written by: Olivia Crozier
It’s a common misconception among athletes that a higher sweat rate automatically means they need a hydration beverage with a higher electrolyte concentration—and vice versa for those with a lower sweat rate. While it’s true that longer or more intense workouts often lead to increased electrolyte losses, this doesn’t always mean athletes need to consume more electrolytes than their counterparts.
One of the key factors that should guide an athlete’s hydration strategy? Sweat Composition.
Sweat composition refers to the amount of electrolytes lost per ounce or liter of sweat. Along with fluid losses and electrolyte losses, the Nix Solo app also calculates your personal sweat composition on average and for each individual workout logged. This number is highly individual and influenced more by personal biology than external conditions. Two athletes may lose the same total amount of fluid during a workout, but their sweat can contain vastly different amounts of sodium, potassium, and other key electrolytes.
This means the right hydration approach should be based not just on how much you sweat, but the composition of your sweat.
While two athletes may lose the same total volume of electrolytes the concentration within their sweat can vary dramatically.
This difference matters because hydration isn’t just about replacing fluids, but also about replacing the right amount of electrolytes based on how concentrated your sweat is.
Many factors influence sweat rate: workout intensity, temperature, humidity, clothing, and even fitness level. But when it comes to sweat composition, the primary influence is your own personal biology.
Some people are naturally “salty sweaters,” meaning they lose a high concentration of electrolytes in a relatively small volume of sweat. Others can lose large volumes of fluid but have relatively low electrolyte content in their sweat. This biological difference is why hydration needs vary so much from person to person—even within the same sport, under the same conditions.
To better understand this, let’s compare two female runners with completely different sweat profiles.
Athlete A
Athlete A doesn’t necessarily sweat a lot in terms of fluid volume, but her sweat is packed with electrolytes. Her body loses over 100 mg of electrolytes for every ounce of sweat. As a result, even though she’s not losing a ton of water, she must be highly strategic about replacing the electrolytes that she’s losing during a workout. She should choose a beverage that is rich in electrolytes—ideally over 100 mg/oz. Brands like Hydralyte, SOS, and Pedialyte are good matches for her sweat profile.
Athlete B
Athlete B sweats a lot more than Athlete A, but her sweat is much less concentrated. Although she loses more electrolytes in total, her composition is less than half that of Athlete A. This means she should hydrate with a lighter electrolyte beverage—something in the range of 40–50 mg/oz. Brands such as Nuun, Näak, and FastFood are well-suited to her needs.
While both athletes lost a similar amount of total electrolytes during their one-hour workouts, their optimal hydration strategies are vastly different due to the concentration of those losses.
This has important implications, especially in team sports where athletes may be expected to hydrate with the same beverage brand that is provided to them on the sidelines. In those cases, an athlete can choose to dilute or concentrate the beverage with water to adjust its electrolyte composition to better match their personal sweat profile.
Hydration is not one-size-fits-all. By understanding your individual sweat composition, you can make smarter decisions about when, what, and how much you need to drink. Whether you're training for a marathon or playing in a team setting, tailoring your hydration approach to your biology can help you stay properly hydrated and performing at your peak.
The Nix Solo app not only calculates your sweat composition based on your fluid and electrolyte losses, but also provides educational materials and guidance to help identify which electrolyte brand or beverage is best for you based on your individual sweat composition.