Long-lasting high-intensity workouts, especially those done in the heat, will invariably cause dehydration and therefore decrease body mass. For every one percent of body mass you lose, your body temperature also increases a half-degree Fahrenheit. The better hydrated you are, the cooler your body temperature, and the better your performance. This means it's crucial to be fully hydrated at the start of exercise. While athletes should hydrate the day before, don't begin the process at night – it will cause a handful of bathroom breaks when you're trying to get a good night's sleep. Hydration expert Doug Casa says starting the day before, in the afternoon, allows you to urinate excess fluids before bedtime. Drinking an extra 20 to 30 ounces the morning of game day will also give you time to get rid of excess fluids.
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