What performance profiling can do is to help scientists and authorities determine the range of what is “acceptable”, and then use this information to screen and select athletes who might warrant closer scrutiny. Profiling could be particularly useful when athletes are training and most likely to dope, says Yorck Olaf Schumacher, an exercise physiologist at the Medical University of Freiburg, Germany. “It’s all about narrowing down a large collection of athletes to suspect ones.” It’s economically unfeasible to monitor every athlete 365 days a year, and performance profiling could help anti-doping authorities apportion limited resources.
One sport that has sought to analyse performances on such a scale is also one of its most tainted: road cycling. Since 2008, professional road cycling has taken a similar approach to performance profiling with the “biological passport,” which tracks physiological indicators associated with blood doping over an athlete’s career. A suspect passport led to more frequent tests for Italian cyclist Antonio Colom, and in 2009 targeted anti-doping tests turned up the banned blood-cell boosting drug erythropoietin (EPO). He received a two-year ban.
Performances in cycling’s biggest races during this period reveal some unusual trends, according to a 2010 study in the Journal of Sports Sciences that analysed the average speeds of the top finishers in 11 races over 116 years. Performances tended to improve over time in a series spurts before plateauing. These spurts occurred around World War I, at the dawn of pro cycling; between 1919 and 1939, when improved training and lighter bicycles joined the peleton; after World War II, when soldier-cyclists returned home; and after 1989 when cyclists began taking EPO, a banned artificial hormone that gives athletes greater stamina. Between 1989 and 1997, the average distance of the Tour de France increased from 3,285km to 3,944km (2,040-2,450 miles) and featured 17,000m (55,770 feet) of additional climbing – the equivalent of two Mount Everests. Average speeds should have slowed 11.3% during this period, instead they rose 4.5%.
Historical performance profiling suggests that athletes in other endurance sports may have been culpable too. In a 2009 paper titled Performance Profiling: A Role for Sport Science in the Fight Against Doping?, Schumacher and a colleague uncovered similar trajectories in distance running. Men’s 5,000m and 10,000m times fell dramatically in the 1990s and began rising again in the 2000s, only after a test for EPO was developed by anti-doping scientists.
EPO and other blood boosters aren’t the only performance enhancers whose introduction created blips in sports statistics. Schumacher’s study found that women’s discus throws became dramatically longer in the 1960s, 70s and 80s during a boom in steroid use; they came down to earth in the late 1980s when authorities introduced out-of-competition testing.
Performance profiling is already happening informally, says Tucker, because athletes who turn out gold-medal-winning performances are tested more frequently in and out of competition than also-rans. But proponents of profiling argue that statistical modelling, not just success, should be used to identify the athletes to watch most closely.
In a 2010 paper published in the open access journal Plos-One, Geoffroy Berthelot, a computer science researcher at Irmes Insep in Paris and his team studied thousands of top track and field and swimming performances recorded between 1891 and 2008, and came up with three statistical measures for how atypical an individual race or swim was, leaving any doping accusations aside. Their metrics looked at how much of an outlier a performance was from other athletes, as well as how long it took another athlete to eclipse a time. Florence Griffith Joyner’s 1998 world record of 10.49sec in the women’s 100m sprint scored high on the latter rating. Joyner, who died in her sleep from a sudden epileptic seizure in 1998, never tested positive for performance enhancers but her career was stained with the suggestion she used steroids.