Sweat, Science, and Performance: The Truth About Hydration

Imagine two athletes run the same 5 km race on a hot day. Athlete A drinks nothing. Athlete B sips water throughout. At the finish line, Athlete A's time is noticeably slower — and they feel dizzy. Here is the surprising part: Athlete A lost only about 2% of their body mass in sweat. That tiny percentage was enough to measurably hurt their performance. Why would such a small change make such a big difference? Think about what your body is actually made of and what it needs to keep working. Jot down your best guess before reading on.