The purity of running is that it simply measures how fast a human can propel him/herself. Things like roller skates, ice skates, and bicycles utilize the power of humans without any exogenous sources such as gasoline or electricity. However, their function is to alter human power and transmit it differently. Essentially, the new shoes perform the very same function. We know speed skaters can travel more than twice as fast as runners over a distance and we know men can cover a kilometer in about a minute on a bicycle. Yet, we would never think to classify such things as running records. A shoe that provide a mechanical advantage, however simple or complex, is a machine, something we have heretofore not recognized in the official running records.