Does potassium before exercise help prevent cramps?

 While many athletes eat the ritual pre-race banana as insurance against cramping, the potassium-rich fruit can't buy you blanket protection. First, because potassium isn't absorbed into your system as quickly as water or sugar, you'd be better off eating that banana for breakfast (on a daily basis would be even better). And while it's true that potassium is essential to normal muscle contraction, so is calcium. In simplified terms, whenever a muscle cell contracts, calcium outside the cell wall trades places with potassium inside the cell. When the cell relaxes, the two nutrients switch back. "Cramping occurs for a number of reasons," explains Elaine Turner, an assistant professor of food science at the University of Florida. "Potassium deficiency is just one possibility. If you're eating plenty of fruits and vegetables, you're getting enough potassium to prevent cramping." The recommended daily allowance (RDA) of potassium for adults is 2,000 mg a day (an eight-ounce glass of orange juice has 496 mg of potassium; a banana has 467 mg). If you still experience muscle cramps, make sure your calcium intake is up to snuff (the RDA is 800 mg, which translates into three cups of skim milk or 500 grams of tofu), and that you're drinking plenty of water.