Sports Illustrated ranked its 50 fittest athletes in all of sports and the list features seven mixed martial artists, with UFC interim light heavyweight champion Jon Jones coming in at No. 4 on the men's side and former UFC women's bantamweight champion Holly Holm clocking in at No. 9. Sports Illustrated worked with a panel of trainers, strength and conditioning coaches, performance experts and more to come up with the list. It's not surprising that track and field athletes topped both the men's and women's sides with decathlete and 2012 Olympic champion Ashton Eaton leading the way for the men and heptathlete Jessica Ennis-Hill standing tall for the women.