Kenyan long distance runner Eliud Kipchoge sets a new world record at the Berlin Marathon.
EPA-EFE/Hayoung Jeon
Under the right conditions marathons could be run in under two hours.
Alexandr Zadiraka/Shutterstock
In some distance events, disabled athletes already outcompete their able-bodied counterparts.
Paula Radcliffe holds the world record in the women’s marathon, at 2:15:25.
REUTERS/Shannon Stapleton
Just like an efficient car on a long trip, the best marathon runners also use less energy to run at a given speed.