The Fat Man is an Olympic distance road duathlon, it is contested on a very scenic course on a mesa top next to the Rio Grande valley, and is most likely the hardest Olympic Road Duathlon in the United States.
Fat Man has been selected as the USAT Rocky Mountain Region regional duathlon championship in 2013.
The Little Boy is a touch easer and shorter, with a 4k - 15k - 4k format.
Both Fat Man and Little Boy start/finish in the town of White Rock.
The course is at high altitude (6300ft - 7200ft) and the course is quite hilly.
The bike leg on Fat Man, in particular, features approximately 2000ft of climbing and goes through the scenic Ancho canyon as well as passing the historic Bandelier National monument.