The Unexpected Cursor: Exploring the Uniqueness of Humans as Endurance Runners

Multiple lines of evidence, including the fossil record, offer compelling evidence that the evolutionary origin of a modern-like human body (i.e., genus Homo) was connected to a profound behavioral and ecological shift in which endurance running became vital to survival. Humans are alone, among all primates, in being adapted for long-distance running, both morphologically and physiologically. At the same time, humans are also unique among all terrestrial vertebrates in being the only known example of a tailless, striding biped that has become a superior cursor. While the uniqueness of the human running machine has its advantages, it also presents significant challenges, especially those related to the control of balance and the dynamic loads that it imposes on the foot and ankle. In this respect, humans are among the most vulnerable of all runners to serious, debilitating injury.

This presentation will examine the morphological, biomechanical and physiological underpinnings of human running within an evolutionary framework and contrast human performance with that of other vertebrates known for their cursorial abilities. Special attention will be given to the ways in which humans both conform to and depart from the conventional “rules of cursorial specialization” and how the departures are linked to their evolution from an unconventional ancestral platform. The most striking exceptions to the typical pattern of cursorial specialization are found in the human foot and ankle complex. Recent work suggests that several unusual structural and functional features, unique to Homo, may have arisen as modifications to help mitigate the stresses imposed on the foot and ankle during running. Included are the suspension of the arm and its kinematic and kinetic profile and even the interaction of runner’s breathing pattern with gait. Both may influence mechanical loading of the foot and ankle in small but meaningful ways, especially over long distances. These factors, operating primarily above the hip, have largely escaped the attention of researchers concerned with the biomechanical performance and pathology of the foot-ankle complex, but may warrant a deeper examination going forward.