I looked for the answer to this question, but unable to find. I recently started the first week of the Marathon Level 1 training. I did Long Run #1 and at 4.5 miles in zone 2 and 1.5 in zone 1, it took me 2 hours to complete. That means later, when I’m doing 20 miles, it could take me 7 hours to complete. This can’t be right. Am I missing something? Do I need to run according to pace instead of zone?