This is where articles like the one quoted initially fail, because they make a statement about an issue, without providing actual research, how much does a runner need to drink to get water intoxication, is it a relatively small amount, or is it a considerable amount. Has anyone actually tracked this to see? Does what applies to a runner actually apply to a cyclist who travels much faster, where the passage of dryer air around the body makes sweat more efficient, and therefore less sweat is needed to cool the body.

The normal guideline for cyclists is 1L/hr (a little more then a US quart, a little less then a UK quart), the kidneys can eliminate up to 1L/hr if healthy. Water is heavy, 1L of water weighs 1kg, so if your losing 2kg over a 4 hour ride, then you need an extra 2L of water beyond this to stay at your initial hydration level, providing your initial hydration is at optimum, which it may not be. The club rider who had 9 beers last night and then 5 cups of coffee this morning, is already starting out dehydrated. So before a ride, drink a full 1L of water in the hour before, to get your initial hydration level up, then 1L/hr during the ride. Weigh yourself before (pee before you weigh yourself) and after (don't pee before) , the weight difference is mostly lost water, so if you lost 5lbs that's 2¼kg or 2¼L (2.38 US Quarts or 2 UK quarts) your down on water, so the next ride of a similar length at a similar temperature you need that much more, spread over the ride. If the next time you are up 1lb then you know that your drinking about 1/2L per hour more then you need to, so you can cut back.