I Can't Even Run 40 Miles a Week

Humans May Be Biologically Able to Run 40 MPH, New Study Shows | Popular Science: "Human running speeds top out near 28 mph, if the record-breaking feats of Jamaican speed demon Usain Bolt prove anything. But scientists say that the biological limits of human running could theoretically reach 35 or even 40 mph -- assuming that human muscle fibers could contract faster and allow people to pick up their pace."