Boring Electrolytes

Short answer About one cup, roughly 240 ml, every 15 to 20 minutes while you are working hard in the heat. That comes to close to one litre an hour, and you should not push past about 1.5 litres in any single hour. Across a hot shift it adds up to 6 litres or more. But water is only half of it. You sweat out roughly 0.5 to 1.5 grams of sodium for every litre, and drinking a lot of plain water without replacing that salt can leave you flatter than when you started. Match the water to how...

Short answer Alcohol dehydrates you because it switches off the hormone that tells your kidneys to keep water. That hormone is vasopressin, also called antidiuretic hormone. With less of it, the kidneys stop reabsorbing water and send it straight to your bladder, so you pass more fluid than the volume you drank. Every gram of alcohol pushes out roughly 10 ml of extra urine, and that urine carries dissolved sodium, potassium and magnesium out with it. By the end of the night you are down...

Short answer As often as you like, as long as you put back what each session sweats out. A normal 15 to 20 minute session costs you around half a litre of sweat and somewhere between 0.25 and 0.75 g of sodium, and going daily or twice a day simply stacks those numbers up. The thing that dehydrates you is not the frequency. It is finishing every session with plain water and no sodium, so the water dilutes what you have left instead of replacing it. What actually limits how often you can...