Since organised sport began, those involved have been united by a common goal: to become progressively better. It's a natural desire shared by athletes, coaches, fans and sponsors alike, and there are many ways improvement can be sought, from the light areas of professionalism to the dark arts of doping.But there is another way: a shady middle ground where advances are equally likely to be met by applause as by accusations of cheating. Technological innovation in sport occupies this ambiguous position.Once so in vogue, the term 'marginal gains' may have taken a near-fatal knock in the wake of Sir Dave Brailsford and Team Sky's prolonged and wince-inducing fall from grace. Nevertheless, the idea of finding small advantages and collating them to generate an edge remains a universal concept across professional sport.But with everyone chasing the same thing, what is the difference between acceptable and unacceptable technological advances? Where should the line be drawn? The answer for many sports lies in their rulebooks, which are written in language that is sufficiently vague as to be interpreted to fit a variety of agendas.Read more on VICE Sports.