Drinking too much fluid during long workouts can actually be dangerous — it can lead to a serious condition called low blood salt (hyponatremia), especially if you're gaining weight during a race because you're taking in more fluid than you're losing.

Even if endurance runners take in a lot of salt, they can still develop low blood sodium if they drink too much water — it’s the overdrinking, not the salt intake, that’s the main problem.

If endurance runners drink too much during long races, it can dilute their blood and cause dangerous low sodium levels — not just from losing salt, but from drinking too much. Cutting back on fluids in events over 4 hours could prevent this problem.

Even if endurance runners take a lot of salt pills during long races, drinking too much water — like 10 liters — can still give them a dangerous condition called low blood sodium. Salt alone won’t protect you if you’re chugging way too much water.

Some athletes who do long, tough workouts like marathons or triathlons can end up with low sodium in their blood — a condition called exercise-associated hyponatremia — and it’s actually pretty common depending on the event.

If you're doing long workouts like marathons, drinking when you're thirsty is safer than chugging water all the time — it helps avoid a dangerous low-sodium condition.