How to Calculate Total Fluid Replacement

If you are preparing to run long distances and train for events such as a half marathon or a marathon, one of the most important lessons you will need to learn has to do with total fluid replacement. While you're running, you're not just losing water -- you're losing sodium and electrolytes that are crucial for optimal bodily function. If you don't replace those nutrients while you're running, you're setting yourself up for a metabolic crash late in the race and the dangers of dehydration.

Instructions

    • 1

      Calculate the pace at which you want to run the race. A four-hour marathon takes around a nine-minute mile pace; however, a five-hour marathon is well more than an 11-minute mile pace. While both of these paces require considerable stamina, they don't require the same level of fluid replacement.

    • 2

      Consume 30 to 36 ounces of water and/or sports drink for every hour if you are planning to run your marathon in less than four hours, or at a faster pace than nine minutes per mile. During the course of the race, you should plan to consume as much as 4 liters.

    • 3

      Drop your replacement rate to 24 ounces per hour if you are aiming between four and five hours, or between nine and 10 1/2 minutes per mile, with a total consumption between 3 and 3 1/2 liters.

    • 4

      Reduce your fluid consumption further if you plan to take longer than five hours to finish the marathon. Plan for about 18 ounces per hour, not exceeding a total of 3 liters for the race.