See this string from Low Carb Friends. The general accepted rule is 50 daily carbs per hour of cardio. There are a few special cases, but if you're doing 7 miles in a day, you should be eating 50-80 carbs (depending on who the poster is). I'm really interested in everyone's input, but you've really gotta sort through. You'll find hugely deferring numbers, and trial and error will have to suffice. I feel fantastic after an hour of cardio, but I don't want to overdo it, so I go for less time. Please, people, let me know what you think!
LC ?? for Endurance Training - Low Carb Friends