For those who want to read the primary research, here is the link to the original article from Harvard scientist Dan Lieberman published in Nature. Dan compares barefoot runners who strike with the front of their feet versus rear-foot strikers and demonstrates that the invention of the padded shoe has arguably changed the way humans run, and not necessarily for the better. http://www.nature.com/nature/journal/v463/n7280/full/nature08723.html.