This question is about Running
Marathon runners need carbohydrates to maintain output and blood sugar during a long distance run [ 1 2
Inadequate carbohydrate intake before and during a long distance run can result in decrements in speed, duration, and energy levels, a phenomenon known as “hitting the wall” [ 1 3 2
Rothschild, J. A., Kilding, A. E., & Plews, D. J. (2020). What Should I Eat before Exercise? Pre-Exercise Nutrition and the Response to Endurance Exercise: Current Prospective and Future Directions. Nutrients, 12(11), 3473. https://doi.org/10.3390/nu1211347
Burke L. M. (2007). Nutrition strategies for the marathon : fuel for training and racing. Sports medicine (Auckland, N.Z.), 37(4-5), 344–347. https://doi.org/10.2165/00007256-200737040-00018
Rapoport B. I. (2010). Metabolic factors limiting performance in marathon runners. PLoS computational biology, 6(10), e1000960. https://doi.org/10.1371/journal.pcbi.1000960