The use of performance-enhancing drugs (doping) is prohibited within the sport of athletics. Athletes who are found to have used such banned substances, whether through a positive drugs test, the biological passport system, an investigation or public admission, may receive a competition ban for a length of time which reflects the severity of the infraction. Athletes who are found to have banned substances in their possession, or who tamper with or refuse to submit to drug testing can also receive bans from the sport. Competitive bans may also be given to athletes who test positive for prohibited recreational drugs or stimulants with little performance-enhancing effect for competitors in athletics. The sports body responsible for determining which substances are banned in athletics is the W