This speed limit probably is not imposed by the strength of our bones and tendons. Rather, a 2010 study suggested that the limit comes from our bipedal stride, in particular how quickly we can rearrange our legs while still leaving time to push off from the ground.

Peter G. Weyand, a biomechanics researcher and physiologist at Southern Methodist University and one of the authors of the 2010 study, said that our running speed is limited because we are in the air for most of our stride. During the brief moments that our feet are touching the ground, we have to exert a lot of force.