PARIS: Middle distance runner Shelby Houlihan lost her appeal against a four-year drugs ban after the Court of Arbitration for Sport said Wednesday her defence “presupposes a cascade of factual and scientific improbabilities”.The 28-year-old USA 1,500m and 5,000m record holder missed the Tokyo Olympics after testing positive for a banned steroid last December, which she blamed on eating contaminated meat contained in a burrito. Houlihan was sanctioned by the Athletics Integrity Unit, a decision upheld after an appeal to CAS in June.CAS released its full decision Wednesday, explaining that Houlihan had argued her positive test came after eating pork meat from an uncastrated boar.The athlete said she had mistakenly been served pork despite ordering beef at a food truck, but the CAS panel said the uncastrated boar argument “simply cannot be accepted”. “The explanation presupposes a cascade of factual and scientific improbabilities, which means that its composite probability is (very) close to zero,” CAS said in its decision.Houlihan will miss the 2022 world championships on home soil in Oregon as well as the Paris 2024 Olympics, with her ban due to end on January 14, 2025.