The <i>"Effective Mass at Impact"</i> between heel listed ~ <a href="http://www.barefootrunning.fas.harvard.edu/4BiomechanicsofFootStrike.html" rel="nofollow">http://www.barefootrunning.fas.harvard.edu/4BiomechanicsofFo...</a> is interesting. 6.8%/1.7% of total body mass and forefoot means the later has reduced vertical momentum. Small efficiencies make for less wear and tear on joints, especially the knees. I tried running on my forefoot (with runners) and noticed it works easily uphill, very hard down hill and difficult on the flat. It's really hard on the top half of the calf and quads. There is no chance I'd be wearing the flimsy runners they suggest. The terrain is rough, hot and covered in rocks, dry grass and the chance of snakes.<p>I'd like to see how this technique would work with running and rotating sports like (basketball, tennis, football) which have high levels of knee injuries. The 5% efficiency might give an improvement in running life though canceled out in jumping sports such as basketball.  Useless for running over rough terrain with heavy weights.