Former NCAA and USATF pole vault champion Demi Payne tested positive for a banned substance in 2016 and has received a four-year sanction, the U.S. Anti-Doping Agency (USADA) announced on Friday. Payne, 26, accepted the ban, and her four-year suspension began on March 31, 2016. The 2015 USATF Indoor and NCAA Outdoor…