LORI NEdescu,




Board certified sports dietitian, pro athlete, freelance nutrition writer, published author, social content developer & personal chef.



All athletes sweat as a way to thermoregulate the body during exercise, but not all athletes sweat the same. When it comes to sweat there are two main factors to pay attention to: amount & composition.


Sweat Rate

This is how much you sweat. Generally provided in a measurement of liters per hour.

  • You should know your sweat rate as it influences how much fluid you need to be replacing during your training (see calculation below).

  • Fluids do not need to be replaced at a one to one ratio, this could lead to hyponatremia or a sloshy stomach.

  • Not hydrating enough leads to dehydration.

  • Over 4% dehydration can lead to decreased performance.

  • Endurance training (2+ hours) depletes glycogen which exaggerates true water loss.

  • Sweat rate changes based on temperature, clothing, humidity, altitude, etc…

  • Men sweat more than women (generally) & sweating decreases with age.

Sweat Rate Calculation

Sweat rate = pre-exercise body weight - post-exercise body weight + fluid intake - urine volume/exercise time in hours. Simply this is your weight before vs after your workout. Aim not to urinate during your sweat test as measuring urine volume outside of a lab is… not gonna happen. Keep track of all fluids consumed, weigh naked before and after, and keep the training to less than an hour at tempo pace.

Sweat Composition

Sweat is more than water. It contains sodium, potassium, magnesium and calcium.

  • These electrolytes (except for Sodium) are lost in micro amounts and do not vary much athlete to athlete.

  • Sodium losses can vary greatly athlete to athlete from 200mg to 2000mg per liter of sweat.

  • Many athletes do not consume enough sodium during training which can lead to cramping, decreased performance and reduced recovery.

  • Look at what your gels/ chews/ bars and drink provides and determine how much you take in per hour of training.

  • The only way to know your composition is to get a sweat test conducted. If you notice salty skin or white markings on your clothes after a workout, you are likely a saltier sweater.

Want to know more?

Listen to the latest PODCAST where we chat with sweat test expert, triathlete & sports dietitian Brooke Schohl about sweating.

Read this in-depth journal on sweating & sodium concentration.

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