A marathon is an endurance race that needs a lot of mental and physical preparation. The old adage is true that says: "The race is run between the ears." It simply means that a lot of mental preparation is needed. This is important as the rest of the body is governed by a sound mind. In addition, more physical training is need to make sure that the muscles can stand the strenuous action. This prepares the oxygen reserves in the muscles.
Running so you can build up both endurance and stamina. It’ll keep you in shape so you can last longer in a marathon. Constant conditioning will do the trick.
