolyte-rich foods, such as bananas or potatoes for potassium, soy sauce for sodium, and dark leafy greens for magnesium, potassium, and calcium.

And remember: Drink to your thirst to stay hydrated!

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