Very interesting. (Link: the main illustration of the different running gaits is at <a href="http://www.barefootrunning.fas.harvard.edu/3RunningBeforeTheModernShoe.html" rel="nofollow">http://www.barefootrunning.fas.harvard.edu/3RunningBeforeThe...</a> ). I'm surprised to see that they didn't find a difference in kinetic energy between heel and forefoot impacts; my naive assumption was that the "rolling" motion of the foot in a heel strike would result in a higher-energy bound forward...