Caffeine is a diuretic in the textbook sense, and for habitual drinkers at ordinary doses that turns out not to matter. What the controlled trials actually measured, and the two situations where the caution still applies.

A trial designed to separate water from salt found that fluid volume, not sodium, protected performance in the heat. The company that funded it sells sodium.

Races are moving their dates and start times because cool mornings are disappearing. Runners are not moving at all, which is why the heat plan has to be built in August.

Texas high schools now run practice off wet bulb globe temperature instead of the heat index, and the switch quietly rewrites how anyone who trains outdoors should read a hot day.

Weight-loss shots quietly switch off thirst and drain electrolytes. Here is how active people stay hydrated without losing a step.

This summer's heat proved a hard truth: sweat rates vary wildly, and the electrolyte scoop that saves one athlete leaves another cramping.

You don't have to force down eight glasses of plain water. Here's how to hit your daily fluid needs through food, flavor, routine, and a little help from tech.

Skin sensors, sweat patches, and smart toilets are all racing to solve hydration tracking. Here is what the research actually shows about whether any of them work.

Most workouts do not need electrolyte drinks, but long, hot, or sweat-heavy training changes the equation. Here is when water is enough and when electrolytes actually help.

The hydration industry says water needs fixing, then sells you the fix by the tub. The cheaper answer is in your produce drawer. Here is the science of eating your water.