VIEWPOINT The two-hour marathon: who and when?

In this Viewpoint we ask if information about the physiol-ogy, genetics, and empirical history of elite endurance perfor-mance can provide insight into the question of “who ” will break the 2-h marathon barrier and when this might happen. We also identify several physiological questions that we be-lieve need attention. The current world record in the men’s marathon is 2:03:59 (Gebrselassie 2008). This record has fallen by more than 16 min since the early 1950s after high volume/year round train-ing was adopted widely. Except for the 1970s, the record has fallen by 1–5 min/decade since 1960 when Africans entered international competition. Improvements since 1980 likely also reflect increased prize money and competitive opportunities that allowed top athletes to earn a living running. Figure 1 shows the history of marathon times and projected improve