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Coffee Before Running: How Much, When, and Is It Worth It?
Taking 3 to 6 mg of caffeine per kilogram of body weight before running can make endurance time trials about 2.22% faster, roughly 5 minutes for a 4-hour marathoner and about 1% for a 5k. Start at 3 mg/kg and finish your coffee 45 to 60 minutes before the start; a 12-ounce (355 mL) cup has about 130 to 200 mg. Moderate coffee doesn't dehydrate you, you don't need to cut back before a race, and coffee works as well as pure caffeine, so choose what your stomach tolerates.
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