In January 2013, the world of sports was shaken by an interview conducted by the American powerhouse broadcaster Oprah Winfrey with the cycling champion Lance Armstrong. Armstrong, who had won seven consecutive Tour de France titles from 1999 to 2005, publicly admitted using banned substances to enhance his performance during official competitions, confirming long-standing suspicions that had followed him for years. Armstrong left a mark on the history of doping. As a cancer survivor, his achievements represented a sign of hope and resilience, and what happened next was described by many as the fall of a hero. It goes without saying that Armstrong鈥檚 case was neither the first nor the last doping scandal.But why exactly do athletes resort to doping? What substances do they use, and why are they so difficult to detect?Euronews Tech Talks set out to better understand doping with Andrea Petr贸czi, professor of public health at Kingston University in the United Kingdom. She also regularly provides consultancy to the World Anti-Doping Agency.What is doping? Petr贸czi said that researchers have not yet agreed on the exact definition of doping. However, she said the World Anti-Doping Code provides clear rules for athletes to understand what doping is and who can be accused of it. 鈥淒oping is defined as the occurrence of one or more of the anti-doping rules violations set forth in Article 2.1 through Article 2.11 of the Code,鈥 the Code states. There are 11 anti-doping rule violations, which include not only the use of substances but also the attempted use of these agents. Moreover, even if an athlete did not intend to cheat, they can still face sanctions if a banned substance is found in their system. Some of these rules apply not only to the athletes but also to their support personnel.According to the Code, any substance or method that meets two out of three criteria is classified as prohibited. These criteria are: evidence that the substance enhances performance, evidence that it poses a health risk, and evidence that it goes against the spirit of sport.Based on these criteria, 鈥渁 substance doesn鈥檛 necessarily have to be performance-enhancing to be prohibited”. Petr贸czi said. “If it鈥檚 deemed risky to the athlete鈥檚 health and against the spirit of sport, then it can be added to the list,鈥 she added.The most well-known doping substances are EPO and anabolic steroids. EPO, or erythropoietin, is a hormone produced by the kidneys to stimulate the production of red blood cells, helping transport oxygen to the muscles. It is commonly used in sports like marathons or cycling, as it boosts endurance. By contrast, anabolic steroids are synthetic compounds similar to testosterone that promote muscle growth, and they are used in sprint or weight lifting competitions. Caffeine was also considered a prohibited substance and was reintroduced only in 2004. Although now allowed, it has since then been on the World Anti-Doping Agency’s monitoring programme.Is doping too difficult to detect? Andrea Petr贸czi stated that 鈥渄oping is not difficult to detect because the detection limit is low鈥. However, she acknowledged the major challenges in detecting doping and argued that they depend on multiple factors, including whether the anti-doping authorities know or not about the substance being used and the timing of the doping test. For instance, Petr贸czi explained that microdoses of prohibited substances are complicated to identify, not because of their small amount, but because they remain in the body for only a short time. This makes them hard to identify unless testing occurs within a narrow window.She also pointed out that given the advancements in equipment, diets and training, it is more difficult to understand the limit between excellent preparation and the use of doping substances. 鈥淚n the future, what poses a challenge for anti-doping is not a new drug necessarily,” Petr贸czi said.”But the combination of the existing drugs with data science, with specialised training, with equipment, each providing a marginal gain, but in combination, the synergistic effect,鈥 she added.