Winning athletes keep getting bigger.

• Position: Sports Medicine

While watching swimmers line up during the 2008 Olympic Games in Beijing, former Olympian and current sports commentator Rowdy Gaines quipped that athletes seem to keep getting bigger, with the shortest one in the current race towering over the average spectator. What may have been seen as an offhand remark turns out to illustrate a trend in human development--elite athletes are growing larger and larger.

What Gaines may not have known was that a theory by engineers at Duke University, Durham, N.C., has demonstrated that, not only have Olympic swimmers and sprinters gotten bigger and faster over the past 100 years, they have grown at a much faster rate than the normal population. Furthermore, this pattern of growth can be predicted by a constructal theory--a theory of design in nature that explains such diverse phenomena as river basin formation and the capillary structure of tree branches and roots.

In a new analysis, Jordan Charles, an engineering student, collected the heights and weights of the fastest swimmers and sprinters for 100-meter world record winners since 1900. He then correlated the size growth of these particular athletes with their winning times. "The trends revealed by our analysis suggest that speed records will continue to be dominated by heavier and taller athletes," concludes Charles, who worked with senior author Adrian Bejan, the engineering professor who came up with the constructal theory 13 years ago. "We believe that this is due to the constructal rules of animal locomotion and not the contemporary increase in the...