Running a marathon, which spans an intense 26.2 miles (42.2 kilometers), is one of the ultimate tests of human endurance, pushing both body and mind to their limits. This extreme effort triggers a number of physical responses, from muscle breakdown and dehydration to hormone surges. In fact, new research published in Nature Metabolism shows that running a marathon can cause the brain to even start eating itself.
Click on to explore what really happens inside your body during a marathon, and why preparation and recovery are absolutely essential.