Instead of cycling for fitness, riders at Equinox, New York, have been cycling for survival.

In February and early March, 13,000 people attended events at Equinox clubs in 10 cities for Cycle for Survival, an indoor team cycling event that raises money for research into rare cancers.

The events raised $13.8 million, and within six months, the money will be allocated to clinical trials and research studies led by Memorial Sloan-Kettering Cancer Center, New York.

"We are grateful to all of the participants who make such a difference in the lives of so many by riding in these events and raising money for critical research," Scott Rosen, chief operating officer for Equinox, said in a news release.

Celebrity participants included New York City Mayor Michael Bloomberg, Huffington Post founder Arianna Huffington, Saturday Night Live's Seth Meyers, NBA All-Star Grant Hill, Olympic gymnasts Shannon Miller and Nastia Lukin, and Olympic figure skater Sasha Cohen. NFL players Mark Herzlich, Robbie Gould, Nick Roach, Antwaan Randle El, and Jarvis Green, "Survivor's" Ethan Zohn and "Top Chef's" Padma Lakshmi also took part in Cycle for Survival.

"We are grateful to the thousands of volunteers who have taken part in events around the country, generating critical support and giving new hope to all those whose lives have been touched by the work that support makes possible," Craig Thompson, president and CEO of Memorial Sloan-Kettering, said in the release.

Since it was created in 2006, Cycle for Survival has raised more than $31 million for research trials and clinical studies. This year, the number of participants doubled, and the amount of money raised has already increased by more than $5 million.