Running Is a Total Body Affair

Much of this research came from the mind and laboratory of Daniel Lieberman, a professor of human evolutionary anatomy at Harvard University and author of the new book “Exercised,” which delves into exercise and evolution. At first, most of his and other scientists’ work related to evolution and running centered on lower bodies, since legs play such an obvious part in how we get from one place to another.

But Dr. Lieberman also was interested in runners’ upper bodies and, especially, their heads. As a longtime marathon runner himself, he knew that a stable head is critical for successful running, but not necessarily a simple thing to achieve. Running is propulsive. You push off, rise and then brake forcefully against the ground with every stride, placing forces on your head that could make it flop uncontrollably, like that bobbing ponytail.

How we manage to keep our heads stable, however, has not been altogether clear. Like most cursorial species, or animals that run, including dogs and horses, we have a well-developed nuchal ligament, a tissue that connects the skull and neck. That is not the case in species that aren’t natural runners, like apes or swine.

When he was a young