Electrolytes can be the difference between finishing as a champ, or struggling with fatigue, cramping and nausea. These small but mighty elements — sodium, potassium, calcium, magnesium and chloride — play a pivotal role in muscle contraction, blood pressure, and keeping you cool (i.e sweat).

Put simply, if you're not replacing electrolytes during your training, your performance will tank.

That's all great, you might say, but I need specifics. Like, do I need more electrolytes on hot days? What about humidity? Or altitude? Do I take electrolytes before, during, or after training? How do I figure out how much water to drink?

All great questions, and like many aspects of nutrition, it depends. Everyone sweats differently. Even your own sweat rate and concentration can vary widely, depending on temperature, level of fitness, altitude, or humidity.

It can get confusing fast, so to help demystify, we're following the journey of five athletes as they dive into "Sweat Science." Each athlete will test their sweat rate, electrolyte loss rate, and sweat composition using the Nix Hydration Biosensor, which provides athletes with personalized hydration data in real time. Athletes will then use their sweat data to adapt their fluid and electrolyte intake accordingly.

Follow along as our team breaks down the science behind what's working and what's not, so you can build a knockout hydration routine of your own.