Forgive me for reposting this excerpt from a long-winded posting of my own, but I didn't get an answer. I'm using this theory to kinda calculate how much to take in during my longer runs this year so I'd like to have a clue if it seems viable.
repost: For the marathon distance, I proposed my theory that since we should have enough glucose in us for about 20 miles, all we need to do is add sufficient to complete the 6 that are left over. Let's say 18 and 8 to give a comfort zone. So, at about 150 cal/mile, we need to shove back 8 times 150 equals about 1000 cal. plus.
So the plan is to eat early and often. Splitting the intake between 4 or so tasty gels, some ju-jubes, some cookies and adding some liquid carbs too.
