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 followed the journey of five athletes as they dove into "Sweat Science." Each athlete tested 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 then used their sweat data to adapt their fluid and electrolyte intake accordingly.

Check out their Sweat Science journeys below, and find out how you can use their findings and takeaways to build a knockout hydration plan.