Drugs such as erythropoietin (EPO) and growth hormone are natural chemicals in the body. As technology advances, drugs have become harder to detect because they mimic natural processes. In a few years, there will be many undetectable drugs. Haugen’s analysis predicts the obvious: that when the risk of being caught is zero, athletes will all choose to cheat.

The starkest example is the Finnish skier Eero Maentyranta. In 1964, he won three gold medals. Subsequently it was found he had a genetic mutation that meant that he “naturally” had 40–50% more red blood cells than average.15 Was it fair that he had significant advantage given to him by chance?

More than 2,000 track and field athletes participated in the study, and according to the findings, which were reviewed by The New York Times, an estimated 29 percent of the athletes at the 2011 world championships and 45 percent of the athletes at the 2011 Pan-Arab Games said in anonymous surveys that they had doped in the past year.

In 2006, every player in the USA’s National Hockey League was tested between January 15 and the end of the season. There were 1,406 tests, and no positive results

Without a doubt, tinkering with an athlete's genes has enormous potential to increase performance—initial results from basic research in this area are impressive. Transgenic mice created in an effort to understand muscle growth and muscle disease were soon baptized ‘Schwarzenegger mice' owing to their enormously increased strength and muscle mass (Barton-Davis et al, 1998; McPherron et al, 1997).

In fact, there are some people who have mutations that turn them into natural athletes. For example, Finnish Nordic skier and 1964 Olympic gold medallist Eero Mäntyranta had unusually high amounts of red blood cells, and a boy born with a myostatin dysfunction has larger than normal weight-lifting capacities (Schuelke et al, 2004). However, if gene doping were to be banned, would such people still be allowed to compete in sports? “I don't see any reason why somebody with a myostatin mutation should be excluded from any kind of competition,” commented Se-Jin Lee, from Johns Hopkins University (Baltimore, MD, USA), one of the researchers who described the myostatin case.

If gene therapy becomes sufficiently safe to be used not only as a medical treatment but also for normal enhancement purposes, it will raise the question of whether gene doping should remain forbidden. There is already a grey zone of performance enhancements that are legally used in sports because they are accepted as standard medical treatments. Professional golfers, for example, have subjected themselves to laser eye surgery to enhance their vision. Although some feel that this amounts to doping, Michael Knorz, founder of the FreeVis LASIK Centre in Mannheim, Germany, commented that this does not, in his view, go against the spirit of sport: “Refractive surgery is detectable and does not need to be considered as [a] new form of doping. It simply replaces contact lenses. A perfectly normal eye with good vision cannot be enhanced.”

The use of technological aids to improve sport performance (‘techno doping’) and inclusion of Paralympic athletes in Olympic events are matters of ongoing debate. Recently, a long jumper with a below the knee amputation (BKA) achieved jump distances similar to world-class athletes without amputations, using a carbon fibre running-specific prosthesis (RSP). We show that athletes with BKA utilize a different, more effective take-off technique in the long jump, which provided the best athlete with BKA a performance advantage of at least 0.13 m compared to non-amputee athletes.

Gene doping is not merely gene manipulation, but also includes indirect genetic technologies, such as biosynthetic drugs (drugs for increasing oxygen). Genetic performance-enhancement technologies should consist of the full range of possible applica-tions. Blood oxygenation is a fundamental factor in optimising muscular activity. Increasing oxygen transport to tissues is associated with improvement in athletic performance

The Halo isn’t on the market yet, but it’s already being used in elite athletics—a world where a vanishingly small improvement in performance can mean the difference between finishing first or 18th. Some Olympic athletes, including sprinters and swimmers, used a premarket version of the Halo to prepare for the Rio games

The company validated its standard protocol in several double-blind, sham-controlled trials, which it published as white papers. One study showed that the Halo Sport’s stimulation enabled users to exert more force in a finger-pinching task [pdf], while another demonstrated its positive effect on a fine-motor-skill task [pdf] requiring subjects to strike different keys on a keyboard. Now the team is writing up a study that examined muscle output via a bicep-curl machine, a setup that more closely resembles real-world athletic training. Going forward, Chao says the company will publish its findings in peer-reviewed journals.