The marathon is a long-distance running event with an official distance of 42.195 kilometers (26 miles 385 yards) that is usually run as a road race. The event is named after the fabled run of the Greek soldier Pheidippides, a messenger from the Battle of Marathon to Athens. It was one of the original Olympic events in 1896, though the distance did not become standardized until 1921. More than 800 marathons are contested throughout the world each year, with the vast majority of competitors being recreational athletes. The larger marathons can have tens of thousands of participants.

Most coaches believe that the most important element in marathon training is the long run. Recreational runners commonly try to reach a maximum of about 20 miles (32 kilometres) in their longest weekly run and a total of about 40 miles (64 kilometres) a week when training for the marathon, but wide variability exists in practice and in recommendations. Many training programs last a minimum of five or six months, with a gradual increase (every two weeks) in the distance run and finally a little decrease (1 to 3 weeks) for recovery. The decrease, commonly called the taper, should last a minimum of two weeks and a maximum of three weeks, according to most trainers. For beginners looking to merely finish a marathon, a minimum of 4 months of running 4 days a week is recommended. Many trainers recommend a weekly increase in mileage of no more than 10%. It is also often advised to maintain a consistent running program for six weeks or so before beginning a marathon training program to allow the body to adapt to the new stresses.