The general principle behind many human genetic studies is to compare the genetics of a group of individuals with shared characteristics of interest (such as being good at sport) to a control group lacking those characteristics. We would expect that genetic variants related to the production of those characteristics would be more common in the former group. With as much as 66% of athlete status being the result of heritable factors (13), elite athletes must have a genetic profile that predisposes them to being good at sport, responsive to training, and resistant to injury as well as ensuring that they train hard, eat well, and have a skilled team of coaches around them. The more extreme and well-defined this group of athletes is, the more pronounced we would expect any genetic difference to be. Defining that group of individuals well is key to this process.