The big business behind running marathons

Runners participating in the 2013 ING New York City Marathon on November 3, 2013.
Cem Ozdel | Anadolu Agency | Getty Images

Thirty-nine year old Meg Keflezighi is hoping to add to his already impressive resume and win his second New York City Marathon this Sunday.

New York's champion in 2009, he won a silver medal in the 2004 Olympics though his most memorable race happened earlier this year. After a 31 year drought, he became the first American male to win the Boston Marathon since 1983. It is a victory cherished by Keflezighi as it followed the horror of the 2013 marathon, when three people were killed and 264 were wounded by terrorists bombs.

Marathon man Meb Keflezighi

The victory also came with Keflezighi wearing the shoes of an unlikely sponsor, Skechers. Nike has cut ties with Keflezighi before Boston so he signed with the upstart maker of athletic footwear. Keflezighi talked with CNBC's Mary Thompson about what he looks for in a sponsor.

Read MoreMeb Keflezighi Runs His Way Into a Perfect Sponsor

The business of marathon running

Keflezighi vets potential sponsors with his brother to make sure they fit with the image the champion wants to project.

One of ten children, Keflezighi's family came to the U.S. from Eritrea when he was a child. As his running career winds down, he spoke to CNBC about his next step.

Read MoreNike thought I was'too old'

Marathon winner