Drink when you're thirsty

For thirty years, athletes were told to drink before they were thirsty, as much as they could tolerate, because thirst was a lagging signal and dehydration was the enemy. Then runners started dying, and the cause wasn't dehydration. It was too much water.

Tim Noakes, a South African sports scientist, had been documenting the problem since the 1980s, and in 2012 he wrote Waterlogged to lay it out: exercise-associated hyponatremia, the dilution of the blood's sodium by over-drinking, had killed marathoners and hikers and soldiers, and the advice to drink ahead of thirst was the cause. His correction was the oldest one: drink to thirst. The body's thirst signal, he showed, is accurate, and it protects you in both directions. The American College of Sports Medicine's 2007 position stand had already moved in the same direction, and the guidelines now say roughly what Noakes said.

The practical rules. Drink when thirsty; don't force it. In long efforts in heat, somewhere around four hundred to eight hundred milliliters an hour is the typical range, with sodium, because sweat carries salt out and plain water alone can tip the balance. Weigh yourself before and after a long session once; losing a little is normal, gaining is a warning. And the old eight-glasses-a-day rule for ordinary life has no evidence behind it; food and thirst handle it.

It closes the table keys of this chamber because it's a story about trusting the body over the rule. The same body that tells you it's full, that tells you it's tired, that tells you it needs protein after a lift, tells you when to drink. The whole table chamber has been about learning to hear it.