You don’t need to replace all the salt you lose during long workouts because your kidneys hold onto salt to balance things out. But if you need to recover fast—like within a day—eating more salt might help your body get back to normal quicker.

If fit guys cut down on salt for 9 days, they pee out less sodium—even when exercising in the heat—showing their bodies are adjusting and they’re sticking to the low-salt plan.

If endurance athletes drink a lot during long workouts and also take in sodium, it might help prevent low blood salt levels — but it probably won’t make them perform better just by itself.

Drinking a salty drink before working out in the heat might help your body hold onto more water and stay hydrated, but it might taste bad and be hard to drink a lot of.

If endurance cyclists drink fluids with sodium during long rides, they pee less and keep more fluid in their bloodstream, which helps prevent dehydration—even though the salt level in their blood stays the same.

If elite cyclists drink as much as they want during a 3-hour ride in cool weather, taking in 700 mg of sodium per hour helps keep their blood fluid levels stable—or even slightly increases them—while skipping it leads to a small drop.