In summary, E runs help build resistance to injury, strengthen the heart muscle, improve the delivery of blood, and promote some useful characteristics of the muscle fibers that will help you run at your best. In addition, increasing the duration of E runs (and it’s much easier to increase mileage or duration of your runs if they are easy) is a good boost for your confidence that you can last a long time if you so desire. Never overlook the mental side of the training you are doing.
