This chapter presents a framework that shifts the perspective on doping and performance enhancement from "human nature" as enduring personal and general dispositions to the "nature of human activity". Human activity is described as displaying circumstantial, embedded, autonomous, dynamical, extended and embodied characteristics that provide some grounds for reflections as they relate to athletic performance enhancement, the relationship with human nature, and the ethical consequences in the context of sports. From this perspective, doping is not a factor of athlete's progressive dehumanization. It can instead be seen as one of the circumstantial and cultural actualizations of the possibilities for enhancing their resources, emerging in a dynamic, extended and distributed athletic activity system. In contrast, but not in opposition, to an ethical approach of "clean" sport based on general moral principles, such as respect for equal opportunity in competition, a dynamic and situated anti-doping ethics in sport can thus be built in close relationship with athletes' activity.