Shelby Houlihan said on Monday she had received a four-year ban for testing positive to an anabolic steroid but the American record-holder in the 1,500m and 5,000m denied she had knowingly taken a prohibited substance. Just days before the U.S. Olympic Track and Field Trials are set to begin, the 28-year-old said in a written statement that the Athletics Integrity Unit informed her in January a World Anti-Doping Agency (WADA) test showed an "adverse analytical finding" for nandrolone. Houlihan, who won the 1,500m and 5,000m at the USA Outdoor Track and Field Championships in 2019 and was considered a medal contender for the Tokyo Olympics, thought the positive result might have come from eating pork, which she said could lead to a false positive for nandrolone, the night before the test. "I did everything I could to prove my innocence. I passed a polygraph test. I had my hair sampled by one of the world’s foremost toxicologists," she said. "WADA agreed that test proved that there was no build up of this substance in my body, which there would have been if I were taking it regularly. "Nothing moved the lab from their initial snap decision." WADA and USA Track and Field did not immediately respond to a request for comment. Houlihan, who competed at the 2016 Rio Olympics but has not raced in 2021, said she learned on Friday that the Court of Arbitration for Sport had handed her the ban, dashing her hopes of competing in Tokyo or at the 2024 Paris Games. "I feel completely devastated, lost, broken, angry, confused and betrayed by the very sport that I’ve loved and poured myself into," she wrote. "I have never taken any performance enhancing substances." Four-time Olympian Shalane Flanagan, who coaches at Houlihan"s Bowerman Track Club, wrote on social media: "We are living a nightmare that we can"t seem to wake up from. "If this is where the sport I love is headed, then I don’t know if I can continue to be part of it," wrote Flanagan. "I refuse to believe this is acceptable and neither should you."