During a marathon, carbohydrate intake bottles should be less concentrated at the start and more concentrated as the race progresses.

“how I always did things is we would make them not very concentrated the first — bottle and then they'd get increasingly concentrated as the race was going on and then they' get decreasingly concentrated later later in the race and the reason for that was like it's easier to absorb things when you're not as tired right so you kind of want to make sure you're front loading your carb intake during the marathon because your body can just process it a lot easier”